Tire size / dimensions and choices

[Blair Robertshaw]

I have been reading that some of the F1000's run 6" and 8"s and 8"s and 10" and more recently was told that 7"s and 9"s are the tire to run.

if a person was running Hoosiers what would the experienced successful teams run?

and if running Goodyears, what would the experienced successful teams run?

and can you run a 7" and 9" tire on Jongbloed wheels that normally run 6" and 8" tires?

Thanks for any and all input.

[S Lathrop]

I have been reading that some of the F1000's run 6" and 8"s and 8"s and 10" and more recently was told that 7"s and 9"s are the tire to run.

if a person was running Hoosiers what would the experienced successful teams run?

and if running Goodyears, what would the experienced successful teams run?

and can you run a 7" and 9" tire on Jongbloed wheels that normally run 6" and 8" tires?

Thanks for any and all input.

The guys with 6" and 8" wheels are just using FC wheels and tires. I don't think that this is enough for the extra performance of the FB.

The class allows for 8" and 10" wheels but the tires available for those wheels are designed for cars that weigh 200 lbs. to 400 lbs. more than an FB.

The 7" and 9" wheels allow FBs to run FC rubber but increase the capability of the tires to the level required by FB. This was the recommendation of Bruce Foss at Hoosier when FBs were first hitting the track. I don't see any reason to second guess Bruce.

The FB is an odd creature. It is not a souped up FC, but is in a class of its own. At some tracks, the mid corner speed for an FB will be 20 mph more than an FC. The straight line speed is greater than an FA and the car can generate lateral acceleration numbers 1G greater than an FC. A lot of this performance is due to the 17% less mass a HP to weight ratio of an FA.

[Ivinsea]

My brother and I have been running 8" and 10" GY 160's on 8" and 10" Jongbloeds on our Stohrs. Stohr and GY said we can use 7" and 9" tires on these 8" and 10" wheels although I believe it is not ideal. We are going to try out the narrower tires in June at the NJMP SCCA National.

7" and 9" tires are required by Jon Lewis's F1000 pro series.

[openwheeler37]

The Speads car i'm running came with 8 and 10 rims but with 7 and 8 tires mounted on them. I am currently running that set up and it seems to work well. Will be trying 8 and 10 tires in few weeks at the next race. I have only used Hoosier tires so far.

[Blair Robertshaw]

Thanks everyone for your replies. Please keep your results coming. we will try a set of 7 and 9's on a set of 6 and 8's Jongbloeds and advise our findings

[cparsons]

If one were to use 7 and 9 inch tires and the wheel choices were 6, 8, and 10 inches, wouldn't it be better to put the tire on the larger wheel, ie 7" tire on 8" wheel rather than on 6" wheel, and 9" tire on 10" wheel rather than 8" wheel? I'm thinking the sidewall would be a bit stiffer on the wider wheel, and a bit softer on the narrower wheel. I may have just answered my own question...but i would still like some feedback because my thinking has often been wrong!

[R. Pare]

Yes, the tire will stiffen up on wider wheels.

[crowe motorsports]

I ran my Van Diemen F1000 at the double at VIR last month on 8/10 with 7/9 tires and then ran the double at MO two weeks ago and ran a few sessions on the 8/10 tires from VIR and then 6/8 with 7/9 tires for the remainder of the weekend. I can tell you the tires wear so much nicer on the bigger rims and I worked with cambers at MO to get the tires to wear more consistently across the tire and the 6/8 just never replicated what the tire looked like on 8/10.

I thing the only reason you might want smaller wheels is if you think reduced aero drag and weight are critical for you to find the last tenth of a second. I personally like the 8/10 package.

Michael