Lift Required for 33" Tires on K30?

[Cheng]

It is becoming time to put new tires on my K30 and I am considering a slight increase in tire diameter.

Currently my K30 sits on the stock 235/85R16E tires (31.7" Diameter) and is running stock suspension.

I use my truck for towing and hauling so an offroad style lift is not really an option for me; however at many of the jobsites I work at it can get slick and muddy.

I would like to put on 255/85R16E Mud Terrain Tires (33" Diameter) and am hoping some of you may have done the same thing.

I am thinking that by putting on 1" Zero Rate Add A Leafs like these:

http://www.offroaddesign.com/catalog/Zero%20Rates.htm

And also finding a set of the 5/4 ton CUCV Springs for added stiffness in the rear end that I can run these tires without rubbing problems.

Pictures or advice would be most appreciated.

[Cheng]

This is how the truck sits right now:

[junkman8302]

You should have no problems running the 255/85 tires, although that size seems to be harder and harder to find these days. You may also want to think about a 285/75-16. The 285s should clear without issues, especially if you added the ORD 1" leaves. Nice truck by the way.

[bohmankid]

I run 285/75R16 on my truck. It has a 2.5 inch lift. The tires come close, but don't rub. If you can get a tire skinnier than a 285 but still 33" tall, I think you could get away with it with an add-a-leaf. The front is your main concern for rubbing. Cheapest way to raise the front? Small shackles.

[Your41Plague12]

I ran 285/75/R16's on my K20 with stock suspension and had no issues at all. They didn't rub for me, and with a K30 being even stiffer in the suspension area, I can imagine they will work well for you.

[rustyMUD]

You should be fine running the 255/85r16 BFG Mud Terrains on a stock one ton. I have the exact same tire on my 81 GMC K25. It has the HD(8,600 lb gvwr) suspension which currently is sagging a bit due to broken springs from previous owner neglect. I have no rub issues, even at full lock and also flexed off road. I use the truck to haul firewood and have had just shy of 3,000 lbs of logs in the bed with no rubbing issues in the rear, again, that's with the saggy springs. My brother owns an 84 K30 and it has an additional one or two inches of axle to wheel-well height over my 3/4 ton. In summary, you'll be fine with no modifications to the suspension. It's good to see someone else interested in 255/85r16. I'm a big fan of that size, especially on the 73-87 trucks.

[Number21]

I've got 33s on my '73 K20 at stock height, they fit great - no rubbing.

[cory d]

wow 33's at stock height looks dang good. i would do it with pizza cutters, i just like that look

[Cheng]

Thanks to everyone for the replies and photos.

I really like hearing this first hand information rather than apples to oranges comparisons.

I am going to try to get all the life I can out of the current set of tires, but now at least I have a plan and can start shopping for some deals.