Autocross today - Page 2

TomsSVX · #16 10-14-2007, 12:15 AM

what he said!!! watch the back end it'll come around in a hurry

Tom

porschekiller · #17 10-14-2007, 12:50 PM

i never did autocross. i prefer roadracing, especially at limerock and watkins glen. have you ever noticed the oe svx tire pressures are 33 front and 29 rear to compensate for the low cost imbalance? a comparable overengineered 3000gt vr4 has 245/45-17 fronts, the same as the lotus esprit v8 rears. isnt precedent a wonderful thing? it keeps bad history from repeating itself. your welcome.

Quote:

Originally Posted by wawazat??

Yes I am. I appreciate your advice but I'll balance the traction of my same sized tires (245/40-17 Bridgestone RE-01r) with pressure and suspension tuning. I doubt that tire size swaps will help me with a 3-4 second deficit in my class (STX) and as I just bought these tires, I won't be buying any more in the near future.

What type of autocross experience do you have with what types of vehicles? Have you autocrossed your SVX? Just curious as to who/how/what type of experience you have. Lots of free information available on the intraweb and you typically get what you pay for.

Todd

Evil One · #18 10-14-2007, 01:27 PM

Quote:

Originally Posted by porschekiller

a comparable overengineered 3000gt vr4 has 245/45-17 fronts, the same as the lotus esprit v8 rears.

It also has the 245/45-17s on the rear of the 3000GT VR4.

Jim

wawazat?? · #19 10-14-2007, 03:46 PM

Well, that was different. Took third in DS versus a two driver WRX and a Crossfire (4 total entries). One upshift to second and the rest of the course was in second (damn, I paid for 6 gears and only got to use two today

). After many many laps in the SVX on coilovers, this car wallows like a pig. My hats off to you stock guys

Rear end stayed relatively planted. Turbo power was nice. Car transitioned pretty well for a stock heavy sedan. Probably won't do that again though as I have more fun in the SVX with the NA powerband. Ben, sorry to report she didn't blow up

That, radio fans, ends the MI autocross season. Now to the batcave for mods for next year.

Todd

wawazat?? · #20 10-14-2007, 03:49 PM

Quote:

Originally Posted by porschekiller

i never did autocross. i prefer roadracing, especially at limerock and watkins glen. have you ever noticed the oe svx tire pressures are 33 front and 29 rear to compensate for the low cost imbalance? a comparable overengineered 3000gt vr4 has 245/45-17 fronts, the same as the lotus esprit v8 rears. isnt precedent a wonderful thing? it keeps bad history from repeating itself. your welcome.

For what am I welcome, more obscure tire size references

What does low-cost imbalance mean? And yes, I have noticed the recommended tire pressures are different front to rear. So what?

porschekiller · #21 10-14-2007, 05:30 PM

yes indeed, because the engineers werent so bold as to use a smaller sizes in the rear, but the gm engineers were on the '08 monte carlo ss: 255 front 235 rear. it's all weights and measures. the svx is basically a backwards porsche dynamically and should've been engineered as a rwd rx7 beater. perfect balance would be achieved with 245/45-17 front w/ vr4 tire pressure and 205/55-17 rear (same height) w/ cayman tire pressure. then maybe the auto wouldnt shift into second.

Quote:

Originally Posted by FOMOGO

It also has the 245/45-17s on the rear of the 3000GT VR4.

Jim

Evil One · #22 10-14-2007, 05:35 PM

Are we forgetting the whole "AWD with diff circumference tires eats the drivetrain" part of the equation?
Do you know how many different manufacturers tires you would have to go thru to actually get the same circumference?

Jim

porschekiller · #23 10-14-2007, 05:47 PM

you get diff circ with diff tire pressure. tirerack.com has specs on all there tires to click on. 205/55-17 has the same circ as 245/45-17. you could always have them shave them if you wanna be precise, but dont forget to run the same pressure too.

Quote:

Originally Posted by FOMOGO

Are we forgetting the whole "AWD with diff circumference tires eats the drivetrain" part of the equation?
Do you know how many different manufacturers tires you would have to go thru to actually get the same circumference?

Jim

benebob · #24 10-14-2007, 07:49 PM

Quote:

Originally Posted by FOMOGO

Are we forgetting the whole "AWD with diff circumference tires eats the drivetrain" part of the equation?
Do you know how many different manufacturers tires you would have to go thru to actually get the same circumference?

