9.4 mpg with 37s and Gobi rack - whats wrong

[Kerr]

your mph and mileage are off.

Lets say you went from stock 35's bfg's they rotate 601 rpm if you stayed with bfg and just went to a 37" they rotate 574 rpms. the stock 35's are 34.5 tall and a "37" is 36.00 tall. Spedo wise at 65 your really going 67.9 mph, 70 is really 73mph, 75 is really 78.3

If my math is correct ever 10 miles is really 13, every 100 is 113, ever 1000 miles is really 1113 miles.

so if you go 300 miles on 30 gallons, = 10 mpg, you really going 339 miles on 10 gallons which is 11.3 mpg.

also try some lucous fuel injection cleaner, i run that in my cars about ever 4-5 tanks. Its $10 Bucks for the large bottle. all it does is clean the junk in the tank. In the suburban i gained 3 mpg after the fist bottle went threw. 2 mpg on the armada but its a 07 so it shouldnt have to much dirt in the fuel system.

As for the rpm difference the taller tire lowers the over all gear ration.. ( taller tire turn the gears less in a nut shell) So 4:10 gears with 34.5 inch tires now feel like 3:73 gears with 36 inch tires.


I just adjusted my sububran. i went from a 30 to 33.5 in the computer tuning once the tire size was recalculated it said my gear ratio was 3:44 instead of a 3:73... So the game plan is to insall 4:56 gears so the truck will run like it has 4:10...