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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Help Needed - Suspension Experts Please!



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      07-15-2012, 04:22 PM   #1
plokij
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Exclamation Help Needed - Suspension Experts Please!

hey all,

i've done the following susp mods to my m-sport e91:

koni yellow struts/shocks
eibach pro-kit springs
front lowering perches
upsized from 17" to 18x8.5et35 235/40 F and 18x10et30 265/35 R with negative camber

honestly, what a nightmare its turning out to be....

the shop that installed the wheels, tires, koni's & springs did a terrible job. they broke one of my headlight leveling sensor adjusters and zip tied it back together without telling me about it (this was discovered when the lowering perches were later installed by another shop). the dealer quoted me $165 to fix during the annual service. NOT COOL.

they also put too much negative camber on the rear wheels (something like -2.5) which primarily looks bad against the front wheels which are not as flush and do not have as much camber.

the first problem i have noticed during regular driving is that the rear of the car bottoms out in certain conditions. this should not happen with a mild drop and the stiffer shocks. could it be that the camber settings in the rear are to blame for this? what else can i do to alleviate this problem?

next, due to the lowering perches adding an additional 1/2 inch of drop, should i be concerned about the reduced stroke range of the koni struts? accordning to koni, these struts do not depend on position or ride height as long as they do don't bottom or top out. that makes sense that they will operate anywhere in their stroke range, but will the reduced stroke range induce bottoming or topping out? i have no interest in trimming the bump stops or replacing them with smaller ones. the question is, is the total lowering in the front within the recommended 1.5" limit after EPK and lowering perches? i HARDLY noticed the front EPK springs lowering the car AT ALL from stock ZSP height.

it goes without saying that i should find a very reputable shop to perform the following:

* full inspection of the strut/shock & spring installation
* full alignment to bring the geometry within OEM specs

any other recommendations?

thank you in advance. i've enjoyed modding my car so far but this portion has been sour.
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      07-15-2012, 04:38 PM   #2
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Sorry to hear about your troubles.

Bottoming out the rear wouldn't be related to camber; typically that's caused by not having enough damper travel. Would you look in there and measure how much there is? Also how tall are the bumpstops? I agree it's highly unusual with the spring/damper combo you have, especially something as mild as Eibach Pros ... actually I'm going to say that's almost unbelievable you're bottoming out.

Regarding the lowering perches - here's a post I made in another thread:
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Originally Posted by CJ421 View Post
All these perches do is shorten the amount of travel your dampers have. That's bad because you'll be hitting the bumpstops more often and there is a greater chance of bottoming out the suspension. Over smaller bumps you may not notice a difference but on anything that would normally compress the damper fully or close to it, you're going to go from normal to jarring quick. When you decrease the amount of damper travel, you need to increase the spring rate to compensate (and no, that doesn't mean stiff lowering springs are a good alternative).
Your dampers will wear more than usual as well since they are compressing more for each bump as well.
However if you haven't had issues in the front - I wouldn't worry about it. Inspect your bumpstops and see how worn they are - they're a good indicator of how often they get utilized. Should you get your springs/dampers reinstalled, I would have the perches removed however.

Regarding your ride height - the Eibach Pro springs don't do much so that much sounds normal.

Absolutely have a trusted shop go over the install. Check the torque of all bolts and so on - sounds like the shop you visited was terrible indeed. I hope you go back and complain - you should at least get an apology from the manager.
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      07-15-2012, 05:05 PM   #3
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thanks man,

i'll take a look at the rear dimensions and post up. it just should not be hitting back there. the road conditions that force the crunching are not that extreme. and the tire sizes are likewise mild.

i was really hoping that the lowering perches would be OK because they really do get my front height down to where i want it. i suppose the koni's don't make a difference, or the fact that the car is not being lowered passed their recommended range. i think i will also ask koni for their input, especially if this may cause premature wear on the dampers.
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      07-16-2012, 11:51 AM   #4
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I can't get enough access to the rear components to measure the shocks and bump stops. I will have to wait until its in the shop to inspect.

Koni got back to me regarding the perches and said they are fine with my setup. By my calculation, worst case I am 0.2" beyond their recommended lowering range and I can tell that the Eibach front springs did not lower my car as much as they advertised they would. They are barely beyond OEM sport spring which was 0.6" from standard stock. I was hoping the Eibach fronts would add another 0.6" but it didn't happen, hence the perches...

So, I'm going to try the smaller bumpstops from the M cars that some people use just to be on the safe side for the fronts, and to hopefully take care of my problems on the rear shocks (assuming they were installed correctly and suffer from limited stroke range).

As I recall, my stock sports suspension used to hit the bumpstops in the front all the time over any inconsistencies in the road. The front Koni's have since done a nice job absorbing those bumps before having to engage the stops. Only on big potholes do they need to hit the bumpstops.

Well anyway, I'll keep posting with what I find when the car goes into the shop. I also found out the perches weren't put on right either. So annoying!!!
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      07-17-2012, 12:32 AM   #5
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Yeah I don't think the perches are affecting the performance to a degree that would affect normal operation. If the damper compresses to the point where that extra 0.2" matters, you'll probably be worried about other things. You could trim the bumpstop up there if you want and regain that travel instead of buying new ones.

Very interested to hear what the shop finds about the rear. Like we both agree it's near impossible you're bottoming out - but that's assuming a proper install. Unless you have fat chicks back there and you're not admitting that?
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      07-19-2012, 02:13 PM   #6
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Susp is installed OK, but rear wheels do not fit properly. Those sizes need fender rolling and more camber. I'm going a different direction with new wheels that fit without mods.

Dude, fat chicks are super lame but they always suck a mean dick.

Thanks for your inputs, I was totally drained of all the nonsense on this forum with appearance mods for the sake of appearance.
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      07-19-2012, 04:04 PM   #7
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Quote:
Originally Posted by plokij View Post
Susp is installed OK, but rear wheels do not fit properly. Those sizes need fender rolling and more camber. I'm going a different direction with new wheels that fit without mods.

Dude, fat chicks are super lame but they always suck a mean dick.

Thanks for your inputs, I was totally drained of all the nonsense on this forum with appearance mods for the sake of appearance.


Yep totally in agreement on the aesthetic stuff. It's one thing to clean up the appearance, but another thing to pose.
I have done more suspension upgrades than I care to think about (not a single stock part remaining) and kept the stock ride height. Sleeper FTW!
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