CrashDummy None
April 23, 2012 4:39 p.m.

I have an 08 Mazdaspeed3 that I autocross. It is stock with Star Specs (new tires for this season). 225/45/R18 I chalked the front tires for every run at a recent event. I started with 40psi, then 42, and then 45 but the tires were still rolling over too much based on the chalk. My question is: Is there a point at which adding pressure becomes counter productive and can actually make things worse? My car could really use more camber (but it can't be adjusted) so it's going to abuse the outside edge of the tire...maybe it is rolling over too much because of the (lack of) camber and not a lack of pressure? Any tips would be appreciated.

On the rear tires chalk doesn't tell me much because the tires don't roll over very much. I have been told that both high rear pressures or low rear pressures will help the car to rotate. Is this true? Any advice on rear pressures? Any tips for a good starting point or some upper/lower bounds that I shouldn't exceed? Again any advice is appreciated.

For the record I think the stock (aka door jam) pressures are 34 front and 32 rear.

N Sperlo UberDork
April 23, 2012 4:51 p.m.

I can't answer, but you may want to include the type and size of tire.

mazdeuce Reader
April 23, 2012 4:51 p.m.

Can you not run camber bolts for some reason?
A girl I autocross with runs a VW Rabbit on star specs with no camber to speak of and she has been happy at 36 psi if that is useful at all. She drives quick, but very smooth and very rarely overdrives a corner and I think thats a big part of it. I've only just done my first event on my star specs and I settled at 34 psi for now but I'm in a lighter car with less power and 2.5 degrees of camber so I'm not sure if that really applies. The star specs do react quite a lot differently to over cooking a corner though. Things I could get away with and massage back into a useful corner before I can't now. They certainly trade grip for forgiveness compared to all seasons.

CrashDummy New Reader
April 23, 2012 4:56 p.m.
N Sperlo wrote: I can't answer, but you may want to include the type and size of tire.

Edit made...225/45/R18. Thanks.

mazdeuce wrote: Can you not run camber bolts for some reason?

I am not aware of camber bolts for the Speed3. I would be very interested if they are avaliable. To be Stock-Class legal I believe they need to be specified in the factory service manual? If anyone knows of Speed3 camber bolts please tell me!

April 23, 2012 4:58 p.m.

I've always heard up the tire pressure by 10psi from the factory spec. Up by ten in the front and rear.

Could also try reversing the pressures, higher in the rear than front. The idea is extra pressure in the rear will mean slightly less grip and hence more rotation. That's what I've heard, I've always done +10 front and rear

mazdeuce Reader
April 23, 2012 5:01 p.m.

I'd just run the damn things and not worry about it. As long as you're not in the trophies nobody should care and they'll pay for themselves in increased tire life. Why run stock instead of a ST class? They're certainly legal there.
Edit for bad advice. Don't cheat. If you're going to stay in stock then don't run the bolts. If you don't have a compelling reason to stay in stock though, look into ST (the speed is in STU?) where you'll almost certainly be outgunned, but you have a bit more freedom. Some people are really driven to pick a class and win at it. Others just want to learn to drive faster and let the finishes fall where they may.

jrw1621 PowerDork
April 23, 2012 5:28 p.m.

Video Instruction:
Not unheard of to have 50psi in the fronts of a fwd car.

Since you are chalking, keep this in mind... 3lbs of air for every 1/4" you want to move the wear mark.

Try setting up a skidpad and use a themometer on the treads

wbjones UltraDork
April 23, 2012 7:30 p.m.

this will answer many questions anyone might have when it comes to ST tires

You'll need to log in to post.

Also on Grassroots Motorsports

Eric Foss Sets Fastest Time Ever at the Tire Rack Ultimate Track Car Challenge

11 hours ago in News

47 of the country's fastest cars battled it out for track supremacy.

Who Wants to Design the Next GRM T-Shirt?

12 hours ago in News

Blipshift is involved, so you know that it will be cool.

Reader's Ride of the Week: Improving Upon the Ultimate Driving Machine

16 hours ago in News

This E36-chassis M3 just keeps getting better.

What Was the Most Powerful Car at the Grassroots Motorsports Dyno Day?

17 hours ago in News

What if we told you it was an Audi?

Up to the Challenge

3 days ago in Articles

Torque: It's how Glen Bunch's vintage Dodge keeps pace with today's machines.

This Friday: The Ultimate Track Car Showdown

4 days ago in News

Come watch some of the country’s top track cars duke it out for fame, glory and some tasty prizes.

You Need This: Metallic Brown Toyota Celica

4 days ago in News

This looks a lot like one that we had in our fleet back in the day.

GRM Live Tonight: Learn to Drive VIR With Pro Driver Mike Skeen

5 days ago in News

Want to learn to drive Virginia International Raceway from a pro?

Are V6 Mustangs Fun, Too?

5 days ago in News

Can a V6 Mustang be just as much fun as a V8-powered car?

Our Miata Needs a New Engine

5 days ago in Project Cars

Our Mazda racer heads to Treasure Coast Miata for a new heart.

Mercedes-Benz 500 E: Like a Drug

6 days ago in Articles

Many of us dream about the perfect Q-ship. Mercedes-Benz rolled one right out of the factory.

Meet the GRM Crew at Carlisle This Weekend

6 days ago in News

We’re loading up the van, and tomorrow morning we make tracks for Carlisle, Pennsylvania.


Grassroots Motorsports Magazine

Subscribe Today

Also get your instant access to the digital edition of Grassroots Motorsports Magazine!

Learn More