Bump steer and my Dinan suspension

[Freiheit]

My car has the dark blue Dinan Stage One coils. It exhibited a bit of tramlining at speed, so I figured that the car wasn't set up to Dinan specs by the previous owner. I also had some brake chatter on hard(er) stops, and a bit of wheel vibration at 80mph.

The dealer agreed to do the Dinan numbers, and along with correcting the balance and alignment, found out that the stock front ZCP rotors needed to be replaced. Prior to the service, I did the Alpine 93 octane tune with Servotronic update. I also gained the Euro MDM and the DCT/GTS software.

Now the tramlining and vibration are gone, but I get a bit of bump steer thats actually quite disturbing. It feels reminiscent of the lane-departure "helper" that BMW builds into their X vehicles now, where the driver experiences noticeable force feedback upon deviating from the center of the lane. If I'm not firmly holding the wheel, the car likes to go its own way on hitting any road reflector between lanes. I'm not used to bump steer on an M vehicle so this is a first for me.

I have no idea if the previous owner installed the Dinan-recommended support parts to make the best use of their Stage One coils, and since that kit is over double the cost of the coils alone, perhaps that person didn't add the parts.

Is there any way I can tell if the Supplemental Ride Quality kit is installed, either by glancing in the right place or by doing some kind of mechanical check - without dismantling the car?

Or is the bump steer caused by something else? The rear tires are new, but my SA said the front tires were catching up to the wear bars. I have about 4mm left. Perhaps the difference in the tread depth is causing this?

What should I be looking at?

[wyatth]

Sorry I cannot help, but are saying that rotors, alignment, and balancing got rid of the 80mph vibrations? I have this too.

[Solo_M_Tech]

Your tension arms are worn out. The bushing and ball joint wear out quickly in these cars, especially if you live in an area with bad roads and or you see track time. The arm is responsible for centering the wheel in respect to the axle center line. If the bushing is worn out, it allows fore and aft movement of the wheel, at which will affect steering angle. You feel this as bump steer and tram lining. It's hard to determine if the bushing is bad with a visual inspection, but at the price, it's worth upgrading to a monoball of your choosing. Dinan makes a nice piece, as does many other companies.

[Freiheit]

Originally Posted by wyatth

Sorry I cannot help, but are saying that rotors, alignment, and balancing got rid of the 80mph vibrations? I have this too.

I can't say if those services fixed the vibration, but after having them done the vibration is gone.

I should also mention that in addition to this, I had new TPMS installed. Previous owner either deleted them, or the wheels on the car were the result of a trade from stock Style 359 to these gun metal coated 359's and whomever did the coating didn't install TPM sensors prior to mounting tires. The little bit of weight from those sensors might help even things out.

[Freiheit]

Originally Posted by Fubar_M3

Your tension arms are worn out. The bushing and ball joint wear out quickly in these cars, especially if you live in an area with bad roads and or you see track time. The arm is responsible for centering the wheel in respect to the axle center line. If the bushing is worn out, it allows fore and aft movement of the wheel, at which will affect steering angle. You feel this as bump steer and tram lining. It's hard to determine if the bushing is bad with a visual inspection, but at the price, it's worth upgrading to a monoball of your choosing. Dinan makes a nice piece, as does many other companies.

Now that is some good info. Thank you.

I'm wondering if the car saw the track. It looks pristine, but to need new rotors at 19k miles leads me to believe it saw a lot of apex work. Do you think its more likely to have been autox or road course?

[Solo_M_Tech]

Originally Posted by Freiheit

Now that is some good info. Thank you.

I'm wondering if the car saw the track. It looks pristine, but to need new rotors at 19k miles leads me to believe it saw a lot of apex work. Do you think its more likely to have been autox or road course?

Impossible to tell. I'd look into getting new arms with monoballs installed. Then redo the alignment.

[Freiheit]

Originally Posted by Fubar_M3

Impossible to tell. I'd look into getting new arms with monoballs installed. Then redo the alignment.

Does the monoball increase NVH?

[Solo_M_Tech]

Originally Posted by Freiheit

Does the monoball increase NVH?

No

[Freiheit]

My search took me through Turner, ECS, BW, and I finally landed on Rogue. Apparently Ben is now producing a lot of bushings for our cars.

I found a monoball offering:

http://www.rogueengineering.com/Rogu...-F3X_p_96.html



followed by a much lower cost sleeve bushing:

http://www.rogueengineering.com/Rogu...F8X_p_101.html



I'm not predisposed to either of these. Can you point out why one would be more desirable than the other?

[Solo_M_Tech]

First one is a true monoball. Second one is a poly bushing replacement. You won't notice a huge difference between the two on the street. The poly being cheaper might be the better option for you.

Personally I'd buy these. Complete arm with monoballs installed. Easy installation.

https://www.turnermotorsport.com/p-2...ding-m-models/

[Freiheit]

Originally Posted by Fubar_M3

First one is a true monoball. Second one is a poly bushing replacement. You won't notice a huge difference between the two on the street. The poly being cheaper might be the better option for you.

Cheaper doesn't as matter as much as harshness. With the tires more planted as a result of the correct alignment, I was surprised at how much harder the car road. I wouldn't want it any worse, and in fact I'm debating going back to ZCP coils if it would help give me a more pliant ride.

Its kind of difficult to move away from how glued to the road the car is, though, so I really can't say what I'm going to do yet. I've driven stock ZCP cars that didn't take turns the way this car does. Everything is a trade off.

Originally Posted by Fubar_M3

Personally I'd buy these. Complete arm with monoballs installed. Easy installation.

https://www.turnermotorsport.com/p-2...ding-m-models/

That is exactly what I was looking at prior to your post. Thank you.

[Freiheit]

Originally Posted by Fubar_M3

First one is a true monoball. Second one is a poly bushing replacement. You won't notice a huge difference between the two on the street. The poly being cheaper might be the better option for you.

Personally I'd buy these. Complete arm with monoballs installed. Easy installation.

https://www.turnermotorsport.com/p-2...ding-m-models/

well, that went bad pretty fast:

"Front Upper Control Arm Monoball Upgrade - Left and Right - E82, E89, E9X (including M models)
Turner Motorsport
T#: 221983 | Part#: TSUE9080QIS-ARMS
This product is no longer available for purchase."