SE and SI front suspension differences

[Peggy924]

Hi all,
I wonder if anybody could tell me whether the Z4 SE and Z4 SI Sport have the the same shock absorbers. I know the springs are different, but I am hoping the shocks were the same part number.
When I bought my 2007 E86 SI Coupe, the previous owner had fitted brand new genuine BMW shocks and springs all round, to make the ride softer. I wouldn't mind fitting the genuine SI springs back on, to drop the car by 15 m/m. But the shocks have only done a few thousand miles, so would like to use them with the SI springs.
I know that ride hardness is personal preference, but how much harder do you think the ride will be on the correct springs.

 

[Meds]

I think.....
{Edit: someone came along with far more experience}

But I'm sure someone with far more experience will be along soon to answer.

 

[enuff_zed]

When you remove original shocks they are Sachs and say sport on them if on a sport model.
However, if you try to source Sachs dampers now you don’t get that option. One size fits all.
Having done many refreshes using Sachs dampers I can say that it makes no discernible difference. The shorter length of sport springs does not affect the dampers as it’s not an excessive amount. The spring controls the ride height.
The only difference is that with sport springs you use a shorter bump stop.


OP, I would suggest you carefully check the existing dampers. Usually 50k is their limit. Make sure both are hard to compress and fully extend on their own. For perfect balance they should both extend at the same rate.
Obviously these checks can only be done once the struts are dismantled with springs off.

 

[Peggy924]

Hi, thanks for the quick replies. I have learnt something, that the sport bump stops are shorter. The previous owner did change the bump stops and dust covers, that must be why. All the suspension springs and dampers were changed, for genuine BMW parts. I have the invoices for this. He imported them from Germany. He is the agent for AC Schnitzer parts in the UK. The shocks have done less than 5000 miles. I have all the sport shocks and springs, and they have only done 35,000 miles. But obviously the newer shocks, if the same, would be a better bet. The car is never going to be raced or rallied, so the stance, ie body height is probably just cosmetic. But probably most of you on this forum would prefer the lower ride height.

 

[Mr Tidy]

Just so you know all the UK E86s are SI, the difference is the Sport models had the M-Sport suspension that sits 15mm lower and is a bit stiffer than the SE.

If you have the invoices for the new springs the Part Number should determine what got fitted. If you are happy with the ride and handling as it is I'd be inclined to leave the 5,000 mile parts on rather than replace them with 35,000 mile ones! It isn't unusual for rear springs to snap so newer ones should avoid that problem.

 

[Peggy924]

Hi,
Thanks Mr Tidy. That is why he probably imported them from Germany. One thing that was strange was that everything was new, except the old top mounts back and front were refitted. I had to change the rear top mounts, because they were knocking. I bought Lemforder mounts back and front. Obviously the back ones are easy enough to change, but the front ones require a bit more effort. So I was waiting for the weather to improve. But while the top mounts were off, springs could be changed, and it got me thinking. My daily is a lowered Clio 182, so I already know about stiff suspension. I would prefer the car to be lower, but don't want to create more hassle for myself. There is another thing, if the back springs that are fitted now break, it might be difficult to get springs to match the fronts. It might be easier to source Sport springs!

 

[Mr Tidy]

It's a shame the PO didn't fit new top mounts as I would have thought most people would when fitting new springs and shocks.

If I liked how the car drove I'd leave the newer parts on and worry about a broken spring if/when it happened, but that's a personal choice.

 

[enuff_zed]

Given that the front top mounts appear to be the weakest link, with the rubber splitting, they would be the first thing I’d change!

 

[Peggy924]

The top mounts will be changed in the next couple of weeks. I changed the back ones first because of the knocking coming from them. Noise disappeared when new mounts were fitted. But that is why I bought all four mounts. I suppose I have a set of spare springs if and when needed. I will check the part numbers on the invoice, to see if the dampers are the same part number. RealOem only list Sport or Z4M dampers.

 

[Mr Tidy]

RealOem only list Sport or Z4M dampers.

I think that is what "enuff_zed" was getting at then he said this:-

"When you remove original shocks they are Sachs and say sport on them if on a sport model.
However, if you try to source Sachs dampers now you don’t get that option. One size fits all".

 

[enuff_zed]

RealOem only list Sport or Z4M dampers.

I think that is what "enuff_zed" was getting at then he said this:-

"When you remove original shocks they are Sachs and say sport on them if on a sport model.
However, if you try to source Sachs dampers now you don’t get that option. One size fits all".

Yes, M is a different thing, but for all others they now seem to only list the one damper to fit either height.
If you go to Bilstein or other makes then I suspect you can start specifying more bespoke dampers.