Jim

I'm sure that would've killed Subaru with tranny replacements (although I think he's wishing the SVX was rwd but rwd with 205s back there?) We do 23x10 hoosier slick burn outs from a start with all 4 tires driving!

What he says makes so sense but as you pointed out you run into that issues plus then you add on no tire rotation to the mix and trannies dying weekly!

Oh and sorry to hear you didn't blow your Mazda up Todd, its always nice to return to the basics isn't it. Did you order a new suspension for it yet?

It's Just Eric · #25 10-14-2007, 09:14 PM

But see...here's the problem.You are coming into a group of people who have seat time in the svx. You have never raced an svx, and have never done an autocross...
From what gather,all obscure tire sizes and weight measurment aside, is that your suggestions are basically to increase the height of the sidewall, increase front width, and make the rears more narrow. Now, I understand the idea that you need to balance the car out tractionwise, but your suggestions seem a little off to me. Apparently there's a link between the weight over the wheels and the height of the sidewall...but whatever effect it has on the overall handeling is being lost in jargon.

Possibly, if you could explain the physics or motives behind making the suggested changes, as applicable to the svx in an autocross or similar track environment, it would shed some light on the information you're trying to provide

And..I think wawazat is taklking about two cars here? Im guessing a legacy as well? Lol, aint no turbo 4 door svxi, thats for sure

porschekiller · #26 10-15-2007, 04:19 AM

i think the fastest SVX here has already done that. pay attention: 275/45-16. not the height of the sidewall, the height of the tire! ideally the sidewall shouldnt be under 235/40 or over 235/50 on any wheel.

Quote:

Originally Posted by It's Just Eric

But see...here's the problem.You are coming into a group of people who have seat time in the svx. You have never raced an svx, and have never done an autocross...
From what gather,all obscure tire sizes and weight measurment aside, is that your suggestions are basically to increase the height of the sidewall, increase front width, and make the rears more narrow. Now, I understand the idea that you need to balance the car out tractionwise, but your suggestions seem a little off to me. Apparently there's a link between the weight over the wheels and the height of the sidewall...but whatever effect it has on the overall handeling is being lost in jargon.

Possibly, if you could explain the physics or motives behind making the suggested changes, as applicable to the svx in an autocross or similar track environment, it would shed some light on the information you're trying to provide

And..I think wawazat is taklking about two cars here? Im guessing a legacy as well? Lol, aint no turbo 4 door svxi, thats for sure

wawazat?? · #27 10-15-2007, 04:39 AM

I now use 245/40-17 tires on my SVX and they work very well plus are the widest tires allowed in my class. I have used 225/45-17 and 235/40-17 as well as 225/50-16 to autocross.

porschekiller · #28 10-15-2007, 04:49 AM

the 245/40-17 is oe on the back of an NSX and the front of a ferrari F40, but the NSX is alot lighter than the svx. i liked the 245/50ZR16 on my car with enkeis, they fill the fender gap with no rubbing. i'm waiting to see if i can get away with a 255/50WR16s. the big tires and an awd allow me to get away with using all temp all season tires with long tread wear and a comfortable ride: $87 Falken Ziex 512.

Quote:

Originally Posted by wawazat??

I now use 245/40-17 tires on my SVX and they work very well plus are the widest tires allowed in my class. I have used 225/45-17 and 235/40-17 as well as 225/50-16 to autocross.

porschekiller · #29 10-15-2007, 05:23 AM

if you wanna use the same size tires on 17" wheels then 235/50-17 off the new cayman would be ideal and they would look better without the fender gap. the new 235/50zr17 falken ziex ze912 $88 at tires-easy.com.

Quote:

Originally Posted by wawazat??

I now use 245/40-17 tires on my SVX and they work very well plus are the widest tires allowed in my class. I have used 225/45-17 and 235/40-17 as well as 225/50-16 to autocross.

benebob · #30 10-15-2007, 07:03 AM

Quote:

Originally Posted by porschekiller

i think the fastest SVX here has already done that. pay attention: 275/45-16. not the height of the sidewall, the height of the tire! ideally the sidewall shouldnt be under 235/40 or over 235/50 on any wheel.

Naw, the fastest track SVX uses 23x10 Bias Ply Hoosiers. 22.5 inches in overall height baby! Sidewall. Yeah it does have a little.