Tire Diameter: 16" wheel to 18" wheel? And ride height adjustment.
11-30-2007, 02:35 AM
#16
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11-30-2007, 02:42 AM
#17
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[edited to get the math correct - after Dennis helped me out]
Now for the used Toyo Proxes RA1's that I can get at a pretty good price (shaved and heat cycled twice btw) that will spoon on my 8.5 x 18 and 10 x 18 wheels nicely for track days. Ok, now for the math to see how the diameters compare.
Fronts: 245/45 18
245 x .45 = 110.25mm = 4.34"
4.34 x 2 = 8.68"
8.68 + 18 = 26.68"
Rears: 275/45 18
275 x .45 = 123.75mm = 4.87"
4.87 x 2 = 9.74"
9.74 + 18 = 27.74"
Lets call the fronts 27" and the rears 28".
Stock vs Toyos:
Front stock = 25" vs 27" for the Toyos = 2" taller for the Toyos = raises the car approx 1".
Rear stock = 25" vs 28" for the Toyos = 3" taller for the Toyos = raises the car approx 1.5".
So, I'm looking at approx a 1" height gain in the front, and about a 1.5" gain at the rear.
Ok, I think I have the math down.
Now for the used Toyo Proxes RA1's that I can get at a pretty good price (shaved and heat cycled twice btw) that will spoon on my 8.5 x 18 and 10 x 18 wheels nicely for track days. Ok, now for the math to see how the diameters compare.
Fronts: 245/45 18
245 x .45 = 110.25mm = 4.34"
4.34 x 2 = 8.68"
8.68 + 18 = 26.68"
Rears: 275/45 18
275 x .45 = 123.75mm = 4.87"
4.87 x 2 = 9.74"
9.74 + 18 = 27.74"
Lets call the fronts 27" and the rears 28".
Stock vs Toyos:
Front stock = 25" vs 27" for the Toyos = 2" taller for the Toyos = raises the car approx 1".
Rear stock = 25" vs 28" for the Toyos = 3" taller for the Toyos = raises the car approx 1.5".
So, I'm looking at approx a 1" height gain in the front, and about a 1.5" gain at the rear.
Ok, I think I have the math down.
11-30-2007, 02:44 AM
#18
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11-30-2007, 02:46 AM
#19
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Now for the used Toyo Proxes RA1's that I can get at a pretty good price (shaved and heat cycled twice btw) that will spoon on my 8.5 x 18 and 10 x 18 wheels nicely for track days. Ok, now for the math to see how the diameters compare.
Fronts: 245/45 18
245 x .45 = 110.25mm = 4.34"
4.34 x 2 = 8.68"
8.68 + 18 = 26.68"
Rears: 275/45 18
275 x .45 = 123.75mm = 4.87"
4.87 x 2 = 9.74"
9.74 + 18 = 27.74"
Lets call the fronts 27" and the rears 28".
Stock vs Toyos:
Front stock = 23" vs 27" for the Toyos = 4" taller for the Toyos = raises the car approx 2".
Rear stock = 25" vs 28" for the Toyos = 3" taller for the Toyos = raises the car approx 1.5".
So, I'm looking at approx a 2" height gain in the front, and about a 1.5" gain at the rear.
Fronts: 245/45 18
245 x .45 = 110.25mm = 4.34"
4.34 x 2 = 8.68"
8.68 + 18 = 26.68"
Rears: 275/45 18
275 x .45 = 123.75mm = 4.87"
4.87 x 2 = 9.74"
9.74 + 18 = 27.74"
Lets call the fronts 27" and the rears 28".
Stock vs Toyos:
Front stock = 23" vs 27" for the Toyos = 4" taller for the Toyos = raises the car approx 2".
Rear stock = 25" vs 28" for the Toyos = 3" taller for the Toyos = raises the car approx 1.5".
So, I'm looking at approx a 2" height gain in the front, and about a 1.5" gain at the rear.
http://marktg.toyotires.com/file/18968.pdf
11-30-2007, 03:04 AM
#20
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Cool. Good resources here. And I'm learning a ton.
Ok, now that I have the dimensions down for reference, I can figure things out. I'll have to talk to Chuck who has the the Toyos on his '83 track car, on what his setup is . He's moving to wider tires (I think something crazy like 11" all around) and doesn't need his Toyos anymore.
Ok, now that I have the dimensions down for reference, I can figure things out. I'll have to talk to Chuck who has the the Toyos on his '83 track car, on what his setup is . He's moving to wider tires (I think something crazy like 11" all around) and doesn't need his Toyos anymore.
11-30-2007, 05:20 PM
#21
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Russ,
you should probably re read my post. It started with the word yes. if the car has a 25 inch rolling diameter, and the car is at the proper ride height, then the suspension has a very specific geometry, in regards to the suspension parts and their relationships to each other. This geometry is the desired result of the height adjustment. So, if you raise the car by 1/2 inch by going to a 26 inch rolling diameter tire if you don't change the suspension and it was adjusted before it won't need to be changed. HOWEVER if the ride height is adjusted after the new tires are on the car then the 1/2 inch gain needs to be accounted for to reach the desired suspension geometry. Please keep in mind that if you lower the car too much which you might do after larger tires are installed (suspension geometry wise) then it may not align properly.
Keep in mind that the goal of adjusting the height is to get the suspension geometry in a range that it performs best at.
you should probably re read my post. It started with the word yes. if the car has a 25 inch rolling diameter, and the car is at the proper ride height, then the suspension has a very specific geometry, in regards to the suspension parts and their relationships to each other. This geometry is the desired result of the height adjustment. So, if you raise the car by 1/2 inch by going to a 26 inch rolling diameter tire if you don't change the suspension and it was adjusted before it won't need to be changed. HOWEVER if the ride height is adjusted after the new tires are on the car then the 1/2 inch gain needs to be accounted for to reach the desired suspension geometry. Please keep in mind that if you lower the car too much which you might do after larger tires are installed (suspension geometry wise) then it may not align properly.
Keep in mind that the goal of adjusting the height is to get the suspension geometry in a range that it performs best at.
Sounds like if I end up using the larger diameter Toyos, that if I set the ride height FIRST with the factory original sized wheel/tire = 25", and THEN mount the larger Toyos, I should be good to go.
I've read its also a good idea to get an alignment right after setting the ride height. Not sure if we touched on that in this thread.
This method would also help out if I was going back and forth between the Toyo track tires/wheels, and a set of 17's that I will use for street duty.
Good deal. Again, thanks for the input everyone, its much appreciated.
Now to find some 16's. Still can't believe I gave my extra set away when I sold the '85!
11-30-2007, 06:55 PM
#22
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