Rubbing sound + tight turns = driving me crazy!

Hello all,

I have a e90 m3 with original tires (at least I think so) and differential. I just shipped the car cross country. Our new home is on a closed street. To leave, I pull out of my driveway and have to crank the wheel all the way to one direction (or the other). When I do this I hear a rubbing sound. I have the suspension set to the stiffest setting. I never noticed this before (but rarely cut it that hard previously). Any ideas? I wouldn't think I need new diff fluid (09' with 19K miles)....just want to make sure there isn't a bigger problem.

All comments welcome!

Do you only hear the rubbing when the car is moving or do you hear it when the car is stationary too?

If it is the latter, it could be your power system. Turning the steering wheel all the way to the stop will induce a noise from the power steering system and it is normal. This should be avoided as it can harm your PS system. When you hit the stop, just dial it back a little.

You don't specify but based on your diff comment can we assume the sound is coming from the rear?

Post the exact tire sizes.

Thanks for the replies.

1) don't seem to hear the noise while stationary. The PS noise when you crank the wheel is a bit higher pitched (try not do this like you suggest)

2) sorry should have mentioned...seems like it is coming from the front of the car, but a bit hard to tell. Reason I mention this diff is it is approximately the same freq (similar drubbing sound)

3) I will post the tire size later today

After paying more attention this morning, it does seem that the noise is coming from the rear of the car... I will get the tire info soon. Thanks guys

Front tire 245/40 18
Rear tire 265/40 18

Are these standard tire sizes or +1?

It is probably your diff.

Check this thread. http://www.m3post.com/forums/showthread.php?t=144569

It's the LSD. Change the fluid to the BMW fluid that contains the proper LSD modifier.

I will be changing my diff fluid this weekend.

100% the diff. My E60 M5 would do it like crazy.

The M3 did it and then they changed the fluid and it's been good for years since.

Before changing the diff oil for the one with extra friction modifiers I would check out the numerous threads on the issue....Not everyone thinks this is a good idea.
Not least because if it was such a good, no downside, fix why not use this oil as the factory fill.

changed the diff fluid...problem is gone so far

SenorFunkyPants wrote  

Before changing the diff oil for the one with extra friction modifiers I would check out the numerous threads on the issue....Not everyone thinks this is a good idea.
Not least because if it was such a good, no downside, fix why not use this oil as the factory fill.

Something about no good when temps get realhigh?


I only get this when car is cold. I tried the twenty circles in the parking lot and felt dupped lol.

pkim1079 wrote

Something about no good when temps get realhigh?

I don't think that temp comes into it.
The main function of the LSD is to lock the rear wheels so that they both turn at the same speed under acceleration (load). However to account for different wheel speeds during cornering the diff has a pack of metal clutches running in the diff oil which will slip under sufficient load to allow the rear wheel to turn at different speeds.
These are heavy duty clutch plates that have to handle a lot of BHPs and last the lifetime of the car. The rubbing noise you hear under a particular set of circumstances (usually tight turns under light load and when the diff oil is cold) are the clutch plates stick/slipping against each other.
Only drivers who complain are offered Castrol SAF-J oil which BMW have modified by adding extra friction modifiers (the SAF-J oil already contains friction modifiers). The purpose of adding this oil is to allow the clutch plates to slip more easily against each other which when you think about it is rather counterproductive.
This topic really ought to be a sticky with both sides of the argument being put so that owners can make an informed decision about whether to go with the modified oil or not.

Was talking about the filler fluid they use.

SenorFunkyPants wrote  

Before changing the diff oil for the one with extra friction modifiers I would check out the numerous threads on the issue....Not everyone thinks this is a good idea.
Not least because if it was such a good, no downside, fix why not use this oil as the factory fill.

Can you link any of these threads?

The updated fluid is something like $400 bucks. It was changed probably about 3 years ago and drastically improved the issue. I don't really experience it anymore. I wonder if heavier use of the LSD reduces the propensity of this problem to occur.

The diff in these cars is really something else. Even the factory 25% locking LSD in my turbo 7 series is quite good, but never had those issues. It was replaced about 10 years ago however. I forget what it was doing.

SenorFunkyPants wrote

...

Really great post. I learned something. Am I understanding this correctly that the LSD clutches slipping noise it not an issue per se for the car only a false worry for the driver who thinks there might be smth wrong when there isn't ?

AIUI the clutch pack has to:
Lock up to near 100% at full load while still allowing some slip in turns...which also reduces the understeer that would overwise occur.
Unlock with no load..ie with closed throttle to stop oversteer in turns.
Transfer torque from a spinning wheel (on a low grip surface) to the wheel with more grip using a shear pump to hydraulically load the clutch pack.

sunsweet wrote

Am I understanding this correctly that the LSD clutches slipping noise it not an issue per se for the car only a false worry for the driver who thinks there might be smth wrong when there isn't ?

I think its going to depend on the nature of the noise...if its a light rubbing noise when making tight turns under light load with cold/luke warm diff oil, then I understand it to be an acceptable trade off from using such a heavy duty diff. The DCT which uses a similarish system of multi clutch disks does have a short temperature band (luke warmish) at which the clutches engage a little less smoothly. Running metal clutch plates in oil presents unique problems - you want the clutch plates to slip smoothly against each other when engaging but then grip at 100% with no slip when fully engaged over a large range of temperatures...ie you want them to slip but not too much. The use of the correct type and amount of oil additives is key to this.
If your diff is making loud noises especially when hot then the oil with the extra additive is probably going to be first fix to try.

Mike Benvo wrote

Can you link any of these threads?

The updated fluid is something like $400 bucks. It was changed probably about 3 years ago and drastically improved the issue. I don't really experience it anymore. I wonder if heavier use of the LSD reduces the propensity of this problem to occur.

The diff in these cars is really something else. Even the factory 25% locking LSD in my turbo 7 series is quite good, but never had those issues. It was replaced about 10 years ago however. I forget what it was doing.

My fluid was 285$ (no labor just material) from the local dealer.

i quote myself from another thread here:

driftflo wrote

the more fm, the less the plates inside the lsd grip (so less noise)... so less locking of course!
it also is aggressive to the oil seal.
so i would only use the fm oil if you really need it and dont want to have noises.

for bmw it is easier and more profitable to sell the fm booster oil and dont have to argue with "customer noises".

if you dont have noise issues or dont mind it, stay with the normal syntrax limited slip for better locking performance and healthy seals!


but when talking about locking performance... if you want a proper performance diff, you will need to swap to a clutch-type lsd anyway... vlsd sucks ;-)

whole thread here: http://www.m3post.com/forums/showthread.php?p=12749600#post12749600