Braking causing wheel shimmy

[BMWManiac]

I'm going nuts over this.....so, I think my tires need to be replaced too because I can't seem to get rid of my steering wheel shimmy that I feel from 60-70....the shimmy gets worse when braking, and I have STOPTECH front BBK 332x32 ST40 up front.

Bought new Rotors (the old ones were out of tolerance)
Installed old pads (because they were almost new)
Re-bed using STOPTECH's recommended process....no change
Steering wheel shimmy still present

Remove old pads, installed new Street performance pads.
Re-bed using same process....shimmy is worse! Especially at slower speeds. i've done the break in procedure at least 3 x times now.

I'm at my wits end. Like I said, I think the tires are a contributing factor, but why would the new pads make the issue worse, especially at slower speeds?

My front end suspension is all new:
-struts refurbished by Ground Control
-Lemford tie rods, both inner/outer
-Lemford control arms with new bushings
-New poly sway bar bushings
-New Meyle HD sway bar end links
-Wheel bearings have about 20k miles on them, make no noises

I've had this BBK since 2007....wondering if they need a rebuild? Something I noticed. Spin passenger wheel, and the wheel can rotate 3 times before stopping using one hand on a spoke. Use the same method on driver's side and I can get slightly more than 2 rotations....sticky caliper?

[bostonaudi]

I'm going nuts over this.....so, I think my tires need to be replaced too because I can't seem to get rid of my steering wheel shimmy that I feel from 60-70....the shimmy gets worse when braking, and I have STOPTECH front BBK 332x32 ST40 up front.

Bought new Rotors (the old ones were out of tolerance)
Installed old pads (because they were almost new)
Re-bed using STOPTECH's recommended process....no change
Steering wheel shimmy still present

Remove old pads, installed new Street performance pads.
Re-bed using same process....shimmy is worse! Especially at slower speeds. i've done the break in procedure at least 3 x times now.

I'm at my wits end. Like I said, I think the tires are a contributing factor, but why would the new pads make the issue worse, especially at slower speeds?

My front end suspension is all new:
-struts refurbished by Ground Control
-Lemford tie rods, both inner/outer
-Lemford control arms with new bushings
-New poly sway bar bushings
-New Meyle HD sway bar end links
-Wheel bearings have about 20k miles on them, make no noises

I've had this BBK since 2007....wondering if they need a rebuild? Something I noticed. Spin passenger wheel, and the wheel can rotate 3 times before stopping using one hand on a spoke. Use the same method on driver's side and I can get slightly more than 2 rotations....sticky caliper?

Sounds like a wheel balance or bent rim issue, as you have shimmy without braking. Have you tried swapping the front and rear wheels?


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[BMWManiac]

Sounds like a wheel balance or bent rim issue, as you have shimmy without braking. Have you tried swapping the front and rear wheels?


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I'm going to give that a try....my only concern is I am not running a square setup. Fronts are 225/40 and the rears are 255/35. The rears have a slight tuck, but I guess I should give it a try. I've had the wheels balanced a couple times, by different shops with no luck.

[AJLM34A]

Fronts are 225/40 and the rears are 255/35. I've had the wheels balanced a couple times, by different shops with no luck.

Are these stock 17" wheels?

Are they using road force when balancing to make sure the tires are true?

[BMWManiac]

No, these are 18 X 8.5" ACS III wheels I've had forever...I've asked for the Hunter Road Force balancing and I hope that is what they used.

[tofunin]

Borrow another set of wheels and tires and try it out to rule out your current wheels. I've seen a bunch of cracked and bent type 3s form my experience of working at a BMW shop. The Hunter Road Force balancer GSP9700 can also tell if the wheel has a lot of run out(bent) if the shop knows how to use the feature with the small arm that rolls on the inner barrel. https://www.hunter.com/gsp9700 is where you can locate a shop with one.

