jeffburch Posted September 25, 2008 Share Posted September 25, 2008 I'm looking at 16 x 255's side by side. Mounted on same wheels. RA1 is 10.25 sidewall to sidewall. R888 is 10.5" jb Quote Link to comment Share on other sites More sharing options...
ST#97 Posted September 25, 2008 Share Posted September 25, 2008 Yes, he said both sets of tires were mounted on the same size rim. I presume a 17x9.5 but I don't know that for sure. But it really only matters what the width is when the tire is mounted to a wheel doesn't it? Or have you figured out a way to run the tires without them? Sure, but I can't run a 275 R888 on my existing complement of 9" wheels without hitting my coil over...(haven't actually mounted them to verify) So I have two choices, run a spacer that puts me at 74.25" track width on a tire/wheel combo with a loosey goosey sidewall (pinched 3/4" more than RA1) Or buy all new 9.5" wheels to properly mount a wider cased tire and clear the suspension... I don't own any 9.5" wheels so I can determine what that offset/spacer needs to be with the R888's... nor do I have the R888's anymore.... However, a local instructor ran 275 R888's on his regular 9" rims and the sidewalls were pinched terribly and he complained the car walked around and squirmed a lot. Now installing an R888 and an RA1 on the same 9.0" rim, MIGHT result in the same width, but I would hardly call it ideal and it probably negates the increased performance we should be seeing from this improved tire... It would be awesome if someone can get their hands on a shaved set of 255's and take the same dimensions I posted for the 275's for comparison. I think that may be my route for 09 so I don't have to buy wheels right now. Quote Link to comment Share on other sites More sharing options...
King Matt Posted September 25, 2008 Share Posted September 25, 2008 (haven't actually mounted them to verify) So this could all be moot. If you are attempting to measure the section width of the tire without it being mounted on a wheel, that's a bogus number, because section width is only measured with the tire mounted on a specific width rim. BTW, was your instructor guy running the R888 unshaved? The new tires are molded at 6/32, so if they are run full-tread, I would expect them to feel very different than if they were shaved even to 4/32 like the RA-1s are often shaved to for dry use. Quote Link to comment Share on other sites More sharing options...
robbodleimages Posted September 25, 2008 Share Posted September 25, 2008 They may appear wider because of the difference in tread pattern, but one of the CMC directors says he stacked four mounted 275 RA1s against four 275 R888s and the stacks measured the same height. He said the tread width of both was the same as well. It should be simple enough to figure this out once more people actually have tires in hand rather than speculating. The R888 is definately wider than the RA1. I can see it with the eye, but I will offer a different example. Mounted on R58's I can pack 6 RA1's left to right in the bed of my F250. I can only pack 5 R888's. The tires are wider. As to the rules question beyond that, with the economy the way it is and the danger of losing entries already significant, adoption of any rule that increases costs to racers is suicide. Period. Quote Link to comment Share on other sites More sharing options...
King Matt Posted September 25, 2008 Share Posted September 25, 2008 How about busting out a tape measure and getting us some real numbers. Quote Link to comment Share on other sites More sharing options...
robbodleimages Posted September 25, 2008 Share Posted September 25, 2008 I will pick the car up on Monday and do that. Quote Link to comment Share on other sites More sharing options...
Red Tornado Posted September 27, 2008 Share Posted September 27, 2008 I will likely go to 18x9.5 in the front now to avoid rubbing coilover also. Now wish I went with huge calipers in front since I will be going to 18's. Quote Link to comment Share on other sites More sharing options...
robbodleimages Posted September 27, 2008 Share Posted September 27, 2008 Chris, I am using a 14" GT Brembo kit. I am not sure that I am out braking anyone with a good 13" kit. I am getting VASTLY better brake wear and no fall off in thru a three hour race. It could be that the 13" kits stop the car as and the larger are just better for longer use. Quote Link to comment Share on other sites More sharing options...
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