stever

HK's post prompted me to take my new Dinan wheels off and measure them and do some research. I think it would be very useful if everyone with aftermarket wheels and/or various tire combinations would post dimensions. Pirelli and Dunlop post tire specs on the web but I haven't found Michelin or Bridgestone and the published tire specs often don't match reality. Instructions for measuring wheels and tires follow after my dimensions. (all offsets are positive and dimensions in inches and pounds).


M5 front - 8W .78 offset 23.2 #
Dinan f - 9W .81 offset 17 #
M5 rear -9.5W .94 offset 25.5 #
Dinan r -9.5W .97 offset 17.5 #

I'm running Dunlop 275/35-18's (original tires)on the front with the Dinan steering stop (haven't noticed lack of turning circle so far) and Michelin 285/35-18's on the rear with the forward edge of the fender rolled by Dinan. No rubbing from either end and I have to believe that Dinan has optimized the offsets to put the tire right in the middle of the available space.

245/40-18 Dunlops on M5 8in rim - 9.44 section, 48# total (Dunlop says section is 10.0in on 8.5 wheel and 24.8# for the tire)

275/35-18 Dunlops on Dinan 9in - 10.25 section, 45# total

285/35-18 Michelin on Dinan 9.5 - 11.06 section, 44# total

Conclusions:
- Dunlops are heavy and seem to have a smaller section (and probably tread) than shown in their specs or than Michelins

- M5 wheels are heavy, Dinan wheels are light

- Dinan rears have only .030 more positive offset than M5's therefore some 285/35's might fit on the rear with the fender lip rolled under

- Dinan front wheels have .125 more positive offset than M5 rears. So if the Dinan steering limiter and a .125 wheel spacer is used with an M5 rear wheel on the front and the front tire section on the 9.5 wheel is no more than 10.5 inches, then the M5 rear wheels can be used on the front. Dunlop says that their 265/35s have a 10.7 inch section on 9.5 wheels but I believe this is over -stated. If we can get some rear tire section measurements of various 275-35 18's that will probably be a good indication of how 265 sections run.

- if you're ordering two or three-piece wheels, get the next larger positive offset from the Dinan dimensions and make up the difference with a wheel spacer

Measuring wheels and tires: Put the Wheel and tire face down and measure down from a level or other straight edge placed across the back of the tire to the wheel mounting surface. Then measure from the back side of the tire to the floor for the tire section. Divide the tire section by two and subtract it from the first measurement to get the offset. If you're feeling strong, pick up the wheel and tire and stand on your bathroom scale. Subtract your weight for the weight of the wheel and tire.