dumb question about odo (1 Viewer)

Joined
Jan 19, 2008
Messages
95
I have 285's on my 2000 lc and was wondering if the trip numbers on the odo is lower then what it really is? I know that the speedo is off by about 3-4 mph so maybe it might be the same with the trip?
 

AimCOtaco

...---...
SILVER Star
Joined
Aug 2, 2010
Messages
1,492
Location
Longmont CO
 
 
Don't ever calculate it ('cuz it aint that big) but your gas mileage is also higher than you think because you traveled farther per rev!
 
Joined
Aug 16, 2010
Messages
1,079
Location
South Florida
The 285 dimension isn't really the part that affects odo/speedo or revs. It's not the width but the height of the tire that will affect it.

Actually I'm a little bit wrong here. If you have a 275/65/18 and a 285/65/18 you'd think by looking at the size that they had the same diameter, and just the width was different. However the 285/65/18 is a 1/2 in taller, I'm not sure how this sizing system came about.
 
Last edited:
Joined
Sep 19, 2010
Messages
2,908
Location
Lost in the Sierras
 
 
Tire Rack has detailed specs on their website for every tire, actual diameter and width as well as revs per mile. For example the stock Mich LTX tire is 31.3 inches in diameter with 666 Revs per mile. A GY Duratrac is 32.8" inches in diameter with 634 Revs per mile OR about 5% difference.
 

AimCOtaco

...---...
SILVER Star
Joined
Aug 2, 2010
Messages
1,492
Location
Longmont CO
 
 
The 285 dimension isn't really the part that affects odo/speedo or revs. It's not the width but the height of the tire that will affect it.

Actually I'm a little bit wrong here. If you have a 275/65/18 and a 285/65/18 you'd think by looking at the size that they had the same diameter, and just the width was different. However the 285/65/18 is a 1/2 in taller, I'm not sure how this sizing system came about.
'65' in your examples is the "aspect ratio" The tire has a sidewall height that is theoretically 65% of the tread width (so 285mm*0.65= 185.25mm sidewall height).
The 285/65-18's diameter can be calculated by converting the sidewall to inches and then adding two sidewalls to one rim, ex:

185mm = ~7.28inch

so 18+7.28+7.28 = 32.56 -Theoretical

Doing a compare on Tirerack for actual values on the first few tires they list yields 32.6 - 32.9.

Hope that helps explain the metric tire size system.

It can be nice for comparison once you know how it works. Then look at the real data tables to compare brand/style...

Happy tires!
 
Joined
Jan 19, 2008
Messages
95
Well thanks for the info guys, its good to know that I'm actually getting better MPG then I thought, not that its the biggest priority when coming to owning a land cruiser but it helps..:rolleyes:
 
Joined
Dec 26, 2009
Messages
862
Location
Bay Area, CA
'65' in your examples is the "aspect ratio" The tire has a sidewall height that is theoretically 65% of the tread width (so 285mm*0.65= 185.25mm sidewall height).

AimCOtaco- said it best. Aspect ratio is the key.

285 x 65 x 16 = ...

the first number, 285, is a measurement in MM of the width; every manufacture gets their number slightly differently but this should be similar enough to be consistent from brand to brand
the second number, 65, is a ratio of the height to the width
the last number, 16, is rim fitment in inches; meaning this 285 x 65 tire fits on 16inch rims
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top Bottom