Quote:
Originally Posted by Racecomp Engineering
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 |
Rolling resistance of the tires are also a factor, it's how low rolling resistance tires help the car achieve better fuel economy after all. In the end, there is no doubting that lighter wheels affect acceleration. I recall there was a guy racing an 86 on 16 inch wheels when the rest of the field was on 17 inch wheels and other drivers simply couldn't keep up with him on the power centric courses. I recall the rules were changed to define allowable wheel sizes in his series when it was apparent there was an unfair advantage.