3.42 Gear Ratio Tire Swap

dcarbs · February 21, 2020

Hey everyone, I’m looking for experience upping your tire size. I have the 6 spd 5.3L with the 3.42 gear ratio and the stock tires are 31.1 inches (255/70/17). I am looking at changing to 33 inch tires max. Im wondering what the experience with the loss of towing power, change in MPG, or the amount of “get up n go” you lost with this. I’m guessing since my effective gear ratio stays around 3.31 and that’s still bigger than the 3.23 that also comes with the 1500, then I may not notice a huge difference. Whatcha think?

CamGTP · February 21, 2020

Depends.

How much more weight are your 33's going to add?

If the rim/tire combo is adding 20-30lb per corner, you'll notice something but if it's far less then you won't notice much there at all.

Your speedo will be off some too. MPG should stay pretty close, your driving habits play a much larger role in all this. And again the weight/rolling mass of the new tires may make it take a slight hit but we aren't taking much at all.

I went from 30.5's all the way to 32.9 I think (275/55/20) on a previous truck with 3.73's, yeah it felt a touch slower but I still got the same freeway mpg because once an object is moving it doesn't take a lot of horsepower to keep it at speed.

dcarbs · February 21, 2020

Yeah I will probably be adding about 20 lbs per tire. I didn’t think about that because I was so wrapped around making sure my ratio wasn’t completely messed up. Lol.

yeah I was planning on buying a calibrator for the speedo when I got the tires. Really just trying to decide between 32 and 33 at this point.

Big Adam · February 26, 2020

I recently went with a 275/70r17. 32.6 inches tall. Other that the speedo being about 2mph off, I think it rides better and handles better, definitely better when towing. I have no MPG data, since I added the tires all of my driving has been local with a 16ft trailer. Those MPG's suck no matter what tire you have.

dcarbs · February 27, 2020

11 hours ago, Big Adam said:

I recently went with a 275/70r17. 32.6 inches tall. Other that the speedo being about 2mph off, I think it rides better and handles better, definitely better when towing. I have no MPG data, since I added the tires all of my driving has been local with a 16ft trailer. Those MPG's suck no matter what tire you have.

Can you post a picture of that set up? I am still

undecided between that setup and 275/65/18.