Need Help: Wheel hits caliper after brake job

[ryanlong01]

Ok, so here's the deal. Doing a brake job on my '97 M3 this weekend. I picked up some drilled and slotted rotors (they started out as Brembo blanks) and some PBR Ultimate Ceramic pads for all 4 corners.

I started with the fronts, and took everything apart and put it all back together as usual (I've done brakes on quite a few cars over the years for myself, my girlfriend, friends, etc., although this is my first BMW brake job)...and when I put the wheel back on after finishing up, it just *barely* hits the little ribs sticking out of the caliper. It just needs a tiny bit of clearance, but it's enough to stop me from turning the wheel by hand.

So, I immediately thought that something might be wrong with the way I put them back together -- I take that side apart entirely, I file/sand some burrs and crap off of the brake pads, thinking that might have been responsible for some extra "thickness" of the entire assembly. I also pulled the rotor off and took some time cleaning up the hub surface to make sure the rotor was sitting exactly as it should be. Put it all back together, and same issue.

I had already assembled the other side, but I hadn't put the wheel back on...so I put it on, and it's the same story on that side. I had already pumped the brake pedal from inside the car to tighten everything up, but to make sure I started the car and pumped the brake pedal again several times...didn't help.

I came inside and checked the part numbers for both the rotors and pads to ensure that I didn't get shipped the wrong part by accident...both the Brembo and PBR part numbers check out OK in catalogs and various places online.

So, what gives? Is it possible that brand-new rotors and pads are somehow just barely thicker than the factory setup? I obviously can't drive it to wear down the pads, but should I pull them again and sand them down a bit, or should I grind the small area of the caliper where it hits the wheel? Or, is there anything I may have done wrong? Anything else I can do at this point? I don't want to run spacers, as it really seems like this combination should work, it's not like I got new wheels that don't clear.

Any ideas/thoughts/experience you could share would be appreciated!

P.S. -- this does NOT have the stock wheels on it...it has a set of non-staggered mesh BBS-style (not sure if they are actually BBS or not) wheels that were on the car when I bought it. Who knows, I suppose that these wheels may have been put on the car by the PO when the pads/rotors that I pulled off were already a bit worn down. I just remembered that it does have a OEM wheel in the trunk as a spare, so I guess I can check clearance with that and post the results in a bit.

EDIT: The OEM wheel that's in the trunk as the spare fit just fine. It's the style with several pairs of short spokes (not sure what they are called) and has an "M" emblem, I'm pretty sure they are what was on the car stock. The spokes on that wheel curve outward at exactly the right point to clear the ribs on the calipers.

So, now that I know everything is put together fine and it's just a wheel fitment issue when the rotors and pads are brand new, the question is: Is it OK to grind the "ribs" on the calipers slightly to get the proper clearance?

[GacAttack]

The pad thickness would have nothing to do with the caliper hitting the wheel.

If you know for certain that those wheels were on OK before, then i would look for a missing spacer or something.

[ryanlong01]

The pad thickness would have nothing to do with the caliper hitting the wheel.

If you know for certain that those wheels were on OK before, then i would look for a missing spacer or something.

I guess that makes sense, the caliper is mounted in a fixed position and only the piston moves to compensate for pad/rotor thickness. These wheels definitely fit fine before (although I've noticed in the past that there wasn't MUCH clearance to the caliper)...so when they hit, I just assumed it was a pad/rotor thickness issue without thinking it through.

I did just do some research and realize that the place that drilled and slotted the Brembo blanks mislabeled them left/right. I wondered about the orientation of the cooling vanes, but I went with how they were labeled (handwritten in marker, not a label, on the Brembo box, that's how I figure it was the place that drilled/slotted them and not Brembo themselves). I'm going to go swap the rotors from side to side...not sure if that will have any impact on wheel-caliper clearance, but it should be done for cooling purposes anyway, so I guess it's worth a shot.

I'll double-check everything as it goes back together...if anyone has any other ideas, post 'em. I'll check back in later with an update.

Thanks guys,

[GacAttack]

Just so you're not confused either, the vents should be oriented such that when moving forward the vents draw air from the middle and push it to the outside edge.

