Brakes issue

[paul e]

Does anyone else here use Hawk HPS brake pads, or any other aftermarket brake pads which cause this problem:

After having used them for a couple thousand miles in mostly highway/high speed use, I inevitably get 'Judder' upon braking at speeds of over 65 mph. What it feels like is, upon applying the brakes at over 65 mph, I will feel an annoying steering wheel shimmy or vibration in my hand through the steering wheel.

However, the first few brake applications of the day, at speed, are smooth as silk. Only after they get really heated up does the judder occur. And its not just Hawk HPS pads either.. Ive used another aftermarket brand or two, sometimes with new rotors, sometimes not, and inevitably, the same thing always happens.. Matter of fact, the ONLY time it hasnt happened is the first two months I owned the car when the car still had its OE pads. They didnt produce any judder; all the rest did.

So, its not bearing, or suspenion parts, or even warped rotors, since before it heats up it doesnt happen, and because, at least in the case of the current rotors, Ive been careful to NOT do any of those 100 mph to 20 mph hard stops.

IM very tempted to throw back on my original OE pads which only have about 2 mos of use on them, because Im tired of the judder. New rotors will stop it, but only for a couple thousand miles. Im theorizing it must be Pad material transfer to the rotors. IVe had prior rotors checked for warpage when having them replaced, and they measured true. So, Im kind of going along with this article segment:

"What causes 'Warped Rotors'?

Typically warped rotors are caused not by a failure of the rotor itself.
Warped rotors (in most instances) are caused by the brake pads being operated at temperatures outside of their specified range. When the pads get too hot the pad material actually melts and 'fuses' itself to the rotor surface and creates a 'bump' on the surface of the rotor. In most cases this is not noticeable to the naked eye. This creates an annoying vibration when the brakes are applied. The only solution to this is turning (grinding) the rotors or installing new rotors."

All of which means I need to find a new brake pad that doesnt transfer its material to the rotor where it gets permanently bonded to the rotor creating the judder. As I say, the stock pads were fine, except for the fact that I have Fikse rims, and those pads dust like a MOFO as you all know. I dont want to spend my life cleaning expensive rims, so Im still looking for an alternative. IN that regard, how do you feel about the new Hawk Ceramics? Theyre not primarily a performance pad, so I wonder if they'll be immune from the hi speed transfer issue.

So, anybody have or know of any other pads which will prevent the judder issue, but also dont requre loads of warmup stops before theyll bite?

Thanks for reading this through...

[CABimmer]

Warped rotors do not come from deposits. they come from over heating and then the metal changes shape. This is almost imposible to do on the street unless your rotors are really old and have gone through several sets of pads.

Warped rotors and pad deposits on the street are usually from bad braking technique. (riding the brakes to long) Proper braking is hard on the braks and then off. I thrash my M3 and my street pads last 50k miles.

My wife however goes through pads every 15k miles and has warped rotors on here SUV. She does not ride the brake just starts braking to early.

[paul e]

cabimmer, what you say is contrary to every hi tech brake article Ive read.. Here's one for starters:

http://www.powerbrake.co.za/pages/tech_03_warping.htm

It describes my condition to a T.. The rotor is not warping.. READ.... Read about cementite.. Read about what happens to the pad material when its used beyond its referenced heat range. And mostly read about the difference between Hot and Permanent brake judder.. IF the rotor was permanently warped as you suggest, then cold brake stops would produce just as much judder as hot.. And this is the case with permanent judder.. AS you read in my post, this is not the condition I described.

My post was not so much to debate the cause of the condition, as I have a pretty good idea as to that.. What the thread is about is, what pads are you guys using in hi performance Street use, Not Track, which, over a period of over 5000 miles in highway use at over 65 mph, havent produced any judder.

[marc1119]

You can **try** to clean the deposits up on the rotor, by doing a series of 60-5 MPH slowdowns, ~ 1 minute apart..Do about 10 of them...Get the brakes good and HOT...(you will look like a person who needs psychiatric help if witnessed by others... on the road):)
Then go home and let the brakes COOL down a while..Do not apply high pressure to the brake pedal when/ if you have to come to a FULL STOP (0 MPH) AFTER you bed the pads.....
Try to roll to redlights and stop signs etc..

If that does not work, you may need to borrow or buy a mean set of track pads that rip the crap out of your rotors, and put them on and do the same thing..as above...

Method 1 or 2 will fix your problem, at least for a while....

[JClark]

To form deposits on the street would take some epic street braking, and the deposits would be cleaned off a few stops later.


cabimmer, what you say is contrary to every hi tech brake article Ive read..

But he's correct. Paul, what speeds do you experience the judder? Highway 80mph+, everytime?

Didnt you post a similar brake problem a long time ago? What was that about and did anything good come of it? If memory serves (and it was a long time ago), didnt the discussion come down to technique?

[CABimmer]

[QUOTE=marc1119;8238862]You can **try** to clean the deposits up on the rotor, by doing a series of 60-5 MPH slowdowns, ~ 1 minute apart..Do about 10 of them...Get the brakes good and HOT...(you will look like a person who needs psychiatric help if witnessed by others... on the road):)
Then go home and let the brakes COOL down a while..Do not apply high pressure to the brake pedal when/ if you have to come to a FULL STOP (0 MPH) AFTER you bed the pads.....
Try to roll to redlights and stop signs etc..[QUOTE]

This is the way to remove deposits. When I get off the track, I do this to clean the track pad deposits off.

