M3 Offset Top Mounts

[GermanGorilla]

Hi, this is one for all the M3 owners on the Zone.
Have purchased some offset top mounts for the M3, have positioned them so that they align with the correct spacing / hole mounts at the top of the turrets, and used the position of the existing ones, now removed as a guide for location / setup.

Have FK Coilover / rebound front set up.

Car now sat back on its temporary rubber, and the amount of 'negative camber' to the front wheels is so excessive, it is almost like the front suspension has partialy collapsed.

Am now planning to swap the left top mount to the right and vice versa, but even that appears that it will leave far too much 'negative camber' for a road car. At a calculated guess it would be south of 5 degrees negative camber, with the current top mounts swapped, which would be fine if you owned tyre company.

Any assistance or pointers with regard to offset top mounts, and correct positioning will be gladly received.

Many thanks,

Gorilla.

[Andy335Touring]

Are they BMW ones or after market ?

[GermanGorilla]

Hi, they are BMW OEM, direct from Germany.

I have since checked and they are original.

My concern is that the FK Coilover strut, for whatever reason is a more acute angle than the standard M3 set up, thus when fitting offset top mounts any negative camber increases still further.

Just by looking at the standard top mounts that came off, if they were replaced, it seems that the negative camber would be greater than really needed or desired for a road car.

I can not refit the standard strut / Coil spring set up, as the FK Coilovers work on an exchange basis, so I no longer have them.

It seems very strange that offset top mounts would induce such extreme negative camber.

1 -1.5 degrees of negative camber on the front would be ample for a road car, even that would lead to front inner tread tyre wear issues.

Thanks, any assistance or input will be gladly received.

Gorilla.

[Demlotcrew]

Have you put them on correctly?

Andy part number is, 31 33 1139 484, these are the same for all E30 inc M3.

Andrew

[GermanGorilla]

Hi, they can only really go on one way due to correct alignment of the holes at the top of the turrets and the way that the top of the coilover / strut engages the mount centre bearing from below.

It gets stranger by the hour ?

[Demlotcrew]

got pics of them on?

Andrew

[GermanGorilla]

Hi,

The car is at the sprayers, and taking pictures is not easy with his guys, dust and all the other host of things going on there.

This afternoon I undid the top three retaining bolts and have rotated the top mounts by about 180 degrees, they will only fit certain ways although there are five holes for locating bolts.

This has now poistioned the centre of the strut further 'inwards' making the negative camber better than it was but still not where you imagine it should be.

I have also adjusted the Coilover up by a further 20mm which in lifting up the car by a few mm has also helped.

By placing the orginal top mount over the top, and looking down and lining up the locating the original bolt holes [they only have three holes] with the new fitted offset mounts, I can see that the centre of the strut is now somewhere where it would have been with the standard top mounts, thus what is the purpose of 'offset' top mounts if the standard ones located the top of the strut in the same location ?.

Even the Guy spraying the car said it is almost like the whole front end needs picking up a further 10mm or so.
I will see if I can get some alloy spacer ring made up that fit on top of the top mounts, but under the turret top to act as a lifting spacer, so that I can unwind the coilovers and put more spring travel back into the front struts.

These top mounts were supplied by C3 and I have spoken to Kirby about part numbers, if they are even the right parts and everything else.

Many thanks,

Gorilla.

[Demlotcrew]

Five holes for locating the mounts? Are you sure? I can only see three.

Andrew

[GermanGorilla]

For sure, the replacement Offset Top Mounts supplied by C3 have 5 holes, where as the orginal's that came off only have 3.

Even the sprayer remarked this afternoon, that with five holes it does seem as if the 'new' part is wrong.

As said before, I have double checked with Kirby at C3 and I'm told that these are geniune and are correct.

The mystery is begining to become a right pain in the A*** as fitting replacement Offset Top Mounts should not be this difficult, should it ?.
This is 15 year old or older suspension technology, not a current F1 suspension set up.

Thanks for the input to date.

Gorilla.

[ian332isport]

It's a while since I fitted mine (also from C3), but I seem to remember there being 6 holes. It's possible that one hole is common though, so this could explain why there's only 5.

These mounts can be fitted in two ways. One gives 0.5 degrees more negative camber than standard, and the other gives 0.5 degrees more positive camber ( or less negative than standard if you like ).

Which three holes you use for the mounting studs dictates which setting you are going to use. I used mine to correct for excess negative camber induced by the lowering springs. This has returned the camber back to standard spec, and stopped the tyres from wearing on the inside edge.

Cheers,

Ian.

[M3GTR]

I think you'll find that the offset top mounts you have are actually the ones used by BMW when a car has been in a crash and the chasis cannot be straightened properly. Needless to say, BMW don't promote the fact tat they even exist.

This is why the bush is designed to produce both positive and negative camber based upon which three holes are used. If you look at the mount, you should be able to see a + and a - stamped alongside the appropriate holes.

[Demlotcrew]

Ian how low is your car?

Andrew

[ian332isport]

Ian how low is your car?

Andrew

Andrew,

Not sure to be honest

The springs are regular H&R sport springs (approx 35mm drop), but the engine dropped it a bit further. It looks pretty much the same as a set of H&R cup springs though.

I initially fitted the offset mounts to improve handling (giving 0.5 degrees more negative), but found that this combined with the lowering was munching my tyres quicker than I was happy with. I had the geometry measured, and found that it was a full degree more negative than it should be.

Seeing as I already had 0.5 degrees extra negative camber due to the mounts, I swapped them to the other setting, and this put the camber back in spec. I actually had it measured as an E30 M3 as I have the offset control arm bushes as well. Not had any issues since.

Cheers,

Ian.

[Demlotcrew]

Dude just waiting for my H&R -35mm for a 318is to come from germany, i have the rear arms bushes to sort the camber out for the rear wheels, but do you think i will need it for the front?

Andre

[ian332isport]

Dude just waiting for my H&R -35mm for a 318is to come from germany, i have the rear arms bushes to sort the camber out for the rear wheels, but do you think i will need it for the front?

Andre

If you currently have standard front top mounts, and are only lowering -35mm, then you will probably be okay.

Strangely enough, I don't have any problems on the back. I have poly bushes on the trailing arms, but not offset ones.

Ian.

[GermanGorilla]

Hi, many thanks for all the input on the Offset Top Mounts.

It appears that the the FK Coilovers even when set up quite high, are still allowing the car to ride about 35 -45mm lower than standard.
Couple this with Offset Poly Wishbone bushes and then offset Top Mounts, and well it all gets silly.

Am going to fit some alloy 10mm spacer plates on top of the top mounts but under the turret tops, equall to about a 30mm drop from standard and see if this bring the negative camber back around 1 - 1.5 % [30 minutes] which for a road going car is far enough.

Still many thanks to all.

Gorilla.

[Demlotcrew]

Dude just waiting for my H&R -35mm for a 318is to come from germany, i have the rear arms bushes to sort the camber out for the rear wheels, but do you think i will need it for the front?

Andre

If you currently have standard front top mounts, and are only lowering -35mm, then you will probably be okay.

Strangely enough, I don't have any problems on the back. I have poly bushes on the trailing arms, but not offset ones.

Ian.

thanks mate.