...but that also shouldn't have an impact on clearance.

[ryanlong01]

Yeah, they were labeled so as to "scoop" air from the front, which was wrong.

But after thinking about this more, pad thickness HAS to have a role in the placement of the caliper relative to the wheel, doesn't it?

As the outboard pad wears down, the caliper has to move inboard on it's guide pins, doesn't it? Otherwise, if the rotor was in the same place, the wearing of the outboard pad would create a gap in between itself and the rotor. The caliper itself isn't mounted in a fixed location, only the part that holds the pads is...the caliper can slide on the guide pins, and it seems like it would be furthest outboard with fresh pads...right?

[erobinson]

Yeah, they were labeled so as to "scoop" air from the front, which was wrong.

But after thinking about this more, pad thickness HAS to have a role in the placement of the caliper relative to the wheel, doesn't it?

As the outboard pad wears down, the caliper has to move inboard on it's guide pins, doesn't it? Otherwise, if the rotor was in the same place, the wearing of the outboard pad would create a gap in between itself and the rotor. The caliper itself isn't mounted in a fixed location, only the part that holds the pads is...the caliper can slide on the guide pins, and it seems like it would be furthest outboard with fresh pads...right?
Fresh pads would move the caliper more outboard, that is true. Sounds to me like you need wheel spacers though.

[bmwpowere36m3]

Happened to me as well with a set of aftermarket wheels for winter use. I changed out the pads and all of a sudden the caliper was rubbing the wheel, when it wasn't before. New pads = thicker pads = caliper pushed out further toward wheel.

[papo]

Happened to me as well with a set of aftermarket wheels for winter use. I changed out the pads and all of a sudden the caliper was rubbing the wheel, when it wasn't before. New pads = thicker pads = caliper pushed out further toward wheel.

You will probably need the spacer to clear:help...good luck!

[GacAttack]

I usually install new pads on BOTH side of the caliper-- that keeps the caliper on the same center line regardless of pad thickness.

Regardless, you're going to need spacers.

[ryanlong01]

I usually install new pads on BOTH side of the caliper-- that keeps the caliper on the same center line regardless of pad thickness.

Regardless, you're going to need spacers.

Obviously, I installed new pads on both sides. I was just talking about the outboard pad to explain why the caliper is further out with a fresh pad there vs. a worn one.

Regardless, new pads/rotor DO (and did) reduce wheel to caliper clearance, despite your argument to the contrary. Thanks for the input...I've got it figured out.

[bmwpowere36m3]

You will probably need the spacer to clear:help...good luck!

Yup, ended up using a 5mm spacer.


I usually install new pads on BOTH side of the caliper-- that keeps the caliper on the same center line regardless of pad thickness.

Regardless, you're going to need spacers.

Still, it will push it out some...

[Devius1]

drilled AND slotted Brembo rotors? :rolleyes
:lol different issue.

Are there scrape and/or gouge marks on the wheels from the previous brake set-up?
How different are the "tabs" on the new pads compared to the previous ones? were they "altered" ? :nono
Tough to say w/o seeing what ya got. BTW wouldn't be surprised if some hack job was done i.e WTF I bought these COOL wheels and they don't work.... I'll MAKE it work. :nono

Good luck!

[USCG M3]

I would make sure you got the right parts because changeing you pads should destroy your clearance. I have done brake jobs on a few bmw's with after market wheels and some stock and never had this problem. Who did the cross drilling on the rotors? if they are ebay then it is possible they are A. warped or B. they put the wrong rotors in the right box. what you are describing is the first I have ever heard of something to this nature and I have been a around cars and a mechanic for some time.

[GacAttack]

OP is saying that the caliper is contacts the WHEEL, not the rotors. New pads can be very difficult to slip over new rotors, since there's not much clearance in there. Hitting the wheel is just so damn weird.

[Devius1]

I would make sure you got the right parts because changeing you pads should destroy your clearance. I have done brake jobs on a few bmw's with after market wheels and some stock and never had this problem. Who did the cross drilling on the rotors? if they are ebay then it is possible they are A. warped or B. they put the wrong rotors in the right box. what you are describing is the first I have ever heard of something to this nature and I have been a around cars and a mechanic for some time.


