The Tow specs for the Ram 1500 are 1000 pounds less with the 20" wheels as compared to the 17" wheels.

I can see that part of the de rate for the 20" is the effective gear ratio changes from the 3.92 to 3.73 (approx) as the circumference of the wheel is almost 4.5" more on the 20". This I think would account for about 500 pounds of the loss. The load rating on the tires is 65 pounds greater on the 20", so I see no load limiting factor.

Does anyone know of a structural reason for the de rate or is it all due to the effective gear ratio change when going to the larger 20" wheels??

 

I think it is all weight.

I think the offroad package uses 17's - 265/70R17? 31.6 inches vs 32.9 inches.

1.3 inches can't make much difference on towing capacity - escpecially since the 20's are rated at 2600lbs at 35PSI vs ~2000lbs for basic 17's.

I need some winter tires - and am thinking of Michelin LTX 265/70SR17 tires. Have to find some used cheap used rims to go along with them (with a spare).

Will also need a Superchips tuner to adjust for tire size...

Dave

 

dont need the super chips. the dealer can do it with their drb tool. they have ot go into the abs menu and then go change the pinion factor. youll need to provide them with the new tires revolutions per mile which can be had of the tire manufactures website or with a phone call to them.

 

Sounds like a drag asking the dealer to change it 2x a year though, don't you think? Wouldn't it just be easier and cheaper in the long run to get the superchips?

 

Guys - I appreciate the comments but I was hoping for some insight into the 1000 pound tow penalty for using the Factory 20" rims and tires. I dont see it as a horsepower issue that can be changed with a chip.

 

Perhaps it's the fact that 20's impact the accelleration and decelleration of the vehicle? Maybe they make a big enough difference that would make 1000 lbs less stop in the same distance? Perhaps it's that the 20's aren't as strong as the 17's and that under lateral loads they might crack easier, or shear lugs off easier? Perhaps they take more power to get moving? Perhaps it's a combination of all of the above that made Dodge rate the vehicles with dubs at 1000 lbs towing capacity lower than other ones.