37's on a DD

cdl

cdl

New member
I'm beginning the process of building up my 13 JKUR. It's my daily driver so I'm looking for info from guys that are running 37's on a DD. Is there really that much of a difference between 35's and 37's in MPG? Loss of "power"? I live in southern CA with a 70 mile round trip commute to work. I know that some of this is subjective, but I'm just trying to do it right the first time. Thanks in advance.

Chris
 
wayoflife

wayoflife

Administrator
Staff member
cdl said:
I'm beginning the process of building up my 13 JKUR. It's my daily driver so I'm looking for info from guys that are running 37's on a DD. Is there really that much of a difference between 35's and 37's in MPG? Loss of "power"? I live in southern CA with a 70 mile round trip commute to work. I know that some of this is subjective, but I'm just trying to do it right the first time. Thanks in advance.

Chris
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There is definitely a measureable difference between 35 and 37 but you can mitigate some of that by re-gearing to a ratio that will help bring your Jeep back closer to stock performance. MPG loss is a given and if it really is a concern, you shouldn't be driving a Jeep as it will only get worse the bigger you go. Of course, more than tire size, the type of tire you run can really rob you of MPG. Something like an MT will have a much greater rolling resistance than an AT or street tire and that can easily account for as much as 4-5 MPG. Trust me, I have tested this out on my own Jeep.
 
JKAnimal

JKAnimal

Caught the Bug
Mine is a DD and I am running 37" Nitto Trail Grapplers. I have the 4" EVO Enforcer lift with the 2.5" Spec. Adjustable Shocks. I average about 12-13 mpg around town and it creeps up a bit when I hit the Hwy. to about 15. I'm running 28psi in the tires. I know with a higher tire pressure I could squeak a little more mileage out but it makes the ride not as nice. As mentioned above, tire choice will also make a difference in mileage.

I re-geared to 5.13 and I have more power now than I did when I was running stock rubicon tires (32" if I remember correctly) with 4.10 gears.

I didn't buy 35s because the general consensus was if you go 35s then you'll want 37s within 3 months of buying the 35s. I took their advice and have never looked back. :beer:
 
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el_chupo_

Member
What all is needed to do 37s vs 35s?

Assume 4.10 gearing, 12+, and the Evo Enforcer lift + drag link flip kit, and new front drive shaft.

Gearing would be the obvious choice to get power back, but would anything else need to be updated or changed for the bigger size?

I am currently around 18.5 mpg on the highway, all stock, and while this is not a DD for me, making plans to go places all over the country, I do have to consider MPG as well.
 
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el_chupo_

Member
wayoflife said:
There is definitely a measureable difference between 35 and 37 but you can mitigate some of that by re-gearing to a ratio that will help bring your Jeep back closer to stock performance. MPG loss is a given and if it really is a concern, you shouldn't be driving a Jeep as it will only get worse the bigger you go. Of course, more than tire size, the type of tire you run can really rob you of MPG. Something like an MT will have a much greater rolling resistance than an AT or street tire and that can easily account for as much as 4-5 MPG. Trust me, I have tested this out on my own Jeep.
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Does anyone make a reasonably affordable AT/ hybrid style tire like a Duratrac in a 37" flavor? It is probably due to where I am looking, but it seems most that large are MT tires. Kind of sucks thinking about a Jeep with a lower fuel range than a motorcycle...
 
JK_Dave

JK_Dave

Caught the Bug
el_chupo_ said:
What all is needed to do 37s vs 35s?

Assume 4.10 gearing, 12+, and the Evo Enforcer lift + drag link flip kit, and new front drive shaft.

Gearing would be the obvious choice to get power back, but would anything else need to be updated or changed for the bigger size?

I am currently around 18.5 mpg on the highway, all stock, and while this is not a DD for me, making plans to go places all over the country, I do have to consider MPG as well.
Click to expand...

el_chupo_ said:
Does anyone make a reasonably affordable AT/ hybrid style tire like a Duratrac in a 37" flavor? It is probably due to where I am looking, but it seems most that large are MT tires. Kind of sucks thinking about a Jeep with a lower fuel range than a motorcycle...
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You just need some type of ECU programmer to recalibrate your ECU for the larger tire size and gear ratio if you decide to change that as well.

If you're looking for competitors for the Duratrac, check out the Toyo Open Country R/T or the Nitto Exo Grappler. They're both a hybrid MT/AT that will probably suit your needs and they're made in 37" size (although due to the new release of these, they may not be in the rim diameter that you're looking for)
 
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el_chupo_

Member
JK_Dave said:
You just need some type of ECU programmer to recalibrate your ECU for the larger tire size and gear ratio if you decide to change that as well.

If you're looking for competitors for the Duratrac, check out the Toyo Open Country R/T or the Nitto Exo Grappler. They're both a hybrid MT/AT that will probably suit your needs and they're made in 37" size (although due to the new release of these, they may not be in the rim diameter that you're looking for)
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Thanks Dave. I knew about the computer, just forgot about that. But that would be used for any changes, not specific to 35s vs 37s, correct?

