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Old 02-08-2011, 09:51 PM   #21 (permalink)
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d0sitmatr -

Thanks. This is egg-zactly the kind of feedback I was looking for. I guess it's the law of (quickly) diminishing returns. It makes me feel I was lucky to stick to one-size-up from stock, which added about 1 lb per tire. Two-size-up from stock always added at about 3+ lbs per tire.

I would guess that if you bumped-up the tires and decreased the weight of the wheels by the same amount, then you would be able to negate the flywheel-effect.

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Old 02-09-2011, 01:17 AM   #22 (permalink)
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Wouldn't it depend on what type of driving is done most? For speeds less than say 40 mph a larger tire hurts mpg d/t increased rr. For averaged speeds over 40 mph a larger tire should help r/t the lower engine rpm.
See you're in St. Louis and have an '02 GP. Is it the 3.8L with or without the supercharger? Perhaps 'aero' rims might be a better way to go?
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Old 02-09-2011, 01:28 AM   #23 (permalink)
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Been wanting to put on taller tires on my '83 RX-7. It's nearly impossible to find rims that fit the odd bolt pattern. Even better would be better gears, but same problem about locating them. Has the original rotary with 83k miles. Runs 4k rpm (7k redline) on the interstate on 13' tires.
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Old 02-09-2011, 06:27 AM   #24 (permalink)
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Quote:
Originally Posted by abell75 View Post
I wasn't thinking aero, i was thinking RR/contact patch geometry. Maybe my assumption that narrow tires have better RR is incorrect....I'm fairly new around these parts
According to the Smithers Report:

Barry's Tire Tech

Bigger is better for RR - and that also includes wider.
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Old 02-09-2011, 08:22 AM   #25 (permalink)
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CapriRacer, thanks for getting my head screwed on straight. Now that I think about it more, since the contact patch needs to be the same size for a given load & pressure, a wider tire will have less sidewall deformation. The patch area is WxL; if W is more then L must be less. And I suppose less deformation results in lower RR.

Well written article BTW
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Old 02-09-2011, 10:07 AM   #26 (permalink)
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no problem, but I had to go back and edit some of my numbers, I went through some of my logs and my numbers were off some (that dam memory just not as good as it was 5 yrs ago...)
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Old 02-09-2011, 10:28 AM   #27 (permalink)
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Quote:
Originally Posted by abell75 View Post
............Now that I think about it more, since the contact patch needs to be the same size for a given load & pressure.....
I think there may be data to refute this.

Quote:
Originally Posted by abell75 View Post
............ a wider tire will have less sidewall deformation. The patch area is WxL; if W is more then L must be less. And I suppose less deformation results in lower RR......
But I think the issue of less deflection due to the larger load carrying capacity is true, but I think the size of the fottprint is not connected in a way that can be used in any quanitative way.

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............Well written article BTW
Thanks


Last edited by cfg83; 02-09-2011 at 02:31 PM.. Reason: fix quote
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