OP is saying that the caliper is contacts the WHEEL, not the rotors. New pads can be very difficult to slip over new rotors, since there's not much clearance in there. Hitting the wheel is just so damn weird.

I'm sure that it is the alignment "tabs" on the pad that the guy is talkin' about. The rotor mutulated as it is has no effect on caliper's w/h/l.


pics would :help

[GacAttack]

I'm sure that it is the alignment "tabs" on the pad that the guy is talkin' about. The rotor mutulated as it is has no effect on caliper's w/h/l.


pics would :help

That's what I've been trying to say the whole time! Re-read the posts-- OP makes it clear that he's talking about the caliper hitting the WHEEL (and I made it clear that the pads wouldn't affect that).

I agree with you completely on how the pads and rotors relate to each other-- and that a mutilated rotor would be the likely cause.

[Balthazarr]

The caliper is cast.
There's no way a pad is going to expand the width of it or any other caliper dimension.
The caliper maintains its position relative to the wheel unless it's loose.
The piston does the takeup on the pads.
Without seeing it, it's tough to tell what you are on about.


OP, you said the rotors were mislabeled left and right.

[ryanlong01]

The caliper is cast.
There's no way a pad is going to expand the width of it or any other caliper dimension.
The caliper maintains its position relative to the wheel unless it's loose.
The piston does the takeup on the pads.
Without seeing it, it's tough to tell what you are on about.


OP, you said the rotors were mislabeled left and right.

Caliper is cast, agreed, it is always the same width. The piston extends to keep the pads against the rotor, agreed.

Someone please correct me if I'm totally wrong here:

Picture a setup with a brand new outboard pad. Then, imagine that same system with a totally worn outboard pad...in order to keep that pad's surface against the rotor, the caliper HAS to sit further inboard, regardless of piston position...I don't see any way around it. The distance from the rotor surface to the face of the caliper is based entirely on the pad thickness.

Isn't that the entire point of a floating caliper? Fixed calipers are different -- they are always in the same spot, and they have pistons on both sides that make up for loss in pad thickness 100%. Floating calipers have a piston on one side only, and they "float" or slide on pins/bushings.

On a fixed caliper system, wheel-to-caliper clearance is always the same regardless of pad or rotor thickness. On floating calipers, it has to vary.

So, if these wheels were originally mounted halfway through this set of brake pads, they could easily clear. I buy the car, wear the pads down, change pads, and bam -- they don't. Like I said, the stock wheels (I have one as a spare) DO clear. If the stock wheels didn't clear, I'd know for a fact that something wasn't right. The fact that these wheels don't clear could be explained by the fact that this is the first time they've been on the car with a fresh set of pads.

[ryanlong01]

http://i22.photobucket.com/albums/b324/ryan_long_01/brakecaliper.jpg

OK, quick visual in Photoshop from an image I grabbed on the web. Top shows worn pads, piston is extended. Bottom shows new pads. Outside face of rotors are lined up in both images. The two blue vertical guides on the right show the location of the outside face of the caliper in the two situations. Given that the rotor location is fixed and the distance from the rotor face to caliper face is determined by the pad thickness, doesn't pad thickness determine caliper face location relative to wheel?

Someone please tell me if something is incorrect about my assumptions...I'm not trying to argue with anyone, I'm trying to understand what's going on with my car.

[Balthazarr]

OK, you are correct. I don't know what I was thinking it's been so long since I pulled mine off and the pads are still more than adequate on both sides of the rotors.
I don't recommend grinding the ribs.
Spacers are what is needed.

[fsmtnbiker]

I usually install new pads on BOTH side of the caliper-- that keeps the caliper on the same center line regardless of pad thickness.

If we had fixed calipers, that would be the case...

... But we don't. We have a one-piston caliper, which floats on 2 pins to accomodate pad wear. If you put in new pads, you compress the one piston, which changes the centerline of the caliper with relation to the rotor. It also pushed the outside of the caliper closer to the backside of the wheel, and the OP found out. Pad thickness directly relates to caliper placement and clearance with a floating caliper design.

