Gas mileage/ tire issue!! (1 Viewer)

[Morse_FJ40]

I am trying to figure out what my mileage is on a trip yesterday. But since my speedometer is off because of the tires (33's) I know my results will be flawed. Does anyone know a formula to figure out exactly how much difference there is???

thanks

Ryan

 

[Steve C]

http://www.cosports.com/fwhldr/equipcalc.htm

from the tech links page

 

[Morse_FJ40]

Thanks Steve it showed that my tires mph is off by 5, but How wwould I put that into a formula to show actual distance traveled?

 

[bigndn]

Thanks Steve it showed that my tires mph is off by 5, but How wwould I put that into a formula to show actual distance traveled?

Hours traveled X mph = miles traveled

Minutes traveled/60 X mph = miles traveled.

 

[Steve C]

Thanks Steve it showed that my tires mph is off by 5, but How wwould I put that into a formula to show actual distance traveled?

actual miles travelled = (odometer miles traveled) * (current tire diameter/origional tire dieameter)

so 100 miles indicated is actually 100*(33/28)=117 actual miles. (I think the stock tires were 28")

 

[Morse_FJ40]

Thanks that what I needed. Well it says that I got 14.5 mpg, on my steelhead trip yesterday up on the peninsula. I was doing great on gas until I hit the slow windy section...on the gas off the gas stuff. I know the Conferr roof rack cuts greatly into my mileage. Plus the motor has 280,000 on it. So it has some blow-by!
later

Ryan

thanks
all

 

[FineWynsFJ40]

I believe the stock tires were 29, but for every inch larger you gain approx. 3.44% of an overdrive effect. So, 33*3.14 / 29*3.14 = roughly 13.7% overdrive.

 

[Josie'sLandCruiser]

Hi All:

The "overdrive" effect of oversize tires is quite real; recently I put on a set of 31X10.5 tires after running 33X12.5 tires and I noticed the "underdrive" effect of the smaller tires!

I have a buddy with an Orion t-case, 35 inch tires, and 4.88 R&P gears. Almost think he should go back to 4.1 R&P for highway driving, since there is the 4:1 low-range gearing for off-road.

Regards,

Alan
Seattle