I would rebuild the calipers to rule out binding or sticky pistons. Are the abutment plates where the pads sit and slide on clean? https://www.zeckhausen.com/catalog/index.php?cPath=24_217_7226_7266 is where you can find replacement parts but you may be able to get them cheaper elsewhere.

[BMWManiac]

Borrow another set of wheels and tires and try it out to rule out your current wheels. I've seen a bunch of cracked and bent type 3s form my experience of working at a BMW shop. The Hunter Road Force balancer GSP9700 can also tell if the wheel has a lot of run out(bent) if the shop knows how to use the feature with the small arm that rolls on the inner barrel. https://www.hunter.com/gsp9700 is where you can locate a shop with one.

I would rebuild the calipers to rule out binding or sticky pistons. Are the abutment plates where the pads sit and slide on clean? https://www.zeckhausen.com/catalog/index.php?cPath=24_217_7226_7266 is where you can find replacement parts but you may be able to get them cheaper elsewhere.

So I was getting tired of the ACS III wheels (been 13 years) so I bought another set of wheels and new tires....they are on the way. I used that Hunter site and the closest was a Chevy dealer that I last had my wheels balanced. They didn't say anything was out of the ordinary.

I've also been on the Zechausen site a bunch. If the new wheels/tires don't do anything, I also have a stock pair of M3 brakes to throw on and test while I rebuild the calipers.

[jprottas]

Thanks for this post. I have the same annoying 60mph shimmy. About to install new pagid rotors and meyle/ lemforder suspension parts hoping to solve the problem

Sounds like it may not be the total answer. I'll be staying tuned!

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[BMWManiac]

Installed new wheels/tires....now, car drives fine, but there is the smallest of shimmy whenever braking....so, rotors are new, pads are new. Could there still be air in the system? I can't imagine needing to take the rotors to be turned, but I don't know what else it could be?

[Twright]

I have had a sticking caliper cause the shimmy under braking that you have described. You can tell which caliper is sticking, because the wheel will be warm after you drive the car for a few miles.

[TostitoBandito]

Yeah if it's only under braking then I'd look at the calipers and make sure all their guide pins are lubed and moving freely, and that none are damaged. Same goes for any bushings that they slide in and out of. Can you tell where the vibration is coming from, front or back at least? I assume you bled the brakes after replacing the rotors/pads, so the fluid shouldn't be an issue.

[BMWManiac]

I have had a sticking caliper cause the shimmy under braking that you have described. You can tell which caliper is sticking, because the wheel will be warm after you drive the car for a few miles.

I guess I will remove the calipers, push out each of the pistons, and rebuild them


Yeah if it's only under braking then I'd look at the calipers and make sure all their guide pins are lubed and moving freely, and that none are damaged. Same goes for any bushings that they slide in and out of. Can you tell where the vibration is coming from, front or back at least? I assume you bled the brakes after replacing the rotors/pads, so the fluid shouldn't be an issue.

This is a STOPTECH caliper....there are no guide pins....vibration is definitely coming from the front. Rears are stock e36 M3 brakes and I just rebuilt them, lubed them too.

I did bleed the brakes, but I'm wondering if perhaps there might still be air because you have two bleed nipples on the stoptech caliper and I think the inside one might have had bubbles....don't know, just wondering.

I have a set of stock M3 calipers that I'm rebuilding....I guess I can buy a set of rotor/pads to throw on and test it too.

[MIKYZZ4]

Worn FCABs can produce similar symptoms,
so be sure to inspect,
also internally collapsed rubber brake hose can cause sticking caliper.

[BMWManiac]

Worn FCABs can produce similar symptoms,
so be sure to inspect,
also internally collapsed rubber brake hose can cause sticking caliper.

The FCABs and the rest of the entire suspension were replaced at the same time when this issue showed up because the shimmy was there all the time. Turned out to be tires....however, the shimmy while braking became apparent not to long ago.

When I first replaced the rotors about a year ago (old ones were definitely out of spec), I remember bedding in the brakes and feeling relieved that the shimmy had lessened, so I knew it was party due to the rotors. Over time, shimmy got worse and then I noticed it came back when applying brakes. This led me to replace wheels/tires and now the shimmy is only evident while braking. The lines are stainless steel.

