What kind of average gas mileage and RPM's at 65-70mph with 35's with stock gearing?

I think I got 16-17mpg driving 70mph. Usually around 14mpg though daily traffic. RPMs will be lower than stock.

Wondering if I would be able to clear 315/70/17 with my current Bilsteins adjusted up higher and a 1 inch body lift if I’m willing to trim the bumper and body mount and hammer the pinch weld?

You could do it just as easily without adjusting the Bilsteins.

Depending on wheel offset and alignment, yes, it should be relatively easy.

So just the 1” bl with the right wheel offset and alignment would clear 315s is what your saying?

Yeah, that's a good start, trim and beat the rest of the way. Massage to fit LOL.

Tire Size: 35x12.5x17
Tire Make/Model: Kenda Klever R/t
Wheels: 17x8.5 et 0 1.25” spacer
Bodylift: no
Approx. Suspension lift setting over stock: 3” front probably 2-5-2.75” rear
Aftermarket UCA's: SPC uppers
Caster correction: 2.9 degrees
Bumpers: Lil b’s hybrid
Trimming: body mount, rear bumper, lower quarter
Bumpstop drop? Metaltech rear, Duro bumps front
Notes: Which i went 35” sooner, matches the 4.88’s. No rubbing anywhere except for the rear bumper at full stuff.
Biggest pain-point with running 35's on the 4th Gen? Clearance and gusset you’re spindles.
Running stock length Rockmen lowers links.

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Update on wheels and tires since last post:
315 70r17's
Unique Soft 8 Steelies 9 wides with +0mm offset
Spidertrax 1.5" adapters still on
3.5" Long Travel
Fiberwerx 4.5" bulge fenders

The tires seem more proportionate and can still somewhat tuck. I'm actually ditching long travel next week and going back to the Light Racing UCA's and OEM LCAs because machined lengthened CV shafts are wayyy too much money.

Steering clearance wise though, with long travel, I can go lock to lock through the entire range of suspension articulation without coming close to the body mount or frame.

I'll probably need to update this post in the future when I have everything finalized with pictures, but I'm in the process of fitting 37" KM3s to my truck.

"I have 35's, what do I need to fit 37's?"

Assuming you wheel your truck...
35's are on the threshold of needing a regear, and a stronger diff rebuild on your rear 8", and preferably a rear locker to reduce wheel spin and increase control to help diff strength. A body lift will help gain you uptravel, and an alignment with high caster is helpful to prevent some trimming and cutting into the firewall.


37's require all of the above, and:

Some form of LT kit that pushes your tires away from your frame. With 35's I rubbed the frame but it was driveable, I can't imagine how much it would rub with 37s even with wheel spacers.

A LT kit will gain you more downtravel, which is needed because you will be limiting your uptravel more than likely unless you have fiberglass fenders and/or a huge body lift.

I am able to get street-driveablility with a set of 37's, with the trimming I did to fit 35's, because of my heimed UCA. I maxed the LCA all the way forward with the alignment cams, and moved the UCA as far forward as possible too. This is where a +2" or +3.5" kit will help as well to push the tire forward more than standard length. If I had to guess it moves the spindle 1/2" forward.

A standard LT kit, like mine, helps fit 37's. But a LT kit such as Marlin's or JD Fabrication's that specifically moves LCA mounts or spindles forward by inches is a huge fitment help.

Without one of these specialized LT kits, cutting into the firewall is more than likely needed to maximize uptravel with your 37s, as well as relocating your body mount.

Fitting in the rear is easier, to do it right you will need adjustable axle links to move the axle back 1/2" to 1", and trim your rear bumper. Then space your bumpstop down.

Not to mention having a beefier rear end than an 8" helps too. Something like the 5th gen's 8.2, an ECGS low pinion Dana 60, Currie's high pinion Dana 60, or a couple others.

I love the look of the 37s on 4th Gens, but I feel like that rear axle should be pushed back 3" or so...more wheelbase, better departure angle...more better!

that's just a personal opinion, though. and I'm guessing it's not easy to do that.

J.

I extended my rear links about 3/8", and it rubs the door at the same time it rubs the top of the fender. A full 3", which is quite a bit, would probably require custom length links. It would be easy to trim an aftermarket rear bumper back a couple inches to keep it looking clean, and of course require cutting off the rear pinch weld and re-sealing it.

Yes it would improve departure angle, but it would decrease breakover angle.

It might look pretty cool though, I'll think about it.

oh yeah, it's all custom setup. I'm coming from the Jeep world where getting a 94" wheelbase wrangler to a 100" wheelbase is everyone's goal who wants to run 37s or bigger.

ideally, a 3" stretch in the rear would be awesome with 40s...but then you need SAS and other mods and lots of cash, haha. big dreams.

J.

I could fit 40's in the rear pretty easily, just limit uptravel, move the axle back 1.5", and cut the pinchweld out. I already have a Dana 60 so I'm good strength-wise.

The front it's trickier of course. It can be done but it'll be near the cost of a cheap solid front axle swap if you want to wheel it hard.

What's the consensus on bump stop extensions? I currently have durobumps front and rear. I see a 2" from toytec and metal tech, as well as a 3" from metal tech. Curious as which to get. Going for 35's no body lift.

Wheeler's sells some for front and rear, and spacers can be bought or built for them as well. That is what I have.

I had 35's and 1.5" body lift and barely didn't need spacers in the rear, so you'll be looking at 1.5" rear spacers probably. I had 1/4" or 3/8" front spacer so you'll probably need something larger, not sure though.