Wheel Weights
10-07-2011, 02:30 PM
#2
Nordschleife Master
Besides weight, you need the moment of inertia. And then there's the tires.
I was at the track not too long ago. I was running 18" Cayman S wheels with Hoosier and moving pretty good. I mounted up some 16" flat dish S4 wheels with Toyos and the speed on the straight went up a lot. I wish I had hard numbers but the shift point to 5th moved back hundreds of feet. Now there are other issues here (narrower tires are lighter. Was there a change in diameter and hence torque arm.) but it really surprised me.
Thanks for the link. Real Porsche wheels tend to be forged and light. Aftermarket wheels, including replicas, tend to be cast and heavy.
I was at the track not too long ago. I was running 18" Cayman S wheels with Hoosier and moving pretty good. I mounted up some 16" flat dish S4 wheels with Toyos and the speed on the straight went up a lot. I wish I had hard numbers but the shift point to 5th moved back hundreds of feet. Now there are other issues here (narrower tires are lighter. Was there a change in diameter and hence torque arm.) but it really surprised me.
Thanks for the link. Real Porsche wheels tend to be forged and light. Aftermarket wheels, including replicas, tend to be cast and heavy.
10-07-2011, 03:09 PM
#3
928 Collector
Rennlist Member
Rennlist Member
Thread Starter
Rolling radius
Maybe your indicated speed went up Glen? Remember those 18's at speed would cause your speedometer to indicate a far lower speed than the 16's. Yes yes I did see about your shift points
Maybe your indicated speed went up Glen? Remember those 18's at speed would cause your speedometer to indicate a far lower speed than the 16's. Yes yes I did see about your shift points
10-08-2011, 01:21 AM
#4
Rennlist Member
Road and Track has a wheel/tire comparison between 15/16/17/18/19 inch wheels. Each increasing wheel size increased weight. The 0-60 times went up .1 seconds for each larger wheel size with the exception of going from 17 to 18. Same with braking distance. They attributed the 17 to 18 lack of change as they could not get an 18 inch tire to match the lower performance of the tires for the smaller rims. As the wheels and tires got wider with the larger diameter wheels the cornering Gs went up.
So yes, you can accelerate faster on smaller rims because they are lighter.
But, from the data provided by the comparison the performance you lose in acceleration and deceleration with larger rims you gain in cornering speed. So the best choice would be dependent on the track and the ratio of turns and straights. The other consideration is tire manufacturers are focusing their highest performance tires on larger rim sizes and do not offer them for the smaller sizes.
So yes, you can accelerate faster on smaller rims because they are lighter.
But, from the data provided by the comparison the performance you lose in acceleration and deceleration with larger rims you gain in cornering speed. So the best choice would be dependent on the track and the ratio of turns and straights. The other consideration is tire manufacturers are focusing their highest performance tires on larger rim sizes and do not offer them for the smaller sizes.
