Took 20's off today to feel diff
#1
Took 20's off today to feel diff
SO today I realized it was nice and i took my 20's off for the winter and put my stock 17s back on , figured i would feel a hell of a difference since the rim is lighter and less wheel rotation, but it honestly felt slower, i dont know why, is it just me?
#4
diablo's manual is totally wrong they say do 20168 divided by your tire diamater that is incredibly wrong, with my 20s the tire revs were at 715 so i figure 17s are at somewhere like 840
#8
Just so you know, that 20168 isn't really accurate for determining the wheel revs per mile for "rubber" pneumatic tires, though it would be correct for something like a free-rolling steel railroad car wheel.
There is about a 3.5% factor that accounts for the tire tread compressing as it contacts the ground that Diablo is ignoring. This is a number based on tire tests, not something that can be determined mathematically. It is not the same as calculating based on the tire's loaded radius either. For most tires, 3.5% is a good number, though some of the Nittos appear to run closer to a 3.0% correction.
Where the Diablo manual tells you to do 20168 ÷ 29 = 695, the 3.5% correction gives you almost 720 (which should be in much closer agreement with the Specs pages at the Tire Rack).
Best to look up the tire specs for your make and model tire, and use those numbers directly (or as close as possible, maybe rounding up to the higher increment of 5 rather than down to account for gradual tire wear).
Next best (and should be close enough most of the time) is to bump up the Diablo math by 3.5%.
Whiteflash - you're running Nitto NT555's in 255/45-20? (at least those Nittos seem to run with a slightly lower 3.0% correction.) BTW, I agree with Tex that you should have felt the difference. Maybe try checking the moderate driving part throttle response instead of WOT just to keep wheelspin possibilities out of it.
Norm
Last edited by Norm Peterson; 10-28-2008 at 10:07 AM.
#9
Blast, beaten!