Suspension problem E36 M3 + BC Racing inverted coilovers
Discussion
I've had BC Racing inverted coilovers fitted to my M3.
I know that only the front are coilovers, the rears are simply upgraded springs and shocks. All shocks have BCs single adjuster (30 steps from soft to hard IIRC, I've tried changing these settings, makes no difference to the problems described below).
Before these were fitted it was handling and driving fine for normal road use.
After fitting these the front is fine (pressing down on the front wings produces almost no give but driving it is fine).
The rear is a completely different story with multiple problems.
First the nearside rear is clunking when I go over mid sized bumps. Large bumps it doesn't clunk (?).
When either rear goes over a pothole / recessed manhole cover the rear will twitch sideways (regardless if I'm on the power or off it), I'm trying to remember exactly but i think it always twitches towards the side the pot hole is on.
Secondly if I floor it the back goes to the left, i.e. car suddenly is steering a little to the right. Note this is not traction breaking and the rear just sliding, it does it under moderate amounts of power.
Come off the power and the opposite happens, the car's now steering to the left a bit (well, in the same direction is was before I applied power IYSWIM), with a constant throttle it is steering to the right a bit. (as it steers to the right under throttle it does throw me when I come off the gas and it dives towards the kerb, I'm getting used to it but it really upsets the balance of the car, so much so I've now got a nice bashed wing + bonnet where it span out on snow/ice and touched the central reservation - grrr)
It honestly feels like there's a major component of the rear suspension missing and one of the rear wheels is moving forwards or backwards in relation to the other one, skewing the back axle.
Bloody orrible in a nutshell!
I'm going to get it up on the stands tomorrow and see what I can see and see if I can move any thing by hand, but does anyone have any hints as to which bushes could be worn? Or anything else I can check with normal household garage equipment?
i will also be checking the top of the strut mounts to make sure they haven't snapped, but the adjuster knobs on the top of the rear struts are still where they should be so I don't think that's the problem.
I also took the car to PCS garage in Milton Keynes. When I booked it by phone I told them I'd changed the suspension and I wanted it all checked over, alignment, camber, bushes, generally everything.
Booked a days holiday, took the car down there. Got a phone call at 3pm basically saying "Sorry sir, our suspension computer can only deal with OEM suspension so we can't use it to check yours and the engineer doesn't want to touch anything on it incase he makes it worse". Bloody idiots.
Last resort is to remove all the BC stuff and put standard back on, which'll prove it the problem is on the car or in the new suspension stuff.
I know that only the front are coilovers, the rears are simply upgraded springs and shocks. All shocks have BCs single adjuster (30 steps from soft to hard IIRC, I've tried changing these settings, makes no difference to the problems described below).
Before these were fitted it was handling and driving fine for normal road use.
After fitting these the front is fine (pressing down on the front wings produces almost no give but driving it is fine).
The rear is a completely different story with multiple problems.
First the nearside rear is clunking when I go over mid sized bumps. Large bumps it doesn't clunk (?).
When either rear goes over a pothole / recessed manhole cover the rear will twitch sideways (regardless if I'm on the power or off it), I'm trying to remember exactly but i think it always twitches towards the side the pot hole is on.
Secondly if I floor it the back goes to the left, i.e. car suddenly is steering a little to the right. Note this is not traction breaking and the rear just sliding, it does it under moderate amounts of power.
Come off the power and the opposite happens, the car's now steering to the left a bit (well, in the same direction is was before I applied power IYSWIM), with a constant throttle it is steering to the right a bit. (as it steers to the right under throttle it does throw me when I come off the gas and it dives towards the kerb, I'm getting used to it but it really upsets the balance of the car, so much so I've now got a nice bashed wing + bonnet where it span out on snow/ice and touched the central reservation - grrr)
It honestly feels like there's a major component of the rear suspension missing and one of the rear wheels is moving forwards or backwards in relation to the other one, skewing the back axle.
Bloody orrible in a nutshell!
I'm going to get it up on the stands tomorrow and see what I can see and see if I can move any thing by hand, but does anyone have any hints as to which bushes could be worn? Or anything else I can check with normal household garage equipment?
i will also be checking the top of the strut mounts to make sure they haven't snapped, but the adjuster knobs on the top of the rear struts are still where they should be so I don't think that's the problem.
I also took the car to PCS garage in Milton Keynes. When I booked it by phone I told them I'd changed the suspension and I wanted it all checked over, alignment, camber, bushes, generally everything.
Booked a days holiday, took the car down there. Got a phone call at 3pm basically saying "Sorry sir, our suspension computer can only deal with OEM suspension so we can't use it to check yours and the engineer doesn't want to touch anything on it incase he makes it worse". Bloody idiots.
