Outcome of recent suspension mods

[markslc1]

Up till this point I've been driving the 128 on the following suspension
- Koni yellows, HR sport springs, Dinan camber plates, whiteline rsf inserts
- tires: 5 year old warn out BFG G-force rival 245/40/17

this past week I added added in the M3 thrust/control arms and some new track tires (federal 595RSRR in 235/40/17 square). Here is what I noticed at the track this weekend.

1) Massive improvement in front grip (expected due to -2.7* camber)
2) The rear-end was a little less planted (unexpected because the new tires actually measure wider even though they are smaller size)
3) and this is the big one. I couldn't downshift when braking within a corner.



There is a spot at my track where you do some hard braking in a bend, and I just couldn't get the car to downshift when side-loaded. I had to straighten the car out first, brake, then downshift. Here is what I'm thinking
- Replacing the transmission bushings. What is the popular replacement?
- The increased grip is actually flexing the RSFB's more than before, overwhelming the inserts? Time for full poly replacements?
- Maybe I need stiffer springs?

I'm interested in some other theories out there, as the goal is to getting the shifting back to normal and plant the rear better. Keep in mind this is my daily and not a dedicated track car. Thanks.

[MightyMouseTech]

The shifter bushings are easy. Just get the M3 version. Takes 10 min to install.

[chris82]

Originally Posted by markslc1

Up till this point I've been driving the 128 on the following suspension
- Koni yellows, HR sport springs, Dinan camber plates, whiteline rsf inserts
- tires: 5 year old warn out BFG G-force rival 245/40/17

this past week I added added in the M3 thrust/control arms and some new track tires (federal 595RSRR in 235/40/17 square). Here is what I noticed at the track this weekend.

1) Massive improvement in front grip (expected due to -2.7* camber)
2) The rear-end was a little less planted (unexpected because the new tires actually measure wider even though they are smaller size)
3) and this is the big one. I couldn't downshift when braking within a corner.



There is a spot at my track where you do some hard braking in a bend, and I just couldn't get the car to downshift when side-loaded. I had to straighten the car out first, brake, then downshift. Here is what I'm thinking
- Replacing the transmission bushings. What is the popular replacement?
- The increased grip is actually flexing the RSFB's more than before, overwhelming the inserts? Time for full poly replacements?
- Maybe I need stiffer springs?

I'm interested in some other theories out there, as the goal is to getting the shifting back to normal and plant the rear better. Keep in mind this is my daily and not a dedicated track car. Thanks.

Not sure on the other stuff but absolutely upgrade the trans mounts. I used E46 M3 mounts, they were a direct fit, very cheap and easy.

[markslc1]

Yes thanks. I think the transmission bushing upgrade is a no brainer to solve my shifting issues. I have some on order.

Still wondering if the lack of increased rear grip wasnt realized because the RSFB's are now moving a bit more under the increased stresses of better tires and M3 front arms. Maybe the car is twisting more than before?

[drunkenup]

I am running similar front camber, square tire and stock subframe bushings and the back end is very stable and has a lot of grip. It also has the stock rear sway so it leans the entire car on the outside front tire a lot, like in your pic. It still has much more limit understeer than preferred, which is not analogous to what you say you are experiencing.

What are your alignment specs? Your rear toe may be too out