[DoctoRx]

I've already done some basic upgrades to improve handling for daily driving but am looking towards getting "stage 2" modifications to make the xDrive cars more track capable. Does anyone have any recommendations? So far I have S3 coilovers, M3 front strut tower bar, and I switched the non RFT. I plan on doing M3 subframe bushings next and am looking into which rear sway bar to go with (22.5 vs 23.6).

I know I've heard the 22.5 mm as the rear sway that most go with to improve ride handling, but has anyone gone with the 23.6 mm and run the UUC front sways? I'm not sure if there would be any added benefit from this combo.

After the rear SFB and sway bar upgrade, what other recommendations are out there to improve handling?

[tetsuo111]

No replies in a week? It's sleepy around here....

DoctorRX - way to go! I drive an E91 xDrive and take it to the track as often as I can. The BMW platform is a great foundation, and without any further mods your car is perfectly fine for track duties. At this level, vehicle improvements are discretionary and one could choose to focus solely on the driving experience. Having said this, I also believe that pilot skill and car toys are orthogonal. So, if you obtain enjoyment from modding your car, consider these:

1) Stop - The brakes are fine, but will fade with sustained track driving. It's all about thermal management.
- High temp brake fluid.
- SS brake lines
- More aggressive brake pad compound. If they are truly more aggressive, you will want to swap with your street pads before and after track sessions. Track pads WILL squeal on the street. Dual purpose street track pads are an oxymoron
- There's more you can do here, but this is a solid start

2) Grip -
- Coilovers. You already have these. Properly setup coilovers and springs mitigate the excessively soft chassis suspension, reducing brake dive and body roll. These are the most effective suspension mod you can do.
- Do you have camber plates? Part of the recipe for extracting the potential from coilovers is the ability to align the front end with more camber than OEM. Camber plates help.
- non-RFTs. You did this. Solid. Lighter rims are nice, too.
- Forget changing the sway bars. Consider your goals. Stiffening the front end increases push. Stiffening the rear without an LSD reduces traction. ARBs are fine tuning tools. Mitigate excess body roll/dive with appropriate springs.
- RSBs. Another good move. The suspension is designed with compliance to work with RFTs. When replacing RFTs with standard tires, the soft suspension becomes worse. Solid or M3 RSBs remove a major source of squish in our cars. I like the solid Al RSBs. No increase in NVH. Any firmness can be balanced with your dampers. They last forever. Win-win-win.
- LSD. Not necessary and can be expensive. But transfers power more effective to the road.
- Less effective but still improvements: M3 control arms, adjustable toe links, firmer bushings.

There's always more to do, you already tackled the most important with coilovers.

The most important part is always the pilot (you). Interview your driving instructor. Calibrate expectations. Practice. A lot. Stay safe and have a blast!

[refugeeofwar]

Originally Posted by DoctoRx

I have S3 coilovers

How do you find the S3s? I was looking at V1s, but the S3s are a much cheaper option it seems.

[DoctoRx]

Originally Posted by tetsuo111

No replies in a week? It's sleepy around here....

Thanks for the detailed response. I have looked into some of these ideas but haven't pulled the trigger just yet. Originally I figured my progression would go as follows.
1. M3 RSB (+/- sways since subframe has to be dropped anyway. I heard changing out the rear allows for the car to feel more planted an have less understeer)
2. High temp brake fluid, SS lines
3. Pads & Rotors upgraded (not too sure about compounds and best options here)
4. (I figured this may be a sufficient level of suspension upgrades but if anything seems to be lacking I can address at this point)
5. Oil coolers

The S3 coilovers come with adjustable camber plates and pillow ball mount. I'm close to OEM specs currently, but if/when I change wheels I may look into a wider setup (I'm currently 18x8.5 and 18x9.5) I'll go more negative camber which should collectively improve traction. I'd never actually heard of doing an LSD on xDrive but interesting feedback. Will definitely see about making some of these changes at the start of next season (winter approaches in the snow belt).

[DoctoRx]

Originally Posted by refugeeofwar

How do you find the S3s? I was looking at V1s, but the S3s are a much cheaper option it seems.