[marc1119]

[QUOTE=marc1119;8238862]You can **try** to clean the deposits up on the rotor, by doing a series of 60-5 MPH slowdowns, ~ 1 minute apart..Do about 10 of them...Get the brakes good and HOT...(you will look like a person who needs psychiatric help if witnessed by others... on the road):)
Then go home and let the brakes COOL down a while..Do not apply high pressure to the brake pedal when/ if you have to come to a FULL STOP (0 MPH) AFTER you bed the pads.....
Try to roll to redlights and stop signs etc..[QUOTE]

This is the way to remove deposits. When I get off the track, I do this to clean the track pad deposits off.

Yes it is..And I do it periodically with my 4 wheel Brembos....
Since I am doubtful Paul has warped rotors, I thought this method may be useful to him..But I am sure the problem will come back, just because of his personal braking habits, I would guess...:)

[paul e]

But he's correct.

Paul - What speeds do you experience the judder? Highway 80mph+, everytime?

Didnt you post a similar brake problem a long time ago? What was that about and did anything good come of it? If memory serves (and it was a long time ago), didnt the discussion come down to technique?

Yup.. And I altered the technique, and I changed pads/rotors. BTW, you have one hellofa memory.. BTW, heres another tech article, this time from Stoptech, where the author says hes never seen a 'warped rotor'! Its not about a warping of the metal as some people still seem to think.. Read: http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

At any rate, I know what used to cause it with me.. IT was from finding a strech of straight road, my data logger in hand, and trying as many wot runs in second gear to redline as possible in that stretch. .Hard braking to yank it down to zero for my next run, back to back, built up way too much heat without adequte cooling between runs.. So thats a no brainer.. I think wed all agree that its no surprise issues with overheating pads/rotors would and did result.

But on this last rotor/pad change, I did none of it. Its near when I got my second speeding ticket, and driving within the law was the main thing on my mind to avoid that third, license suspending ticket. I know all about proper braking technique. Never ride 'em.. Never keep the brakes applied on a hot rotor at a stoplight.. Always try and minimize the time of brake application, ie, rather than smooth, slow, long stops, use more of a quick on/quick off technique as Marco described... And despite all of it, after a few thousand miles, back it came... AGain, its only present after a few applications at above 65 mph.. The first few applications at that speed are smooth as silk.. Its clearly the Hot Judder scenario described in the prior article link I posted. I will give Marco's suggestion a try, as I ve had some success with it in the past.. From what you guys are saying, youd have me believe its not a search for a better pad I need to do; its a search for a better technique. But from the way Ive braked since this pad/rotor combo was installed, I really dont know how to do it better.. Im an avid reader, and I know pretty much all of whats been written on the subject.. Its a shame to have to replace my rotors so soon; ive only had them on for 15k miles, and theres absolutely NO lip on them theyre so new... bummer.

[CABimmer]

Take your rotors to auto-zone or the like and have them cut them. If they can do one pass and have all new material on the rotor than they were not warped. If they have to make 2-4 pases and still have old material on the rotors then they are warped. (wife). It does happen.

The best way to get rid of the material buildup without removeing the rotors has been covered.

[paul e]

Yea, I know.. maybe its a case of, once the judder develops, sure, it become foremost on my mind, and I become very conscious every time I apply the brakes.. But on a new set, where everything is smooth, maybe I relax and forget about abiding by the proper technique, and fall back to old habits... Maybe its true .. maybe i do that.. So next time I change rotors, Ill have to put a stickie on the hub of the steering wheel or something, so that i dont wait til the problem develops before I become ever cognizant of my braking style.

So i can continue using Hawk HPS? I never developed the problem with oe pads, but searching my records, I see i changed them out at 2200 miles, which probably was about a thousand miles short of the time I need to invoke the judder gods!

Incidentally, could you guys who are responding on the thread please indicate what pads youre using on the street, and how happy you are with them? Next time I change out brakes I think i want to try the newer Hawk Ceramics; theyre supposed to be as good as the HPS for my purposes, but even cleaner. You guys without the problem in tens of thousands of highway miles; is most of your drving on 60 mph or higher speedlimited roads?

[CABimmer]

I havent had problems with Ultimates, blues, HT-10, Carbotecs or HP+ pads

[JClark]

BTW, you have one hellofa memory..

Back when I used to sit in huge lecture classes on Bimmerforums, your brake issue had my undivided attention.


From what you guys are saying, youd have me believe its not a search for a better pad I need to do; its a search for a better technique. But from the way Ive braked since this pad/rotor combo was installed, I really dont know how to do it better.. Im an avid reader, and I know pretty much all of whats been written on the subject.. Its a shame to have to replace my rotors so soon; ive only had them on for 15k miles, and theres absolutely NO lip on them theyre so new... bummer.
(below posted before I read your previous post)
Again the supermemory is churning- This has happened with other pads before, correct? Either you had defective material in the pads all those times, or it doesnt make sense to me. If you want to rule it out, next time try the OEM pads. Plenty of people have reported smoother, quieter, less dusty (etc) braking when going back to the OEMs from the high performance aftermarket street stuff.

Other than that it'd most likely be technique, but to develop that problem so quickly on some hefty OEM braking equipment on the street is weird considering you know everything that you do. You'd have to be using some way funky technique for that to happen, and from what you say, that doesnt sound like the case. :dunno

[JClark]

Incidentally, could you guys who are responding on the thread please indicate what pads youre using on the street, and how happy you are with them? Next time I change out brakes I think i want to try the newer Hawk Ceramics; theyre supposed to be as good as the HPS for my purposes, but even cleaner. You guys without the problem in tens of thousands of highway miles; is most of your drving on 60 mph or higher speedlimited roads?

