08KR525 Posted October 13, 2010 Report Share Posted October 13, 2010 I have been researching drag radials for my KR. I'm tired of not being able to get the car to hook up. After reading TS member KR158's comments about installing Nitto's 315/40/18 NT05Rs on his 9.5" rims, I think that might be what I'm looking for. I realize that Nitto recommends a 10.5" rim, but it is my understanding that Nittos run a little narrower than other brands. I have been unable to contact KR158 to ask him any questions. I do not want to widen my rims, but if I'm going to spend the money I want the widest tire I can fit without doing any wheel/body mods. If anybody knows about this combo I would appreciate your feedback. Thanks. Link to comment Share on other sites More sharing options...
PaulW Posted October 13, 2010 Report Share Posted October 13, 2010 Will you be mounting the tires on the stock KR rims and has your KR stock suspension height been lowered at all? I don't have this combo but from my reading on this and other forums, I think your only challenge will be with the outside edge of the tire and the outside fender lip. I don't recall the backspacing of the stock KR rims so you'll need to check. A 315 would be 30mm wider than the stock 285 (with some slight variances by manufacturer). That would put the tire sidewall 15mm out on each side but there are some other variables to consider. Some tires have a more squared off edge where the sidewall meets the tread (the shoulder). So two tires may have a maximum width of 315 at the sidewalls (where maximum width is measured) but the tread width may be different. Also, squeezing a 315 onto a 9.5 inch wide wheel (no comment from me on whether that is prudent or not) will "pinch" the bead in more so the overall width of a 315 tire on an 11 inch wide wheel will be slightly wider than a 315 tire on a 9.5 in wide wheel. My personal experience is that for every inch in increased width of the tire you loose 1/8 of an inch when you pinch it onto a wheel that is one inch narrower than the wheel it was measured on. For example, if the manufacturer measured their 315 tire on an 11 inch wide wheel and you mount that same tire on a wheel that is 10 inches wide, the overall width would be about 1/8 of an inch less (again this is from my personal experience and not exact as I was using a 45 series aspect ratio tire). So, your 315 tire should stick out about 12mm further than your stock tire on both the inside and the outside of the rim (12mm is just a hair less than 1/2 inch) when mounted on your 9.5 inch wide wheel. With me so far? Now, comes the hard part. Its not as simple as just eyeballing it to see if you have an extra 1/2 inch of clearance on each side of your current tires. To be sure you would need to remove the shock and spring from both sides of the rear and then move the suspension (with the wheel and tire on it) in its full range of motion to see if you have the clearance. The track bar will shift the axle from side to side as the suspension moves up and down and you'll want to be sure you maintain enough clearance to accomodate bumps and sidewall distortions etc. Another good way is using a tool like the Wheelrite Wheel and Tire simulator, but its not perfect either and you'll want to be sure you still have some margin for error. I was able to squeeze a 285 35 18 on the rear of my 69 Mach 1 but I did a lot of measuring first and ordered wheels with a custom backspacing (6 inches IIRC) and was able to fit them without rolling the fender edges or installing mini tubs. I have a watts link in it so I can precisely locate the rear axle and it will not move from side to side as the suspension moves up and down. Hope that helps. Link to comment Share on other sites More sharing options...
08KR525 Posted October 13, 2010 Author Report Share Posted October 13, 2010 PaulW. That is really great info. Yes, I will not be modifying my wheels, as I don't want to do anything to the car where I can't easily return it to stock. As for the suspension, the left tire "sits" out to the outside of the body approximately 1/4" more than the right, so an adjustable panard bar may be required. Link to comment Share on other sites More sharing options...
KR158 Posted October 13, 2010 Report Share Posted October 13, 2010 I had great luck on the stock height suspension and stock wheels. I did have the same issue you have with the left sticking out more and the right side staying flush with the fender. For the price diff on the 285 vs the 315 I just went 315. I had no rubbing issues at all and feel I could have dropped the rear a good .5 of an inch and been ok. Link to comment Share on other sites More sharing options...
08KR525 Posted October 13, 2010 Author Report Share Posted October 13, 2010 Thanks, KR158. I tried to pm you but couldn't get it to send. I'd like to know why you ended up switching this setup for different wheels and tires? Link to comment Share on other sites More sharing options...
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