[McPikie]

Guys, I am installing some eibach springs to my 320d Msport this weekend. Retaining standard dampers for now as they were all changed last year and in good condition.

2017-01-17_05-52-19 by Phil Cookson, on Flickr

I was wondering if the rear bumps will need trimming down a little? Not sure if that 45mm and 35mm drop if from SE spec or if it's Msport.

[Digitalize]

I've never heard of anyone needing to trim bumpstops when fitting springs, it's not that much of a drop and the increased spring rate should mean the damper doesn't travel further.

Besides coming from Eibach they'll have done testing and TUV etc so would advise you if you needed to id imagine.

[McPikie]

Originally Posted by Digitalize

I've never heard of anyone needing to trim bumpstops when fitting springs, it's not that much of a drop and the increased spring rate should mean the damper doesn't travel further.

Besides coming from Eibach they'll have done testing and TUV etc so would advise you if you needed to id imagine.

I suppose so. Just wanted to make sure before I put it all back together again, haha.

Having done some further digging, I came across this thread

http://www.e90post.com/forums/showthread.php?t=731666

Seems they will lower 30mm on front and 10mm on rear when coupled with Msport shocks. I'd be very happy with that

[Digitalize]

Almost all the drop ratings are based off the SE to look as impressive as possible.

[Terryk]

exactly! they always compare their product with the standard chassis option and not the sporty ones, for every manufacturer and model.

[E60525d]

From what I have read, when lowering your car you need shorter bump stops otherwise you are reducing the damper travel. This is why M sport bump stops are different to SE.

People tend to use E36 M3 front bump stop and Z4 rear on the E90 when lowering.

I recently replaced the shocks on mine with OEM and also replace the bump stops with OEM.

[davealfa11]

if eibach recommended you to modify bump stops it would be in literature ...as for the height being lowered they would factor in the spring rate on compression as not to effect geometry too much ..bump stops are there to stop damper rod being damaged on full compression,

[E60525d]

So why are M sport bump stops different to SE? Why are the bump stops in the BMW performance suspension kit different again? Its because they take into account the lowered ride height.

More info;

http://www.e90post.com/forums/showthread.php?t=699650

http://www.e90post.com/forums/showthread.php?t=614778

[Digitalize]

Probably because the dampers are designed to run at a different range, so the bumpstops are different to accommodate that.

Either way the car shouldn't really ever touch the bumpstops anyway so it's not a huge thing to consider. It's a last measure to stop the damper bottoming out and damaging itself. As long as you have some form of bumpstop you'll be fine.

[davealfa11]

Originally Posted by E60525d

So why are M sport bump stops different to SE? Why are the bump stops in the BMW performance suspension kit different again? Its because they take into account the lowered ride height.

More info;

http://www.e90post.com/forums/showthread.php?t=699650

http://www.e90post.com/forums/showthread.php?t=614778

spring rate is totally different thats why they have different rates on front depending on axle load and reason eibach don't go any lower ride height than they state youll need shorter shocks irrespective of what bump stop you have .....same reason that koni fsd are not suitable for some stock lowered cars as the frequency the shock works in at mid ride ,when they are out of this they don't work as designed
ps the valving is different on performance and m sport which controls springs so eibach have to compromise

[davealfa11]

youll know if you hit a bump stop ...imagine a 8kg/mm spring that means every mm you compress it takes 8kg and so forth then 16kg and so on ,that's if they are linear say ...when you hit a bump stop it can go to 30kg then 60kg then 200 as it compresses further ,that will really kick chassis up

[E60525d]

Eibach paperwork does state the rear bump stops need to be cut, see here http://www.e90post.com/forums/showthread.php?t=870594

OP, I'd suggest you check the paperwork the springs came with.