Okay so I have a 2000 chevy blazer 4.3 with the 3.42 open diff, 2 inches of lift(suspension). Im looking to get a set of All terrain 31x10.5r15's and the guy at the tire shop said that my speedo would be about 4mph off (no big deal)and that the bigger tires will tear up my transfer case and drivetrain, so I held off on buying and am coming to you guys for advice.

Im not afraid to trim a little fender, so that is not a big deal.

Will this really cause extra wear and tear on my drivetrain (tranny, t-case etc...)?

 

Lol what..? The stupidity that comes out of some "mechanics" mouths it just insane. You need to fine a new tire shop or stop taking advise from this one lol. But no... 31's are NOT big enough to do any damage to anything. with 3.42 gears you will lug a little more but not a big deal. 40" tires arent even enough to do damage to the drive terrain..

Maybe he was thinking you wanted to run two different sized tires. Which WILL cause damage to your drive terrain so dont ever do that.

 

Yeah that guys just an idiot! You will see a small bit of extra strain on everything just from the additonal weight of the larger tires but nothing extreme or probably even noticable. Where the front end starts to have the biggest issues is when you crank the tbars up and put the front end geometry out of line that will cause the biggest strain on the cv axles but thats not the actual tires themselves. The other issue is the amount of back spacing on your rims if you have less spacing you will see your hubs get eatin up pretty quickly from the strain there as well. Again thats more with the rims than the tires though. I would say the best thing to tell yourself is that anything that isn't factory has the potential to speed up or possibly slow down the wear rate of the parts on your truck. That being said there are a ton of us running 31's and other than a few small things to keep in mind and be aware of there really isn't any need concern

 

OMG I'm in trouble!!! The 3 years I've had the 32 x 11.5 on 10 wide rims are going to make my blazer blow up.

The mechanic is confused or some sort of communication break down is happening.
They won't hurt the drive train unless as stated you have different sized tires on the vehicle at the same time.

 

Yeah when the mechanic was telling me that I was all confused. As long as all tires are the same size they will all be spinning about the same speed except on turns. I thought I needed more knowledge on the issue, but obviously the mechanic needs to do more research. Thanks again blazerforum, you guys always come through.