How much tread do you need?

[holmberg]

How much tread does a P2 need?

I see people running tires with 8" of tread on the front and 9.8" on the rear, or a total of 35.6". A set of these bias-ply slicks (Hoosier 43314 & 43167) goes for $1442.

On the other hand, I see FC and F1000 running 6.75" and 8" of tread, a total of 29.5" (17% less) for $862 (Hoosier 43285 & 43164).

If I have a P2 car that weighs 986 lbs with a driver, and an FC at 1210 lbs is doing fine with these tires, is there any point in paying an additional $580 for 6" more tread?

In other words, if they work for a light-weight F1000, why wouldn't they work with a lightweight P2? Can my little car even get the larger tires up to temp?

What is the advantage of the 8/10 set over the 7/8 set? And is it worth the money?

Greg

[S Lathrop]

What width wheels do you have.

While F1000 is allowed 8 in. front and 10 in rear wheels, they run 7 and 9 inch wheels because that is the maximum rim width for the tires.

The 1 in wider rims work with the F2000 tires but those tires will not work on 8 and 10 inch wheels.

[holmberg]

Steve, I have 6's, 8's, and 10's. But I would be willing to sell those and buy 7's and 9's.

[S Lathrop]

Steve, I have 6's, 8's, and 10's. But I would be willing to sell those and buy 7's and 9's.

The wheel recommendations came from Bruce Foss of Hoosier Tires. He gave me the advise when we were building our first F1000.

You have the same problem that I ran into with the first Citation F1000 car. The tires for 8 and 10 inch rims are for car that weigh 1500 pounds or there about. Like your car, a F1000 is light, compared to a FC.

As a comparison, at turn 1, Road Atlanta, our F1000 was 15 mph faster at mid corner than a Citation F2000.same tires.

Do you have any idea how much down force you are generating?

[David Ferguson]

I successfully ran at the front of the P2 field using 6 & 8" wheels (like an FC), because that's what fit my previously Sports 2000 chassis. You will be fine running the FC tires. If you get to the point where you need more grip, then spend the money on wider tires. I would not discard your 10" rims just yet...

[holmberg]

Do you have any idea how much down force you are generating?

I don't know. It's a 1994 A-Mac AM-6. I just bought it, I don't even have it here yet.

I imagine it's less down-force than a F1000. The front is just a splitter, I don't think it develops much, if any, down-force. It's got a full-width single-plane rear wing, but that's all I know about it. Flat bottom, no diffuser.

I estimate it will weigh 986 with me in it. It's got a 2010 Kawasaki ZX-10R engine, "stock" by George Dean. I don't have a dyno sheet, but I'm thinking maybe close to 200 HP, 85 ft-lbs. It's an incredible power-to-weight ratio--close to P1. But I think it won't be as fast in the corners as an F1000. Lap times for these cars appear to be close to FC times.

Greg

[924RACR]

I ran 7's and 9's for quite some time on my P2, worked fairly well. Then I bumped to 8's up front, and 10's in the rear... etc etc...

[holmberg]

I ran 7's and 9's for quite some time on my P2, worked fairly well. Then I bumped to 8's up front, and 10's in the rear... etc etc...

Did you find an advantage with the 8's and 10's? I assume wider tires to go with that. I guess a lot depends on how heavy your car is and how much down-force it generates.

Greg

[924RACR]

Well, I haven't gone back...

That said, my point is more that you should just get out there with what you have and get seat time. Until you're heavily into that, it won't matter. There's plenty of development to do on you car, as you've noted; wasting it on consumables or replacing functional components doesn't sound efficient.

The 8's and 10's are the tire sizes; as noted, I started with FC takeoffs.

Weight of car is 1100, on par with the Stohrs... downforce, well I don't exactly have strain gauges on my suspension...

[S Lathrop]

If you are going to stay with the 8 and 10 inch rims, consult with the tire manufacturer as to what rim width are appropriate for the tires you plan to use. A tire failure because the tire would not stay beaded on the rim could be very costly.

[holmberg]

For now, I'll just use FC tires on the 6" and 8" rims I have. If I ever get good, I might buy some 7" and 9" rims for the FC tires.

I'm not sure I see a reason to ever use the 20x7.5 and 20x9 tires on 8" and 10" rims.

Thanks everyone for the help.

Greg