I think the S3s are fine for my current usage. They're sort of built to compete with V1s but give you more of the adjustment capabilities. When I had my RFTs on they were a bit harsher in ride quality so my GF complained immediately. I swapped out for continental DWs (will likely go with PSS or maybe a second set of wheels for dedicated track use if I go full bore on my build) and 80% of the complaints stopped. So long as you don't hit a big bump, it's pretty comparable to stock.

[tetsuo111]

DoctoRx, it looks like you have the important parts covered.

A couple of observations:

1) in the future you might consider posting related questions in either the (non-xi / xDrive) suspension forum or the track forum. I think that there are several xDrive people like us interested in this topic. But there are many more RWD people. So you should expect to receive more feedback in those forums.

2) Brake mods: stock is fine, but they will feel more confidence-inspiring after upgrading. Suggest beginning with high temp fluid and ss lines. Have a trustworthy service tech do this service. Mistakes / errors here have consequences. I don't know your level of mechanical / technical involvement - if you do this yourself, double check the system pressure after bleeding the lines. Air in the system makes the brakes feel very squishy and reduces hydraulic efficacy. After fluid and lines, consider pads and rotors. If you want to continue, look at Ti heat shields, and brass guide pins. BBKs are absolutely unnecessary for performance, but some may go this route for aesthetics / style.

3) in terms of sequencing upgrades, at this point it's more about personal preference than which is better or worse. That said, if I am in your shoes, I would upgrade brakes before doing RSBs. Why? RSBs are second only to coilovers / dampers for suspension improvements. The stability improvement they add is significant. But on track, you will be traveling at 100 - 140 mph by the end of the main straight, depending on the specific track. At the end of the straight is typically a significant turn to force a speed check. I'm a fan of stopping power over better handling in this situation, if forced to choose to do one before the other.

Keep us posted and see you in the suspension and tracking forums.

[matteblue3er]

I'm running the E93 rear sway bar in my E90 and the snap oversteer is pretty bad. I have a the stock sway in the front but eventually plan on mounting a UUC bar

If you don't want to run camber plates, you can run Dinan fixed plates. I'm running -2.4 degrees in front with them and the alignment pins drilled out

Btw skip the brass caliper pins. If you don't clean them often, you will run into issues. Fine for a track car, not ok for a daily driven street vehicle

[DoctoRx]

Originally Posted by tetsuo111

DoctoRx, it looks like you have the important parts covered.

2) Brake mods: Suggest beginning with high temp fluid and ss lines. Have a trustworthy service tech do this service.

3) That said, if I am in your shoes, I would upgrade brakes before doing RSBs. Why? RSBs are second only to coilovers / dampers for suspension improvements.

Thanks for this advice! I think perhaps I should move along in the same thought process. The car is currently FBO and I expect to have at the very least a stage 1 turbo upgrade by the time the car sees the light of day so stopping power will be just as important, if not more important than improving handling in turns. Will high temp fluid affect mechanics during the winter times since my car is DD? I'll be looking into a beater for the winters but as I still take my car about 3 miles to work in the winter - it's seen some action at -20 degrees in the snow during some brutal winter days.

[DoctoRx]

Originally Posted by matteblue3er

I'm running the E93 rear sway bar in my E90 and the snap oversteer is pretty bad. I have a the stock sway in the front but eventually plan on mounting a UUC bar

If you don't want to run camber plates, you can run Dinan fixed plates. I'm running -2.4 degrees in front with them and the alignment pins drilled out

Btw skip the brass caliper pins. If you don't clean them often, you will run into issues. Fine for a track car, not ok for a daily driven street vehicle

I'be heard the e92 one is the way to go as the larger e93 can cause more trouble than it's worth. I have always wondered if adding the UUC in front would provide a better balance - let me know if you try it out. A shame the Dinan adjustable fronts aren't available on xDrive.

I have camber plates but currently car is at OEM specs to maximize tire wear (at least until I've modded enough to feel like I'll have a track worthy street vehicle).