97 M3/4/5 running in STU

[97M3]

Re: 97 M3/4/5 running in STU

Okay, tried a set of 600lb in the rear and the car rotated better and corner exit was flatter with no push. I left the 450s on the front though. Objections?

[97M3]

Re: 97 M3/4/5 running in STU

Without changing spring rates what else could be done? Ride height?

She was corner balanced which helped a little but wasn't that far off. 12lbs.

[Fair!]

Re: 97 M3/4/5 running in STU

Oops! No proofreading skills.

Sorry, I quoted an earlier post...

The spring rates are 450F/500R. These are the crappy Dunlops. Loosened the bar already. What spring rates does everyone recommend?

Thanks,

Well if the car is a dual purpose street/autocross car then stiffer rates than that on Konis will probably ride like a dump truck and/or need to be revalved and will ride even worse.

When we sell AST monotube coilover kits for these cars our softest spring rate recommendation is the GT spring kit at 450/550, the GTS is 500/650, and GTR is 600/750. GTS and GTR are what we recommend for people that compete in autocross or track events (GTS outsells the other 2 spring sets by a big margin). My wife Amy drives to work everyday with the GTR springs (which won her 2 Championships) and it rides great, but these ain't twin tube Konis....


Left: on Yokohamas. Right: On Dunlops

Dunlops should have a better feel than RE01Rs, but they are still no Yokohama. The AD07 feels like a race tire - instant response, great transitional feel, etc. Driving the EVO X back to back at the Houston Tour practice on Dunlops and then Yokohamas was pretty interesting. The Dunlop is a damn good tire for the money. The Yokohama was just in another league. Can't wait to try the AD08!

[97M3]

Re: 97 M3/4/5 running in STU

Oops! No proofreading skills.

The spring rates are 450F/500R. These are the crappy Dunlops. Loosened the bar already. What spring rates does everyone recommend?

Thanks,

[Fair!]

Re: 97 M3/4/5 running in STU

...installed a TCK SA setup with 550/540 springs and plates.

...

Pick it apart. 36F/32R. Feels very sloppy. I do plan on loosening up the front bar before the next event.

I doubt the issue is really about tire pressure at all, but spring rate. Rear spring rates too low (relative to the front) + front roll stiffness looks too high (relative to the rear). Front tire in air under corner exit is The Tell. Honestly I see more E36's setup this way, than not.



That picture above is our E36 M3 with 600F/750R springs, AST4200s, big (adjustable) swaybars at both ends, -4° of static front camber. This picture was shot mid corner on clean concrete, rolling into max forward acceleration @ Wide Open Throttle in 2nd gear, laterally loaded at about 1.25g on 255/40/17 AD07s. As you can see the tires are loaded up hard relative to the wheels. Inside front tire looks "light" but is still contributing some work. Rear of the chassis isn't squatting or heeled over - just getting it done and hauling tail out of that corner.

edit: Bridgestone RE01Rs are always going to feel sloppy on 2800+ pound cars. They are no Yokohama. You can improve the RE01R's feel only by shaving the tread under 4/32", stretching the tires onto much wider wheels than you think necessary, and upping tire pressures.

[97M3]

Re: 97 M3/4/5 running in STU

_DSC1338.jpg

Pick it apart. 36F/32R. Feels very sloppy. I do plan on loosening up the front bar before the next event.

[John in Houston]

Re: 97 M3/4/5 running in STU

I run 255x40x17s on a 17x9. Front pressures 35 and rears 30. No rolling over. Ever.

[97M3]

Re: 97 M3/4/5 running in STU

Ran a BMWCCA event at 36F/32R and rolled the sidewalls again. Had at least a 1/2 of deflection. Don't know how your keeping the sidewalls stiff?

[BrianGT]

Re: 97 M3/4/5 running in STU

17x9 with 255/40-17 StarSpecs

[97M3]

Re: 97 M3/4/5 running in STU

-3.5 front, -2.5 rear. What size tire and wheels?

[BrianGT]

Re: 97 M3/4/5 running in STU

How much camber do you have? I started the season with -2.8F and -1.8R, and am now at -3.8F and -2.8R and I am longer rolling over the edges. I run 34 psi all around on starspecs.

My car lifts wheels sometimes:
http://www.briangt.com/gallery/328is/2_wheelin

[97M3]

Re: 97 M3/4/5 running in STU

Someone shot some photos of the car on Saturday. The 245's (Dunlops) on a 17in Koseis are still rolling over at the 32-35psi range, will increase pressures next event. As we learn the car we're picking the insde front tire up under acceleration. Suggestions?

[BrianGT]

Re: 97 M3/4/5 running in STU

I have no rear bar on my '97 328is, and a 28mm H&R fsb connected to the control arms. It works really well with the 650F 750R rates. I am going to try running stiffer rear springs eventually, but for now, the setup is quite well balanced. Was able to put 70 runs on the car on a small test and tune course to get it dialed in with the shocks. I am not a believer in running a rear bar on a rwd car if avoidable.

[Fair!]

Re: 97 M3/4/5 running in STU

Let's put the toothpaste back in the tube...

How will running no rear bar and a huge front bar help with rotation?

Like Chris said, it won't help rotation but should help put power down on corner exit. We kind of did this on our open diff E30, by running a big H&R front bar and the stock (tiny!) rear bar - along with some custom shocks.

On the E36 and E46 M cars I actually like the turn in, transition abilities, mid corner "feel" and rotation with using bigger (adjustable) bars front and rear, and running 5-6x the spring rate of stock. These cars are VERY softly sprung from the factory. Not everyone agrees as some folks like a car the "moves around a lot" (more roll, dive, pitch), as it transmits more inputs to the driver. I think the stiffer setup is faster, especially at ever higher speeds (esp. road courses).

[Chris]

Re: 97 M3/4/5 running in STU

How will running no rear bar and a huge front bar help with rotation?

It won't... At least in my experience. A bigger front bar *will* help front grip to a point, but once you get the roll under control, swaybar tuning in an M3 is just like any other car - A stiffer front bar increases understeer, a stiffer rear bar increases oversteer.