Bigger tires on a 2011 Chevy 3500 srw?
My 2011 3500 SRW comes with 265/70/r18 tires stock. I am looking to possible change to a Terra Grapler 295/70/r18. The diameter change will be from 32.7 to 34.41 inches 1.71 inches larger. The tire...
Forum Discussion
With my GM 2011 truck I replaced the stock 245/75R17 at 31.5" diameter with 285/70R17 tires that are 32.76" in diameter - only 4% larger tire "height". In reality the new tires provided a more accurate speed and odometer reading with a camper load in the bed than was provided by the stock tires. The larger tires under the camper load have a height comparable to the stock tires with the bed empty. Easy to understand how tire height decreases with increases in load.
A GM with the diesel engine can tow more than 17,000 lbs. so a 4% increase in gearing is hardly going to make a difference with performance. The trucks with the gas engine and the 3.73 gears can still tow 10,000 lbs. (13,000 with 4.10 gears) so a 4,000 lb. camper is a relatively light load as far as the engine and drivetrain are concerned and 4% taller gearing is trivial.
People forget that it is the radius that affects whether a tire will hit anything inside the truck and with a 2" greater diameter the radius is increased by only 1". Same applies to wider tires if they are installed on the factory rims. A 1" wider tire is only going to protrude inside the truck an additional 1/2" and is not going to hit anything. If it did it is simple to adjust the turning stops a small amount.
I saw a gain in stability with the higher load rated Nitto tires (3750 vs. 3195) as there is less sidewall flexing at 80 PSI. I wanted to avoid the expense of new rims and the Nitto's minimum rim width was the same as the factory rims. Where people have problems is with new rims that are wider and move the load on the spindles further out from the truck resulting in their failing as much from the leveraged loading as from the heavier tires.
Forget about having the speedometer adjusted by the dealer. They are forbidden by GM from doing this for any truck. There are aftermarket devices that will enable you to do this. I calculated that with 4% large tires if the speedometer showed I was going 65 MPH my actual speed was 67.6 MPH or not enough to worry about one way or the other. With the camper in the bed at 65 MPH the speedometer shows 65 MPH.
I could not find the factory load rating for the forged aluminum rims but worked backwards from the trucks with these rims. The trucks with these rims have the highest load rating of any of the rims provided by GM. They also make an aluminum rim that is not forged and these have a load rating of less than 2500 lbs. and are not going to be found on any truck with a payload rating provided in the glove box. I found 1-ton trucks with these rims that had a sticker stating that the truck was not to be used with a camper.
DRW is a special case as the tires are not going to be fully inflated and this has an affect on tire height with a camper load. There are likely to be tire width restrictions as well with DRW. In terms of the rims and the tires, with twice as many they can easily handle any camper load. Even at a 2200 lb. load rating the 4 tires would support 8800 lbs., and less the 3200 lb. truck weight, leaves capacity for a 5600 lb. camper load. That is why the manufacturers go to a DRW to increase load capacity for their trucks - it is the easiest and cheapest option available.
A GM with the diesel engine can tow more than 17,000 lbs. so a 4% increase in gearing is hardly going to make a difference with performance. The trucks with the gas engine and the 3.73 gears can still tow 10,000 lbs. (13,000 with 4.10 gears) so a 4,000 lb. camper is a relatively light load as far as the engine and drivetrain are concerned and 4% taller gearing is trivial.
People forget that it is the radius that affects whether a tire will hit anything inside the truck and with a 2" greater diameter the radius is increased by only 1". Same applies to wider tires if they are installed on the factory rims. A 1" wider tire is only going to protrude inside the truck an additional 1/2" and is not going to hit anything. If it did it is simple to adjust the turning stops a small amount.
I saw a gain in stability with the higher load rated Nitto tires (3750 vs. 3195) as there is less sidewall flexing at 80 PSI. I wanted to avoid the expense of new rims and the Nitto's minimum rim width was the same as the factory rims. Where people have problems is with new rims that are wider and move the load on the spindles further out from the truck resulting in their failing as much from the leveraged loading as from the heavier tires.
Forget about having the speedometer adjusted by the dealer. They are forbidden by GM from doing this for any truck. There are aftermarket devices that will enable you to do this. I calculated that with 4% large tires if the speedometer showed I was going 65 MPH my actual speed was 67.6 MPH or not enough to worry about one way or the other. With the camper in the bed at 65 MPH the speedometer shows 65 MPH.
I could not find the factory load rating for the forged aluminum rims but worked backwards from the trucks with these rims. The trucks with these rims have the highest load rating of any of the rims provided by GM. They also make an aluminum rim that is not forged and these have a load rating of less than 2500 lbs. and are not going to be found on any truck with a payload rating provided in the glove box. I found 1-ton trucks with these rims that had a sticker stating that the truck was not to be used with a camper.
DRW is a special case as the tires are not going to be fully inflated and this has an affect on tire height with a camper load. There are likely to be tire width restrictions as well with DRW. In terms of the rims and the tires, with twice as many they can easily handle any camper load. Even at a 2200 lb. load rating the 4 tires would support 8800 lbs., and less the 3200 lb. truck weight, leaves capacity for a 5600 lb. camper load. That is why the manufacturers go to a DRW to increase load capacity for their trucks - it is the easiest and cheapest option available.