Ultimates, OEM, HPS are what I'm using/have used on the street. I never had any problems with any of them and used the (correct) techniques described above. Now the car sees the track so often with different pads, by the time I grind off the track deposits, I'm usually at the next track day.

[paul e]

>>Plenty of people have reported smoother, quieter, less dusty (etc) braking when going back to the OEMs from the high performance aftermarket street stuff. <<

'LESS DUSTY' when going from aftermarket to OE??? Thats a new one on me.. I thought one of the prime reasons people switch from OE to aftermarket is expressly to Lessen the amount of dust the oe pads are known to create.. as for the rest of it, Im thinking that, at some point, even without changing out current rotors, I may just try to install the oe pads I removed back when the car just had 2200 miles on it, so theyre practically new. I never recall having had any trouble, aside from dust, from using stock pads. It should be worth a try.. If only the Fikse FM-10s (honeycomb design) werent so damned hard to clean!

[m3jasper]

You can **try** to clean the deposits up on the rotor, by doing a series of 60-5 MPH slowdowns, ~ 1 minute apart..Do about 10 of them...Get the brakes good and HOT...(you will look like a person who needs psychiatric help if witnessed by others... on the road):)
Then go home and let the brakes COOL down a while..Do not apply high pressure to the brake pedal when/ if you have to come to a FULL STOP (0 MPH) AFTER you bed the pads.....
Try to roll to redlights and stop signs etc..

If that does not work, you may need to borrow or buy a mean set of track pads that rip the crap out of your rotors, and put them on and do the same thing..as above...

Method 1 or 2 will fix your problem, at least for a while....

+1

What your experiencing is brake pad deposits. There is no way you could have warped your rotors driving on the street. Listen to Marco's advice and follow the steps on bedding them in again.

[DADx2]

Wow, I am glad Paul e has brought this up. I am at 5000 miles on my brake job which included turning stock rotors and using Ferodo pads. The shudder he is describing is exactly how mine is acting. I even(as probably most of you do) used my torque wrench to tighten each lug stud exactly the same.

I will try to bed mine in as described, and hopefully it will help. The shudder is annoying, and even feels a little unsafe when you hammer the brakes at 120mph.

[calypso]

To form deposits on the street would take some epic street braking

Don't know why but that made me laugh.:D Sounds like something from a movie or the local high school hangout.

[fsmtnbiker]

I had the pad deposits show up, but I know why... I went to the track before properly bedding the Hawk HP+ pads I had, and then proceeded to really abuse them. It was also on new rotors too, which didn't get seasoned properly. I have switched my stock pads back on, which almost immediately cleaned off the pad deposits. I'm going to season the rotors with these pads and then stick a new pad of some kind (probably HPS) back on after they're properly seasoned.

I think that not seasoning the new rotors with my old pads is what really gave me trouble. You might try getting the rotors turned (taking as little off as they can) and then following one of the many rotor seasoning techniques out there with an older set of pads. I suspect that might solve your problems.

[skiboard06]

links to a rotor seasoning write-up?

[JClark]

I think he just means bedding them in with old pads, not new rotors and new pads at the same time.


>>Plenty of people have reported smoother, quieter, less dusty (etc) braking when going back to the OEMs from the high performance aftermarket street stuff. <<

'LESS DUSTY' when going from aftermarket to OE??? Thats a new one on me.. I thought one of the prime reasons people switch from OE to aftermarket is expressly to Lessen the amount of dust the oe pads are known to create.. as for the rest of it, Im thinking that, at some point, even without changing out current rotors, I may just try to install the oe pads I removed back when the car just had 2200 miles on it, so theyre practically new. I never recall having had any trouble, aside from dust, from using stock pads. It should be worth a try.. If only the Fikse FM-10s (honeycomb design) werent so damned hard to clean!

The wheels are the problem. I'd be happy to take them off your hands tho, I'll even come down and pick them up. ;)


+1

What your experiencing is brake pad deposits. There is no way you could have warped your rotors driving on the street. Listen to Marco's advice and follow the steps on bedding them in again.

People warp rotors on the street all the time, usually due to improper technique or inadequate equipment. Forming judder-causing pad deposits on the street is FAR less likely, especially with HPS or similar pads.

[paul e]

>>People warp rotors on the street all the time, usually due to improper technique or inadequate equipment. Forming judder-causing pad deposits on the street is FAR less likely, especially with HPS or similar pads.<<

Im going to say it once more, cause I dont want to be repetitive.. MOst of the drivers who have responded are aware, as I am, that its NOT traditional rotor warpage that is the cause, but rather, pad material fusing to the rotor.. I can point you to many expert sites describing the process. Can you even show us one reptutable brake site that still uses Rotor warpage as the usual cause of street caused judder? Im not trying to harp on this, but you continue to bring up the rotor warpage thing, and yet, most of us have seen very little if any support for that idea anymore.

[JClark]

My previous post was meant more towards (m3jasper)"There is no way you could have warped your rotors driving on the street." than anything else, because I've done it and know it occurs.

I dont think its pad deposits or rotor warpage. If it's either, to the best of my knowledge and experience in warping rotors (proven by the machine shop as the cause), I would bet on that. Pad deposits get ground off overtime, so if you were driving in a manner that would not create NEW deposits, the old ones would wear off and the judder would subside. I dont remember if I read every post; do you have any evidence that your issue is caused by deposits other than the linked sites?
Correct me if I'm wrong. (Dont want to beat a dead horse either way.) Regardless, everyone is shooting around with unknowns and guesses. Please post up what you do and the results for those interested.

[Rob Levinson]

People warp rotors on the street all the time, usually due to improper technique or inadequate equipment. Forming judder-causing pad deposits on the street is FAR less likely, especially with HPS or similar pads.

