It's no secret. They 2003/2004.

Dooood easy 2 seconds right there.

Don't be too hasty to throw fresh race rubber on there...

One advantage of running on rocks (vernacular for old, age-hardened race tires), is that they're a lot more tolerant of abuse.

Fresh race tires with a new driver can result in some very rapid depletion of bank accounts. Think "flat spots"... 'nuf said...

-Josh

These were just 200TW street tires.


KT

I'm guilty of that sort of stupidity.


One has to resist the urge to try to "improve" the car after the first AX. Trust me on that one, the car is not the problem and neither are your old tires.

There is much to learn about driving using a stock car with little HP and street tires.

Yeah I killed my right front a couple weekends ago. Car seems to like locking that one first. I think the course had a bunch to do with it but I may also have a sticking caliper. It'll be fixed before I order my A6s next month.

I never did ask mark what tire pressure he was running.

We should have marked the sidewalls and made some quick adjustments.
Looking at the tire yesterday, I'd say they were over inflated, as there is no evidence of sidewall rollover.

All these little things add up.


KT

Might be a good time to publish a list of "to do" items for your students.

Mark knows about tire pressure adjustments. I would wonder what tire pressure he started with though. With my A6 tires he made adjustments without my having to tell him. But my A6 run a lot less pressure than he should be running with his ancient non-R tires.

I thought about adjusting the tire pressure, but decided against it just because I didn't feel like I had enough experience in my car to really feel those differences.

I hope in 2013 I can shake my autocross curse, where whatever autocross I show up to ends up having less runs per car than usual. Hasn't failed yet.

I also need to get to more events with Randal, Rob, Trekkor, etc and actually have ya'll ride along.

We're just hoping you get the oversteer/understeer thing figgered out!

I found it impossible to "flat spot" a tire at AX speeds. The worst I ever saw was a slight scuff on the tread. (slicks).

Seriously? Now granted, I always ran DOT R tires, not slicks, but I have flat spotted more than my share of tires over the years. The two that still stick in my mind though are when an innexperienced corner worker ran out iacross the course as I was coming down into the turn. Didn't know which way he'd go, so I just stood on the brakes. Whoosh! Two brand new Hoosiers up in smoke...

-Josh

Used to flat spot the 205 Hoosiers, especially as they got on the back side of their life cycle, until I changed the pads in front to the cheapest set I could find. Problem solved.

Sure wouldn't want to flat spot the Avon's.

I agree with JP....I think you guys need to get off the brakes!...

A true flat spot will cause:
a)Vibration
b) and/or repeated lock in the same spot while on the binders.
Anything else is just a scuff.


I suppose that one could flat spot a narrow tire with a heavy car.
Fortunately, I never used either.

Then again maybe we was goin' too slow.

Just so we are all clear, here is a graphic demonstration of oversteer. Understeer can happen too but it is far more painful and not usually accompanied by a loud yell of 'Yee Haw'.

Click to view attachment

Don't show understeer, otherwise the administration will likely delete your post!

Yup. Found the 'understeer' picture. Kind of bloody!

More appropriate for the sandbox.

Any time now McMark is going to see that Dukes of Hazard post and I'm going to get another demeaning look...

Mark's busy. I'll fill in...

WTF is Rob posting about now?

More neg camber up front, full tank of gas will get rid of understeer in most stockish 914s. And respect for mid engine handling dynamics is always helpful.

Grant, I sent Mark settings for his car. He should be good to go...

Share the settings!!


KT

Noooooooo!

My setup before the rear coil overs. If I remember correctly I have -2.2 degrees camber and the toe straight ahead now on the rears.


Click to view attachment



Click to view attachment

What were your left side/ right side front and rear weights? And assuming these weights will be with you in the car.

Mine wieights worked out to 56%rear / 44% front. That worked out to a ratio of 1.296 which I then used to figure out what sized rears I wanted to run if I was running X sized fronts. You can get it so close that the pounds of weight per inch of tire is exactly the same in the front as in the rear.

Click to view attachment

If I did my arithmetic right we are at the same ratio. Interesting. You about 83lbs heaver.

So if you were running 8 inch slicks in front the ideal rear tire would be 10.4".

The idea being that an 8" slick will get up to operating temperature more quickly and have better grip.

Of course I didn't have the fortitude to practice what I preach and ended up using 8.7 fronts and 10.5 inch rears.

My car still has glass, a roof, and impact beam doors. I'm actually a few pounds underweight for my class although I'm gonna keep lightening it. I'll have to look up the specs for the A6s again but there is only an inch difference between the fronts and rears. It's going to be a fun year.

Tread width is 9" front and 10.1 rear.

That'll work.
I ran 9.5s & 10s with more rear weight bias...IIRC, I had about 660lbs up front & 1060lbs rear. Course ya still gotta set up the suspension to suit.

This has been a very interesting read. Thanks Mark for starting this conversation. I am in about the same situation as Mark and would like to know more about Trekkor's AX training. Will it be posted on 914 World?

Thanks, Warren