37” BFG K02 install with 4” SST Lift

[Nokturnal]

Well guys, I’ve been researching 35” tires and I really love the BFG Sidewall and winter performance but their tires are notorious for coming in under specs. The 35” BFG K02’s are measuring 33.5 before being mounted. So I did some tinkering and found the 37 KO2’s are the same. Many guys were measuring 35.5” unmounted and closer 35.2” mounted on a wheel. I test fitted a 35” Toyo AT3 (34.5”) and I had zero rubbing! So this got me curious if a 37” BFG would fit without much more trimming and it looks like this is gonna happen. I’ll post pics after the install (waiting on the 3 other black rhino solids to show).

So for anyone wanting maximum tire on the fender, know a bfg may be a solid option for those wanting just over a 35” tire with 4” of lift.


Here’s a pic of the wheel tire combo:

17x9.5 Black Rhino Solid (-12 offset)
37x12.5x17 (weighs in a 64 lb!)

I’ll post pics of the trimming and installed wheels when I throw them on. But good god, it looked so GOOD on the test fit.

FYI: 97% highway for me. I don’t get on trails at all and can’t comment if the 37” would be an option for those guys really testing the suspension travel.

 

[olyelr]

 

[Oh Kee Pah]

37s ?!?!
Holy ****!

That's certainly stuffing a lot of rubber under the rig. It will look mean, especially on the 17" wheels, that's for sure

Where are you thinking more trimming will be needed? Both rear wheel well and front bumper(ish)?

Yes - the wheels are heavy. 37" tire on a 17" wheel is A LOT of rubber, and if you have any extra ply from an ordinary passenger spec, then the weight increases drastically.
My current Nitto tires weigh 69.44lbs and are spec'd at 34.29" diameter.
Measurement I've made with tire inflated at 40psi and truck NOT loaded = diameter actually 33.25".
I'm running wheel spacers in the back so they add an additional 5-10lbs to each rear wheel. Let me tell you, I've certainly noticed a difference in power/pick-up after I moved up from the 33" diameter.

Do you have 5.3 or 6.2L? Gear ratio on yours? I'm assuming 6.2L because of the Denali, but not sure about the gearing...
My LTZ is 5.3 with the 5.42 ratio. Wish I had the 6.2L with this much weight added underneath; honestly, I think that could make all the difference.

Following & can't wait to see some photos of this bad boy.

 

[Nokturnal]

When we test fit the wheel and tire it was just barely catching the frame by the door maybe by 1/4-1/2”. It wasn’t crazy or I would have said hell no to chopping on the body. The rear looked like it might need just about the same on the plastic rear piece but it may not need any. I’m adding a set of airlift coil spring helpers for the rear to give it a little rise in the rear that’ll hold. But I really think it may not need much or any trimming in rear. I’ve just noticed in building window reflections my rear end is lower than the front under acceleration and it bothers me I’ll get pics of any trimming for the final photos.

These 37” KO2’s weigh less than my current 295/70/18 ST Maxx!!! The C load 37” BFG ko2 weight 64lb. My St Maxx weight in at 69lb per tire. Like I said, not a true 37” tire since BFG is so under spec, but it’s definitely more like a true 36”. I have the 5.3 motor and it’s done very well with the heavy ST Maxx I’ve had. I want to say my SLE has the 3.27 gearing, as it’s not the 3.73 for sure that I know of. I have the trailer package and I’d have to look up what it actually is. I’ve had zero issues running down the highway at 85-90mph regularly. I dont think I’ll need to regear with the BFG bc they’re a little less in weight and still only just about .75” taller than what I already have. We shall see though! I’ve got plans for a Lew Tune with the Diablo In Tune 3, but it doesn’t have to have it. That’s me just wanting my Speedo correct, AFM delete, and 25-30 more HP and TQ (93 octane).

Air spring Helpers go on Tuesday in the rear and I bet the wheels make it in by Wednesday.

 

[Nokturnal]

OKP- My calculations have the BFG mounted at 30psi coming in at around 35.2”. Of course the BFG site claims 36.5”, but that’s wayyyy off.


Here’s a pic of a new Cooper ST Pro 35x12.5x17 next to a 37x12.5x17 BFg K02.

 

[Nokturnal]

The non rounded sidewall of the BFG actually helps you out a little bit in fitting more tire in the fender, if that makes sense too.

 

[Nokturnal]

Not on my vehicle; but off a jeep with 17” x 8.5” wheel with the 37”. My measurements were just like this when we test fitted.

 

[olyelr]

I would recommend a simple spacer in the rear over air helper bags, if you are just looking for a consistent height increase.

 

[Nokturnal]

I would recommend a simple spacer in the rear over air helper bags, if you are just looking for a consistent height increase.

I haul a trailer 3-4x a year and it feels like I’m always loading the back down with 150-200lb of stuff. My dual 12” subwoofer setup that’s always back there is 140lb.

I just figured the airbag may be beneficial for the trailer hauling and heavier vacation luggage. The spacer was a cheaper solution, but I’m only paying $450 installed for the air bag helpers.

 

[Oh Kee Pah]

@Nokturnal - I think it's probably worth it to go with the airbags, particularly since you're towing and loading up often.

I see exactly what you're saying with the BFGs and "rounded sidewall."
I'm not doubting the 37" riding at 35.5" once the vehicle's weight is on them.

Also, I do think that the recommended wheel mounting width has some effect on overall tire height under vehicle weight, though probably very minimal in reality.
I'm pretty sure that I've read a wider wheel will create less overall tire height and a narrower wheel will cause more tire height, when compared to manufacturers recommended wheel width for each tire.
Ie: Recommend 9.0" x 20 wheel for a 32.5" tire, but install that tire on a 8.5" x 20, and you may realize increased height. Or maybe for argument sake on our discussion here, a 0.5" narrower wheel width than recommended as per manufacturers specs MAY get you closer to the actual spec'd diameter.

Anyway, those are going to look great.
Dig the idea of getting such a meaty tire under the truck without a BIG lift.
I hope you really don't have to trim much at all, great to save the effort and go have some fun!
Keep us posted