My experience is the exact opposite; we've never seen a set of modern BMW rotors that are actually warped. Usually, it is the pad deposit issue, and it really is easy to cause it in street use.

All it takes is a single high-speed deceleration and then a complete stop with the brakes applied... holding the nearly-overheated pads against the rotors transfers pad material at the molecular level, and no amount of driving will remove it. The difference in heat absorption characteristics between clean iron and iron impregnated with pad material becomes apparent when the rotors get hot, much as PaulE describes. As was posted above, a mild cut (correctly called a "surface truing") will remove the deposits.

Avoid advertised "dustless" pads like the plague. Every brand I've seen advertised that way works horribly, damages rotors (either through premature wear or surface crazing), and has poor pedal feel.

As far as low-dust brake pads ("dustless" is a myth, a brake pad must generate some dust to function) go, much better results can be had with the Akebono ProACT Ceramic, Hawk Performance Ceramic, and even the Satisfied Pro Ceramic. These brands are superior, but need a better cheerleader in the "group buy" lists to get the dollar-focussed to try them.

The difference between these three pads is not "one is better than the other" but differences in characteristics that differentiate them based on an individual person's preferences.

If I were to rate these three pads which I have used on the same car by characteristic on a 1-10 scale for the street pad class:

Hawk Performance Ceramic
Initial bite: 10 (strong bite)
Linearity: 8.5 (strong initial bite, then levels out, very easy to modulate)
Dust: 9 (light dust, but it's gray and hard to see)
Smoothness: 9.5
Noise/squeal: 9.8 (nitpicking here, once in a very rare while, I discerned a slight sound)
Strength: Good for the performance-minded driver who wants a quick-reacting pad. Surprisingly good for auto-x events, maybe even a light track day.

Akebono ProACT Ceramic
Initial bite: 9 (good bite, but not as sharp as Hawk)
Linearity: 10 (the harder you press the pedal,the more they respond)
Dust: 9 (light dust)
Smoothness: 10
Noise/squeal: 10 (virtually silent at all times)
Strength: Excellent all-around pad, velvety operation.

Satisfied Pro Ceramic
Initial bite: 7 (still good, but off the pace from the other two)
Linearity: 9
Dust: 9 (light dust)
Smoothness: 9
Noise/squeal: 10
Strength: Great economy choice priced much less than others. Think of it like store-brand breakfast cereal... almost (but not quite) the same thing, with money left over for chocolate milk!

[paul e]

Rob, thanks alot for chiming in. Ive decided to try the Hawk Perf. Ceramics next.. Can you do any comparison between them, and the more traditional Hawk HPS Im currently using?

[yod88]

*subscribing*
i just installed hawk hps pads today, and so far they are great, a very noticeable braking response over the oem pads..
ill let you know if i run into any problems with the pads in a couple thousand miles, but on brand new they run great..as expected

[Rob Levinson]

Rob, thanks alot for chiming in. Ive decided to try the Hawk Perf. Ceramics next.. Can you do any comparison between them, and the more traditional Hawk HPS Im currently using?

HPS is a more "traditional" sport pad, in that it's an upgrade over OEM, but not a heck of a lot. It's a good choice for many people as an alternative to OEM pads, but may be insufficient for those that place heavier demands on their brakes.

The Hawk Performance Ceramics are really another generation ahead in technology; the heat range and release characteristics of this pad are practically a low-level race pad, although they work great cold. The fact that they are extremely low-dust is simply further testament to how far the technology has progressed in recent years. Hawk is one of the top companies for street and race pads without any doubt.

- Rob

[paul e]

*subscribing*
i just installed hawk hps pads today, and so far they are great, a very noticeable braking response over the oem pads..
ill let you know if i run into any problems with the pads in a couple thousand miles, but on brand new they run great..as expected


I think youll find that, when cold, they lack the bite youre used to with stock pads.. But all it takes is one or two moderate stops to get them gripping to what youre used to.. Aside from the judder issue, I like them alot.

[4ZPN]

Thanks for the brake pad comparison Rob. I have HPS on my truck and don't really car for them. They don't stop well when cold. I had Axxis/PBR Ultimates (ceramic) on my truck before and they were much better than the HPS. I'm current am using the Ultimates on my M3 and they are pretty good. I get a little noise, but I don't really mind.

As for the pad deposits, try this: When your brakes are still cold, get some speed going and do a few medium-hard stops. When brake pads are cold, they tend to be more abrasive. As they heat up, they become more adhesive. The cold stops will help "clean" your rotors. Also, at when at a stop, try to apply the brakes as lightly as possible.

[paul e]

Hey Rob.... Given the 'hot judder' Ive picked up, which exhibits itself, as Ive described ad-nauseum, as occurring at speeds of over 65 mph once the brakes have heated up, is there any likelihood that a change over to the Hawk Performance Ceramic pads without a change of rotor would do anything to lesson the judder? Id describe the judder I have now as being in the light to moderate category. The resulting steering wheel vibration is just that.. a small vibration upon brake application with hot brakes, and not a wholesale Shake as Ive seen before, and experienced in the past with what Id call Major judder.

thanks for the tips..

[Rob Levinson]

Hey Rob.... Given the 'hot judder' Ive picked up, which exhibits itself, as Ive described ad-nauseum, as occurring at speeds of over 65 mph once the brakes have heated up, is there any likelihood that a change over to the Hawk Performance Ceramic pads without a change of rotor would do anything to lesson the judder?

I really don't think it would matter what pads you switch to at this point - pad deposit that causes a shudder is almost impossible to remove by using the brakes or by swapping pads (except for using some real race pads).

