Infidel Edition
03-31-2013, 05:26 PM
While at the pick'n pull I found an xj that just rolled in to the donor yard.
It had 215 75r15 and I still have the stock 215 70r15 (I know...) and they were in good shape vs. mine are still bald (remember I've only had the xj for 3 weeks and have other things that are in great or need...). & they wanted $100.
The math works out to 1" taller (.87 +/-) and that comes from the tread width ~ is 1" narrower.
That equates to 3% further per rotation...
... yes, my odometer will be off by 3%. & it will require # more torque off the line.
But the thinner tread is less resistance and the energy to maintain the highway speeds should remain the same.
So everything else being equal, I should net a 3% gain in MPG.
Right?
....... granted my previous best average was 26 and a 3% gain on that is only gonna be like 26.6 or something. But over a tank of gas, that's like an extra $5 in gas.
It had 215 75r15 and I still have the stock 215 70r15 (I know...) and they were in good shape vs. mine are still bald (remember I've only had the xj for 3 weeks and have other things that are in great or need...). & they wanted $100.
The math works out to 1" taller (.87 +/-) and that comes from the tread width ~ is 1" narrower.
That equates to 3% further per rotation...
... yes, my odometer will be off by 3%. & it will require # more torque off the line.
But the thinner tread is less resistance and the energy to maintain the highway speeds should remain the same.
So everything else being equal, I should net a 3% gain in MPG.
Right?
....... granted my previous best average was 26 and a 3% gain on that is only gonna be like 26.6 or something. But over a tank of gas, that's like an extra $5 in gas.