So the dealership dropped the bomb on me yesterday, after having my jeep for a week, saying they couldn't get the parts. Now the story is they're not going to cover it under warranty because the aftermarket tires create more torque on the axle witch caused it to break. After much argument and pleading my case that the tires are only 6% bigger they haven't budged so I called a friend of mine who is a mechanical engineer with Lockheed Martin who informed me that larger tires in fact do not create any additional torque on the shaft and the only way I could create more is to change the gearing or add horsepower to the engine. I thought it was pretty interesting so he is going to write down the formulas so I can show the dealer (in case this turns into a legal thing).
Anyone got any input on this?

 

dealership told me that the bigger tires voids my warrenty for my axles, axle shafts, brakes and in some cases transfercase and transmission due to the added stress of the heavier tires

 

thats funny because the dealership here in el paso told me it didnt and tomld me as long as i stayed under 3.5" of lift it would be covered. funny how they are all different. i never understoood what satisfaction the shop managers get out of saying no. the dealership isnt fitting the bill. its the Corperate. i guess we all should quit our jobs and become service managers at jeep dealerships so that we can all be empathetic.

 

I know you have already thought of this, but you need to find another dealership to give money to.

 

Yep, I'm on the lookout. Another thing I'm going to do is never bring it in without the stock tires again. The funniest part of this is this is the same dealer that asked me when I was getting larger tires and a lift and also said it wouldn't effect my warranty.

 

The way I understand it is if you are wheeling and one of the tires comes off the ground and is spinning, when it makes contact with the ground there would be more torque applied to the axle if the tire is heavier than the torque that would be with a stock tire.

 

According to them that isn't true. In that same scenario the weight of the tire doesn't factor into it only the horsepower of the motor and gearing. They informed me that it would have the same force on it regardless of tire size. I believe there actual wording was you could have a 10' diameter tire and the torque would be the same.

 

I think it only stands to reason that a larger diameter tire requires more force to move and stop than a smaller tire. This is due to a combination of leverage and inertia along with some other factors I am probably overlooking, but rolling resistance would be another likely suspect as a larger tire will probably have a greater contact patch and be less inflated than the stock tire.

A heavier tire will also present more inertia (when stopped, it will take more torque to move and when moving, it will require more braking force to stop).

This is one of the major reasons I chose Goodyear MT/R Kevlar tires when I went from stock Rubis to 37s. The MT/R weighs 20 lbs. less than the same sized Toyo, for example. Since I don't expect Mother Mopar or Father Fiat to cover my brakes, suspension or drivetrain under warrenty after going to 37s, I wanted to put the least amount of stress on my D30 front diff and stock axles as possible.

The full EVO gusset, magnum tube reinforcement and suspension armor treatment will be the next major mod along with an ARB front locker and aftermarket axles.

-meljr

PS: From my drag racing days, there was a rule of thumb that said for every 100 lbs. you remove from the race car, your Elapsed Time (ET) will go down about a tenth of a second. Now, ET is a function of torque as torque moves you down the race track and top end speed is more a function of Horsepower. When I heard this, I started tossing everything that wasn't required out of the car or replacing heavier parts, like the one remaining seat, with lighter components. Guess what, the rule of thumb was right. I had the same amount of tourque, but I went quicker (not much faster -- horsepower was also unchanged) and broke fewer driveline parts as a result. Then I could have slightly detuned the race car to stay in my class and run the same ET with lesser torque and broke even less often.

 

I originally thought the same thing and was contacting him to find out how much when he informed me that the weight of the tire doesn't matter unless the tire is suspended off the ground. He actually said the weight of the jeep itself would matter more.

 

I guess my B**CH is that I went from a tire with a 32.05" diameter at 61lbs. to one that is 34" at 86lbs and that is going to break axles? That's only 6%?