As I originally posted, I would strongly recommend a surface true on your rotors first or simply getting new rotors. From then on, switch to the Hawk Performance Ceramic.


Id describe the judder I have now as being in the light to moderate category. The resulting steering wheel vibration is just that.. a small vibration upon brake application with hot brakes, and not a wholesale Shake as Ive seen before, and experienced in the past with what Id call Major judder.

Just to double-check, have you gone through every part of the front end already? Ball joints, lower control arm bushings, wheel bearings, tie rods? Even strut bearings can be a culprit in a juddering issue.

- Rob

[Rob Levinson]

Thanks for the brake pad comparison Rob. I have HPS on my truck and don't really car for them. They don't stop well when cold. I had Axxis/PBR Ultimates (ceramic) on my truck before and they were much better than the HPS. I'm current am using the Ultimates on my M3 and they are pretty good. I get a little noise, but I don't really mind.

Hawk has a newer recommendation for trucks, their HP-LT. That formula seems to be in response to the weight-gaining trend of SUVs that are overwhelming traditional OEM or basic sport pads.

If you like Ultimates on your M3, you will absolutely love the Hawk Performance Ceramic. Really a much better pad in every respect.

- Rob

[acastillo]

If you like Ultimates on your M3, you will absolutely love the Hawk Performance Ceramic. Really a much better pad in every respect.

- Rob

When you say "every respect" I'm assuming your really meaning "every" respect...cold bite, temp range, dusting, squeaks, rotor friendly...etc.

I really like the cold bite on Axxis Ult Ceramic, but on the track, my instructor was getting them to fade after pushing it toward the end of a session (I know these aren't track pads). After that, I've got a reduced cold bite and they now squeak. Thinking of giving the Hawk Ceramic's a try if they are everything you say. Intended use is mainly a street pad where cold bite takes priority.

Edit: just saw your post #28...I might even try the Akebono's. I like how they ranked higher in linearity. Axxis Ult Ceramic have a great cold bite, but the bite from 80 to 55 is not as good as HPS, R4S, etc. Is this what you mean by "linearity".

[Rob Levinson]

When you say "every respect" I'm assuming your really meaning "every" respect...cold bite, temp range, dusting, squeaks, rotor friendly...etc.

Correct.


I really like the cold bite on Axxis Ult Ceramic, but on the track, my instructor was getting them to fade after pushing it toward the end of a session (I know these aren't track pads). After that, I've got a reduced cold bite and they now squeak.

Sounds like you cooked them out. In my experience, any of the ceramics that I recommended will have a higher temp range where they can recover.

Nevertheless, and I can't stress this enough, it's always cheaper in the long run to get real track pads for a track day. Despite the initial expense, you have "savings" in that 1) you don't cook out your street pads, 2) you don't destroy your rotors with melted street pad deposits, and 3) the track day itself is not wasted due to cooked pads. I was testing a new compound for a manufacturer once... but they sent me the wrong pads, a street compound. Got a few good pics of my car in the grass with smoke and flame coming out of the front wheels. Fun!


Edit: just saw your post #28...I might even try the Akebono's. I like how they ranked higher in linearity. Axxis Ult Ceramic have a great cold bite, but the bite from 80 to 55 is not as good as HPS, R4S, etc. Is this what you mean by "linearity".

By linearity, I mean correlating pedal pressure with brake response. It's not really speed-dependent, but a measure of relative response rate. Imagine if perceived brake torque were expressed on a scale of 1-10, and likewise pedal pressure expressed the same way. A perfectly linear pad would have the characteristic of 1 brake pedal force unit resulting in 1 brake torque level increase, and linearly increasing in the same 1:1 ratio. Using the Akebono ProACT as a baseline for 1:1 response, the Hawk Performance Ceramic has a subjective response of 1:2 up to pedal effort 3, and then 1:1 afterwards. Again, that's a subjective description, but is still a reasonable concept.

- Rob

[acastillo]

Thanks for your detailed description. I'll do some research and likely pick up a set of either Hawk's or Akebono's soon. Feel the same way now about dedicated track pads...it was my 1st HPDE and felt the street pads were going to be fine for my skill level until the instructor decided to take over and show me how slow I really was. :)

[fsmtnbiker]

Paul - given the fact that you're seeing this happen after a period of time with the pads, and only after driving at higher speeds, I have to wonder if you've got a sticky caliper. It would explain the cause as well as the effects. How many miles on your calipers, and have you ever rebuilt them? Same with the caliper guide pins?

[paul e]

Paul - given the fact that you're seeing this happen after a period of time with the pads, and only after driving at higher speeds, I have to wonder if you've got a sticky caliper. It would explain the cause as well as the effects. How many miles on your calipers, and have you ever rebuilt them? Same with the caliper guide pins?

No ive never had them rebuilt, but Ive examanined them several times over their 70k mile life, greased the guide pins, and have had no trouble with them.. Keep in mind that when I say it happens after driving at speeds over 65 mph, what I mean is after using the brakes a few times at the higher speeds, thats when the judder starts.. The first few brake applications at high speeds are smooth.. But by then, theyve heated up, hence the term, 'Hot Judder'. Perhaps I will have them rebuilt soon.. thanks for the tip..

Listen to this.. Heres my front rotor replacement history, each time from judder:
4/01 26k mi rotex pads and rotors;
6/03 49k mi Hawk HPS pads and rotors;
4/04 56k mi rotors only;
2/05 64k mi rotors only!!

