Need help with rev per mile specs for goodyear eagle f1 supercar tires in 285/40/18
 

Looking for the actual rev per mile specs for Goodyear Eagle F1 Supercar tires in 285/40/18. According to Goodyear's website, they list the revs per mile specs at 775 on a measured 10" rim. However, when I checked Tire Size.com, they list the revs per mile specs at 748. At any rate, I just recently swapped my rear axle gears and I'm not really sure as to which is the correct rev per mile specs for my particular application, as my measured rim width is 9.5 inches. In the meantime, any help/feedback provided would be really appreciated.


Thanks.

I would believe Goodyear for the rev per mile. Load your tune with 775, have a passenger with GPS on their cell phone. Go 60 mph on your Mustang and see what the gps on the cell phone is showing. Then you can make adjustments. :)

Tirerack.com agrees with Goodyear - 775.

Thanks, David. I'll have a friend of mine ride along and do a test run with his GPS and see what it shows compared to the speedo at 60MPH :nice:

Update! as of 8/18/18. David, here's the latest info. I loaded the tune at 775 as recommended by Goodyear, did a test run comparison with the speedo and from a friend's GPS. The speedo read 100 mph in 5th gear at 2000 RPM whereas the GPS read 65 mph. Needless to say, the speedo was way off by 35 mph set at 775 RPM. We then reset the revs per mile at 748 as recommended by TireSize.com. After we reset it to 748 revs per mile, the speedo is now within 4-5 mph of the GPS actual readout speed at 60 mph. At any rate, it appears that TireSize.com was spot on about how Goodyear does not take into account that revs per mile are not the same when it comes to unloaded vs installed onto a vehicle when under actual load.

Just keep in mind that what Goodyear and Tire Rack doesn't mention is, their specs are based from tires mounted on an unloaded measured rim. Therefore they are not taking into consideration what the true revs per mile are when being installed on an actual vehicle that is under full load. According to Brenspeed and VMP, they go by the specs listed by TireSize.com and American Muscle also lists their rev specs identical to Brenspeed and VMP as well. Anyhow, just saying :dunno: