Buttoning down the rear end

[robertm]

[quote=bdaddylo;13365068]

Originally Posted by redux

Well said. HP is worthless if you can't utilize it. The 1M's biggest weakness is how abrubtly it transitions to oversteer. Thanks for sharing your quest to resolve this characteristic.

Actually I'd say it's biggest weakness is the @#$@#! CBC that can't be turned off. This 'feature' has caused me far more grief on track than oversteer ever caused. The oversteer is somewhat fun and predictable. I have a hard time controlling/knowing when CBC will kick in and dayum it's no fun.

If we are making a list of weaknesses I'd add the lack of overboost until in a perfectly straight line as well. Really wish I could get the FULL power out of the motor before having the car in a completely straight line.

[TXmtrhed]

Originally Posted by MDORPHN

Harold -

I'm running Swift springs. 7" 392# front/10" 672# rear.

Neil

Sorry to hijack this thread somewhat but Bimmerworld is setting me up with a JRZ RS1 setup with 6" 392# front (w/ helper spring) and 9" 672# rear Swift springs.

Neil, what led you to go with the longer springs? Did the shorter springs give you too much drop? I'm looking to drop mine ~3/4" since my car is a DD. How much drop did you end up with?

Since Bimmerworld had to order the springs and won't ship out my order until next week, I still have time to change it.

[MDORPHN]

Originally Posted by TXmtrhed

Sorry to hijack this thread somewhat but Bimmerworld is setting me up with a JRZ RS1 setup with 6" 392# front (w/ helper spring) and 9" 672# rear Swift springs.

Neil, what led you to go with the longer springs? Did the shorter springs give you too much drop? I'm looking to drop mine ~3/4" since my car is a DD. How much drop did you end up with?

Since Bimmerworld had to order the springs and won't ship out my order until next week, I still have time to change it.

I lowered mine by around 3/8"-1/2" and those spring lengths allow me to adjust the height up or down with that drop.

Neil

[p66]

Originally Posted by MDORPHN

Yes, I understand. I went through three limted slips (including a Quaiffe) on my previous car (a highly modified M Coupe) before I had it where I wanted with a custom 3 clutch variable ramp set-up built by Dan Fitzgerald (diffsonline).

However, I'm very pleased with the diff in my 1M and have no plans to change it.

As has been discussed ad nauseum, the 1M is not an easy car to drive on the edge, although steps can be taken to tame it just a bit.

Among other things, I'm running camber plates, JRZ dampers and a stiffer E93 M3 front sway. Car still requires quick hands (and feet), but I really dig how it handles.

Neil

Neil, I have a very Similar setup. AST 4200, similar spring rates, Vorshlag camber plates, etc. I have considered a heavier front bar. How did the bar change your cars handling characteristics? I'm running 9.5-275f / 10.5-295r on 18" R6 for track use.

Philip

[MDORPHN]

Originally Posted by p66

Neil, I have a very Similar setup. AST 4200, similar spring rates, Vorshlag camber plates, etc. I have considered a heavier front bar. How did the bar change your cars handling characteristics? I'm running 9.5-275f / 10.5-295r on 18" R6 for track use.

Philip

Philip -

I don't have any good data to back it up, but feel that I can get on the gas just a bit earlier when coming out of a turn with the stiffer front bar.

BTW, how much did you lower your car and do you have any rubbing with the 275 in front?

Neil

[bdaddylo]

Originally Posted by MDORPHN

I lowered mine by around 3/8"-1/2" and those spring lengths allow me to adjust the height up or down with that drop.

Neil

Do you think helper springs are really needed?

[HP Autowerks]

Originally Posted by bdaddylo

Do you think helper springs are really needed?

Yes, unless you don't mind the main spring becoming unloaded.

[HP Autowerks]

Originally Posted by MDORPHN

Philip -

I don't have any good data to back it up, but feel that I can get on the gas just a bit earlier when coming out of a turn with the stiffer front bar.

BTW, how much did you lower your car and do you have any rubbing with the 275 in front?

Neil

That is exactly what a larger front bar will do for you on the 1M!

[Robin_NL]

[quote=bdaddylo;13365068][quote=redux]
The 1M forum seems to be all about HP figures, selling crap, stupid ass "exclusive" polo shirts. So, I made this post just to stir up some actual suspension talk. The transition to oversteer in my car is actually better than it was stock, but not as progressive as an m3. So it's not bad, it's just not where I want it.

Well said. HP is worthless if you can't utilize it. The 1M's biggest weakness is how abrubtly it transitions to oversteer. Thanks for sharing your quest to resolve this characteristic.

True, the shorter wheelbase, enormous torque, all true, and also other tyres than PS2s will help to reduce that abrupt-ness and make it a finer car with smoother transitions. OEM PS2= GRIP---nanosecond---SLIP.



Cheers
Robin

[MDORPHN]

Originally Posted by HP Autowerks

Yes, unless you don't mind the main spring becoming unloaded.

Harold -

Would helper springs primarily be of benefit in the rear?

If so, how would you suggest I modify my current set-up?

Really appreciate your contributions to this discussion.

Neil

[HP Autowerks]

Originally Posted by MDORPHN

Harold -

Would helper springs primarily be of benefit in the rear?

If so, how would you suggest I modify my current set-up?

Really appreciate your contributions to this discussion.

Neil

This only applies to 1M/M3. If a 6" front main spring is used, a helper spring is necessary. With a 7" main spring you can get away not having helpers if you don't lower the car too much.

You would only need a helper in the rear if you rear main springs become unloaded with the suspension at or near full droop. Is that the case right now? I personally ran both 7" and 8" rear main spring with a helper on my 1M.

Here is a photo of the RS1 front strut with 6" main and helper. You can see how a 6" or even a 7" spring can become unloaded without a helper in place.

[Blue55]

Redux - let me know when you're headed out next - I'd love to give you a little competition!
BTW - My only suspension mods are lowering springs (for more camber) and Vorshlag plates. I don't think the car 'snap' oversteers at all compared with other vehicles, but it does rotate more quickly than the M3. Putting power down on exit is the most challenging aspect of driving the car.

[HP Autowerks]

Originally Posted by Blue55

Putting power down on exit is the most challenging aspect of driving the car.

That is the main reason I recommend a staggered setup with the widest possible wheel and tire combo for the rear of the 1M or M3.

[Blue55]

Redux - quick question - was that John Mueller or you driving the car in the video?

Harold - I agree that bigger contact patch at the back aids in applying power, however the biggest drawback is the inability to rotate the tires fully. This becomes a legitimate issue as track time increases. Most M3 guys run 275 square because of this.

[HP Autowerks]

Originally Posted by Blue55

Redux - quick question - was that John Mueller or you driving the car in the video?

Harold - I agree that bigger contact patch at the back aids in applying power, however the biggest drawback is the inability to rotate the tires fully. This becomes a legitimate issue as track time increases. Most M3 guys run 275 square because of this.

There is always a compromise. If you must rotate your tires, then you are stuck with the square set-up.

[ozinaldo]

Originally Posted by HP Autowerks

There is always a compromise. If you must rotate your tires, then you are stuck with the square set-up.

Harold-I don't need to rotate my tires. And I want to keep using stock 19 inch wheels for now. Dropping the car's ride height is out of consideration for me due to road/garage conditions. What would be the best in my case; 275/30 19 all around or 275/30 19 ft and 295/30 19 rear? Almost exclusively street/highway and back road use. I have stock size PSS all around which work remarkably well. I can think of using camber plates if that would provide anything noticeable with one of these set ups.

[HP Autowerks]

Originally Posted by ozinaldo

Harold-I don't need to rotate my tires. And I want to keep using stock 19 inch wheels for now. Dropping the car's ride height is out of consideration for me due to road/garage conditions. What would be the best in my case; 275/30 19 all around or 275/30 19 ft and 295/30 19 rear? Almost exclusively street/highway and back road use. I have stock size PSS all around which work remarkably well. I can think of using camber plates if that would provide anything noticeable with one of these set ups.

275 front and 295 will fit fine, but may want to consider wider wheels to support the wider tires. Otherwise, just go up to 265 front and 285 rear on 35 aspect ratio PSS.

Camber plates will give the 1M the much needed camber and reduce some or maybe all of the understreer.

[ozinaldo]

Originally Posted by HP Autowerks

275 front and 295 will fit fine, but may want to consider wider wheels to support the wider tires. Otherwise, just go up to 265 front and 285 rear on 35 aspect ratio PSS.

Camber plates will give the 1M the much needed camber and reduce some or maybe all of the understreer.

I can't put 265/35 on the front since they will rub crazy, almost won't turn. Even stock 245/35 is there, could rub. The diameter difference is like 0.5 inches between those sizes.

And worse, PSS don't come with 285/35 (or 30), not yet as far as I know. You heard anything about release of those sizes?