Each time after the rotor replacement, Id go a few thousand very smooth miles.. then the judder would slowly set in.. At first, Id just notice a very slight hint of steering wheel vibration when applying the brakes at high speed.. INterestingly, it seems that with new rotors and a few thousand miles, its usually a couple of high speed hard brake applications which precedes the onset of the judder. I dont think its my around town braking thats doing it; rather, just a few high speed, hard applications of the brakes seems to be all it takes for the judder to develop.. Its pissing me off cause I know there are other guys out there that have no problem hauling their beast down hard from 100 mph to nothing and never have any judder issues.. Havent had much luck with the Hawk HPS, so next time, Im going to try the Hawk Performance Ceramics most likely with Zimmerman oe type rotors. This time, the judder is not as bad as its been in the past, so I can live with it awhile.. I now have 70k miles, so its only 6 k miles since my laset rotor change! Theres no lip on them so i could have them slightly cut or surface trued, cept I hate to do anything which will make them less of a heat sink by removing material. And, at around 100 bucks for the pair of rotors, it wont exactly break the bank. Still, with so much surface left it seems like a shame to just chuck them.. Maybe Ill try a cut this time. Never done that .. And with most of the original metal still on the rotor from such short usage, I think im going to have them trued.

[mikea128]

Rob, I understand your ratio concept, but I just want to clarify. Are you saying the Akebono's or Hawk's tend to grab more initially as you press the brake pedal?

The max operating temp (MOT) I've seen listed for the Hawk Performance Ceramic is around 750F, which is quite a bit lower than the Ultimates 932F. Also, the Hawk's coefficient of friction apparently falls off rapidly once MOT is exceeded, although most of that I've seen is in reference to the HP+ and HPS. The Ultimates supposedly fade in a somewhat more linear fashion. I'm not sure we can say they're better in every way if that's the case. Although Hawk doesn't list MOT themselves, so this may just be an estimate.

Any MOT on the Akebono's?

[Rob Levinson]

Rob, I understand your ratio concept, but I just want to clarify. Are you saying the Akebono's or Hawk's tend to grab more initially as you press the brake pedal?

The Hawks grab harder - similar characteristics as HP-Plus, but with the typical benefits of a ceramic formula.


The max operating temp (MOT) I've seen listed for the Hawk Performance Ceramic is around 750F, which is quite a bit lower than the Ultimates 932F.

I don't think that is accurate - I might be wrong, but I will double-check the technical data I have back at the office... thought the Hawks exceeded 900 degrees.

(EDIT- Confirmed: I have technical literature here from Hawk's engineering department that rates the Performance Ceramic material to 900F.)

I am also a bit leary of comparing different manufacturers' spec sheets - just like different dyno sheets, they're often 10% data and 90% BS. Does the MOT of one pad mean when the Cf starts to fall off, or when there is complete failure? Quite often, between different manufacturers, this data is not supplied. You almost never see a Cf value, and (as far as I have seen), only Wilwood provides actual Cf curves. Here's an example of a comparative Cf curve provided by Wilwood:


http://www.uucmotorwerks.com/pbc/images/pads_eqbp10.gif (http://www.uucmotorwerks.com/pbc/BIAS.htm)

The graphs above represent Wilwood's street pads (most manufactured by Raybestos). Most are losing Cf by the time they hit 750 degrees, as do most street pads. Their "max" temperature at their Cf peak is quite a bit lower than their still-operating temperature at a lower Cf. Interestingly enough, the BP-20 street pad has, in my opinion, response characteristics very similar to the Axxis Ultimates - meaning that it's not my favorite.

I've not been saying much about how I feel about the Ultimates, but I think since a direct comparison is being asked... I do npt prefer the Ultimates, there are several better choices. Every application that I have experienced has resulted in a "dead" feeling pedal with poor feedback, and excessive rotor surface micro-cracks which are indicative of a hard pad that is heat-spiking the rotor surface. They also seem to chew through the rotor faster than the ceramics.

Nevertheless, tech specs themselves are only part of the equation and is also a number that can give a false sense of what the compound is good for. The Cf curve itself often is a pretty good indicator of response (not directly, as friction build-up varies with materials, but close). But again, that has to be looked at as a complete curve, and not just a "max" number.

As the topic has come up of using various street pads at the track, I'll repeat again: street pads for street use, track pads for track use. There is no such thing as a "dual purpose" pad.


Also, the Hawk's coefficient of friction apparently falls off rapidly once MOT is exceeded, although most of that I've seen is in reference to the HP+ and HPS. The Ultimates supposedly fade in a somewhat more linear fashion.

That's the idea of MOT - if that's the max, pad failure is often right after.

But again, does the MOT of one pad mean when the Cf starts to fall off, or when there is complete failure? We cannot answer this question without the various pads tested together with the results displayed the same way. No single "max" number is of use.


I'm not sure we can say they're better in every way if that's the case.

Because, in my extensive experience under controlled situations, they simply give an overall more-satisfying experience. MOT differences at that level are immaterial for a "street" pad anyway - see above about street/track pads.


Any MOT on the Akebono's?

There is this very interesting technical white paper on the Akebono ProACT Ceramic:
http://www.automotivedigest.com/WhitePapers/Akebono_Ceramic_Friction_Tech.pdf

- Rob

[acastillo]

http://www.uucmotorwerks.com/pbc/images/pads_eqbp10.gif (http://www.uucmotorwerks.com/pbc/BIAS.htm)

...the BP-20 street pad has, in my opinion, response characteristics very similar to the Axxis Ultimates - meaning that it's not my favorite....They (Ultimates) also seem to chew through the rotor faster than the ceramics.