Last resort is to remove all the BC stuff and put standard back on, which'll prove it the problem is on the car or in the new suspension stuff.
Clunking could be down purely to the springs - some brands provide or also sell a sleeve that fits around half-a full coil. It's this which gives the noise suppression you're looking for.
That of course assumes none of the bushes are gone, especially the ARB (anti-roll bar) ones.
Regarding the pitching - could be damping setting, but equally could be spring rate too stiff, and that's even before you get onto alignment.
I'm not fully au fait with the alignment process, but I'd have thought that if they pulled up the OE specs on the system, and measured yours, even lowered, they'd be able to bring it back or close to OE numbers, if there's sufficient adjustment in the OE parts.
If not, then you're looking at upgrading those so you can dial out the excess camber, toe, etc.
Might be worth a bit of a ring around, to see who sounds the most confident provider of the service, or check one of the BMW-centric forums, to see if there's any highly recommended outfits in your locale or worth a bit of a trip to.
That of course assumes none of the bushes are gone, especially the ARB (anti-roll bar) ones.
Regarding the pitching - could be damping setting, but equally could be spring rate too stiff, and that's even before you get onto alignment.
I'm not fully au fait with the alignment process, but I'd have thought that if they pulled up the OE specs on the system, and measured yours, even lowered, they'd be able to bring it back or close to OE numbers, if there's sufficient adjustment in the OE parts.
If not, then you're looking at upgrading those so you can dial out the excess camber, toe, etc.
Might be worth a bit of a ring around, to see who sounds the most confident provider of the service, or check one of the BMW-centric forums, to see if there's any highly recommended outfits in your locale or worth a bit of a trip to.
Cheers mate.
Just to update this thread I did have a look underneath the rear of the car on Sunday.
First thing I noticed is that the 4 main rubber bushes where the diff mounts to the body are completely shot. I would think I'm safe in assuming that if those are gone then there will be smaller bushes that are in just as dubious a condition.
It's booked into Thorneys Motorsport, which are luckily close to me. I've asked them to replace all bushes that need doing, inspect / replace anything else that needs it, and set up the full alignment, front and back.
One would hope that should sort it and give me a nice toy that's usable on the road and set up for the coming spring / summer trackday season
Just to update this thread I did have a look underneath the rear of the car on Sunday.
First thing I noticed is that the 4 main rubber bushes where the diff mounts to the body are completely shot. I would think I'm safe in assuming that if those are gone then there will be smaller bushes that are in just as dubious a condition.
It's booked into Thorneys Motorsport, which are luckily close to me. I've asked them to replace all bushes that need doing, inspect / replace anything else that needs it, and set up the full alignment, front and back.
One would hope that should sort it and give me a nice toy that's usable on the road and set up for the coming spring / summer trackday season
Hiya,
The problem was my mate just fitted them, he doesn't have the equipment to do a proper alignment.
Took the car to Thorney Motorsport in Milton Keynes to get it sorted and have a major service too.
They replaced a couple of front suspension bushes (can't remember exactly what now) and then set up all the suspension parts.
A couple of lock nuts (that they loosen off before they start) were seized but luckily those adjustments were bang on so not a problem.
With the new bits and suspension adjusted by somewhere that knows BMW inside out, it handles really well.
The 4 bushes that the rear subframe is mounted on were a bit worn and causing the knocking from the rear, but those were also seized on and the time slot wasn't long enough to get the plus-gas onto them to get them off and change the bushes, I never got round to changing them as they just caused a noise, they didn't affect the handling at all.
I could have told them to keep it longer and sort everything out but with the service and two new rear tyres, the bill was close to £2k already so decided against it!
The problem was my mate just fitted them, he doesn't have the equipment to do a proper alignment.
Took the car to Thorney Motorsport in Milton Keynes to get it sorted and have a major service too.
They replaced a couple of front suspension bushes (can't remember exactly what now) and then set up all the suspension parts.
A couple of lock nuts (that they loosen off before they start) were seized but luckily those adjustments were bang on so not a problem.
With the new bits and suspension adjusted by somewhere that knows BMW inside out, it handles really well.
The 4 bushes that the rear subframe is mounted on were a bit worn and causing the knocking from the rear, but those were also seized on and the time slot wasn't long enough to get the plus-gas onto them to get them off and change the bushes, I never got round to changing them as they just caused a noise, they didn't affect the handling at all.
I could have told them to keep it longer and sort everything out but with the service and two new rear tyres, the bill was close to £2k already so decided against it!
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