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Discussion Starter · #1 ·
Hey guys, looking to finally buy some new rubber. Looking heavily at 31x10.5r15 bf goodrich at ko2 with rims @ 4.75 backspacing. My question is, would my car need a regearing? (coming from stock), and would the speedometer also read wrong? how much mpg would I be losing? Thanks a bunch
- Joe
 

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https://tiresize.com/calculator/

Check this link out, you can put in your current tire size and new tire size and it will show you about how much your speedometer will be off.
This is kinda cool. Says I'm only off by like 3mph at 60 mph with my 32x11.5s though.. So either my phone speedo is off or that is (probably my phone) because I thought it was off more than that with my 31x10.5s lol
 

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On the 2001, moving up from the stock tire size to 265/75/16's results in the speedometer and odometer under-reporting by 5.5%.
 

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Discussion Starter · #6 ·
Thanks a bunch, I have a 03 X. So, if on 31's, and I'm going 60mph on the highway, it would actually be 55mph?
Hmm, and I am deciding whether or not I should get crager soft 8's or american baja 8's. Cragers are steel and baja's are alloy. Any pro's con's? Would mileage be worse with the steels since it is heavier? for those who do have those rims.
 

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Thanks a bunch, I have a 03 X. So, if on 31's, and I'm going 60mph on the highway, it would actually be 55mph?
Hmm, and I am deciding whether or not I should get crager soft 8's or american baja 8's. Cragers are steel and baja's are alloy. Any pro's con's? Would mileage be worse with the steels since it is heavier? for those who do have those rims.
I have steel Crager 15x8s and there hasn't been a noticeable change in mileage for me.

Steel
Pros:
-cheaper
-can be hammered back into shape if damaged offroad
Cons:
-"heavy" compared to alloy

Alloy
Pros:
-lightwight
Cons:
-expensive
-(almost)unrepairable if damaged
 

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Mine is on 31s. With a pml. No Need to regear. Mine has plenty of get up to it. 4 high has problems spinning in the mud some times. 4 low i can almost hit 3 gear so no big deal. 33s i would probably want 4.9 gears. My 4.6s are a tad long.
 

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Thanks a bunch, I have a 03 X. So, if on 31's, and I'm going 60mph on the highway, it would actually be 55mph?
Hmm, and I am deciding whether or not I should get crager soft 8's or american baja 8's. Cragers are steel and baja's are alloy. Any pro's con's? Would mileage be worse with the steels since it is heavier? for those who do have those rims.
I'm not sure what stock tire size is on the 03, but on mine with the 31.6" tires (265/75R16), if the odometer reads 70 mph, then my actual speed is just a touch under 74. The larger diameter causes me to get a few more inches out of every revolution than the speedometer/odometer accounts for.
 

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Discussion Starter · #11 ·
Alright. 31x10.5r15 bf Goodrich at ko2
Mounted on 15x8 American racing baja ar172 6/5.5 bolt pattern with 4.25 backspacing. Would I need to trim plastics on 4.25 backspacing?? Stock height or PML
 

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A 15x8 would need something closer to 4.75 or 5 on the BS not to rub, it is a wider rim and less backspacing means way more protrusion outside the fender well

Darin
01 Xterra SE 4x4
COMING SOON:
Intake mod, timing belt, hoses, belts
Wish list:
PML, EFan conversion, shocks, 32" tires, and eventually UCA'S
 

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Discussion Starter · #14 ·
A 15x8 would need something closer to 4.75 or 5 on the BS not to rub, it is a wider rim and less backspacing means way more protrusion outside the fender well

Darin
01 Xterra SE 4x4
COMING SOON:
Intake mod, timing belt, hoses, belts
Wish list:
PML, EFan conversion, shocks, 32" tires, and eventually UCA'S
There is a 5.25 backspacing option available. I found a super sweet deal for them, 365 for all 4 wheels, all lug nuts ,stems, whatnot included.
 

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Discussion Starter · #15 ·
better yet, heres the question. should i go for a 5.25 backsapcing or a 4.25 backspacing? 15x8 on 31x10.5r15 wheels on a stock suspension / PML soon
 

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5.25 as I believe that is stock or closer to it so that it isn't looking like a Tonka truck

Darin
01 Xterra SE 4x4
COMING SOON:
Intake mod, timing belt, hoses, belts
Wish list:
PML, EFan conversion, shocks, 32" tires, and eventually UCA'S
 

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Here is a handy link
http://www.galantvr4.org/docs/backspacing.htm
the stock rim has a 40mm offset and as you can see in the link, that is closer to a 5.5" backspacing for a 7" wide rim, and an 8" wide rim would be closer to 6" to make it the same

Darin
01 Xterra SE 4x4
COMING SOON:
Intake mod, timing belt, hoses, belts
Wish list:
PML, EFan conversion, shocks, 32" tires, and eventually UCA'S
 
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