[GacAttack]

Ah damn it!!@$^#$!~!!! Stupid floating rotors making me wrong.

[tauntedmonster]

You can grind the ribs down. do it just enough to clear the wheel. That tolerance doesn't ever change, so if it clears in your garage, it will clear all the time on the road.

You can add spacers if your stance allows it, but if you're already nearly poking, or rubbing, you can grind the caliper as long as it isn't too much. 2-3mm should be fine. You might as well smooth it out and give them a coat of paint as long as you're down there. please don't use red, yellow or blue lol

[ryanlong01]

You can grind the ribs down. do it just enough to clear the wheel. That tolerance doesn't ever change, so if it clears in your garage, it will clear all the time on the road.

You can add spacers if your stance allows it, but if you're already nearly poking, or rubbing, you can grind the caliper as long as it isn't too much. 2-3mm should be fine. You might as well smooth it out and give them a coat of paint as long as you're down there. please don't use red, yellow or blue lol

That's what I'm thinking. I could use spacers, but I know that once the pads wear down just a bit, there would be no need for them anyway, so I hate to go that route. I'll probably grind the ribs just a bit (it won't take much at all, as they just BARELY hit), and then go ahead and paint the calipers...maybe I'll do black and fill in the ///M with red, that's reasonably tasteful :)

I haven't done this yet because as I was swapping the rotors from side to side and I hung the drivers side caliper from the spring, I noticed that it was rusted completely in two up near the top. The protective rubber coating was basically all that was holding it together. The top part of the spring must have just compressed against the bottom part pretty well, as it really wasn't too obvious at all driving the car. These aren't factory springs, they are H&R Sports on Bilstien struts that the PO installed, BTW. I need to make sure the rear springs look OK, and if so, the task of finding someplace that will sell me a pair of front springs only (and not a set of 4) will be underway.

If I can't find anyone to sell just the fronts, I might just replace all 4...if the rears are the same age, they might soon meet the same fate, and the rears are the easy ones to change anyway.

So, it's sitting on jackstands in the garage until I can get some parts and put it all back together...luckily, I recently bought a beater truck that I've been driving in the meantime. Anyone got any leads on a pair of front springs only? H&R Sports -- or something that lower the same amount -- are what I'm looking for.

[CMG]

You're saying your H&R springs rusted all the way through?

[Devius1]

is this / fer real?

[ryanlong01]

You're saying your H&R springs rusted all the way through?

Well, rusted/broke. There was some corrosion, but I guess I don't know if I'd say it rusted all the way through. More like it rusted, which created a weak spot, where it broke under load. Or, it could have broken purely from failure, and then the unprotected metal corroded -- but I'm guessing it was weakened first. Check out this search for "broken spring" on all the forums here:

http://forums.bimmerforums.com/forum/search.php?searchid=9760708

You'll read about several people, mostly living in the "Rust Belt", who have had springs break in two. I live in Indiana, and the previous owner lived in Michigan -- prime rust (and road salt) country.

Most of the stuff you'll find on the search seem to be regarding OEM springs on E46 cars, but there are some E36 owners who have had it happen, and some people who have had it happen to front springs. I don't know if I found it through the above search, but I read a post from one guy who even had his H&Rs replaced by the company when it happened -- if I had the original paperwork from when the previous owner purchased them, I might give that a shot...too bad I don't.

I wish this was a joke...when it rains, it pours.

[tauntedmonster]

broken springs aren't that uncommon, at least in the salt belt of the US.

happens to a lot of fords too. you get your wheels to fit?

[ryanlong01]

broken springs aren't that uncommon, at least in the salt belt of the US.

happens to a lot of fords too. you get your wheels to fit?

Haven't messed with it yet...waiting on some springs so I can put it all back together at once.

[LuxoM3]

off topic - well springs are eventually gonna lose their coating - I got a set of used springs from a guy on the forums from delaware - the outer coating was pretty much all faked off and the springs were a little rusty but nothing broken...

given the constant motion of the car, the best you can really do is maybe dip them in some sort of latex-y goop and reinstall or occasionally go in there... wipe them down... and spray them with a coat of rustoleum paint....