Chevy expert/Guru needed (Non-Valk)

[Tx Bohemian]

Just bought a '08 Chev Silverrado Ext cab 1500 and will be needing tires in about 5-8K miles.

I would like to go with a slightly taller tire due to the massive opening of the wheelwells.

The manufacture calls for a 245/70R17 and Discount has a 265/70R17 which I like and to my calculations is a smidge over 1" taller (1.1)

Does anyone know if there is a range (max/min) to go to without having the speedo/anti-lock brakes re-calibrated?

I would think the difference in tread height of a brand new tire and the same size tire that's needing replacment is close to the same difference I'm talking about.

Any thoughts/suggestions/comments?

[Pete]

You can calculate, just do the circumference or each, subtract the smaller from the larger and divide by the smaller will give you the percentage difference to apply to your speed.

I would not think the 1 inch would matter that much. I went 245 to 265, did not notice the difference.

[Brad]

Another thing to keep in mind is the spare.  If you get a flat with the larger tires and put on the smaller spare, that could cause a problem with the anti lock brakes.  If you have a posi in the rear end it could toast that also.

[John U.]

Carry a plug kit and air compressor and you've got the flat situation 90% covered, if you have a blowout, don't run the spare for long. All car manufacturers have been selling cars with the little spare tires for some time. They aren't the same diameter as the rest either.
I have a Siverado diesel which takes 245/75R16. I am running 265/75R16. I know the rim and aspect ratios are different. Anyway, I think  that the larger size is not so different that it will cause problems. I wouldn't go larger than 265 though, you may have clearance problems with the front tires.
I am using an aftermarket program that replaces the original ECM programming, it also allows for tire size modification so I can't comment on the speedometer error, except to say it won't be much.

[wizard -vrccds#125]

I was a Sales Mgr. at a GM dealership for some 20 years. One size up or down will make no difference in shifting or anti-lock. With a different size spare it may trip the low tire warning light and also will make no diff. But do check your speed against a GPS to let you know how muck it is off.

[Black Dog]

Here is a good site that lets ya plug in various sizes of wheel/tire, and gives ya the difference in speed/miles traveled between two sizes...

http://www.dakota-truck.net/TIRECALC/tirecalc.html

Black Dog

[olddog1946]

These newer trucks are electronically controlled and so are the transmissions, which is where the Vehicle Speed  Sensor is (2WD) or the transfer case (4wd)..at any rate the computer can be programmed to work with any tire that you choose..tire size should not effect the anti-lock system.

[Red Diamond]

keep in mind that when the anti-locking brake light comes on, it does not mean there is something wrong with your brakes or that you will not have any brakes. That light is controlled by a speed sensor, also sometimes located in the rearend housing. Next is my opinion only, Air pressure sensors are an item added to a vehicle as a selling item and has nothing to do with whether you will or will not have a flat. If you are in the habit of looking at you tires occassionally, you can discard them. My point is this, if it has nothing to do with the vehicle continuing to be mechanically sound and running good, it's only there as a trinket. And we buy a lot of those. LOL

[Tx Bohemian]

Thanks for all the comments guys.

That's a great site Black Dog, I'll put that in my favorites.

That's my thinking too Wizard, the small amount of difference will probably not make a hill of beans in the operation.  Shoot, I may even get better MPG!!
I was thinking the same thing to check it with our GPS.  Incidently we're heading your way (Houston)tomorrow.  May swing by your place if I got time. 

[scoot]

keep in mind that when the anti-locking brake light comes on, it does not mean there is something wrong with your brakes or that you will not have any brakes. That light is controlled by a speed sensor, also sometimes located in the rearend housing. Next is my opinion only, Air pressure sensors are an item added to a vehicle as a selling item and has nothing to do with whether you will or will not have a flat. If you are in the habit of looking at you tires occassionally, you can discard them. My point is this, if it has nothing to do with the vehicle continuing to be mechanically sound and running good, it's only there as a trinket. And we buy a lot of those. LOL

Da^%&%, my rear seat DVD player doesn't get me better gas milage and make it go faster 

[Robert]

As long as you do all the tires it doesn't make a difference

[blackcat]

after installing taller tires you can use a programmer such as a Hypertech or Superchips to recalibrate the speedometer if it throws things off to much

[flcjr]

I have been a gm tech all of my adult life and that little change wont make a big difference but your local dealer can program the new size in for you so all is correct. just make sure all are the same

[Tx Bohemian]

I have been a gm tech all of my adult life and that little change wont make a big difference but your local dealer can program the new size in for you so all is correct. just make sure all are the same

I too was a Chevy tech many years ago, till '92, and I was the Brake/frt end man.  Through the times the anti-lock brakes were in their infancy.

Back then when people changed tire size, to adjust for the speedo and correct anti-lock brake function, we had to figure the tire circumference, rear end ratio, and a couple of other things, plug that info into a formula then pull the speedo, remove the ROM, break off certain pins on a new ROM ( I think there was like 12 of them) and reassemble...

I kinda figured there is an easier way to do this by now.  Also they said it will cost about $100.  I'll just see how bad it is first.

Thanks for the info.

[flcjr]

the process is much eaiser than it used to be just a matter of a few minutes and a scan tool the cost may be close too a hundred bucks depending on your dealer and shop rate if you lived closer you could swing by and i would do it for a cold adult beverage.

[Tx Bohemian]

the process is much eaiser than it used to be just a matter of a few minutes and a scan tool the cost may be close too a hundred bucks depending on your dealer and shop rate if you lived closer you could swing by and i would do it for a cold adult beverage.

Hey, wish i lived closer too!

But, you know, we have great riding weather down here this week, would make a fantastic bike ride for you!!!!

[flcjr]

i would love to ride but way too much snow and only about 10 degrees out