cool hand luke Posted November 6, 2011 Share Posted November 6, 2011 Are there any guidelines to figure out what size tires would work best for a given set up? My car was very competitive in SCCA solo running 20 x 8 hoosiers, but I'm going to have three times as much horsepower. I have no idea how much tire I will need. Is bigger always better? Is there a point of diminishing returns? Are there rules of thumb, or is it simply a trial and error process? Quote Link to comment Share on other sites More sharing options...
brkntrxn Posted November 6, 2011 Share Posted November 6, 2011 Since you are posting in the Time Trial forum, I will state the following: "Build your car around the widest size Hoosier A6 you can have and still stay in your existing class" Period. Enough said. Feel free to quote me. Quote Link to comment Share on other sites More sharing options...
kbrew8991 Posted November 6, 2011 Share Posted November 6, 2011 which may work well for TTA 'vettes, but the jury is out on alot of other cars that are actually hard on tires. What class you're building for would help, as would the car you're starting with Quote Link to comment Share on other sites More sharing options...
jason Posted November 6, 2011 Share Posted November 6, 2011 It's TT. Tire life isn't a factor. Quote Link to comment Share on other sites More sharing options...
cool hand luke Posted November 6, 2011 Author Share Posted November 6, 2011 I'm starting with a 67 fiat 850. Well, the shell is a 67 fiat 850. it has none of the stock suspension left. The front end is an aftermarket Abarth kit replacing the insane front transverse leaf with A-arms and coil overs. The rear is trailing arms. It will have a subaru ej20 twin turbo, mated to a porsche 915 transaxle (rear engined). race weight should be about 1600-1650 lbs, I should have between 275-300 hp at the flywheel. So I'm flirting with the top end of the HP to weight ratio for TTU. Quote Link to comment Share on other sites More sharing options...
laze1 Posted November 6, 2011 Share Posted November 6, 2011 WTF Quote Link to comment Share on other sites More sharing options...
cool hand luke Posted November 6, 2011 Author Share Posted November 6, 2011 it's called Im poor, and this was cheap. The previous owner one two national titles with it as an SCAA solo car. He nuked the fiat engine and wanted to build something faster so he gave me the shell. He had posted it on the lemons racing forum and the original plan was to get a cheap VW engine, and throw it in and go lemons racing. However, I figured that it would most likely NOT go over well with the lemons crowd, and it was just to nice to do that too, so i started looking around at the cheapest way to get it up and running. The subie powerplant is cheap cheap horsepower, and the porsche transaxle was way cheaper than trying to build a VW to handle the HP, plus it has 5 speeds. It has been dubbed the FrankenFiat. Quote Link to comment Share on other sites More sharing options...
cool hand luke Posted November 6, 2011 Author Share Posted November 6, 2011 more info, it's really small wheelbase 79.8 inches 10" less than a miata, here is a link to the car running with the old setup of a fiat 850 engine and vw transaxle Quote Link to comment Share on other sites More sharing options...
Varkwso Posted November 6, 2011 Share Posted November 6, 2011 which may work well for TTA 'vettes, but the jury is out on alot of other cars that are actually hard on tires. What class you're building for would help, as would the car you're starting with Based on what I see it is universal good advice. Quote Link to comment Share on other sites More sharing options...
cool hand luke Posted November 7, 2011 Author Share Posted November 7, 2011 I can run 9.5" tires with no ballast 10.5 with an additional 100 lbs, or as wide as i can fit with another 100 lbs. This is what I'm having trouble with. Quote Link to comment Share on other sites More sharing options...
drivinhardz06 Posted November 7, 2011 Share Posted November 7, 2011 my take...on a car that light, 9.5" tire vs 10.5" tire ain't gonna matter. go 9.5" for more power Quote Link to comment Share on other sites More sharing options...
Varkwso Posted November 7, 2011 Share Posted November 7, 2011 my take...on a car that light, 9.5" tire vs 10.5" tire ain't gonna matter. go 9.5" for more power Some tracks might like a bigger tire but a lighter car with 9.5 tire would be my first choice. Quote Link to comment Share on other sites More sharing options...
cool hand luke Posted November 7, 2011 Author Share Posted November 7, 2011 good deal, The 9.5 will be easier anyway, less clearance issues. Quote Link to comment Share on other sites More sharing options...
kbrew8991 Posted November 7, 2011 Share Posted November 7, 2011 sounds like the 9.5 will be the winner Quote Link to comment Share on other sites More sharing options...
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