If I remove the wheels/rotors and apply the brakes slowly, I should be able to see if one of the pistons doesn't extend....is that a good way to tell if one of them are seized? How often do STOPTECH calipers need to be refreshed?

[BMWManiac]

I pulled the pads out and stepped on the brake a couple of times, slowly, and I can clearly see:
1) The passenger side caliper pistons are all the same distance
2) The driver side, 3 of the caliper pistons are the same distance and the smaller, inside piston is much further out....

I want to thank David Zeckhausen who greatly helped me diagnose the issue....will be ordering rebuild kits through them shortly, once I get the pistons out and see their size. I'm also taking my rotors to a performance shop who will turn them...

[BMWManiac]

Rebuilt the calipers, no change.

Had a conversation with STOPTECH customer service and they said my pads (Street - now called Sport Performance) aren't being utilized at their operating temp, causing the issue with pad transference.

So, up next is some really aggressive stopping/bedding to see if the problem subsides and then switching to a more street friendly pad. Worse case, I order a set of track pads to clean the rotors.

[BMWManiac]

Update:

Bought some tools to hone at home with my drill. Course, followed by medium. The rotors definitely had pad material/imprint and I did my best to remove everything. Reinstalled, and installed a new set of pads....not a bit of difference. Still shimmy when braking, and horrible around 40 mph.

So, I bent over and bought another set of rotors, and unfortunately, the prices in just a year have skyrocketed up 75%.....so, if this DOESN'T cure it, I'll buy a stock set of rotors, brake lines, and install stock calipers and live with it....I don't track the car anymore, but the BBK sure does look cooler.

[hc1001]

Did you try cutting the new set of rotors from a year ago?

FWIW i was never able to heat up the front rotors enough to cause brake judder on the street. Once i took it to the track, i experienced judder after a lap or two. I checked run out and they were .003 and .004. I had them cut and no more problems.

Does the shimmy happen from a cold start or after the brake heat up?

[BMWManiac]

Did you try cutting the new set of rotors from a year ago?

FWIW i was never able to heat up the front rotors enough to cause brake judder on the street. Once i took it to the track, i experienced judder after a lap or two. I checked run out and they were .003 and .004. I had them cut and no more problems.

Does the shimmy happen from a cold start or after the brake heat up?

The shimmy is always there....I kind of feel like it gets better after going through the bedding process, but I think its just me hoping for it. I haven't been successful finding any place that would "cut" them. Where did you take them?

[MIKYZZ4]

Most automotive machine shops,
and some parts stores will cut your rotors.
I do it every brake job, if using same rotors,
or just replace with new, if they have worn/been cut too thin.

[BMWManiac]

Most automotive machine shops,
and some parts stores will cut your rotors.
I do it every brake job, if using same rotors,
or just replace with new, if they have worn/been cut too thin.

I've tried professional shops, race shop, and no one wants to touch the two piece rotors

[MIKYZZ4]

I see,
sorry I don't have any experience with those.

[BMWManiac]

Yeah, I am debating trying to sell the rotors or keep them and buy a set of race pads to clean them down the road

[BMWManiac]

New rotors, prepared and brake bed in complete....no shimmy, brakes like a dream, all is well with the world again. Even though it costs $650 for 2 x rotors, can you really put a price on happiness?

[MIKYZZ4]

A BMW with no wheel shimmy=Priceless!
Glad you got it all figured out, life is good again!!

[BMWManiac]

A BMW with no wheel shimmy=Priceless!
Glad you got it all figured out, life is good again!!

Yeah, when it boils down to it, I'm in love with the car all over again....now, I wonder if I should keep the old rotors (less than a year old!) and when the time comes to replace my new ones, try the race pads on them or sell the set I have to someone who will use them on the race track....

[MIKYZZ4]

I say cut your losses and sell them,
why create a problem, when now you have none.