Tire Pressure and racing?

[Skyman]

I've got a question regarding tire pressure and racing. I was told these marks were on the tires to help indicate proper pressure, and you should show cornering wear to the marks. Did some laps at Miller Motorsports Park tonight. Here are photos (bad ones) of the front and back. It would appear that the fronts should be where they should be, but the rear is not worn to the same mark. Do you run staggered pressure? I know, total noob question.

Front


Rear


Thanks.

[pebbles]

i dont know much about racing, however i am running 26 in front and 24 in back, in my cheapo noob tires.
so far so good. 28 f 26 r is next.
lower pressure creates a little more drag, which equates to more traction, right?

[Garm]

^ Only if there is enough pressure so that the tire doesn't roll over. I haven't raced the Roadster yet, so I don't know pressures. On my Yaris (FWD) I run higher pressures in the back to help the tail come around.

That second shot shows some scuffing way down the sidewall. That's from contact with the pavement, and not fender or other rubbing?
Again, I don't know Roadsters and racing yet, but that would not be acceptable on my other race car.

Next time you go out, try chalking up your tires so you can see exactly what your contact patch. It's a great trick. If you have a laser heat reader, that can help too.

[Skyman]

^ Only if there is enough pressure so that the tire doesn't roll over. I haven't raced the Roadster yet, so I don't know pressures. On my Yaris (FWD) I run higher pressures in the back to help the tail come around.

That second shot shows some scuffing way down the sidewall. That's from contact with the pavement, and not fender or other rubbing?
Again, I don't know Roadsters and racing yet, but that would not be acceptable on my other race car.

Next time you go out, try chalking up your tires so you can see exactly what your contact patch. It's a great trick. If you have a laser heat reader, that can help too.

Hmm, maybe its just a bad photo? I don"t think I have any sidewall scuffing that I can see? I was told (not by anyone reputable) that the imprinted triangle markings, with the triangle in the center indicate where you should be wearing to when hard cornering. If you are going past the marks, you have too little pressure, not to the mark, too much pressure. On the first couple of runs, the tires where at 32 PSI, I dropped them to 28 and it made a big difference. The car didn't feel like it was going to break away like it did with higher pressure. As you can see in the first photo, I was just getting to the mark at 28 PSI. Not to them at 32 PSI. I'm still trying to learn as much as I can about the racing gig. A lot more to it than just trying to drive fast. Thanks for the input.

[SLOroadster]

The fronts you can get some sense of roll over, however on the rear since there should be no camber or toe, there should be nearly 0 tire scrub. On the front you can get a better sense of whats going on. Yes, the scrub should extend over to the markers, but not at the expense of sidewall rigidity. You appear to be running Falken Azenis tires. They have horribly soft sidewalls for track use. Yes, you can use them, but you have to run them at fairly high pressures, 30-40 or so. The sidewalls mush too much when pushed hard. Take some shoe polish and dab a dot on the edge of the tire and see how much gets worn off in a session. That will give you a pretty good idea where the tire roll over is. Do both the inside and outside shoulders that way you can see the full picture.

On DOT-R compounds, I've run as low as 24 psi up front and 25 in the rear. Those were on Kuhmo V710s and the grip was amazing. It all comes down to the sidewall stiffness. For a street tire, the Dunlop Direza Sport Z1 Star spec is a pretty awesome tire, hands down the best performace tire money can buy for a 14" wheel. http://www.tirerack.com/tires/tires.jsp ... mpare1=yes" onclick="window.open(this.href);return false;

They are fast in the rain and in the dry. Heck, they are scary fast in the rain. For 15 inch wheels there are a few more options. The Dunlop is again hard to beat however the Hankook Ventus RS3 is a solid performer. I've been running a set of those on my M3 autoXing this year and have won class a few times. Those might be tough to fit on a roadster however.

Will

[Skyman]

The fronts you can get some sense of roll over, however on the rear since there should be no camber or toe, there should be nearly 0 tire scrub. On the front you can get a better sense of whats going on. Yes, the scrub should extend over to the markers, but not at the expense of sidewall rigidity. You appear to be running Falken Azenis tires. They have horribly soft sidewalls for track use. Yes, you can use them, but you have to run them at fairly high pressures, 30-40 or so. The sidewalls mush too much when pushed hard. Take some shoe polish and dab a dot on the edge of the tire and see how much gets worn off in a session. That will give you a pretty good idea where the tire roll over is. Do both the inside and outside shoulders that way you can see the full picture.

On DOT-R compounds, I've run as low as 24 psi up front and 25 in the rear. Those were on Kuhmo V710s and the grip was amazing. It all comes down to the sidewall stiffness. For a street tire, the Dunlop Direza Sport Z1 Star spec is a pretty awesome tire, hands down the best performace tire money can buy for a 14" wheel. http://www.tirerack.com/tires/tires.jsp ... mpare1=yes" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

They are fast in the rain and in the dry. Heck, they are scary fast in the rain. For 15 inch wheels there are a few more options. The Dunlop is again hard to beat however the Hankook Ventus RS3 is a solid performer. I've been running a set of those on my M3 autoXing this year and have won class a few times. Those might be tough to fit on a roadster however.

Will

Thanks, Will. I got a really good deal on the Azenis. Not really the tire of choice, but cheap on clearance. Doing the best I can to wear them out.

[SLOroadster]

I run a set of Azenis on my car on the street. I've also got lots of laps on them racing 24 hrs of lemons. They work, but the limits on them are far lower than they should be. They will however teach you to be smooth and clean if you really start pushing them. With a FWD car, I got to the point where I could push them till they went greasy and then my lap times would get faster (I can't drive fwd cars well.)

Still, work with what you have and go have fun. Next time around look into the Dunlops. The next set of street tires I buy for the roadster will be a set of those. From what I have seen, they are the best 14" tire on the market hands down. I've been blown out in the rain by people running them. I really can't say anything bad about them because I haven't seen anything bad about them. The falkens however, been there and done that, and I've failed to set a good good time ever on them.

If you are looking to play on the track, get yourself another set of wheels and pick up a set of track tires, the Toyo RA1 is a fantastic choice. They wear well, and are hard to heat cycle out. If you happen to have a spare set of 15s, go looking at the track for take off Spec Miata tires. You might be able to get a set for free if there is a tire shop at the track.

Will