New Tires For My TV

sawdust · 02-19-2016, 02:24 PM

I have a 2010 GMC 1500 p/u and just purchased a 2005 25Z. My factory trucks tires are about do for replacement. They are P245/70R17s now. I plan on installing LT tires. The tire store told me that a LT 265/70R17s are more common for this size truck. There is less than $10.00 difference in the price per tire. Has anyone made this tire size change and how did it work out?

clubhouse · 02-19-2016, 02:41 PM

I went from 245 to 265, primarily for looks, and have no issues. Wish I went to 285, again for looks, but was concerned about the increased fire size having a negative affect on towing performance do to increased final drive ratio.

If I was to do it again, I would have 285 since there was no noticeable impact at 265.

ROC-REQS · 02-19-2016, 02:59 PM

I also went from 245 (LT245/75R16E) to 265 (LT265/75R16E) on our previous TV - 2006 GMC 25OOHD, same as clubhouse indicated - primarily for looks.

The change had no impact on ride or towing.
But it did impact the speedometer reading by ~2mph

oldmanAZ · 02-19-2016, 04:55 PM

It seems very likely the diesel TVs in the group would have little problem changing to larger tire sizes.

I had a class B; E-250, V8, automatic. I changed to a larger LT tire for the looks. Loved the look, but any highway uphill ability went into the crapper! When those tires needed replacing, I went back to the OEM (smaller) size in an LT tire. Didn't care for the looks with the smaller tires, but I hated the downshifting on moderate highway hills with the larger tire size. (Sorry. I don't have info on the various tire sizes or rear axle ratio.)

Paintinfool3 · 02-19-2016, 06:45 PM

yeah all depends on gears and rpms, I went larger on my last diesel to try to lower rpms on highway. I was at 2400 at 70 and didn't like running that high

sawdust · 02-22-2016, 10:31 PM

Are the 265s wider or taller then the 245s?

clubhouse · 02-22-2016, 10:57 PM

Both

etex211 · 02-23-2016, 05:40 AM

Be careful putting on larger tires. It is the same thing as taking gear out of the truck, and it hurts towing performance.

At the very least, if you go to the larger tires, get the computer reprogrammed for the larger tires so the truck will at least know what it's dealing with.

need-a-vacation · 02-23-2016, 05:58 AM

Sawdust,

What is the specs of your truck drivetrain wise? 5.3/6spd/3.42, or 4.8/4spd/???, or ???

The 245/265 is the width of the tire, while the sidewall height is the 70 which is 70% of the width of the tire.

If you have the 5.3/6spd/3.42, you should be fine. Look in your glovebox for the gear code.

Gone campin · 02-23-2016, 06:37 AM

Quote:

Originally Posted by etex211

Be careful putting on larger tires. It is the same thing as taking gear out of the truck, and it hurts towing performance.

At the very least, if you go to the larger tires, get the computer reprogrammed for the larger tires so the truck will at least know what it's dealing with.

X2 - if you don't reprogram the computer when changing tire size (circumference), your speedometer and shift points/convertor lockup will all be off. A slight change may not be too noticeable, but they will be off none the less...

Gone campin · 02-23-2016, 06:41 AM

I do computer programming on GM trucks - if you post up your gear ratio, original tire size, and new tire size, I can input the numbers and tell you how many MPH you will be off...

Poppy · 02-23-2016, 07:36 AM

There are tire size calculators on the internet that you can use. One that I used for my truck was at tacomaworld.com.
My truck is an 06' Chevy CC 4x4 6.0 gas with 4.10. Stock tires were 245/75r16, but the p.o. put on 285/75r16 and I wanted to know what the speed difference was. It went from +1.55 @ 20mph to +5.04 @ 65 mph. (The + is what I have to add to the speedo reading to get the accurate speed.)

Gone campin · 02-23-2016, 07:41 AM

I didn't realize they were out there - should have guessed... it is the internet after all LOL!

sawdust · 02-23-2016, 08:26 PM

Thanks for all of the information everyone.

My truck is a 2010 GMC 1500 with a 5.3 engine and a 6 speed trans. The rear end is 3:42 with limited slip diff. My original tires are P245/70R17s. I had a tent trailer when I bought the truck and now have a 2005 jay feather 25z and this why I am looking into the LT tire.

Gone campin · 02-26-2016, 05:25 PM

Quote:

Originally Posted by sawdust

Thanks for all of the information everyone.

