Calculating speed and MPG with 285's? (1 Viewer)

Joined
Jan 19, 2005
Messages
311
Location
Redlands, CA
 
 
 
Tired of searching. What calculations are used to determine actual speed and mpg when running 285/75/16's? I know I need the speedo correction gear from Slee, but in the mean time I'd like to know what my numbers are.

Thanks,
Perk
 
Joined
Mar 30, 2003
Messages
1,643
Location
LA, CA
 
 
 
From Slee's website:

http://www.sleeoffroad.com/products/products_speedo.htm

"The most common size tire installed to gain extra clearance is 285/75R16. When the diameter of this tire is calculated, it comes to 32.8". The stock tire size is 275/70R16, which equated to a 31.2" diameter. So when installed the larger tires, your speedometer will read 57 mph when you are traveling 60 mph. Using the correction gear, your speedometer will read 58.9 mph."
 
Joined
Apr 10, 2003
Messages
1,186
Location
Kansas City, MO
 
 
 
(32.8 - 31.2)/31.2 = about .05

Your speedometer/odometer are about 5% off right now without the speedo correction gear.

Take your current speed or odometer readings you gather during this time and multiply them by 1.05
 

NorCalDoug

problems solved daily...
Joined
Oct 27, 2003
Messages
6,217
Location
uhhhh...duh...Northern CA
 
 
 
when I went to 285s, my speedo was off by about 5% per my GPS.

Now with 315s, it's off by about 10% (also per my GPS).

...the math is easier for me now ;)
 

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