Unfortunately the Toyo is only in 37" for a 20" rim, and the Nitto is only showing 35s on their site.

May be better to do 35s first, then when those need replacing do a regear and bigger tires at the same time, let the market catch up a bit.

Thanks!
 
cozdude

cozdude

Guy with a Red 2-Door
el_chupo_ said:
Thanks Dave. I knew about the computer, just forgot about that. But that would be used for any changes, not specific to 35s vs 37s, correct?

Unfortunately the Toyo is only in 37" for a 20" rim, and the Nitto is only showing 35s on their site.

May be better to do 35s first, then when those need replacing do a regear and bigger tires at the same time, let the market catch up a bit.

Thanks!
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those two tires just got released so they have limited sizes as of right now. they will be offering more sizes in the near future
 
C

CrazyLarry

New member
I daily drive my rig on 37s and couldnt be happier. Is gas mileage a bit worse than my 35s? Yes. Did I spend more money in upgrades to my steering and axle reinforcement? Yes. Would I change anything or regret anything? Hell no. Point is dont let anyone discourage from doing what you want to do to the point you end up running a size tire you dont want to run. Ill tell you this the best thing I ever did after getting my tires was regearing my manual to 488s. By far the best mod I ever made to my jeep. I say go for it just make sure you do your research and budget accordingly for upgrades
 
JKAnimal

JKAnimal

Caught the Bug
el_chupo_ said:
What all is needed to do 37s vs 35s?

Assume 4.10 gearing, 12+, and the Evo Enforcer lift + drag link flip kit, and new front drive shaft.

Gearing would be the obvious choice to get power back, but would anything else need to be updated or changed for the bigger size?

I am currently around 18.5 mpg on the highway, all stock, and while this is not a DD for me, making plans to go places all over the country, I do have to consider MPG as well.
Click to expand...

One thing I don't see mentioned is you will need to gusset your Cs in either instance (35s or 37s).
 
CJW

CJW

New member
I'm running 37s with 4.88 gears. I drive about 90 miles a day total commuting for work. I love it! If I'm carful about the gas pedal I can squeeze 22mpg out of it on the highway but in town sucks. I have a combined average of 15-16mpg.
Even with the bad mpg I still love it! Only thing I'd consider would be going with 5.13 gears instead based on where you live but I'm happy with the 4.88s given all the highway driving.
Plus I love my bigger tires off road. One outing with the 37s and you won't care about what you think your losing from not having a smaller tire.
Lastly, everything I've ever bought that I compromised on (say 35 instead of 37) I've regretted and ended up with what I originally wanted in the end. Don't waste your money buying things twice.

Edit: I'm running 37 x 12.5 nitto trail grapplers on the stock wheels w/ spacers
 
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Flat Top

Flat Top

Member
CJW said:
I'm running 37s with 4.88 gears. I drive about 90 miles a day total commuting for work. I love it! If I'm carful about the gas pedal I can squeeze 22mpg out of it on the highway but in town sucks. I have a combined average of 15-16mpg.
Even with the bad mpg I still love it! Only thing I'd consider would be going with 5.13 gears instead based on where you live but I'm happy with the 4.88s given all the highway driving.
Plus I love my bigger tires off road. One outing with the 37s and you won't care about what you think your losing from not having a smaller tire.
Lastly, everything I've ever bought that I compromised on (say 35 instead of 37) I've regretted and ended up with what I originally wanted in the end. Don't waste your money buying things twice.

Edit: I'm running 37 x 12.5 nitto trail grapplers on the stock wheels w/ spacers
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In honor of the Jeep Meme thread........ :D:D

image-2734970203.png
 
CJW

CJW

New member
Flat Top said:
In honor of the Jeep Meme thread........ :D:D

View attachment 111386
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Hahaha! Good one!!! LOL!
I seriously can get that though. If I reset the mpg computer on the highway. It will climb up that high and stay there until I get to "in town" traffic. Figuring it out manually on road trips I get high numbers as well but it'll be 20 for the average.
 
13_gecko_rubi

13_gecko_rubi

Caught the Bug
What's your secret? I have 37s on my 13 with 4.88s and I avg about 14-15 around town and 12 on the hwy (12 because I refuse to slow down).

As far as dd'ing with 37s, it isn't bad at all

Sent from my SM-G900V using WAYALIFE mobile app
 
EZ-E

EZ-E

New member
I have a 2012 Auto with 37's that I DD. ~14mpg around town 16mpg on the highway going 70. Unless there's hills, then it dips down to about 14 as well. Really not bad, just gotta get the hang of hopping up to get in the jeep.
 
trailless

trailless

Caught the Bug
EZ-E said:
I have a 2012 Auto with 37's that I DD. ~14mpg around town 16mpg on the highway going 70. Unless there's hills, then it dips down to about 14 as well. Really not bad, just gotta get the hang of hopping up to get in the jeep.
Click to expand...

What gear ratio are you running?

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