What tire pressures do you run? (street)

[blue2000s]

Originally Posted by Boxtaboy

That's only 99%. What's the last 1%?...hot air?

See my post above. Ar, CO2, water.

[thstone]

Originally Posted by Dale_K

Thanks for the replies. I tried 35 all the way around but the car rode too rough over cracked pavement. What I'm trying to understand is how the front/rear bias changes understeer. I always thought a low front tire pressure was kind of a bandaid to create understeer because the car companies felt that was best for their customers. Probably they arre right, too. I think Corvairs had unbelievable tire pressures - something like 15 psi on the front and 26 on the rear.

When I bought my car a year ago I was impressed with the neutral steering and when I checked the tire pressures, the previous owner had a reverse bias with roughly 35/29. I would have kept it that way but one of the fronts was cupped and so I bought new fronts only. Unfortunately I picked a "grand touring" tire instead of a sports car tire. I'm pretty sure that is the root of my handling issues. I test drove a newish Miata and it steered ten times as good as my Boxster. The new rear tires I just put on are the same brand (Kumho) but they are more of a sports car tire. I think I need to get something better for the front.

Dale - exactly which make/model and size of tires do you have front/rear?

Increasing the front tire width ~20mm beyond stock is a common approach to reducing the interrent understeer in a Boxster. If you are still running the stock tire widths front and rear, then no amount of tire pressure adjustment is likely to fully or completely address the issue.

Addititionally, a mis-match of tires from front to rear (stickier tires in rear and not so sticky tires in front) could also exacerbate the understeer problem beyond the ability of any tire pressure adjustment to address.

Let us know what tires you have installed so we can help pinpoint a good solution.

[Dale_K]

Tires are stock size 18's for a 2000 S. Kuhmo's front & rear but different types. Fronts are Ecsta LS Platinum and rears are Ecsta LE Sport. I think the fronts are killing my steering response.

[Topless]

Originally Posted by Dale_K

Tires are stock size 18's for a 2000 S. Kuhmo's front & rear but different types. Fronts are Ecsta LS Platinum and rears are Ecsta LE Sport. I think the fronts are killing my steering response.

Oh my, two completely different classes of tires. No amount of fiddling with tire pressures can fix this. I would lose those Platinums pronto and put LE Sport 225/40/18s on the front. It will transform your car.

[vath2001]

Originally Posted by Boxtaboy

That's only 99%. What's the last 1%?...hot air?

Vaporized Tiger's Blood..... Winning

[blue2000s]

Originally Posted by Dale_K

Tires are stock size 18's for a 2000 S. Kuhmo's front & rear but different types. Fronts are Ecsta LS Platinum and rears are Ecsta LE Sport. I think the fronts are killing my steering response.

I think we've found your problem.

[Overdrive]

Looks like that's the culprit. It's like only putting snow tires on the driving wheels, they'll grip while the other two slip. The same would happen even on dry pavement with two different types of tire.

[thstone]

Yep! Well beyond the range of a tire pressure adjustment.