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Thread: Brake upgrade question

  1. #1
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    Brake upgrade question

    If I was to upgrade my front brakes to the 13" Wilwood kit (https://www.iemotorsport.com/product...13-wheels-e21/),
    would it be necessary (or recommended) to upgrade the booster and master cyclinder?

    Thanks!

  2. #2
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    Most likely no because the four pistons in each caliper are most likely close to the same volume as the two big ones in the E21 stock calipers.

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  3. #3
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    Quote Originally Posted by GraphitE21 View Post
    If I was to upgrade my front brakes to the 13" Wilwood kit (https://www.iemotorsport.com/product...13-wheels-e21/),
    would it be necessary (or recommended) to upgrade the booster and master cyclinder?

    Thanks!
    My beer thoughts, first question is what application and powerplant? Honestly there is no reason IMO to uprate front brakes to that size unless your shoveling lots of weight and or power.

    I doubt the piston area is equal to stock fronts. Like some have found out the "volvo" upgrade area is higher than stock. It throws off the front to rear bias. Can't use a "bias valve" to fix the issue either as all they do is decrease line pressure to the rears.

    In a nut shell what can be done with factory brakes with a good pad is more than enough for most applications. If have a huge powerplant I could see needing or wanting more brake but it opens the can of worms. Might as well upgrade the rears too with a disc conversion using appropriate size calipers. Honestly E21 drums suck bad and if can afford a front BBK i'd get the rear too. Car will be more balanced and much easier to dial in.

    Another extreme thought/example on this for me is comparing to my M3 track car. Uses a 300mm wiwood setup on the front with 6pots(sl6r). Sure weight and motor play a factor but damn. Your looking at a 330mm front kit(huge). I'm sure it has the cool kid factor but IMO you'd need a sled that warrants it. That's a lot of brake power for a 2000 lb ish car.

    Another example; Our E21 is 2000 lbs with driver. Run stock 77 vented rotors up front with Brembo Alfa calipers stock 48mm. Rears stock vw 10" solid discs with stock e30 (33mm) calipers on them. Use centric sport compounds for autox and street use. Use PFC 11's for track duty. Plenty of fast stopping power for our lightweight setup. Then again weight isn't the only factor we aren't shoveling a V8 power plant or turbo setup either. So yeah higher hp than our stroked M10 I'd maybe uprate to a larger setup. . . maybe.

    Food for thought.
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  4. #4
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    I have their 15" big brake kit and I had to us an e12 master. I think they use the same caliper with both kits, so I would say yes you need to switch.

  5. #5
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    Narrow Dynapro Radial Piston 1 Dia: 1.12 Piston 2 Dia: 1.12
    Narrow Dynapro Radial Piston 1 Dia: 1.75 Piston 2 Dia: 1.75

  6. #6
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    Thank you all for your time and input.

    I'm aware it would be overkill to do this upgrade on an 320i with a stock engine but as I get older, I feel like you can never have enough brake power especially here in Los Angeles where I find myself constantly on the defensive from other's haphazard driving.

    Of course, I still have coilovers and bushings that need to get sorted first...

  7. #7
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    I just justify mine by they look grate and I want them, Good enough for me. But I do have an S52 engine swap and do several track days a year with the car so its not all for looks.

  8. #8
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    If you use a master cylinder with a larger diameter piston, that gives you weaker brakes. Because the smaller diameter will give you more pressure in the hydraulic lines.
    Pressure is force divided by area. And a smaller piston has less area, so the pressure would be higher.

    Just saying. Don't assume you should get a master cylinder with larger diameter.

  9. #9
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    Quote Originally Posted by pofo View Post
    I just justify mine by they look grate and I want them, Good enough for me. But I do have an S52 engine swap and do several track days a year with the car so its not all for looks.
    Curious what rear brakes? Booster still installed? S52 swap is nothing to sneeze at; I'd opt for a BBK IMO. I see the IE 13" kit isn't floating rotor so if buying from them yup the 15" is only way to go spending that much. MassiveBrakes has a 300mm(11.75) floating hat kit version. Although I'm not 100% sure Lee is still selling them.


    Another main train of thought on this; BBK's to me is what tire am I using. For most using street tires in narrow widths there's not much more grip available. Can easily overcome the wheel ie locking with stock brakes. BBk could lock them easier. High speeds it's harder to lock so will reduce distance, but again street tread 15's have a limit. But say on a 15x10 slick/track tire would need more brake torque.


    I tend to be a minimalist, and guess I always evaluate "do I really need this". Some things like big brakes to me need to be thought of a system with tire, car weight, power available.

    I get it some just want things, and that's cool to each their own. But that's not me. I'm function first.
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  10. #10
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    I have stock drums at the moment but will be upgrading to IE's rear willwood's over the winter on the new chassis. The breaking is very well balanced for the most part with the 225/50/15 RE71R's that I've been using the past couple seasons. The tires seam to heat up and get a little slick after 2 hot laps. If I keep driving hard I do notice some fade in the rear and the car tends to nose over a little more, but its still manageable. But this next season I will be running 245/40/15 so I am hoping that with the extra grip and larger brakes on all 4 corners I can balance my braking more and shorten my braking distance.

    But I agree I could have stayed with the Volvo calipers and they mostly perform the same, but I do notice a little better braking feed back over the 240 calipers under hard braking (This could also be due to different pads). Not going to lie I like having a car that looks the part as much as it can perform. The little details like the calipers give me the look im after especially building a group 2 inspired car.

  11. #11
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    Quote Originally Posted by autox320 View Post
    My beer thoughts, first question is what application and powerplant? Honestly there is no reason IMO to uprate front brakes to that size unless your shoveling lots of weight and or power.

