Tire Pressure & Understeer... hmmmm

Went to a local autocross event, got there too late for entry but was allowed to participate in the "fun runs". Mine is a pan based w/ the standard VW front sway bar, 185x65 f & 195x65 r. Was running 22/23 f & 27 r air pressure. These seemed ok for the street but , whoa Nellie did it plow, push, understeer, make every attempt to go through the fence nose first when pushed. I was anticipating oversteer, boy was I suprised. Took the tire pressure up to 28 all around after the fact. Still feels Ok on the street but won't be able to assess the push 'till next month as I have no real desire to be introduced to the court system by trying it on the street. Any of you go fast guys have any recommendations for air? Sway bars are in order this winter, but I'd like a decent base line to start them from. Any ideas?

There are so many variables in understeer & oversteer, the sway bars you mentioned as well as shocks, type of tire i.e side wall flex, tread design, heat and traction ratings all are part of the equasion.

Years ago I attended a Formula Vee school (VW powered small open wheeled cars)weekend in Lime Rock, they ran air pressure that I then thought was way too much pressure but what did I know...I was in "school".
On a oval ,a couple of lbs difference inside to outside tires pressure what a world of difference.

Thanks Alan,

You're right about a whole lot of variables. Everything I've set up before has the engine in the other end, sort of a new ball game. Want to get as good a baseline as I can to try to keep future changes to only the variable of that modification.
Bill

Bill: For auto cross I have been using 34 F 38 R cold. Your optimum numbers could very as much as +-10psi. A pyrometer or some sort of tire temp data logging is you best bet for sorting that out.

Some things that will make a significant improvement to your handling are tires, alignment and a set of sway bars / compensator. To get good performance tires you will probably have to use 50 series or lower which may cause gearing issues. Mine are 195 50 15 and I had to change my 4th gear for highway driving.

Another very common cause of under steer is bottoming out the front suspension. If your car is lowered this is likely. The combination of braking and turning uses up all the travel overloads the tire and sends you off into the weeds.

Bruce: WOW those tires pressures are higher than I anticipated.
I went up to 28 all around after the fact to see what that did for the push. Fwiw it's a ball joint IRS car. It has front torsion bar adjusters, but only one (?). Tried messing and tightened it a bit last night and it seemed to increase the bump resistance, rebound seems about the same. Sway bars are in order. Have a TR6 that was a FTD contender when I quit running in '74 but this is a whole 'nother animal. Really pretty fired up about it. Trying to gleen info to get off the steep slope of the learning curve. They have another go the end of Sept. I'll bump the tire pressure, easier to go down than up, and a pyrometer and see what happens.

Bill: The single front torsion bar adjuster only makes that spring work more or less. If it is completely off then the other spring is doing all the work of supporting the car and the ride will be softer but the car will sit lower and bottom out sooner. If the adjuster is anything less than all off the spring rate is constant (2K) and that adjuster will only control the ride height. If you adjust the ride height to the maximum were the ball joints limit the travel of the suspension and then adjust it further then you will be preloading the springs. A good thing to try is to adjust the ride height a few inches higher and see if that helps the understeer, if it is reduced then you were bottoming out.

If all your bushings, tie rods, ball joints and steering box are healthy then you might try a more aggressive wheel alignment. I have a ball joint IRS car, my settings are:

Front: Toe 1/8

Bruce,
A couple of questions about your front alignment:
1/8" toe - out
Doesn't the toe-out make your car wander or hunt? I thought toe-in was preferred.
1.7 degrees negative camber
How did you achieve that? Even with the aftermarket adjusters I can usually only get to 0 or maybe 1 degree negative.

I assume that the above is for a ball joint front end.
Link Pin front beams are even harder to achieve negative camber.
Thanks,
Greg B

Greg: Yes 1/8

Bruce, Apparently the adjuster was totally backed off as I cranked it 'quite a bit' trying to raise the front end and it didn't move much at all - but got quite a bit stiffer, like maybe the spring was unloaded. If it were bottoming out it would account for some of the understeer. Spent a lot of time under there checking things and that's only reasonable conclusion I can come up with. Anyway I'm off to get some camber adjusters with more latitude and some caster shims, realign and we'll see what happens at the next event. Don't want to introduce too many variables at one time. Sway bars this winter, retrain me how to drive and maybe we can keep 'em honest next season - I hope.

This might help: https://www.speedsterowners.com/knowledge/article.asp?id=202