2017 GMC Denali HD 2500 Tire question!

lpabsolute · May 18, 2017

Hey guys.

I've ordered a 2017 GMC Denali HD 2500 Diesel. It will be delievred in 2 weeks. i would like to upgrade my tires ASAP and have a question. If i turn up the front end forks to level out the truck what size tires can i fit with keeping the stock 20" chrome rims. I have the truck fully loaded with off road package.

I want to buy BFG Mudd Terrain. I was hoping to be able to fit 325/60R 20 tires. Will these fit with out doing a lift kit and by just turning the front forks up to level out the truck? Please help, Thanks guys. Great site!

Lance

Buckshot556 · May 20, 2017

I think from a width perspective the biggest you can go is 295. Diameter would be whatever ratio gets you around 34"... Maybe 35" if you crank it all the way (whole host of other issues will be caused by cranking your bars all the way up.). This is all dependant on if you keep the stock wheels. If you go aftermarket be careful about keeping a positive offset. Your current wheels are 8.5" wide with a +31mm offset and 5.97" backspace.

My buddy has 20" wheels but they are 0 offset so they stick out away from the truck. This causes his 35"x12.5" tires to rub ever so slightly even though he lifted 4" up front. If he stuck with a positive offset he wouldn't have any issues but he wanted that Fuel wheel and liked the poking out look.

ETA - I've been researching this for five months. Still haven't pulled the trigger yet but the above is information I've gathered off the forums. If anyone disagrees please comment so we don't steer in the wrong direction.

wade_660 · May 20, 2017

I've got 35/12.50 with 1/4" wheel spacers and don't scrub at all. I'm too lazy to convert it to the size you are looking at but this will give you an idea.

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lpabsolute · May 21, 2017

I think from a width perspective the biggest you can go is 295. Diameter would be whatever ratio gets you around 34"... Maybe 35" if you crank it all the way (whole host of other issues will be caused by cranking your bars all the way up.). This is all dependant on if you keep the stock wheels. If you go aftermarket be careful about keeping a positive offset. Your current wheels are 8.5" wide with a +31mm offset and 5.97" backspace.

My buddy has 20" wheels but they are 0 offset so they stick out away from the truck. This causes his 35"x12.5" tires to rub ever so slightly even though he lifted 4" up front. If he stuck with a positive offset he wouldn't have any issues but he wanted that Fuel wheel and liked the poking out look.

ETA - I've been researching this for five months. Still haven't pulled the trigger yet but the above is information I've gathered off the forums. If anyone disagrees please comment so we don't steer in the wrong direction.

I do want to keep the stock 20's chrome. I don't mind cranking up my bars to make bigger tires fit. Will cranking them up some but not all the way be ok? What issues arise from cranking them up all the way? I just want the leveled out look and bigger tire fit, but don't want it to ride like shit. In the bfg mud terrains, what size can I get on the stock 20's? I won't have mud flaps in the way either. Thanks for the reply

lpabsolute · May 21, 2017

I've got 35/12.50 with 1/4" wheel spacers and don't scrub at all. I'm too lazy to convert it to the size you are looking at but this will give you an idea.

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What brand tires and size are you running? Did you crank your bars up? I'm trying to Avalon paying for a lift kit. Can you post close up pic of your tire? Any pros/cons you have ran into with your setup? Thanks for sharing!

wade_660 · May 21, 2017

Toyo mt 35/12.50 20. Yes on cranking stock bars. Front sits 1" lower than the back. No real pros or cons, it just works.

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lpabsolute · May 21, 2017

Toyo mt 35/12.50 20. Yes on cranking stock bars. Front sits 1" lower than the back. No real pros or cons, it just works.

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Looking at their website now and see two 35/12.50/20. One is 121Q and one is 125Q whats the difference? all the specs look the same

wade_660 · May 22, 2017

I have no idea

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Kyleb100 · May 23, 2017

Wade, any tips on trimming the front air dam since it looks like you have done yours? I want to do this but am a bit nervous.

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wade_660 · May 26, 2017

I followed the curve of the air dam with painters tape, then cut it with a die grinder, the took a knife and shaved all of the little rough spots. Be careful in the middle, there's a bracket back there. I just did the sides of mine

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2016HD · May 26, 2017

Looking at their website now and see two 35/12.50/20. One is 121Q and one is 125Q whats the difference? all the specs look the same

121q and 125q are the speed ratings. Would have to check memory. But probably around 100mph maybe less. Nothing to worry about etc. as long as you stay with a 10ply tire.

lpabsolute · May 27, 2017

Hey guys. I have narrowed down my tires to these two.

BFG Mud Terrain 305 55 20's on stock rims

Or

Nitto Trail Grapplers 35 12.5 20's on stock rims

Any suggestions on the two? Thanks

Truck arrives next Sat!!!!!

newdude · May 27, 2017

121q and 125q are the speed ratings. Would have to check memory. But probably around 100mph maybe less. Nothing to worry about etc. as long as you stay with a 10ply tire.

The 121 and the 125 is the load index not the speed rating. On some HD truck tires, its load at single rear wheel and dual rear wheel (it will say 124/121Q for example). Q is the speed rating (99mph).

On the tire in question above the Toyo Open Country MT https://www.toyotires.com/tire/pattern/open-country-mt-off-road-maximum-traction-tires

Two versions of the 35x12.5x20 exist. One is 121 (3197lbs) load index, the other 125 (3638lbs) load index. You should always meet or exceed the factory load rating on the truck. So, if you are using the stock 20" wheels, those have a load index of 121 (Goodyear Wrangler SRA 265/60/20). Both applications of that Toyo could work, but the 125 index may allow for higher pressures. Its more than likely that the 121 tire is a C or D load while the 125 tire may be an E load.

Load Index

P195/60R15 87S - The load index (87) is the tire size's assigned numerical value used to compare relative load carrying capabilities. In the case of our example, the 87 identifies the tire's ability to carry approximately 1,201 pounds.

The higher the tire's load index number, the greater its load carrying capacity.

89 = 1,279 pounds

88 = 1,235 pounds

87 = 1,201 pounds

86 = 1,168 pounds

85 = 1,135 pounds

A tire with a higher load index than that of the Original Equipment tire indicates an increase in load capacity. A tire with a load index equal to that of the Original Equipment tire indicates an equivalent load capacity. A tire with a lower load index than the Original Equipment tire indicates the tire does not equal the load capacity of the original.

2016HD · May 27, 2017

The 121 and the 125 is the load index not the speed rating. On some HD truck tires, its load at single rear wheel and dual rear wheel (it will say 124/121Q for example). Q is the speed rating (99mph).

On the tire in question above the Toyo Open Country MT https://www.toyotires.com/tire/pattern/open-country-mt-off-road-maximum-traction-tires

Two versions of the 35x12.5x20 exist. One is 121 (3197lbs) load index, the other 125 (3638lbs) load index. You should always meet or exceed the factory load rating on the truck. So, if you are using the stock 20" wheels, those have a load index of 121 (Goodyear Wrangler SRA 265/60/20). Both applications of that Toyo could work, but the 125 index may allow for higher pressures. Its more than likely that the 121 tire is a C or D load while the 125 tire may be an E load.

Dont forget that any HD truck should have an E load rated tire. As long as that is followed the load index wont matter as the tire will already have the correct load rating for the truck. Nice info post though!