Tire size-internal debate

[Upnover]

The age old story…what size of tire.
I am debating between 37 and 39 KOs. My struggle is do I go with 39s. Haven’t ran that size before but I have always wanted to do it.
Or do I go with the tried and true 37s, which I have ran all the time. I like the BFGs don’t plan to go with any other tire brand.

I have an 24 XR with the newer axles. Know plenty of folks who run larger tires on them. I know of the risks blah blah bigger axles.
I can always do that later but I am not sure if I would regret just sticking to 37s.

DD 37s is just fine. Not sure 39s.

What says everyone?

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[GATORB8]

I'd expect the 39s to be equivalent to 37 or maybe 38 Nittos. My 37" KO2s were definitely on the small side.

Anything over 37" always comes with a big price jump, but it'd be really hard for me to swallow the extra $1500 for the 2" jump on the KO2s.

 

[Ratbert]

I'd expect the 39s to be equivalent to 37 or maybe 38 Nittos. My 37" KO2s were definitely on the small side.

It looks like 38X12.50R17 Nitto Ridge Grapplers are 37.76" while 39X13.50R17 BFG KO2s are 38.5".

Based on https://tiresize.com/tiresizes/38-inch-tires/ and https://tiresize.com/tiresizes/39-inch-tires/.

 

[GATORB8]

It looks like 38X12.50R17 Nitto Ridge Grapplers are 37.76" while 39X13.50R17 BFG KO2s are 38.5".

Based on https://tiresize.com/tiresizes/38-inch-tires/ and https://tiresize.com/tiresizes/39-inch-tires/.

I'll see if I can find my real world measurements of the 37" KO2, IIRC they are not the advertised size (36.5") mounted.

This is 37" KO2 and 38" TG:

 

[mrtm1970]

The age old story…what size of tire.
I am debating between 37 and 39 KOs. My struggle is do I go with 39s. Haven’t ran that size before but I have always wanted to do it.
Or do I go with the tried and true 37s, which I have ran all the time. I like the BFGs don’t plan to go with any other tire brand.

I have an 24 XR with the newer axles. Know plenty of folks who run larger tires on them. I know of the risks blah blah bigger axles.
I can always do that later but I am not sure if I would regret just sticking to 37s.

DD 37s is just fine. Not sure 39s.

What says everyone?

Forgetting to mention what size lift you have…

 

[GATORB8]

I did this too (I measured the spare), but here's CarbonSteel's measurement on the C Load 37" and I remember getting similiar measurements on my D loads:
https://www.jlwranglerforums.com/forum/threads/37-ko2-c-rated-size.108482/post-2254700

EDIT: I can't find a picture, but I found a discord post where I ran a line around the circumference of a new 37" KO2 D Load, my response said it mathed to 36" Diameter.

 

[mrtm1970]

I'll see if I can find my real world measurements of the 37" KO2, IIRC they are not the advertised size (36.5") mounted.

This is 37" KO2 and 38" TG:

Dang the 37s look tiny compared to the 38s

 

[GATORB8]

Dang the 37s look tiny compared to the 38s

Very much so in real life. The TG isn't under load in this pic like the KO2 is (and the KO2s are worn), but:

 

[Jmazz]

Once mounted, they will sag a bit under load as well depending on tire pressure. I assume you already Jscan in tire size to correct the speedo and have a 4.10 or 4.56 axle gear? Otherwise you trade cool looks for driveability

 

[azwjowner]

Very much so in real life. The TG isn't under load in this pic like the KO2 is (and the KO2s are worn), but:

That is a very misleading photo because the tire closer to the camera lens is going to look larger, plus all tires lose at least an inch under load on a vehicle.

 

[GATORB8]

That is a very misleading photo because the tire closer to the camera lens is going to look larger, plus all tires lose at least an inch under load on a vehicle.

This one was more misleading, lol. They are substantially bigger in person.

 

[3TV]

39" KO2s are ungodly expensive. Depending on where you buy, they can be $900 to $1000 per tire. At least that was the quotes I was given locally. So, that means about $1500 more for a set of tires. Are BFGs worth that to you?

 

[GATORB8]

39" KO2s are ungodly expensive. Depending on where you buy, they can be $900 to $1000 per tire. At least that was the quotes I was given locally. So, that means about $1500 more for a set of tires. Are BFGs worth that to you?

Not quite that much here, but the delta is correct, 85% increase in tire cost.

 

[Beachbumb]

If you want AT’s, look at the new Toyo’s. The 37’s are more true to size. I wouldn’t plant a flag on BFG’s. Tires are huge investment these days..

 

[Glamisfan]

I just retired 39” BFG Mud Terrains after 54,000 miles and 5 tire rotations. I was super happy with them. This is on a 2.0 JLUR with the stock 4:10’s. They were $420 at Costco in 2021. I would not pay the $700 that they want now.

I just put the new Nitto 38x11.50x17 Ridge Grapplers on it and find that the pizza cutters ride smoother.

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