Rob, I believe Ultimates are ceramic too. Also, perhaps I've got it wrong, but looking at the chart, the BP20 pad appears to have a low friction coefficient at cold temps, but seems to work best at temps between 800-1000, correct? My experience is that Axxis Ultimates behave quite the opposite.

Lastly, for the street, wouldn't you want a pad like the BP10? Good cold bite, consistent friction levels across entire temp range?

Perhaps I'm interpreting the chart wrong?

[Rob Levinson]

Rob, I believe Ultimates are ceramic too. Also, perhaps I've got it wrong, but looking at the chart, the BP20 pad appears to have a low friction coefficient at cold temps, but seems to work best at temps between 800-1000, correct? My experience is that Axxis Ultimates behave quite the opposite.

My comparison was in the feel of the pads; yes, the BP-20 does not have as sharp of an initial bite, so they seem "dull" and unresponsive in normal driving... my same impression of the Ultimates.


Lastly, for the street, wouldn't you want a pad like the BP10? Good cold bite, consistent friction levels across entire temp range?

Exactly! That's why we've been using the BP-10 as the standard street pad in our Wilwood-based BBK.

- Rob

[paul e]

Aside from poor braking technique on the part of the driver, can we say anything else regarding a specific pad's likelihood to transfer some of its material to the disk in a way that produces judder? I know that a small amount of material, evenly distributed to the rotor surface is part of the purpose of seasoning a rotor, or bedding it in, but im speaking about the kind of transfer that contributes most to the judder issue... Ceramics seem to be resistant to contributing to this condition, but how bout some of the other pads weve been mentioning? Ive yet to hear from anybody who had judder while using a stock M3 pad.. perhaps thats because any potential judder candidate likely to use a set of pads hard enough to produce judder has already switched to an aftermarket maker? Or is it that the stock pads are just judder resistant? And, weve been talking mostly about the pads in the context of judder; what about the rotors? Are they blameless? Are the Zimmerman, or OE style simple, vented rotors all pretty much the same, and all pretty much fine to use for non track or non mountain-descending-at-prodigious-rates-of-descent speed type use?

[Rob Levinson]

I don't think that is accurate - I might be wrong, but I will double-check the technical data I have back at the office... thought the Hawks exceeded 900 degrees.

Confirmed: I have technical literature here from Hawk's engineering department that rates the Performance Ceramic material to 900F.

- Rob

[Rob Levinson]

Aside from poor braking technique on the part of the driver, can we say anything else regarding a specific pad's likelihood to transfer some of its material to the disk in a way that produces judder? I know that a small amount of material, evenly distributed to the rotor surface is part of the purpose of seasoning a rotor, or bedding it in, but im speaking about the kind of transfer that contributes most to the judder issue... Ceramics seem to be resistant to contributing to this condition, but how bout some of the other pads weve been mentioning? Ive yet to hear from anybody who had judder while using a stock M3 pad.. perhaps thats because any potential judder candidate likely to use a set of pads hard enough to produce judder has already switched to an aftermarket maker? Or is it that the stock pads are just judder resistant?

First, to restate the cause of judder; getting the pads hot enough to transfer excessive amounts of material to the rotor, usually after a high-speed decel and a complete stop, the overheated pad held against the rotor in one spot. The pad material literally melts to some point.

We do see it with OE pads all the time, it's not accurate to say that OE pads are "judder free". However, what's more likely is that OE pads generally have a lower max temp and lower Cf, so are less able to generate the amount of heat necessary to cause the problem. Not impossible, but less likely. The trade-off, of course, is that the OE pads are not effective at the higher temps as the aftermarket performance pads.


And, weve been talking mostly about the pads in the context of judder; what about the rotors? Are they blameless? Are the Zimmerman, or OE style simple, vented rotors all pretty much the same, and all pretty much fine to use for non track or non mountain-descending-at-prodigious-rates-of-descent speed type use?

As long as we're talking about good name-brand rotors, they are generally blameless. All will be the same type of "gray iron". Some may be more or less resistant to cracking, but it's only the no-name stuff that is potentially more porous and likely to imprint with pad material to the point of judder.

- Rob

[paul e]

Rob, I just want to thank you for contributing so much to this thread, and for exposing so many myths alot of people hold dear.

[mikea128]

Good info here, Rob. When I emailed Hawk, they wouldn't give me MOT or any other temperature or Cf data for their street pads, so this is certainly useful. Neither would Performance Friction. Obviously, we all wish all the brake pad manufacturers would give us data like Willwood is, or better yet that there were some sort of independent test that including this information.

It's interesting that you note the Ultimates to not have great pedal feel since the majority of direct comparisons with Hawks HPS pad state that the Ultimates have better initial bite and pedal feedback. Of course, if you're saying the Hawk Ceramics are that much better on all accounts, maybe this comparison is irrelevant.

While I understand there's no good compromise for a dual duty street/track pad, I'm still very much a beginner student (with just 1 DE under my belt so far) and with my schedule, I can probably only make it to 1, maybe 2, DE's per year, so it's hard for me to justify dedicated track pads. I just want the best compromise that I can get, for whatever it's worth, with an eye towards safety - meaning a reasonable/gradual failure mode. FWIW, I'm probably on the less aggressive side of the spectrum as far as DE students go.

Dave Zeckhausen has stated that the Hawk HPS/HP+ (and presumably the Ceramics) all have consistent Cf until MOT and then fall off rapidly. Carbotech told me the same about their Bobcats. That is the scenario that I would like to avoid and that scares me quite frankly. With that research in mind, my top pad possibilities have been the Ferodo DS2500 (although they supposedly squeal like mad), Performance Friction Z-Rated (bimmerworlds rec), the Ultimates (seems like DZeckhausen's rec for a beginner on the track), and the Carbotech Bobcats (despite the poor failure mode).

