335xi Suspension Refresh

once-ler

Lurker
Sep 18, 2017
11
Since my recently acquired 2008 335xi has just crossed 100K miles I would like to take the opportunity to do a refresh / preemptive maintenance on the suspension components with possibly upgraded parts to improve handling. The car already has PS tires and KW V3 coilovers.

The car is a DD and I may start to take it to the track infrequently. My present goal is to improve handling and keep the car planted, but not at the expense of a lot of NVH on my two-hour round trip commute J

In this vein, I’ve purchased:

1) The TRW M3 Rear Upper Control arm upgrade from ECS. (The M-Spec front control arms unfortunately don’t fit on the xi). Some forum posts have suggested that the rear arms are not a worthwhile upgrade if you don’t do the fronts.

2) 034 Motorsport's Density Line motor mounts.

Initially I was considering just purchasing the “ECS Tuning Front and Rear Suspension Refresh Kit – Level 3”.

https://www.ecstuning.com/b-assembled-by-ecs-parts/front-and-rear-suspension-refresh-kit-level-3/31126768989kt3/

However, I would like to use some polyurethane bushings so it may not be worthwhile to buy this
kit just to throw out the rubber bushings. Also, even if used it as a guide, I’m unsure which items from this kit provide little bang for the buck, and can be skipped.

As mentioned, I am considering upgrading to poly bushings for the front and rear subframe, control arms and front and rear anti-roll-bars, as my understanding is that this will keep the car flat while maintaining ride quality. I’m also considering poly front lower control arm bushings since the inspection found them to be shot.

1) What are other suspension components/bushings I should consider refreshing? Here are all the bushings powerflex makes for the 335xi:
http://powerflexusa.com/e9x3seriesxdrive05-13.aspx

2) Which ones should be rubber vs. poly for performance but with minimal additional NVH? (for example, I’ve been advised that the shock mounts should be rubber).

3) For the poly bushings, should I go with PowerFlex, SuperPro, Whiteline or something else?

4) For the rubber bushings, which bushings are worth the cost of upgrading to M spec?

5) When upgrading suspension components, can the existing bolts be reused or should they be replaced with new ones?

6) Could you please let me know the size of the anti-roll-bars that come stock with the 2008 335xi. The poly bushings are available in 11mm-15mm, and I’m not sure which ones to get, and I did not see this information in the Bentley manual.

I have found a lot of information on different forums, and a wide range of advice. This includes replacing the following:

Ball Joints & Suspension Arm Bushings
Tension Struts
Guide Rods
Upgrading to M3 Sway Bars (front and rear)
Wheel Bearings
Trailing Arm Bushings and Transmission Mount
Sway bar end links & Bushings
Thrust Arms (SyncroDesignWorks makes some for the XI but they are not cheap) and Lemforder also offer beefier looking ones than stock:
https://syncrodesignworks.com/collections/syncro-signature-parts/products/e90-xdrive-syncro-thrust-arms
https://www.fcpeuro.com/products/bmw-10-piece-control-arm-kit-e90-e91-e92-e90caxdrive2

Some of the posts I’ve read are older than others, and I understand that some vendors start making better products while the quality of others diminish. What I’m hoping for is some advice on which components I should purchase to achieve my goals without making frivolous purchases.
My friend who has agreed to help install everything (and his shop) are out of state and we need to do everything in a small timeframe, so I’d really like to purchase everything before traveling out to him.

Since I’m a novice, I would greatly appreciate any advice, the more specific the better, so that everything can be upgraded in one go. Thank you!
 

Velocity26

Specialist
Feb 7, 2017
61
Tampa, FL
Regarding "It is useless to upgrade the rear suspension, unless you upgrade the front" comment:
I am one of those that are pretty happy with my low mileage M-Sport suspension on 19" wheels. My biggest complaint is that, with significantly increased power, the rear suspension has a lot of "squirm" under hard acceleration in the lower gears. I have LSD and 17" 275 DR's, but the stock suspension seems to flex too much and can make driving more challenging that it should be. My plan is to start with the rear and upgrade to M-3 or MFactory (rubber) suspension arms and go from there.
 

Mike335xi

Lurker
Feb 13, 2017
10
07xi here

I did the suspension on mine last year

ST coilovers
Front upper shock mounts
Front thrust arms

Rear upper shock mount
Rear lower shock mount
Rear lower spring pad

And a few other things I think. Basically everything that is rubber and touches the dampers or springs got replaced. At over 100k miles they were literally falling apart anyway.

I made a spreadsheet with part numbers and prices at the top 3 online vendors if anyone wants to look at it shoot me a message. It’s a year old but the part numbers should still be relevant.
 

