17 X 9 Front and 18 X 10.5 rear, handling effects?
12-03-2003, 01:41 PM
#5
The big deal with the different sized wheels and tires for the F-Body is that supposedly the ABS and Traction Control are not designed for the use the different overall diameters on the tires.
So you have to carefully choose the right tire combination so that the OD is close to the same. The OD of the tires on the Vette are different and the computer is calibrated for that.
In my honest opinion I do not like the looks of the 17" 18" combo on the F-body since the front sidewall will be noticably taller than the rear side wall.
As for wheel offsets they should be between 38 mm and 50 mm.
So you have to carefully choose the right tire combination so that the OD is close to the same. The OD of the tires on the Vette are different and the computer is calibrated for that.
In my honest opinion I do not like the looks of the 17" 18" combo on the F-body since the front sidewall will be noticably taller than the rear side wall.
As for wheel offsets they should be between 38 mm and 50 mm.
12-04-2003, 02:43 PM
#6
Staging Lane
Join Date: Nov 2003
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With a little geometry you can calculate the overall diameter of the wheel and come very close to the original diameter of the 245 16s.
I changed to 275 18's and my overall circumference is very close to the 245 16's.
245 16 OD:
16"wheel * 25.4(mm/in)=406.4mm = Wheel height.
245*50%(Aspect ratio)= 122.5 *2(sidewalls)=245mm
So Total overall height of wheel/tire is 406.4+245= 651.4mm diameter
Wheel height 18" wheel* 25.4(mm/in)=457.2mm= Wheel height
Tire sidewall height 275*35(Aspect ratio)=96.25*2(sidewalls)=192.5
Total height = 457.2+192.5=649.7mm
16" 651.4 versus the 18" 649.7
Pretty close. But the circumference is what will give you the most accurate number.
Circumference = 2x Pi x radius. or Pi x diameter
3.14 x diameter = [16"] 2045.3mm or 2040.1(rounded)mm
That's a difference of barely 5mm. or about 1/5th of an inch. for the entire circumference.
Please y'all correct me if I've made a mistake. Do the math right and see if you can get a tire that will fit the 10.5 rim without changing overall diameter too much. What you're looking for is the right size aspect ratio; to see if a tire is made in that aspect ratio.
The other consequence from larger(as in wider) rear tires is that you will have more grip at the rear, adding to understeer. You can, however, tune some or all of it out in the suspension. But it's part of the big picture to consider.
I changed to 275 18's and my overall circumference is very close to the 245 16's.
245 16 OD:
16"wheel * 25.4(mm/in)=406.4mm = Wheel height.
245*50%(Aspect ratio)= 122.5 *2(sidewalls)=245mm
So Total overall height of wheel/tire is 406.4+245= 651.4mm diameter
Wheel height 18" wheel* 25.4(mm/in)=457.2mm= Wheel height
Tire sidewall height 275*35(Aspect ratio)=96.25*2(sidewalls)=192.5
Total height = 457.2+192.5=649.7mm
16" 651.4 versus the 18" 649.7
Pretty close. But the circumference is what will give you the most accurate number.
Circumference = 2x Pi x radius. or Pi x diameter
3.14 x diameter = [16"] 2045.3mm or 2040.1(rounded)mm
That's a difference of barely 5mm. or about 1/5th of an inch. for the entire circumference.
Please y'all correct me if I've made a mistake. Do the math right and see if you can get a tire that will fit the 10.5 rim without changing overall diameter too much. What you're looking for is the right size aspect ratio; to see if a tire is made in that aspect ratio.
The other consequence from larger(as in wider) rear tires is that you will have more grip at the rear, adding to understeer. You can, however, tune some or all of it out in the suspension. But it's part of the big picture to consider.
