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Discussion Starter #1
Do I give up a lot of handling/grip with a 16"x8" wheel versus a 17"x8" autocrossing?
 

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Discussion Starter #3
My limited understanding was that diameter helps lateral acceleration(?) to a certain point. Past that, diminishing returns and unsprung weight of big wheels makes them a detriment. I do agree that contact patch size matters most for traction overall. I guess what I was wondering was do higher skidpad numbers translate to better handling cars? If yes, how? Also, are there better tires available for 17" versus 16" wheels? Thanks!
 

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I have 16x8 wheels with 225 50 16 tires and the car handles great with the lower aspect ratio compared to stock. You will also have less unsprung weight with a 16x8 wheel than a 17x8 wheel. Also 16" tires are less expensive than 17". If you want to keep stock outside wheel diameter, then you're better off going with 17" rims and the correct tires. Brake size will also dictate what rims you will need to use. You can still get some very good tires in 16" size! I'm running Firestone Firehawk SZ50.
 

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plus, a 16-inch wheel will in essence give you better gearing! :joy:
 

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markfhp said:
plus, a 16-inch wheel will in essence give you better gearing! :joy:
why would a 16" wheel result in better gearing. If the overall tire diameter stays the same then the gearing won't change.
 

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ND4SPDLSC said:
My limited understanding was that diameter helps lateral acceleration(?) to a certain point.

Diameter of the wheel or the tire? If you increase wheel diameter but keep tire diameter constant (by using a lower profile tire), that seems to test out. Probably due to stiffer sidewalls.

FYI, Dave Schotz ran 16" tires on the back of his National Solo2 winning Cobra R on the theory the taller sidewall would increase forward bite out of the corners.

If you increase diameter of the tire you raise the cg. How would that be good?

Tire cost and availability matter a lot more for sedans (don't F-1 cars use 13" wheels?).
 

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The 17" rims and lower profile tires should increase the "grip" of the car due to the stiffer sidewall but the improvement over a 16" rim/tire combo can be easily outweighed by the tire choice and suspension set up. There was an article in either "Road and Track" or "Car and Driver" a few years back that compared the same tire model on 15" through 18" rims on a street car and they found that the improvements to lateral grip maxed out at 17" rim/tire combo. Of course the type of surface you are driving on and the suspension set up also are part of the equation of maximizing grip. If the surface is extemely smooth then the stiffer the better (tire, springs, shocks). On a rougher surface a more compliant set up may result in better grip. Which is why the above mention test (based on real world conditions) probably did not show any improvement with the 18" combo.
 

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why would a 16" wheel result in better gearing. If the overall tire diameter stays the same then the gearing won't change.
sorry ... i'm so focused on the competition aspect of this forum, i guess i'm assuming the available competition tires for an 8-inch rim. in which case, it WOULDN'T be the same diameter ...

take the victoracers:

245/45-16: 24.3"
245/45-17: 25.3"
255/40-17: 24.8"
 

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markfhp said:
sorry ... i'm so focused on the competition aspect of this forum, i guess i'm assuming the available competition tires for an 8-inch rim. in which case, it WOULDN'T be the same diameter ...

take the victoracers:

245/45-16: 24.3"
245/45-17: 25.3"
255/40-17: 24.8"
Ok, I was just assuming if you went with a 17" wheel you would try to get the overall diameter the same. As ussual there's some real world limiting factor on that.
 

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Discussion Starter #11
Thanks for the opinions. I was just curious about how much the wheel diameter matters overall in handling. I'm starting out autocrossing and I was just wondering which wheels to use.
 
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