larger tires on dually's

[Mark_Z]

I have a 2005 GMC 3500 crew cab dually with LT215/85R16 tires. I would like to switch to LT225/75R16 tires instead. Is this alright to do? Will going up 1 tire size effect towing or the rear duals in any way? Please help me out with this.

[Heartbeat Hauler]

Are you sure about the new tire size? It is actually a smaller (shorter) tire than what you have. There has been a lot of conversation about this and no one was more interested in getting bigger tires on a dually than me. However, you will find that there are some stumbling blocks to doing this. First, the most common upsize is the 235/85/16, but because of the wheel offset the duals may rub each other when loaded...not safe. You will get those who argue this is not an issue, but a blow out at speed with an RV attached is not my idea of fun. Second, you will need to buy a programer(pricey as in 3 - 800 bucks) to correct the speedo as the dealership either won't or can't make the change especially on the '01 model. And finally, GM will deny any warranty work (concerning drivetrain performance) if the original size tires are not installed. So, good luck in your endeavor it can be done but, it ain't cheap or simple.
JP

[c5dura]

I run 235/85/16's and generally don't have an issue with the rears touching, but when I'm really loaded, I do need to maintain 85 PSI. Here's a shot showing the gap with a moderate load @ 65#:

http://www.cstone.net/~dk/BFGGap.jpg

And no load @ 65#:

http://www.cstone.net/~dk/silverado/rear%20gap.jpg

[Mark_Z]

c5dura, Thanks for your reply & pictures. Do you have a side view of your dually, so I could see the tires?

[c5dura]

Here is one showing a front tire:

http://www.cstone.net/~dk/silverado/Front%20BFG.jpg

And this was the best one I could dig up showing the rears:

http://www.cstone.net/~dk/silverado/C5Dura%20vette%20rear.jpg

[SLT556]

c5dura, that is pretty sharp looking with the bfg's. definately a good move.