Need some help with “true size” of a couple tires

[Kurt0]

Hey all. Trying to select what tire to run, and picking gears. Rims will be sized correctly, so no ballooning issues

looking for true measure on:

duratrac 35“
general a/tx 35”
general a/tx 37”

all will be 12.5r17

thanks all.

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[DOOKEY]

Need more info. 35" and 37" isn't a tire size.

 

[Kurt0]

Need more info. 35" and 37" isn't a tire size.

all 12.5 R 17 at that measurement.

 

[DOOKEY]

35x12.50R17 Duratrac = 598 revs per mile.
35x12.50R17 ATX = 594 revs per mile.
37x12.50R17 ATX = 561 revs per mile.


So the two 35" tire options are so close to each other the gears wouldn't change. Might change for 37's.

Instead of basing your gear selection on tire size alone what does the rest of the vehicle look like? A stripped down bare bones Jeep on 35's won't require the same gear selection as an over lander built with every single bolt on option on 37's.

 

[Kurt0]

35x12.50R17 Duratrac = 598 revs per mile.
35x12.50R17 ATX = 594 revs per mile.
37x12.50R17 ATX = 561 revs per mile.


So the two 35" tire options are so close to each other the gears wouldn't change. Might change for 37's.

Instead of basing your gear selection on tire size alone what does the rest of the vehicle look like? A stripped down bare bones Jeep on 35's won't require the same gear selection as an over lander built with every single bolt on option on 37's.

yeah thanks. I hasnt thought of doing math by revs per mile.

i was looking at gearing calculator and know (for example) the ko2 37” only actually measures about 35.5”

probably splitting hairs, but this will be an overland build and im ocd about informations and maths. Lol

 

[AnnDee4444]

yeah thanks. I hasnt thought of doing math by revs per mile.

i was looking at gearing calculator and know (for example) the ko2 37” only actually measures about 35.5”

probably splitting hairs, but this will be an overland build and im ocd about informations and maths. Lol

You might be interested in this post: https://www.jlwranglerforums.com/forum/threads/gearing-calculator.38206/page-2#post-1320803

For a K02, the advertised revs/mile is on average 97.1% of the calculated revs/mile.

 

[Kurt0]

You might be interested in this post: https://www.jlwranglerforums.com/forum/threads/gearing-calculator.38206/page-2#post-1320803

For a K02, the advertised revs/mile is on average 97.1% of the calculated revs/mile.

ill take a look through it. Thanks.

 

[CarbonSteel]

@Kurt0 - here is a chart I created of various 35" tires:

https://www.jlwranglerforums.com/fo...res-size-weights-specs-pics.8603/post-1328822

 

[Kurt0]

@Kurt0 - here is a chart I created of various 35" tires:

https://www.jlwranglerforums.com/fo...res-size-weights-specs-pics.8603/post-1328822

awesome. Thank you.

 

[MrKnowitall]

Assuming it’s an auto, the answer is 5.13. With the huge 8th gear overdrive, there’s just no reason to go with anything less, even on 35s. That’d have you turning 2700at 80mph.

 

[CarbonSteel]

Assuming it’s an auto, the answer is 5.13. With the huge 8th gear overdrive, there’s just no reason to go with anything less, even on 35s. That’d have you turning 2700at 80mph.

Unless the OP is going to eventually move to 37" or larger, I would stick with 4.88 for 35" tires, but that is just me.

 

[DOOKEY]

Unless the OP is going to eventually move to 37" or larger, I would stick with 4.88 for 35" tires, but that is just me.

Agreed. I could have pulled 5.13's with 40's.

 

[Kurt0]

this is more or less my dilemma. I plan on running 37’s. But if i get sent overseas again, its likely that 35” is the limit. So im running different gearing and tire calculations to see what kind of rpm’s the truck is actually going to turn.

i was leaning towards 37 and 5.13, figuring at worst im turning extra rpm. Better to spin 100rpm faster than end up not geared enough. After using the rev per mile method im actually leaning towards 4.88. The 4.88 seems to be enough to still add a couple hundred rpm bump over stock even with the biggest tires im looking at.

Knowing the stock tire is only really a 31.8 is helpful.

 

[Kurt0]

Goodyear says their 35x12.5r17 measures 34.8 but the revs per mile put it an inch smaller than that.

why is that?

 

[AnnDee4444]

Goodyear says their 35x12.5r17 measures 34.8 but the revs per mile put it an inch smaller than that.

why is that?

34.8" x 97.1% = 33.7908"

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