[kujo]

Originally Posted by speedball3

Drag racers reduce rear psi...for more REAR traction, right?

More rear traction = harder to break the rear loose and hence, less oversteer, more understeer.

Of course the under/oversteer difference is not hugely noticeable on the street (I hope you don't drive like that on the street). But if you're running on a track/autox course and want to fine tune your car then yeah, playing with tire psi can make a difference.

So untrue.

I can feel a 2 psi difference, even just hitting a bendy offramp.

Rear TRACTION and rear GRIP are two different things.
Why don't people undertand that.

Traction and GRIP aren't the same thing.

First MOD most car guys should mod is THEMSELVES, the driver.
Everyone, THINKs they are Michael Schumacher.
Get seat time with a qualified instructor and really learn to 'feel' the car.

All these kids these days with 500WHP cars and no real clue how to handle it, other than dumping the clutch at 5K and video themselves street racing.

Oh well..... rant over......

[STI_SLC]

i think you're reading what i said incorrectly in my first response.

anyways... of course i know what kind of difference 1 or 2psi up or down..
you're coming off as the only person to track your car around here..


i would stop throwing out random tire pressures to people based on weight of a car.. you have no idea of what tires, temps, setup etc..
to tell someone to start at 36lbs on any tire is a bit ridiculous. you're going to have them ice skating once that tire is up to temp and they're sitting at 44, 45lbs..

Originally Posted by kujo

you agree ?
But you said you needed to make HUGE adjustments in PSI.....

So not true......

1psi in my Kart, makes HUGE differences.
3-4 in a 3300lb STI, would also make a big difference, but only to someone that has some finesse.

Anyone that's a mash and go, drop the clutch at 5K kinda driver, isn't going to notice that.

Eyes up, hit your apex and track out !!!

[STI_SLC]

man... you really are ranting. sound like a bitter old man/know it all.. and to think im 36 writing this..
as far as some of the things you say.. of course i agree..
i experience all the "kids" both young and old that show up to the track on their first day with their balls hangin out... thinkin - oh, my car's pretty fast.. that means im gonna be fast on the track. (best is when we teach porsche owner days)..
it's fun to humble them and teach them.. yes, im an instructor..

eitherway.. some of those "beliefs" above arent exactly correct.. it also doesnt sound like you're running an awd car? i could be wrong... but jus from reading...

Originally Posted by kujo

So untrue.

I can feel a 2 psi difference, even just hitting a bendy offramp.

Rear TRACTION and rear GRIP are two different things.
Why don't people undertand that.

Traction and GRIP aren't the same thing.

First MOD most car guys should mod is THEMSELVES, the driver.
Everyone, THINKs they are Michael Schumacher.
Get seat time with a qualified instructor and really learn to 'feel' the car.

All these kids these days with 500WHP cars and no real clue how to handle it, other than dumping the clutch at 5K and video themselves street racing.

Oh well..... rant over......

[speedball3]

Originally Posted by kujo

So untrue.

I can feel a 2 psi difference, even just hitting a bendy offramp.

Rear TRACTION and rear GRIP are two different things.
Why don't people undertand that.

Traction and GRIP aren't the same thing.

Ok, I was agreeing with you... but now I'm confused. What are your definitions for TRACTION and GRIP?

[Turninconcepts.com]

Originally Posted by STI_SLC

i think you're reading what i said incorrectly in my first response.

anyways... of course i know what kind of difference 1 or 2psi up or down..
you're coming off as the only person to track your car around here..


i would stop throwing out random tire pressures to people based on weight of a car.. you have no idea of what tires, temps, setup etc..
to tell someone to start at 36lbs on any tire is a bit ridiculous. you're going to have them ice skating once that tire is up to temp and they're sitting at 44, 45lbs..

I agree. There is a MUCH more to setting tire pressures than weight.

With stock suspension on a stock alignment, I ran 34 PSI all around in the stock tires. I had no problem with understeer.

