265-70-16

[pouly]

will 265-70-16 fit hd with out cranking t bars how about back spacing like a little wider tire ???

[SteveSierra]

Pouly,

They would be no problem.

Today I'm having 265 75 R16's put on my truck.  I was going to go with 255 85 R16's, but the tire I really wanted to put on was being discontinued(Dunlop Radial Rover RV) and after some consideration, I don't want to put BFG Mud Terrains on it(very limited as to what tire you can use in 255 85 16.

The 70 series will actually have a shorter sidewall than the 75 so you will have no problems.  I think the tire size your looking for will have an overall diameter of about 30.7 or so.  Mine will be about 31.7 and the 85's that I was looking at had a diameter of 32.7 and would fit with no crank on the t bars.

So, you're good to go!

If you want wider, you'd need to go to 285, 295, 305 or 315

and definately should get aftermarket rims.  I think I'm pushing it with the 265's on the 6.5 inch rim.  I know others have put 285's on the stock rims, but they should check their center tread after 25000 miles or even less, dollars to donuts it would be prematurely worn down.

 

Steve

[browntrout]

I am looking at buying a 2002 GMC 2500HD 6.0 4.10.  I don't like the small 245 tires either and will have them swapped to 265/75R16 before I take delivery.  One question the dealer's not sure on, what do you do to adjust the speedometer?  Are you guys buying a chip or having the dealer monkey with the computer?  Or is the difference between 245 & 265 not big enough to worry about?

 

Any advice is appreciated.

[Beaux Duke]

Pouly, you didn't say what brand tire you're considering but the Firstone Steeltex that came on my 2001HD have the following specs.

o Size: 245/75R16

o Load Rating: 3042 lbs

o Rim Width Range: 6.5 - 7.0

o Diameter: 30.6

 

Firestone doesn't offer the Steeltex in the size you want so I used the Wilderness to derive the following information.

o Size: 265/70R16

o Load Rating: 2403 lbs

o Rim Width Range: 7.0 - 9.0

o Diameter: 30.6

 

As you can see it is suggested that a rim with a minimum width of 7.0 inches be used.  Anything smaller will definitely cause premature wear of tread down the center. You can try to compensate for that by running reduced air pressure but that could be very dangerous.

 

The diameter between the two tires appears to be the same so your speedometer will probably not be affected  unless the narrrower rim you are using raises the tires height.

 

Be sure to get a tire with the proper Load Range.  The 2500HD should have a tire with a load range of "E" if you plan to do any serious towing or hauling.

 

You can get lots of additional information at www.tirerack.com

 

Good luck!

[Beaux Duke]

Browntrout, I used the Firestone Steeltex as a basis for the following comparison.

 

o Size: 245/75R16

o Diameter: 30.6

 

o Size: 265/75R16

o Diameter: 31.7

 

The 265/75R16's are 3.3% larger meaning your speedometer and odometer will be off by 3.3% also.  I'm no math whiz so there could be some discrepancies in my calculations but I'm "in the ballpark."

 

Your GM dealer can recalibrate your truck's computer for your new tire size (for a fee) or if you think you'll be swapping wheels/tires again in the near future, you may want to buy a Hypertech or Superchips unit so you can do it yourself.

 

Good luck!

[SteveSierra]

Just to make a note here.  On the new trucks, if your model does not show up as having 265 75 16 size tires available as an option, the dealer cannot reset the computer for this tire size.  GM does not nor will they probably ever make a code for it if it is not a factory available option tire size.

Last night I spent a half hour on the phone with the QC manager at my dealer going over all kinds of questions and this was one of them.  He recommended using a HPP or similar to recalibrate for different tire sizes.  He also said, and most should already know this, that if you get an SES light say for a trans problem, that you should take out the HPP or whatever programming you have in the truck and revert back to stock because if they need to put an update in your computer for the trans problem, this will erase the HPP programming.  He said this has happened more times than he can remember because people forget to tell the service writer or take the programming out before they take their car/truck in for service for an SES light.  

I'm lucky in that I have a  great dealer close to me that also has a performance shop as well.  Want a dealer installed supercharger? ;) No kidding.

Oh yeah, I just ordered the HPP for my truck, through my dealer.  he he he.  I love dealers that are into performance as well.

They should all be like this.

Steve

[gandolphxx]

Can we all adopt your dealer, or at least clone him. Some dealers will walk away if you change out the bowtie.

[SteveSierra]

Sure!  Come on over!  Actually, there are 2 dealers near me that are into performance.  A Pontiac/GMC dealer across the bridge in Jersey, and a Chevy dealer here in Delaware.  I know someone who had an LT4 conversion done on his 94 Firehawk over at the Pontiac dealer about a year ago.  The car is wicked.

[browntrout]

Beaux Duke -

 

Thanks for the reply.  I'm thinking that a 3.3% difference (I will need to verify your math  ;) ) is not enough to worry about, as long as I remember I'm going 2-3 miles an hour faster than the speedo says.  Of course the speedo is probably 1-2 fast to begin with; might need to check with a GPS after the swap and make my decision then.  

 

One question:  why does GM always use that non-standard crazy backspacing that is hard to find in the aftermarket?  Ford and Dodge make it easy to swap wheels.  GM owners who aren't aware of the backspacing end up getting wheels that stick out (especially in the front) that look, well, ummm...not so good.

[Beaux Duke]

Browntrout,

You got me on that one.  I've never had a Ford or Dodge so I've never really thought about it although I was aware that their wheels were interchangeable.

 

I think the problem arises because we all like wide tires/wheels.  When the back spacing is correct the only direction the rest of the wheel can take is out.  

 

I agree with your assessment on the appearance.  Plus wheels that stick out past the fenders sure increase the number of paint chips.