Tire Size With 6 inch lift

[Nick_92]

Hi all,
I have recently purchased a rough country 6 inch lift kit for my 1992 gmc Sierra k1500. I’m now in search for some rims and tires but mainly trying to figure out tires. I have been doing some research and it looks like 35s are the way to go but I wanted to see if there was other suggestions and what everyone else’s thoughts are. I was looking at some 35x 12.50 r17 centennial dirt commanders but I just wanted to make sure I wouldn’t have any rubbing with that size of tire. The rims I was looking at to go with it are some pro comp Xtreme alloys that are 17.9 with a 4.75 back spacing and a -6.00mm offset. I found this setup on a Silverado and read that there was no rubbing with this setup. I was also wondering if I could run this setup but with a 0 offset as I have not been a huge fan of tires sticking out without fender flares as my plan was not to put fender flares on. I have also seen this setup on a Silverado step side with 0 offset rims which did not run into any rubbing issues. Just looking to see some opinions and any other setups everyone else is running.

 

[Sean Buick 76]

17x9 with a 4.75” backspace would be about perfect without flares. Yes a 35x12.5-17 is a good sized tire. I wouldn’t go to a zero offset personally. Look on the “custom offsets” site you will see a ton of combos!

 

[Nick_92]

17x9 with a 4.75” backspace would be about perfect without flares. Yes a 35x12.5-17 is a good sized tire. I wouldn’t go to a zero offset personally. Look on the “custom offsets” site you will see a ton of combos!

Thank you, I checked them out that’s were I got some of the combos for rims and tires for my truck. I also took a look at trail built which also had quite a few combos of different peoples setups. By chance would you know if this setup would bog the truck down quite a bit? I’m assuming it will but my future plans is to do a 400 ci sbc blue print crate motor off summit. Currently I am in the process of doing a frame off restoration and starting with the suspension first.

 

[Sean Buick 76]

When I did the 6” lift on my 91 back in the day it had 3.73 gears and it became a total dog after the lift and 35s. I swapped to 4.56 gears and it was much improved but the fuel mileage, cornering, etc was always downgraded compared to stock. The 4.56 gears actually helped the fuel mileage compared to 35s with 3.73 gears as it was just working so hard and SLOW. You may get away with 4.10 gears with the torque of a 400 SBC.

My 01 Yukon runs 4.10 gears and 35s with a 5.3 LS and it would also benefit from 4.56 gears but I likely won’t bother.

On my 2012 GMC 2500HD with the 6.0 gas and 6 speed auto it’s got the 3.73 gears and 35s. But the 6 speed has a way better 1st gear and 2 overdrive gears vs one. I was doing some long distance commuting, like 450 miles each way and I swapped to 33s for a bit and gained 11% fuel economy.

 

[Nick_92]

Interesting, I appreciate the information! I have not dug into the rear diff just yet so I’m unsure what gear ratio I have at the moment but currently what I can see is it’s a 14 bolt rear end which after doing some digging sounds like they may have came with 4.10 or 4.56 gears, maybe you might have some knowledge on that? It sounds like a 4.56 ratio is the way to go with this setup as I also took a look at some other forums seeing what gear ratios other people are running with 35s on.

 

[Sean Buick 76]

Check the glove box sticker to see if you have RPO code of GT-4, GT-5 etc. my 14 bolt in the 92 has 3.73 gears but mines staying stock height tires so I’m staying with that.

 

[Nick_92]

Check the glove box sticker to see if you have RPO code of GT-4, GT-5 etc. my 14 bolt in the 92 has 3.73 gears but mines staying stock height tires so I’m staying with that.

Took a look and came to find out I have GU6 which would be 3.42 gears unfortunately.. I do have a buddy who is good with rear ends who could swap a 4.10 or a 4.56 gear into it but I’ll do some more research on what gear ratio may be best as 4.56 may not be to bad as I don’t do a lot of high way travel with the truck anyways, its more of a weekend driver.

 

[JPVortex]

I have 315s on my lifted 94. It was lifted 6 inches but I lowered it to 4 inches.

The handling definitely isn’t great but I wouldn’t say it’s dog slow or anything.

It’s not a race truck but it still moves just fine. Gas mileage is awful though, like 8mpg.

And I have a 350 tbi with a 5LM60 5 speed, and 4.10s.

 

[Sean Buick 76]

3.73s with stock tires is almost the same as 35s with 4.56:

 

[glock20]

I have 315s on my lifted 94. It was lifted 6 inches but I lowered it to 4 inches.

The handling definitely isn’t great but I wouldn’t say it’s dog slow or anything.

It’s not a race truck but it still moves just fine. Gas mileage is awful though, like 8mpg.

And I have a 350 tbi with a 5LM60 5 speed, and 4.10s.

Yikes, you have some other issues if you're only getting 8mpg