[kujo]

SLC,
I've ran/tracked 3 Audi S4s over the years.
The last two cars I've run were BMWs.
I'll probably be picking up my STI in about 5 weeks.

Anyone that seriously tracks their car will know this basic stuff already.
It was geared towards the 90% of owners that don't track their car and could still enjoy the benefits on the street.

I'm not an old fart know it all and I know I'm not the only track junkie in this forum.

Humbling the 'Mavericks' is fun.
I've thought about instructing, but think twice when I see cars go off after dropping a wheel.
I'd rather just run my own car.

36psi would be for Street/Daily driver area, to start, as I said.

Curb weight of the vehicle and driver weight, 10% of that number is good starting point, usually.
Hence, Suby's recommended pressures... 32/33, with a curb weight of 3300 lbs.

I'd go up to around 35/33 or 36/34 depending on the tire.

Miller Motor sports park is a killer track. I'll have to come out for a track day, one of these days and follow you around the line.

[kujo]

Originally Posted by Turninconcepts.com

I agree. There is a MUCH more to setting tire pressures than weight.

With stock suspension on a stock alignment, I ran 34 PSI all around in the stock tires. I had no problem with understeer.

I know that, it was a starting point, compared to his quote of the stock psi recommendation.

If they come stock at 32/33, I'm sure it pushes like a plow if thrown into a corner.

[DrPhyzx]

Originally Posted by kujo

I know that, it was a starting point, compared to his quote of the stock psi recommendation.

If they come stock at 32/33, I'm sure it pushes like a plow if thrown into a corner.

This is a great thread... to bad it's gotten a little off track. The OP is right in line with old autoX wisdom that is pretty much right when working from mfrs. suggested setup.

Dealer had my car setup at about 35F 33R and it felt not too bad... a little more understeer than I would like but never felt like it was running away with me. For the heck of it, I decided I would try to setup more according to SOA recommendations and went to 33 all around. In my very windy daily drive (100+ turns where the traction limit is 30-50 MPH) I feel a huge difference. Despite still being able to steer the rear under power, I've had the front run badly wide a few times. So... I'll be going to 36F / 33R (or maybe 32R) ASAP and really thinking about adding some negative camber in the front, one degree at a time, until I get something I like with more equal pressures.

[RG]

Thanks for this post Kujo. I never considered that tire pressures would affect straight line performance the opposite of cornering performance.

[STI_SLC]

ya nice man.. i came from a b5, st3 1.8t avant.. im a huge audi head at heart.. except for the power distribution of the older quattros.. fyi, i have sessioned a stg3 s4 with a rear 80% LSD.. man, cant even tell you how much that livened up that car.. made it so much better in the canyons and on the track.
im feeling a bit of your psi numbers now.. like i said, in your original post some of that jus doesnt seem to make sense.. as far as the psi adjustments for increasing/decreasing understeer/oversteer.. but maybe that's just me.. especially when adding in c/o's with bump and rebound adjustments...
as far as instructing....... honestly, i do it for the free track time. this will be my 3rd season teaching.. grew up in socal, driving canyons.. then discovered the fun of tracks about 8yrs ago. the company i teach for, doesnt charge instructors.. and most of the time i will teach a beginner, then an intermediate, then freerun in my sti in the advanced group.. *all 20min sessions.. its a good gig and, it's actually fun teaching and seeing progression from your instruction.. its also one of THE most annoying and frustrating experiences when you can NOT get anything through to a random student.. which happens only once in a while.. we are pretty quick to pull on the reigns and take someone back to the pits.. so we dont have many incidents.
good luck on the sti... i've really been amazed with mine on the track and the lack of money you have to put into it compared to an audi.. even with just c/o's, sways, camber plates, rubber and of course stg2 programming you can really surprise some people and have a very good time......
i'll be picking up an 08, hopefully be we start tracking for the summer/fall.

miller really is pretty amazing.... and such a nice facility.. not sure where you live but if you ever feel like making it out... let me know.

