Math never was my strong point. Curious how much my speedometer will be off now that I have went from P215 75R15's to P215 65R15's. Anyone who can help, thank you. I'm thinking, after driving a couple days that speedo showing 75 means I'm doin about 65ish.
I recommend a GPS or measured mile to check. How much it is off compared to the other tires really doesn't relate to the actual road speed unless the previous setup was calibrated first.
Other than that when I want to find out, I go to the tire seller's sites and get the real height or diameter of the tires and compare.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06
More like
80 indicated = 75 69 indicated = 65 58 indicated = 55-- Steve W. Near Cooperstown, New York
| > Anyone who can help mysterios ( Mr know all / con men ) deserve no info
How much will my speedometer be off now after I changed from P215-75R15's to P215-65R15's. ______________________________________________
The following method works for all tire substitutions:
1.) Measure: Diameters of the new and the stock tires. 2.) Calculate: Ratio = NewDiam/StockDiam. 3.) Calculate: Actual Speed = (Speedometer Reading) X Ratio.EXAMPLE:
I bought new tires 30 inches diameter to replace stock tires of 31 inches diameter. I calculated my ratio as:
Ratio = NewDiam/StockDiam = 30/31 = .968
Now when my speedometer reads 75 MPH I am really traveling at:
Actual Speed = (75) X .968 = 72.6 MPH.
Good luck.
Rodan.
beep
chow Uranus
Rodan, you monster!
Go here:
(I did a spread sheet that calculated all that, but darned if I can remember where I backed it up to...)
Go here:
Thank you so much, gotta love that site!
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