(please) HELP! Big problem after M3 suspension bits install

[wespar]

Had the following installed on my 2010 135i convertible by my VERY cooperative BMW dealer (a highly rated & very large racing oriented dealership) who has always played along with whatever I want to do to my cars:

- 4 springs (Eibach ProKit)
- 4 shocks (the Bilsteins that come in the ProKit)
- Upper AND Lower front M3 arms
- front M3 sway bar
- rear M3 guide rods
- rear M3 subframe bushings
- alignment

As so many have reported, the car felt transformed.

However, running 235 tires up front - at first the front tires hit the fenders & BMW quickly wound up installing springs from a 335is convertible up front (& leaving the Eibach Pro-Kit rears) This drove fine - the rear end was loose (& I liked it) & no rubbing.

BUT, once the car stopped rubbing in the front, I could brake harder & I then noticed a BIG PROBLEM

On hard braking - at any speed above 15mph, the rear end kicks out severely to the left. At speed (50-60mph) I darn near can't keep control of the car. At high speed it would be potentially deadly.

I think it's important to note I can make it happen with the handbrake too - or by engine braking, though you need to be in lower gears to get that much decelerating force.

At first I thought they screwed up the alignment (& still kind of do) - maybe only adjusting one side & that really one side in the rear is toed out. But they claim they've had the alignment re-done - & double & triple-checked by all their best techs & that it's right. And certainly seem to have sophisticated alignment equipment. (though whether they're checking the rear suspension loaded & unloaded to see if toe is changing when the weight shifts forward - I doubt it.

Anyway, could it be a bushing is softer in one of the guide rods or one of the suspension bits than the other? or maybe one of the rear springs is a different rate that the other? Is there is some kind of alignment adjustment possible for bump steer?, Something else? I unfortunately only know enough to be dangerous.

BMW Dealer wants to put on the rear springs from 335is convertible as they figure springs could be the problem… That theory seems odd to me but absent another explanation I'm at their mercy.

What COULD this be?

ANY HELP / thoughts would be VERY much appreciated… THANK YOU!!

[RimasRS]

I would think the problem is somewhere in the front suspension

[JimD]

I don't understand why the stability control is not kicking in to prevent this (is it on?). But I would have them bleed the brakes. It would seem you could have air in a line on the right (and thus reduced braking).

[Zombie1]

I don't like that they mismatched springs on the car. I have a bunch of M3 bits my self and when I slam on the brakes the car stops straight no problem. Like JimD said you may have air in the line preventing the brake from biting hard. Also does anyone know the OP rear spring rates to the front ones?

[RimasRS]

Originally Posted by Zombie1

I don't like that they mismatched springs on the car. I have a bunch of M3 bits my self and when I slam on the brakes the car stops straight no problem. Like JimD said you may have air in the line preventing the brake from biting hard. Also does anyone know the OP rear spring rates to the front ones?

He said that it is not brake related even engine braking does the same

[Stohlen]

Go to a super flat road, let go of the steering wheel and tell us which direction the car drifts to and how severly.

[wespar]

Originally Posted by Stohlen

Go to a super flat road, let go of the steering wheel and tell us which direction the car drifts to and how severly.

car doesn't drift at all - only exhibits this rear end kick out when quickly decelerating - feels like a toe out condition in the left rear - but only when the suspension is loaded by deceleration

Originally Posted by RimasRS

He said that it is not brake related even engine braking does the same

exactly - and with handbrake it does it & with engine deceleration it does it - though it's hard to get the same amount of decelerating force those ways.

AND - it seems to me anyway that even with 2x4's or cotton balls in the rear - as long as both sides were the same - that the effect shouldn't be laterally. Or at least not to the same side all the time - if it were the front/rear mismatch, I could see it manifesting itself in one direction when the road was cambered one way - and the opposite way when the road was pitched oppositely - but it's always to the one (left) side.

Does anyone know - is there any adjustment for bump steer on these cars? PS: really appreciate any & all thoughts/ideas

[RimasRS]

few things which came on my mind, maybe bad subframe bushing or some other bushings, something is loose not tightened to spec or even rear sway bar

[Dackelone]

Have a second alignment shop look at your car. Sounds like something is loose or maybe you have too much toe on your alignment.

Also in the rear... those stock upper arm links will go bad over time. That can cause weird toe problems under accel or decel.

[Zombie1]

I bought new axle bolts when I got my car aligned the shop said they get real lose and can cause problems on cars with decent amount of miles on them

[wespar]

Originally Posted by Dackelone

..... Also in the rear... those stock upper arm links will go bad over time. That can cause weird toe problems under accel or decel.

There's about 17k miles on the car & it's a 2010

Originally Posted by RimasRS

few things which came on my mind, maybe bad subframe bushing or some other bushings, something is loose not tightened to spec or even rear sway bar

I'd agree possibly a bad bushing in one of the new M3 arms or one of the new m3 subframe bushings could be bad? Seems unusual, but possible. The "something loose" I'd go for as well.

[Dackelone]

Originally Posted by wespar

I'd agree possibly a bad bushing in one of the new M3 arms or one of the new m3 subframe bushings could be bad? Seems unusual, but possible. The "something loose" I'd go for as well.

No, No. I think you have an old suspension component that is worn out. In the rear you still have these upper links....

BMW Rear Guide Rod Kit - Better traction and handling
http://www.1addicts.com/forums/showthread.php?t=223464


When you had your alignment was it out of specs? You should have another alignment done, by someone who knows how to check for worn out stuff.

All the suspension bolts are a ONE TIME use. So I hope you also replaces all those bolts for the M3 bits. Could be one of those bolts has cracked IF your mechanic reused them. ???

Dackel

[Stohlen]

Originally Posted by Dackelone

All the suspension bolts are a ONE TIME use. So I hope you also replaces all those bolts for the M3 bits. Could be one of those bolts has cracked IF your mechanic reused them. ???

Dackel

I know Bmw says these are one time use bolts, but i don't believe that. They don't yield when torquing, so to me they are reusable.

[cheshirecat79]

imo sounds like a subframe bushing was installed incorrectly.

[_Ryan_]

Originally Posted by Stohlen

I know Bmw says these are one time use bolts, but i don't believe that. They don't yield when torquing, so to me they are reusable.

They don't stay tight. Check your bolts.

[Stohlen]

Originally Posted by _Ryan_

They don't stay tight. Check your bolts.

If the bolts weren't reusable they'd damage the threads and stay tight. Likely you didn't torque yours properly.

[Lester]

What is the update on this?

[miro2296]

Originally Posted by Lester

What is the update on this?

+1

[_Ryan_]

Originally Posted by Stohlen

If the bolts weren't reusable they'd damage the threads and stay tight. Likely you didn't torque yours properly.

They were torqued to spec and checked after alignment. They have now been tightened and have stayed tight.

The initial torquing wasn't by my hand.

[Dackelone]

The reason why BMW says not to reuse the suspension bolts is bc they are STRETCH BOLTS. Meaning once they are torqued down... they will get longer. Use them more than once... and they can break or loosen. This is why you always need to use new bolts when a manufacturer(BMW) tells you too.

I would also use some anaerobic Blue Loctite on those bolt threads.


OP - What is the update on your suspension problem?