-cjs

Originally Posted by kujo

SLC,
I've ran/tracked 3 Audi S4s over the years.
The last two cars I've run were BMWs.
I'll probably be picking up my STI in about 5 weeks.

Anyone that seriously tracks their car will know this basic stuff already.
It was geared towards the 90% of owners that don't track their car and could still enjoy the benefits on the street.

I'm not an old fart know it all and I know I'm not the only track junkie in this forum.

Humbling the 'Mavericks' is fun.
I've thought about instructing, but think twice when I see cars go off after dropping a wheel.
I'd rather just run my own car.

36psi would be for Street/Daily driver area, to start, as I said.

Curb weight of the vehicle and driver weight, 10% of that number is good starting point, usually.
Hence, Suby's recommended pressures... 32/33, with a curb weight of 3300 lbs.

I'd go up to around 35/33 or 36/34 depending on the tire.

Miller Motor sports park is a killer track. I'll have to come out for a track day, one of these days and follow you around the line.

[STI_SLC]

this is what im saying........
you're stating that you were losing the front so you're adding pressure to the front and lessoning the rear?
a harder tire is not going to adhere as well as one down a few lbs from that setting..
from my experience, i would be doing the following in that situation:
32 front, 34 rear.......... that is more bite in the front and less in the rear..
this is why i was commenting on the original statements posted..
please also note, that you can max your oem front end to -1.6.. until you have camber plates you should at least be at that spec.............. it will help you a bit.

Originally Posted by DrPhyzx

I decided I would try to setup more according to SOA recommendations and went to 33 all around. In my very windy daily drive (100+ turns where the traction limit is 30-50 MPH) I feel a huge difference. Despite still being able to steer the rear under power, I've had the front run badly wide a few times. So... I'll be going to 36F / 33R (or maybe 32R) ASAP and really thinking about adding some negative camber in the front, one degree at a time, until I get something I like with more equal pressures.

[tshrey]

I'm certainly not about to argue with a track instructor, but you are the first knowledgeable person I've ever heard to state that lowering a tire's pressure increases lateral grip. Once you get up to crazy high pressures used in drifting I would agree, but my car had 32F, 35R pressure when I picked it up and it pushed like crazy. I'm currently running 34F,32R and am happy with the setup.

This is pasted from TireRack's handling setup page...


Adjustment Decrease Understeer Decrease Oversteer
Front Tire Pressure Higher Lower
Rear Tire Pressure Lower Higher

Well, that didn't paste too well. The upshot is, you want to lessen understeer and get more bite in the front you raise the front tire pressure and lower the rear.

[STI_SLC]

*noted and we are also speaking of "cold temps" i would hope.....
i am definitely stating this more based on high temp psi's / track situations..
i good example being that most tires go up between 7-10lbs as they heat up..... for instance, on an RA-1..... i will start the morning at around 31lbs.. sometimes less.... this is to achieve a hot temp of 40-41, depending on the day.
you need to realize that you car, from the factory...... is designed to push for safety.... some camber, some psi adjustments etc... will obviously make a difference.. you will be amazed the difference also once you get either a larger rear sway or front and rear..........
i might be telling you nothing new at all.... but i dont know your background.

i will also admit, that even with my years of canyons and tracks.... i have really just started learning about pressures over the last two years.. well not "learning about them" but learning about them correctly..

[kujo]

SLC,

Yes, we should all be talking about COLD psi.

And I did the same.
On a HOT So Cal day at Willow, I'd start my RA1s at 30psi and they'd get up 40 easily.

-2.0 camber and proper PSI and you're golden !!!

kj

[STI_SLC]

ya no doubt.

you must have had fun getting -camber on those audis.... ha...

one thing you'll be happy with on the sti's is, are the suspension options as compared to the german world...