Turner rear subframe bushings questions.

[AirborneFF]

Gents,

I have been racing my E90 M for 2 years with about 10 average track days a year. I have no other suspension mods. I bought hotchkis f&r sway bar and Turner aluminum rear bushings. My indy whom races multiple spec porches and bmw's. VIR etc... I brought the parts in for install and he advised me against it. Constant counter steering, car being upset on rumble strips, and saying that I would need to weld plates on the frame to prevent cracking. I trust my indy. Though I have searched on this and other forums for a few months and did not see negatives in responses of those that have installed the bushings. Maybe a couple issues max. I need some advice on rather to return these parts. I am confident but humble in my driving skills and never try to out drive the car. Any honest feedback of those that have this installed would be appreciated.

[nycplumber]

The only downside to solid subframe mounts is your wallet.

[Redd]

Unless your indy has had specific negative experiences with solid subframe in the E9x M3 platform then he might be advising you based on experience on other cars which may not apply to our cars. Yes solid subframes are generally harsh and require chassis reinforcement. But in the E9x M3 platform there is truly no downsides at all. It should have come from the factory with solid rear subframes and the M3 GTS did. If there is only one must-do mod for all E9x M3s whether its a track car or grocery getter, it's solid rear subframe bushes.

[AWDBooSTIn90]

Originally Posted by Redd

Unless your indy has had specific negative experiences with solid subframe in the E9x M3 platform then he might be advising you based on experience on other cars which may not apply to our cars. Yes solid subframes are generally harsh and require chassis reinforcement. But in the E9x M3 platform there is truly no downsides at all. It should have come from the factory with solid rear subframes and the M3 GTS did. If there is only one must-do mod for all E9x M3s whether its a track car or grocery getter, it's solid rear subframe bushes.

Or at least the Poly Inserts for the stock bushings. Very cost-effective solution thats often overlooked. I think because people assume it wont work well. But for the money and ease of install, the slight trade-off from true solid replacement bushings isn't much.. especially with stock suspension..
Now if you start putting poly or even solid Diff bushings in, then yeah the difference its drastic and increases NVH alot, i would consider that really a track car mod.
Solid rubber or just new M3 Diff bushings are okay

[nycplumber]

Bmw put solid subframe mounts in the gts and crt with no additional chassis modifications to make it work.

[Bartledoo]

Indy is wrong. Gives you better feeling of the rear which will lead to less counter steering. Not sure why he thinks it would cause upsetting on curbs either. You are causing the spring and damper combo to control motion rather than letting the rubber bushings to add an extra undamped oscillation into the mix.

[TboneS54]

Originally Posted by Bartledoo

Indy is wrong. Gives you better feeling of the rear which will lead to less counter steering. Not sure why he thinks it would cause upsetting on curbs either. You are causing the spring and damper combo to control motion rather than letting the rubber bushings to add an extra undamped oscillation into the mix.

I want to say, by forcing more energy into the springs and dampers, that you're thereby decreasing spring rate which would result in slightly more body roll (grip). I imagine it'd be a very small amount though.

[Bartledoo]

Originally Posted by TboneS54

I want to say, by forcing more energy into the springs and dampers, that you're thereby decreasing spring rate which would result in slightly more body roll (grip). I imagine it'd be a very small amount though.

You’d be removing a spring that was in series with the coil spring, so the effective spring rate would increase.