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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Castor is way off after coilovers installed



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      03-28-2020, 06:36 PM   #1
2008_335
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Castor is way off after coilovers installed

Prior to getting m3 control arms, my caster was 7 degrees on driver side and 7.1 on the passenger. After getting m3 control arms installed, my caster changed on driver side to 7.7 and passenger side stayed at 7.1. (Driver side changed, passenger side remained the same)

NOW, after getting coilovers installed, my caster is now at 7.7 on driver side and 8.4 on the passenger! (Driver side remained the same, passenger side changed)

So to summarize, my caster changed on only driver side after M3 control arms. Then after coilovers, driver side stayed the same and the passenger side caster increased from 7.1 to 8.4. After going from stock arms to m3, my driver side caster went from 7 to 7.7 but now maintained 7.7 after coilovers - unlike passenger.

WTF is this? Yes, we reused the top hats on the struts. No. I have not hit any potholes.

Last edited by 2008_335; 03-29-2020 at 01:12 PM..
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      03-28-2020, 08:04 PM   #2
Vulcan50
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Doesn't surprise me. These components are all different lengths. So changing one of the 3 (shock height, front or rear control arms) will throw others off. If you are lower now (assuming you are) camber is likely off what it was as well.
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      03-28-2020, 08:54 PM   #3
2008_335
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camber is actually -1.4 each side. whats up with caster tho? i don't get why it changed
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      03-29-2020, 01:13 PM   #4
2008_335
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What's going on with my caster lol could it have changed because I did not use a torque wrench for my control arms after coilover install? Or could it possibly be that the strut is not fully inserted into the steering knuckle/hub?
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      03-29-2020, 02:50 PM   #5
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More likely the latter than the former
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      03-29-2020, 03:16 PM   #6
2008_335
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Quote:
Originally Posted by Tambohamilton View Post
More likely the latter than the former
Could you clarify? You are saying that it's more likely that the uneven caster is caused by the control arms possibly not being torqued down to spec?
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      03-29-2020, 03:22 PM   #7
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No, I'm saying it's much more likely the discrepancy is caused by something not being installed fully/correctly, than an incorrect torque setting somehow causing it to be out.
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      03-29-2020, 03:48 PM   #8
2008_335
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Quote:
Originally Posted by Tambohamilton View Post
No, I'm saying it's much more likely the discrepancy is caused by something not being installed fully/correctly, than an incorrect torque setting somehow causing it to be out.
Lol my bad wasn't paying attention to which one I mentioned first. Thank you for your help.

Yesterday, I took a video of my suspension bits on both sides through turning my steering wheel all the way to each side. I then looked over the vids to see if maybe a bushing was leaking. On the video of the passenger side, I noticed that the strut pin was actually not sitting all the way on into the steering knuckle. I wasn't able to capture this angle of the strut in my video of the driver side, but I plan on going and taking a look at it later this afternoon (studying rn).

I wanted to drop this pic here and see if the strut not sitting completely into the knuckle could really cause the caster discrepancy. It looks like it could sit another 1/2 an inch, maybe less.

I don't understand how the strut not sitting in all the way could affect caster, as it would seem to only affect the height only.
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      03-29-2020, 04:25 PM   #9
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In suspension that relies on pivots, the position of one thing often affects the position of everything. Hopefully you've found your culprit!
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      03-29-2020, 04:42 PM   #10
2008_335
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Which control arm, if bent, would cause caster change? Is it the upper? and the lower is rather responsible for camber?
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      03-29-2020, 06:06 PM   #11
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Either. Think of them both as sides of a triangle, with the subframe as the 3rd side. Change the length of any side, and the triangle changes shape; all internal angles change, etc.

I would be very surprised if your issue is caused by a bent arm.
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      03-29-2020, 07:05 PM   #12
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You really think it could be from my strut not sitting in all the way?
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      03-30-2020, 01:24 AM   #13
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I bet you a cup of tea at my place (when this covid stuff is over) that it's not caused by a bent arm, and properly installing all parts will help.
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