est8esq

… not really seeing it from straight line acceleration?

Deacon and I were having fun several times over (notice in the vid as he blows my doors off coming out of turn 16) throughout various sessions between PBOC Winterfest and PCA 48 Hour.

He's running completely stock, 20" OEM's and I'm running Forgeline's 19" wheels.

Having taken on and off my wheels probably two dozen times or more at this point, there is a significant weight difference and weight saving w/ the 19's. BUT, surprisingly, I'm not seeing much if any speed gains on straight acceleration?

IMO, it's not to say that it's not worth getting into 19's, though. Again, I feel one has way more choices for tires and there's no question proper tires make all the difference.

Sloopy

Are you sure they weight less. While rim are less tires are heavier so wondering if you really save any weight?

Mech33

Tire plus wheel weight reduction has very minimal impact on acceleration. If you crunch the numbers, you'll see that reducing wheel weight by X pounds gives you a maximum possible acceleration benefit equal to reducing the car weight by 2X pounds (contrary to popular belief of other multiples). 2X assumes all of the mass reduction happens at the outer wheel radius for the maximum effect.

So reducing 5 pounds per wheel / tire combo (20 pounds total) would feel like reducing the car by 40 pounds at best. Not nothing, but not huge.

AudiOn19s

Video starts after you are through 16 and on the run to 17. But based on the same results in 17 on that vid the difference has nothing to do with equipment and everything to do with line and his ability to get back to the gas much earlier than you.

Shahano

Don't forget that with a larger contact patch (20in), there is more grip in mid corner, therefore even though you might save a little bit of weight on the acceleration, its likely that he will have higher midcorner speed if you have the same tire grip.

Zulu Alpha

True dat!

ExMB

There was no comment on the tire sizes used. Tires have the contact patch, not the wheels. You appear to be mistaken wheel diameter for contact patch.

mlpor

FWIW Shahano, I don't believe tire or rim diameter, or even rim or tire width have much to do with contact patch size / area -
they, width & diameter, will affect patch shape, but size (area) is largely a function of (a) weight and (b) tire pressure "." full stop etc.

NateOZ

Biggest benefit from unsprung weight comes in the form of improved handling and less work required by the suspension to keep the contact patch on the ground. Less work also gives you a greater range in which it can operate.

Acceleration and braking benefits are very slight (tough to notice unless under controlled conditions), unless it's an area where the suspension benefits kick in.