If you have any further thoughts or data on any of the pads that might fit this scenario, I'd love to hear them.

[bennyfizzle]

I'm so glad i came upon this thread, i have a road i take on the way home from the gf's house, usually around 1-2am, since i got the m3, which came to me with Axxis Ultimates, i've been having this same judder, before when i had my 325, which had oe pads/rotors i would never have it, but here's the thing:

The road is roughly 10-15 turns, most of which i come into around 75-80, brake to 55-65. for the first ~7 turns, smooth as silk, then when i break at 80 for the last few, it'll progressively get worse and ONLY happens from ~70-~60 above or below that, is smooth as silk.

I do not ride the brakes in these turns, or at all (at least i try not to), even coming to stoplights, after all, that's why god made downshifting ;), but this problem persists, is this similar to your guys' problems?

If so, basically pop the rotors/pads off, have the rotors cut, get the hawk/akebono ceramics, and bed em in?

Thanks rob, you've been a great help :wave

[Rob Levinson]

Good info here, Rob. When I emailed Hawk, they wouldn't give me MOT or any other temperature or Cf data for their street pads, so this is certainly useful. Neither would Performance Friction. Obviously, we all wish all the brake pad manufacturers would give us data like Willwood is, or better yet that there were some sort of independent test that including this information.

Sure would be nice. Working on that.


It's interesting that you note the Ultimates to not have great pedal feel since the majority of direct comparisons with Hawks HPS pad state that the Ultimates have better initial bite and pedal feedback.

I don't put much stock in internet user reviews for brake pads for one very important reason; most are comparing cooked-out old pads to fresh pads. You could swap the same material from old to new and have the same glowing first impression. This is simply the reality of how brake pads age with heat cycling and glazing, and the skewed nature of old vs. new reviews.



Of course, if you're saying the Hawk Ceramics are that much better on all accounts, maybe this comparison is irrelevant.

The HP-S is a relatively mild pad regardless. They're an upgrade over OE, but a different feel than the HP-Plus or Performance Ceramic.


While I understand there's no good compromise for a dual duty street/track pad, I'm still very much a beginner student (with just 1 DE under my belt so far) and with my schedule, I can probably only make it to 1, maybe 2, DE's per year, so it's hard for me to justify dedicated track pads. I just want the best compromise that I can get, for whatever it's worth, with an eye towards safety - meaning a reasonable/gradual failure mode. FWIW, I'm probably on the less aggressive side of the spectrum as far as DE students go.

I understand and appreciate your point entirely. If I were going to make a recommendation for you, then it would undoubtedly be the Hawk Performance Ceramic. From what I know of the material formula, there is more "race technology" in it than the general marketing would suggest.


Dave Zeckhausen has stated that the Hawk HPS/HP+ (and presumably the Ceramics) all have consistent Cf until MOT and then fall off rapidly. Carbotech told me the same about their Bobcats. That is the scenario that I would like to avoid and that scares me quite frankly. With that research in mind, my top pad possibilities have been the Ferodo DS2500 (although they supposedly squeal like mad), Performance Friction Z-Rated (bimmerworlds rec), the Ultimates (seems like DZeckhausen's rec for a beginner on the track), and the Carbotech Bobcats (despite the poor failure mode).

No matter what pads you use, you will rarely have a "everything was fine and then *BAM* failure" with pads. That type of failure can happen, but is more often related to overheating/boiling the brake fluid, highlighting the importance of having good, fresh fluid in your car. This is not to say you can't have pads fail from heat, but there usually is enough warning to back off for a lap or so for some cool-down.

A conscientious driver, all the more so at the track, has to "listen" to what the car is telling him. All brake pads give you feedback - you will know when you're getting close to overheating them through such signals as sound changes and feel/feedback through the pedal. Especially as a beginning driver, this is an important part of your track skill set to work on.

- Rob

[mikea128]

Thanks for the info Rob. You're absolutely right about internet brake pad comparison/reviews - they're all so variable, just like internet tire reviews. I guess there are way too many variables to control for everything. I'll definitley consider to the Hawk Ceramics, but I'm in no rush since I won't be swapping brakes/rotors until spring time anyways.

Definitely agree with you on the brake fluid flush. It's required by the clubs around here actually.

[paul e]

I'm so glad i came upon this thread, i have a road i take on the way home from the gf's house, usually around 1-2am, since i got the m3, which came to me with Axxis Ultimates, i've been having this same judder, before when i had my 325, which had oe pads/rotors i would never have it, but here's the thing:

The road is roughly 10-15 turns, most of which i come into around 75-80, brake to 55-65. for the first ~7 turns, smooth as silk, then when i break at 80 for the last few, it'll progressively get worse and ONLY happens from ~70-~60 above or below that, is smooth as silk.

I do not ride the brakes in these turns, or at all (at least i try not to), even coming to stoplights, after all, that's why god made downshifting ;), but this problem persists, is this similar to your guys' problems?

If so, basically pop the rotors/pads off, have the rotors cut, get the hawk/akebono ceramics, and bed em in?

Thanks rob, you've been a great help :wave

Benny, that sounds just like what IVe been describing. When cold, smooth as silk at all speeds; below 65 mph, smooth as silk at all temps. But after the brakes have been used, ie, warmed up, and braking speeds are over 65, we have the judder.. we have it if we apply them lightly at that speed, or strongly. At some point, Ill get them cut lightly, and apply a pair of Hawk ceramics. And try and become even more aware of only applying the brakes with an on-off type of application, rather than applying them lightly over a longer period. And, hope for the best!