I oversized my tires on my new dakota. I dont think you should get 265/70, you need to get at least 265/75. theres a big difference in tire size by getting 75% instead of 70%. Example, my stock tires were 245/70 on 16;s, if i had gotten 265/70, it woulda been about an inch larger tire from end to end, but i got 265/75 which was 2.5 inches larger, raised my truck 1.25" and looks much beefier. my speedo was off 7%, so at 60mph it was off about 4mph. Dodge fixes this speedo problem, or correct the pinion factor, for $49 bucks. On your ram I would get 285/75, not 285/70.

 

Monkey I guess it depends on whether you are wanting to raise your truck or fill the fender wells. Plus not all tire manufacturers use the same size wheel when they designate tire size so one 265/70 on a 8 inch rim might be more like another manufacturers 265/75 on the same rim if the second manufacturer sized their tire on an 8.5 inch rim. Basically different brand tires will be different sizes even if the numbers are the same.

USN I agree 100% I have 24000 on my truck and I should have replaced the tires about 4000 miles ago but am holding out till I trade it in. I will never by overpriced Michellins unless they come Factory on the truck. Even then I plan to try to make the dealer replace the tires when I trade in.

 

ummm not to correct you strocker but the first number is the tread width of the tire in mm... so it is not affected by the rim (ok maybe very very slightly) what is affected by the rim is section width (the measurement of the widest part of the tire. Tires are generally sized off the rim (does not apply to off road tires that use the 35X12.5 R17 formula, of course we were not talking about them).

 

Just lifted my Truck 6" and put 35x12.5 R17 Toyo Open Country M/T's and it looks awesome. Speedo is off roughly 6mph. Dodge is going to fix it shortly however.

 

Sorry, been sidetracked. Thanks for the calculators guys.

 

I would have to agree with you usnfirefighter, the michelins street tires for trucks do wear out pretty quick. My Michelin M&S tires are mud & snow tires. I already have 35000 miles on them and have a ton of tread on them. Should be no problem to get 60000-70000 miles out of these tires. Plus they filled up my wheel wells beautifully.

 

If you are comparing new tires there is a simple method. The manufacturer lists the # of rotations/ mile. (5,280 ft) Figure the planned replacement tire first so divide 5280 by the number of rotations to get the feet/ rotation number. Now multiply this by the number or rotations/ mile listed for the stock tire to get the distance the replacement tire will travel at the same rpm. Multiply this by 60 mph and divide by 5,280 ft will give the actual mph for the new tire size.

 

I should have pointed out that the same calc can be used to find the expected true speed at any given speedometer reading. Just substitute what ever mph you want to evaluate for the 60 mph in the above formula.

 

I see a lot of people have responded to this, but I've been doing a lot of research on this lately, so here's my 2 cents.

I just ordered some Kumho Ecsta STX 275/60R17's to replace those crappy stock 245's. The Kumho's have a comparable rating to the top of the line Bridgestone Duelers (which I have on my jeep and love them) but they are the cheapest ones (according to TireRack).

Also, 275/60's are only .5 inches smaller in diameter compared to the stock 245/70's. This amounts to a 1 mph difference in the speedo. And if 1mph difference is too much, then you have better eye sight than me. I haven't got them yet, but I am confident in TireRack's ratings and feedback on the Kumho tires. They should be great.

 

What is this "Correct the pinion factor"? is this just an adjustment to the computer like a Super Chips Flashpaq would do, or is it better to just take it to the dealer?