PUTC

Corporal
Oct 14, 2017
206
I’ll be doing my shocks and struts really soon. The roads where I live are horrible. I’ve sent repair estimates to my local DOT office in hopes the will pay for it. Going with KONI strt with Eibach pro springs. No coil overs though. 2008 335xi. Would like to refresh the bushings also as with 138k are probably garbage by now
 

zmon1300

Corporal
Nov 3, 2016
145
Chicagoland
07xi here

I did the suspension on mine last year

ST coilovers
Front upper shock mounts
Front thrust arms

Rear upper shock mount
Rear lower shock mount
Rear lower spring pad

And a few other things I think. Basically everything that is rubber and touches the dampers or springs got replaced. At over 100k miles they were literally falling apart anyway.

I made a spreadsheet with part numbers and prices at the top 3 online vendors if anyone wants to look at it shoot me a message. It’s a year old but the part numbers should still be relevant.

How much of a difference did changing these pieces make? @Mike335xi
 

Jeffman

Lieutenant
Jan 7, 2017
919
Since my recently acquired 2008 335xi has just crossed 100K miles I would like to take the opportunity to do a refresh / preemptive maintenance on the suspension components with possibly upgraded parts to improve handling. The car already has PS tires and KW V3 coilovers.

The car is a DD and I may start to take it to the track infrequently. My present goal is to improve handling and keep the car planted, but not at the expense of a lot of NVH on my two-hour round trip commute J

In this vein, I’ve purchased:

1) The TRW M3 Rear Upper Control arm upgrade from ECS. (The M-Spec front control arms unfortunately don’t fit on the xi). Some forum posts have suggested that the rear arms are not a worthwhile upgrade if you don’t do the fronts.

2) 034 Motorsport's Density Line motor mounts.

Initially I was considering just purchasing the “ECS Tuning Front and Rear Suspension Refresh Kit – Level 3”.

https://www.ecstuning.com/b-assembled-by-ecs-parts/front-and-rear-suspension-refresh-kit-level-3/31126768989kt3/

However, I would like to use some polyurethane bushings so it may not be worthwhile to buy this
kit just to throw out the rubber bushings. Also, even if used it as a guide, I’m unsure which items from this kit provide little bang for the buck, and can be skipped.

As mentioned, I am considering upgrading to poly bushings for the front and rear subframe, control arms and front and rear anti-roll-bars, as my understanding is that this will keep the car flat while maintaining ride quality. I’m also considering poly front lower control arm bushings since the inspection found them to be shot.

1) What are other suspension components/bushings I should consider refreshing? Here are all the bushings powerflex makes for the 335xi:
http://powerflexusa.com/e9x3seriesxdrive05-13.aspx

2) Which ones should be rubber vs. poly for performance but with minimal additional NVH? (for example, I’ve been advised that the shock mounts should be rubber).

3) For the poly bushings, should I go with PowerFlex, SuperPro, Whiteline or something else?

4) For the rubber bushings, which bushings are worth the cost of upgrading to M spec?

5) When upgrading suspension components, can the existing bolts be reused or should they be replaced with new ones?

6) Could you please let me know the size of the anti-roll-bars that come stock with the 2008 335xi. The poly bushings are available in 11mm-15mm, and I’m not sure which ones to get, and I did not see this information in the Bentley manual.

I have found a lot of information on different forums, and a wide range of advice. This includes replacing the following:

Ball Joints & Suspension Arm Bushings
Tension Struts
Guide Rods
Upgrading to M3 Sway Bars (front and rear)
Wheel Bearings
Trailing Arm Bushings and Transmission Mount
Sway bar end links & Bushings
Thrust Arms (SyncroDesignWorks makes some for the XI but they are not cheap) and Lemforder also offer beefier looking ones than stock:
https://syncrodesignworks.com/collections/syncro-signature-parts/products/e90-xdrive-syncro-thrust-arms
https://www.fcpeuro.com/products/bmw-10-piece-control-arm-kit-e90-e91-e92-e90caxdrive2

Some of the posts I’ve read are older than others, and I understand that some vendors start making better products while the quality of others diminish. What I’m hoping for is some advice on which components I should purchase to achieve my goals without making frivolous purchases.
My friend who has agreed to help install everything (and his shop) are out of state and we need to do everything in a small timeframe, so I’d really like to purchase everything before traveling out to him.

Since I’m a novice, I would greatly appreciate any advice, the more specific the better, so that everything can be upgraded in one go. Thank you!
How did you like the e90 xDrive Syncro Thrust Arms?
 

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