Quote:
Originally Posted by Twinz
This test has two samples with the same outer diameter and the results of those two pulls fall within the "noise" of dyno pulls. My 350Z spent a good amount of time on different dynos and no two back-to-back runs ever matched....even when nothing was changed on the car between pulls.
|
315/35/20 and 275/40/20 are both 28.7 inches in diameter, so all 3 wheel/tire combos were the same in that regard. I agree that dyno precision is a concern for a test like this, but there is a pretty consistent trend on the back to back to back runs. I do wish they did the test on a car with less power.
But anyway...reducing rotational mass has more of an effect on acceleration than total vehicle mass and that has been both measured and calculated numerous times by a variety of sources. There are some crap experiments out there, but here's a decent one:
http://www.focusst.org/forum/attachm...wheel-test.pdf
The performance differences in that test are much higher than I'd expect honestly, though not unreasonable.
The physics behind reducing rotational mass and unsprung weight also make sense.
Whether a couple of lbs is noticeable to everyone on the way to the grocery store is a different question. My winter wheel/tire set-up is about 5 lbs lighter per corner with a very slight increase in diameter. It is noticeable for me. Everyone's butt dyno is a little different. Overall diameter (gearing), tire compound, wheel strength, and driver skill may have more of a difference when looking at laptimes/feel/driverconfidence.
- Andrew