My truck is a 2010 GMC 1500 with a 5.3 engine and a 6 speed trans. The rear end is 3:42 with limited slip diff. My original tires are P245/70R17s. I had a tent trailer when I bought the truck and now have a 2005 jay feather 25z and this why I am looking into the LT tire.

That small of a change in size makes it off by only 1 MPH at 20 MPH and only 2 MPH at 70 MPH - you won't even notice it!

rangerdoc · 03-01-2016, 02:22 PM

But your odometer knows, so you're adding miles on faster. Get your speedo recalculated.

Also remember, the tire size is width/aspec ratio-rim size. A 70 aspec ratio on a 245 tire isn't the same as a 70 aspect ratio on a 265 tire. 70 does not equal 70. If you go to tirerack.com and find the tire you like, then look at the specs tab, you'll see it will give the overall diameter of your tire (28", 32", 33", etc). This will allow you to compare the overall diameter to your stock size and other tires. It also gives the RPMs per mile, which is what you change in the computer (at least with a handheld tuner) so the speedo is accurate.

I've actually seen the same tire size, say 275/55-19, from different manufacturers have different overall diameters. Also remember that speed ratings are only consistent within the same manufacturer. There is no mandated standard how they are tested. So a V rated Pirelli tire isn't necessarily the same as a V rated Goodyear tire because the two manufacturers test their tires differently. You can only compare V rated within the same brand.

Honestly, I recommend everyone with a truck get some sort of handheld tuner. Almost all truck engines will benefit from the tune and then you have the ability to read codes and make changes to your computer.

Magnolia Tom · 03-01-2016, 04:59 PM

Quote:

Originally Posted by sawdust

Thanks for all of the information everyone.

My truck is a 2010 GMC 1500 with a 5.3 engine and a 6 speed trans. The rear end is 3:42 with limited slip diff. My original tires are P245/70R17s. I had a tent trailer when I bought the truck and now have a 2005 jay feather 25z and this why I am looking into the LT tire.

I guess I'm the only one that is surprised that a 1/2 ton truck doesn't come with LT tires from the factory? All the new trucks I've owned had LT tires on them

need-a-vacation · 03-02-2016, 12:26 PM

Sawdust,

Here is a tire size comparison.

Rangerdoc,

By going to a larger tire than the stock size the odometer will actually show less miles driven than actual.

The concern with a tuner is the reports of the dealers/ manufactures being able to "see" that a computer has been "played with", resulting in a red flag of your vehicle and a voided drivetrain/ engine warranty (or whatever exactly they try to void). While the Magnuson-Moss act needs the manufacture/ dealer to prove the alteration caused the failure, it would still be a fight if they have already "red flagged" your vin.

rangerdoc · 03-02-2016, 01:00 PM

Ha, good catch on me having things backwards. Still, I say get the speedo set correctly.

As far as the tuner, I'm a mustang guy and I've tuned my cars for years...along with tons of us in the mustang world. I've never heard of anyone being told their tune caused a problem that the dealer wouldn't fix (though bad tunes have blown engines...usually people know they are on the edge). I have heard of a couple dealers say they wouldn't touch a car that had been tuned, but that is dealer specific and they are being dumb. I always return my car back to stock tune prior to going to a dealer, just in case they decide to mess with the computer. That is just the smart way to do things. And it doesn't matter if they can see it has been messed with. I've never heard of someone being flagged. I'm sure it happens, but in all the forums I've read over the last 10 years nobody has complained about it. In the F150 ecoboost world, tuning is also a popular mod and everything is on par with my mustang comments. Truck engines have so much useable power left that getting a tuner really helps in our towing needs. I understand people's hesitation to use one, I was that way with my first one. But man, I wouldn't have it any other way now. The ability to diagnose the car and make changes the way I want is an equal benefit to extra hp/torque...which usually results in 1-2 better mph.

Anyways, way off topic now...sorry. I'm sure there are some threads on here about this. If nothing else, find a forum for your TV and see what they say on there about tuners.

Fill The Coolers · 03-17-2016, 05:55 PM

I've been snooping here and there about tires suitable for towing to go on my Ram 1500 this season. I had the OEM passenger tires on the truck which were fine when I was towing the pop up and then switched to Cooper Discoverer AT/3. That set wore quicker than a pencil eraser and brought me to eyeballing a set of Michelin Defender LTX M/S's. My OEM size was 275-65-R20 but in order to get a LT rated tire in 20" I have to switch to a LT265 60 R20. Has anyone made a switch from passenger to LT rating in a 20" size?

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