So, I feel like my best chances seem to be stay stock or go for 275/295 but on 30 aspect and also add camber plates. Stock wheel size may be less than ideal but likely not prohibitive, at least tire rack suggests so

Will it be possible to stay exactly equal or really close to stock ride height with the camber plates?

[p66]

Originally Posted by MDORPHN

Philip -

I don't have any good data to back it up, but feel that I can get on the gas just a bit earlier when coming out of a turn with the stiffer front bar.

BTW, how much did you lower your car and do you have any rubbing with the 275 in front?

Neil

Neil, I'll need to go check my notes. I'm not at home at the moment. I should probably just go measure where it's at with stock wheels/tires. I think I lowered it about an inch. But don't quote me. Regardless, I have no rubbing and I could probably lower it more. I'm using a 9.5" x 18" Arc 8s with an et35 and a 10mm spacer. Not my preferred wheel et but I got the set super cheap and an adjusted et of 25 is perfect. I'm running about -3.0 camber in front and I have a lot of margin on the fender side. No reasonable margin left on the suspension side with a 275 hoosier R6. I've contemplated getting a 285 and trying it out. It might just fit. I would need a 15mm spacer.

The rears are 10.5" et 27. 295 R6's were rubbing ever so slightly on the suspension side passenger fender liner and on the gas filler tube. I added a 3mm spacer for clearance. What a mess that would have been had a rubbed a hole in the gas filler tube. Yikes.

Philip

[MDORPHN]

Originally Posted by p66

Neil, I'll need to go check my notes. I'm not at home at the moment. I should probably just go measure where it's at with stock wheels/tires. I think I lowered it about an inch. But don't quote me. Regardless, I have no rubbing and I could probably lower it more. I'm using a 9.5" x 18" Arc 8s with an et35 and a 10mm spacer. Not my preferred wheel et but I got the set super cheap and an adjusted et of 25 is perfect. I'm running about -3.0 camber in front and I have a lot of margin on the fender side. No reasonable margin left on the suspension side with a 275 hoosier R6. I've contemplated getting a 285 and trying it out. It might just fit. I would need a 15mm spacer.

The rears are 10.5" et 27. 295 R6's were rubbing ever so slightly on the suspension side passenger fender liner and on the gas filler tube. I added a 3mm spacer for clearance. What a mess that would have been had a rubbed a hole in the gas filler tube. Yikes.

Philip

Philip -

Very helpful. Thanks.

Neil

[HP Autowerks]

Originally Posted by ozinaldo

I can't put 265/35 on the front since they will rub crazy, almost won't turn. Even stock 245/35 is there, could rub. The diameter difference is like 0.5 inches between those sizes.

And worse, PSS don't come with 285/35 (or 30), not yet as far as I know. You heard anything about release of those sizes?

So, I feel like my best chances seem to be stay stock or go for 275/295 but on 30 aspect and also add camber plates. Stock wheel size may be less than ideal but likely not prohibitive, at least tire rack suggests so

Will it be possible to stay exactly equal or really close to stock ride height with the camber plates?

My bad, I meant 255 front and 275 rear.

Originally Posted by p66

Neil, I'll need to go check my notes. I'm not at home at the moment. I should probably just go measure where it's at with stock wheels/tires. I think I lowered it about an inch. But don't quote me. Regardless, I have no rubbing and I could probably lower it more. I'm using a 9.5" x 18" Arc 8s with an et35 and a 10mm spacer. Not my preferred wheel et but I got the set super cheap and an adjusted et of 25 is perfect. I'm running about -3.0 camber in front and I have a lot of margin on the fender side. No reasonable margin left on the suspension side with a 275 hoosier R6. I've contemplated getting a 285 and trying it out. It might just fit. I would need a 15mm spacer.

The rears are 10.5" et 27. 295 R6's were rubbing ever so slightly on the suspension side passenger fender liner and on the gas filler tube. I added a 3mm spacer for clearance. What a mess that would have been had a rubbed a hole in the gas filler tube. Yikes.

Philip

I had 265 front and 295 rear Hoosier R6's, no issues.

http://www.1addicts.com/forums/showp...0&postcount=99

[CarJunkie]

Originally Posted by HP Autowerks

My bad, I meant 255 front and 275 rear.

Won't the 255 front also rub without modification of the fender liner? The new version of the fender liner may be better (posted in another thread). Have you been able to fit 255/35 19 PSS on a 1M without the modified fender liner?