[asus389]

I took my e90 325i in for service a year ago and my brakes were getting low. At the time I had 60k on my OE BMW brakes with about 3-4mm to go on each pad. On top of that, I was getting a shimmy in the steering wheel on braking lightly at high speeds. The shop installed new brakes. They told me they were ATE Premium One rotors and Jurid pads.

The shimmy seemed to go away, but then it came back a few months later. Thrust arm bushings were then replaced (they looked worn and fluid was leaking), but this didn't solve the problem. They told me there was a hot spot on the right front rotor and then they resurfaced them and the shimmy went away. It only took a couple months to come back.

I don't track my car and I have never "warped" rotors on any of my other cars and I drive this car pretty much the same as I always have. It seems odd that this would happen 3 times within 10k miles/1 year across 2 sets of pads/rotors. What could be going on here? Is there something else wrong with my car that could be causing it to do this? Other parts of the braking/suspension/steering system that could screw up my brake rotors? Anyone else have experience with this rotor/pad combo?

[slupie]

Try bed your brakes in http://www.zeckhausen.com/bedding_in_brakes.htm . It most likely will help.

ATE used to make all of the BMW rotors in the past I don't know if it still true.

I have had very good luck with Centric brand rotors and pads, I have been using that brand since my E39 days back in the early 200'0's and everyone in the family is running them because I do their brake jobs.

[asus389]

Originally Posted by slupie

Try bed your brakes in http://www.zeckhausen.com/bedding_in_brakes.htm . It most likely will help.

ATE used to make all of the BMW rotors in the past I don't know if it still true.

I have had very good luck with Centric brand rotors and pads, I have been using that brand since my E39 days back in the early 200'0's and everyone in the family is running them because I do their brake jobs.

Yeah I'll try that. I did it initially when I got the brakes. I then saw something that said that ATE didn't recommend it. Not sure what to think - I guess at this point I don't have much to lose.

Can failure of other components in the front end cause rotors to wear u evenly? Any common install error I can check for?

[slupie]

worn out front end components could appear as brake shimmy, but I doubt that it would cause rotors to warp. Worn out suspension components would definitely show up as steering wheel shimmy at certain speeds. Ask the E39 crowd how they know about that.

As a former E39 owner I had to replace all of the bushings on the front and about half of them in the rear to get rid of the shimmy in the front and rear. It never caused the rotors to warp.

You might be too hard on brakes, meaning that you brake softly for long periods of time. That kind of braking builds up heat and the brakes never have time too cool off and they possibly have pad material burn-n (transfer) to the rotor. Brake as hard as conditions allow for shorter durations. Hard braking but for short periods doesn't build up as much heat, and if it does the rotors have longer time to cool before next braking sequence. More/less never ride your brakes in a sense.

[///Mposter]

Jack the car up in the front . Lock the steering wheel . Go to one side and grab the tire/wheel. Try to turn it in and out . Also try up and down( it should not move this way) If worn it will move slightly, if not it will do nothing. You may have worn bearings that will cause vibrations despite having great brakes installed . You May also have end links/ control arm issues. It seems I remember you saying you replaced the control arms for leaky fluid.

Best of luck.

[mike-y]

what are your lug bolts torqued to? un-even torque can cause rotor warping.

[asus389]

Lately I have been torquing them myself after I take it in to service. I use a digital wrench that is set to 88 lb ft. I guess its possible that in the past they have been over torqued. Is there any way I can inspect the lugs to see if they have been damaged by being over torqued?

Today I took one of the front wheels off. I found what looks like anti-seize applied to the outside of the rotor hat on the rotor to wheel mating surface. There also appears to be some sort of grease coming up from under the rotor hat from the hub itself. Is it possible that the wheel bearing/hub itself is leaking? Or maybe they put some (copper?) grease on under the rotor for some reason? The lugs themselves looks pretty clean.

Would any of these things introduce runout into the brake rotor install?

I also noticed that when I spin the wheel on the hub there is a bit of drag from the pad on the rotor. Sometimes it appears to "catch" on a spot. Is drag normal?

[asus389]

OK so I have found a couple things.

First, when measured on the car, the front rotors have runout according to a dial gauge.

Second, in addition to the vibration while braking described above, I have had a shimmy in the front end of the car (while driving) at 40mph and up for as long as I have had issues with vibrating while braking. You can also feel a bit of a wobble right before the wheel returns to center when turning.

So I have naturally had my tires rebalanced several times to try to figure this out. Tires are balanced to "0" and road forced, so they are as good as they are going to get. Lately I have noticed that just taking the tire/wheel off the hub and putting it back on (no re-balancing) in influences how bad the shimmy is. So apparently the index position on the hub with respect to the lugs seems to influence this vibration? This makes little sense to me, does anyone have any insight into what this means? As far as I can tell the bearings seem OK (no play moving the wheel at 6-12 and 3-9). WTF?

You said the tires/wheels were balanced and road forced, but what were the road force numbers (in lbs for each corner)? Just because they were road forced doesn't mean there isn't a bad wheel/tire in the mix. For instance, a wheel tire could show a "passing" result with 19lbs of road force, but I've found that anything more than 9lbs of road force will cause vibration on these cars. It's a huge pain trying to find tires under that threshold, but in the end it's the only way to get as close to zero vibration as possible IMO.

Not ruling out a bushing, bearing, hub, etc. in this case though...just trying to remove as many variables as possible in hopes of narrowing down the problem.

[asus389]

Originally Posted by FCobra94

You said the tires/wheels were balanced and road forced, but what were the road force numbers (in lbs for each corner)?

Good question. I have tried many times to get clarity on the balance issue.

The rears are below 10 and have remained so. The roller has been on the fronts 3 times. When I first got them, one tire was replaced because it was at 24lbs. The numbers with the new tire installed were then under 10. After several thousand miles and continuing vibration, I took them in a again (to a different tire shop) and a printout showed the front tires were both in the mid teens. So can RF numbers increase with tire wear? Can the tire pressure effect the RF reading?

On the 4th attempt to balance I took it to a place that does on car balancing. They balanced the front tires first on a machine, then installed them on the front hubs. They balanced out fine on the machine, but then when put on the car they vibrated the whole car at high speeds. The left tire/wheel much worse than the right. We put the left tire/wheel on the right side to see if the worst of the vibration would follow. It seemed to. Though they were both pretty bad.

Then they balanced them on the car and they were able to effect *both* the braking shimmy and the driving shimmy. They didn't get it to go away completely, however.

It was during this process when I noticed that re-indexing the front wheels/tires on the hub changed the shimmy. Move it one lug next, vibration much worse, next lug, less. All without changing weights.

Not sure how the legit "put the wheel on the car, spin it up and see how much the door shakes" and then put weights on by hand method is. But it sure is amazing to watch.

Bizzare, right?

Sure, radial force variation can change as the tires wear. It all depends on how the materials within the sidewall "wear in" with mileage. That's why some peeps will rebalance new tires after 500 miles or so in order to give the sidewalls an opportunity to break-in a bit and get a more consistent balance. Air pressure also plays a small role as well, I'd imagine...as in, if the tire was RF balanced at 36psi, the "balance" may change if the tire ends up losing air, etc.

What's also important to consider is that tires can often flat spot, even just overnight. Therefore getting the tires hot by driving on them for a while THEN RF balancing is probably the preferred method of keeping things consistent.

Yeah, before I got a handle on this whole RF notion, I found a place that does on-car balancing too. I was at my whits end at that point and figured that was my only remaining option to cure my vibration issue, but never had the opportunity to try them out given that I eventually found a competent shop with a RF balancer that knew what they were doing.