GMT800 Suburban 1500 wheel/tire clearances

Chips

Mothertrucker
Hi folks. I've just acquired a bone stock '03 Suburban 1500. It took a while to find a good one as I live in BC and a lot of them suffer from quite bad rot up here. Anyway, I've got plans for it and will be starting a build thread in due course.

My question today though is about wheel and tire clearances (yawn) before I put an order in. I realise this topic is often beaten to death, so apologies for that.

I have the Moog HD coils, offset torsion keys and a set of Bilstein 5100s on the way. The truck came with some nasty looking stock wheels with a good set of Cooper Discoverer AT3 4S tires. But I'd like to move up to a set of 285/75r16 Cooper Discoverer S/T Maxx on a 16x8 wheel with 0 offset / 4" backspacing. From what I've read, the tire size should be ok, but on a 0 offset wheel am I going to be able to stuff those tires? And being IFS, do I even need to worry about being able to stuff the front?
 

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1stDeuce

Explorer
Stock wheels are your best bet for "stuffing" a larger tire into the GMT800's tiny wheel openings. Going to a wheel with not only less backspacing, but more width moves the tire outboard not only by the reduction in backspacing, but also half the increase in width. That causes the outside of the tire to swing a bigger arc when you steer, and to swing that arc farther out. It also adds more stress to your wheel bearings all the time, and to your steering components on rough roads.

Without pretty serious trimming, the fronts will rub front and back when you steer with 285's on those wheels. The rears may stuff into the fender lip as well in articulated conditions. If you only want to go to the mall and look good, then a little trimming will allow you to steer, and gentle driving won't rip things apart. If you intend to go offroad, then you're going to need a LOT of trimming, a true 4" lift, or wheels with specs closer to the OEM wheels. FYI, lots of us running 285's on factory wheels, only slight rubbing that's fairly easy to resolve.

You could consider gaining a little tire clearance by putting a 1" body lift on your half ton to mimic the HD trucks, on which the body sits a bit higher... Torsion bar cranking or other methods of making the truck sit higher on the cheap only buy you clearance statically. When the suspension compresses, you're still going to have the same clearance issues you had without the "lift". Going to a true 4" lift would move all suspension components down as well as moving down how far the tire can "stuff" by the lift amount, which is what you're going to have to do if you don't want to do a lot of trimming to make those wheels work.

Good luck!!!
 

nitro_rat

Lunchbox Lockers
Also bear in mind that cranking the bars reduces down travel (sometimes to zero with keys). This is hard on ball joints and everything else in the front end. It also diminishes ride quality and can make driving (especially evasive maneuvers) “interesting.”
 

Martinjmpr

Wiffleball Batter
I had 285/75/16s on my '04. Brand new Z71 coils in the back and keys in the front, with Bilestein 5100's on all 4 corners. No rubbing at all. I had those same stock-type "cyclone" wheels.

Advice: If the truck is new to you, try to lower the spare. Many of these trucks had the awful "secondary latch" that rusts shut and then it is literally impossible to get your tire down unless you grind the "bell" off the tire carrier. Even cutting the cable won't work. Replace it with one that doesn't have the secondary latch.

I was fortunate to discover my secondary latch rusted shut on a sunny day in my driveway. Others have been less lucky and not discovered it until they had a flat in the middle of nowhwere.
 

Bret+famx7

New member
295 75 16s on worn torsion bars maxed out and 5100s all around, it doesn't have much more left as far as uptravel unless that bump is more compressible than I think. Haven't been able to completely flex it yet but it doesn't rub anywhere at all and the rear tucks nicely inside the flare.
20230208_174912.jpg
 

Chips

Mothertrucker
Thanks for all the replies folks. My email notifications were going to spam so I didn't realise anyone had responded.

I tried to find a set of stock 17" wheels locally but I live in a pretty remote area. So I went ahead and ordered a set of 17" steel wheels. Having thought about it, for the places I go and the type of driving I do I don't think I'm really going to be articulating the rear end much, and having driven the front end up on ramps the tires don't seem to get into the wheel well at all.

This is my second GMT800 Suburban and I had to cut the spare off on my old one with a sawzall. I'm actually looking at moving to a rear tire carrier and mounting a fresh water tank in place of the spare underneath.
 
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