    I doubt the piston area is equal to stock fronts. Like some have found out the "volvo" upgrade area is higher than stock. It throws off the front to rear bias. Can't use a "bias valve" to fix the issue either as all they do is decrease line pressure to the rears.

    Food for thought.
    This was interesting to me...I have not heard “complaints” or issues related to the girling upgrade of calipers before this thread...my car has 323 rear trailing arms with disc brakes so this isn’t the issue for me that it seems to be for individuals with rear drum brakes.

    At first blush I’m not sure I understand what’s actually at issue with the girling brake pad surfaces compared to ATE? I have an early ‘77 with 1st generation front discs brakes. What I don’t understand is what your saying that the manufacturers of brake pads reproduce pads with a smaller overall (area) surface than is commonly available in for example in the stock BMW OEM caliper? Is there an assumption here that I’m unaware of related to brake pad availability for each caliper? If not, ya lost me. Help! lol


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  12. #12
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    It's not the brake pad area

    It's the "piston area" because the bigger the pistons at the front the more powerful the front are relative to the rear. So the front could be locked up before the rear.

    and when you go to a 4 piston front caliper you have to add them. So 4 smaller pistons could be "more area" 2 big pistons, depending on the specifics.

    stock front piston area, since they are 48mm pistons, is 48*48*3.14/2 = 3,600 square millimeters. Note that is for two front calipers, left plus right.

  13. #13
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    Yeah, I remember this discussion before it was a sticky memo. Someone did the math, it was a great thread someone did the math differential between the OA circumference of the single pot and the dual pots on each side. The answer was it was marginally recognized at the pedal...here’s the thing for me...once the wheels have stopped moving, regardless of your pick of braking system...once the wheel stops, the actual ‘mechanics’ of braking moves to the footprint of the tires (tyres). As tire Width increases, braking increases.


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  14. #14
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    I see a lot of good discussions regarding the "need" to upgrade brakes. I've been doing a lot of reading to try to figure out if I "need" to upgrade mine. Generally when someone (with any kind of car) asks about brake upgrades, a lot of people say just upgrade the pads. I would say first make sure you don't need to upgrade your tires. If your tires can't grip enough then a brake pad won't help you actually stop faster. The discussion about the # of pistons vs diameter is good point. The surface area of the pistons will give you more "ability" to brake, while the greater number of pistons generally gives you better feel/feedback. All of this is to say that unless your braking distances are increasing over time because of brake fade, I don't see why one would need bigger brakes. Please correct me if I'm wrong? I have a totally factory braking system and I've been doing some reading. I've also heard that upgrading the rear drum pad gives a good performance increase and sounds like it may be the best bang for your buck? Never had a car with drums before but it sounds like the reason to move to a caliper setup is because of better compensation with heat. Which again only sounds like an issue for folks who track their car. Also the typical front brake upgrade just helps with heat via vented rotors right? Sounds like if I start getting my car track ready a rear caliper set up and vented front rotor is the way to go? For the street I could save some $ and just upgrade the existing pads?
    Last edited by I3MW; 11-30-2020 at 02:59 PM.














  15. #15
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    Tom D was recommending the Hawk pads, said they were much better.

    you can look them up on tire rack

    https://www.tirerack.com/content/tir.../homepage.html



    HPS STREET BRAKE PADS
    Premium, Performance Street
    Not Yet Rated | Reviews (601) $66.60

    DTC-60 TRACK ONLY PADS
    Autocross/Track $147.00
    Last edited by okieflats; 11-30-2020 at 03:41 PM.

  16. #16
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    Quote Originally Posted by pofo View Post
    I have stock drums at the moment but will be upgrading to IE's rear willwood's over the winter on the new chassis. The breaking is very well balanced for the most part with the 225/50/15 RE71R's that I've been using the past couple seasons. The tires seam to heat up and get a little slick after 2 hot laps. If I keep driving hard I do notice some fade in the rear and the car tends to nose over a little more, but its still manageable. But this next season I will be running 245/40/15 so I am hoping that with the extra grip and larger brakes on all 4 corners I can balance my braking more and shorten my braking distance.

    But I agree I could have stayed with the Volvo calipers and they mostly perform the same, but I do notice a little better braking feed back over the 240 calipers under hard braking (This could also be due to different pads). Not going to lie I like having a car that looks the part as much as it can perform. The little details like the calipers give me the look im after especially building a group 2 inspired car.
    I know a lot of "series" cars required 200 treadwear and they do use the RE71R. But it acts just as you describe. It doesn't handle the heat well falling off too fast getting greasy. Man I'd move to a track tire; NT01 / RA1. Much more suited for track days. They can handle multiple laps feeling the same once up to temp. Sure they take a full lap or two to heat up.

    Drums will work for track with the right shoes. But they are a compromise to max braking. They get overheated also. The e21 drums don't self adjust so requires constantly tweaking them to keep the same brake pedal. Disc is more consistent and doesn't need constant adjustment in hard use. Street use this probably is never noticed.

    Far as the rest of this discussion yup piston diameters are what I should of been clearer on.
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  17. #17
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    I agree on new tires for this season. I liked the RE71R's because they where decent in the wet and I drove the car a lot on the street also. So they where not to loud and quite. But the largest size they make is a 225 in a 15 so they no longer are an option. I think I will be using the AR-1's this season as they offer a 245/40 15.

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    i run 316mm 4piston e38v8 brembos on the front and 280mm singles from VAG on the back. Indeed plenty of stopping power. car weighs about 2360 pounds
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