Which tire size is better for gas mileage for towing ?

[GMmaniac]

Have a 2010 GMC Sierra Z71 Crew Cab with 5.3 LC9, 6 speed auto, short box, 3.42 gears, towing package. When I bought it, I bought new bigger tires at same time . It had P 265 75R 17 tires on it and I put eight ply 285 70 17 AT on it. Looking forward to start towing with it . Probably around a 6000 - 7000lb trailer with weight dist hitch assembly.

 

It gets pretty good gas mileage ( 18mpg highway )( 14mpg city ) and great power . Will keep the payload of 1575 and 9500lb trailer as the truck manual states within specs. Fixing to buy some new tires and just wondered if the original size would be better size or the size I put on it ? Thinking Michelin 8 ply tires.

 

Any thoughts on which size would be best, are greatly appreciated.

 

Thank you

 

Kenny

[Chris]

Original size. It was designed for a compromise of performance and economy. That is why GM put the 265/70R17 on from the factory. Your pist of 265/75R17 is wrong. The 265/75 combo was pre-2005 when they used a 16" wheel.

[00Silverado4x4]

I'd keep the stock size. When I bought mine the tires on it were 2" taller then stock. Since the tires were shot anyway I replaced them with stock size/type tires. Taller tires would essentially raise (numerically lower) your gear ratio and actually reduce your ability to tow. This would make your engine work harder and therefore "could" reduce gas mileage further.

[pcf]

The ply rating of a tire is really not relevant anymore. Most P rated tires are one ply and E rated LT's usually don't go past three plies.

 

One thing that gets overlooked in tires is rotational inertia. Generally speaking larger diameter and heavier tires have a higher rotational inertia than smaller diameter lightwieght tires. (Duh) The thing to consider is that 10lbs extra pounds per tire, times four tires, can be the equivalent of adding 2-300 pounds of cargo to your truck. And that's weight that is always sucking power out of your drivetrain.

 

If you don't "need" a all terrain tire, I would look at a Michelin LTX MS2 P265/70R17 113T, which at 42lbs a tire isn't the best, but it's a good tire overall. A P XL or C rated LT tire would also be good. With the D and E rated tires your pushing a lot of extra weight, dealing with higher rolling resistance, not getting the benefit of the higher pressure ratings and possibly experience bad wear patterns and poor traction due to under inflation.

[GMmaniac]

Thank you for the replies. Anymore comments ?

 

Thank you

 

Kenny

[Jsdirt]

Yeah I don't play around with tire sizing. I always keep the stock size - if I can't find that size in whatever brand I'm looking at, I buy another brand. Just not worth the headaches.

 

At the very least, your speedometer/trip/odometer is wrong ... and at the worst, you have rubbing over big bumps, or when turning at full lock. The whole package works with the stock circumference.

 

That said, the 20's I ended up putting on my truck are .9% of the 18" wheels that came OEM - if the size is within 3%, it won't be too bad. Over that I'd steer clear.

 

Turns out my 20's are less than 1% - I corrected the figure ...

[GMmaniac]

Appreciate your comments, Computer was reset on truck when new tires put on. Speedometer is correct along with transmission shifting. Been lucky on full lock to lock with this truck as tires don't rub. My 2007 Chevy NBS would rub. :-) Think will go back to original size and lose about an inch, but hopefully with at least an LT tire, if not will stay with Load range D tires.

 

Thank you

 

Ken

[02suburbanZ71]

The ply rating of a tire is really not relevant anymore. Most P rated tires are one ply and E rated LT's usually don't go past three plies.

 

One thing that gets overlooked in tires is rotational inertia. Generally speaking larger diameter and heavier tires have a higher rotational inertia than smaller diameter lightwieght tires. (Duh) The thing to consider is that 10lbs extra pounds per tire, times four tires, can be the equivalent of adding 2-300 pounds of cargo to your truck. And that's weight that is always sucking power out of your drivetrain.

 

If you don't "need" a all terrain tire, I would look at a Michelin LTX MS2 P265/70R17 113T, which at 42lbs a tire isn't the best, but it's a good tire overall. A P XL or C rated LT tire would also be good. With the D and E rated tires your pushing a lot of extra weight, dealing with higher rolling resistance, not getting the benefit of the higher pressure ratings and possibly experience bad wear patterns and poor traction due to under inflation.

Does this mean the extra 300 lbs of cargo (tires) will result in better highway mpg because of all the momentum from the extra weight?

[02suburbanZ71]

I totally agree with everyone here. The stock tire size is the best

[GPGuy]

Agree again. Stock size is your best route for sure.

 

The ply rating of a tire is really not relevant anymore. Most P rated tires are one ply and E rated LT's usually don't go past three plies.

 

One thing that gets overlooked in tires is rotational inertia. Generally speaking larger diameter and heavier tires have a higher rotational inertia than smaller diameter lightwieght tires. (Duh) The thing to consider is that 10lbs extra pounds per tire, times four tires, can be the equivalent of adding 2-300 pounds of cargo to your truck. And that's weight that is always sucking power out of your drivetrain.

 

If you don't "need" a all terrain tire, I would look at a Michelin LTX MS2 P265/70R17 113T, which at 42lbs a tire isn't the best, but it's a good tire overall. A P XL or C rated LT tire would also be good. With the D and E rated tires your pushing a lot of extra weight, dealing with higher rolling resistance, not getting the benefit of the higher pressure ratings and possibly experience bad wear patterns and poor traction due to under inflation.

Ah come on...everyone needs All Terrains.

[02suburbanZ71]

Agree again. Stock size is your best route for sure.

 

Ah come on...everyone needs All Terrains.

I want LTX A/T2 but everyone says they suck in the mud and snow- because of that I'm forced to get nitto grappler G2's LT265/70/17 [emoji35][emoji35]

[GPGuy]

I want LTX A/T2 but everyone says they suck in the mud and snow- because of that I'm forced to get nitto grappler G2's LT265/70/17 [emoji35][emoji35]

Can't speak on those but I do know my BFG All Terrain KO2's are awesome. IMO. My only complaint would be that they are stone throwers if you travel a lot of stone roads. But for me that's not a concern because I'm usually on either pavement or dirt roads.

[Blue2500CC]

Kenny,

 

If you haven't bought tires yet, concerning P vs LT, I would stay with the LT's (at least a LR C) if you plan on towing a 6k+lb trailer. With a heavier trailer, you can get what I call "wiggle" as the tires sidewall flex from the tw (tongue weight). Feels like a couple people are pushing the rear of the truck back and forth sideways a little. We had that with our '10-1500 ccsb 4x4 towing our at the time 6500lb tt. Had a set of Copper A/T3 LR C's mounted up, and the wiggle was gone due to the little stiffer sidewall. Stock tires I would air up to 44psi so it wasn't a lack of air pressure. This is based on a tt or enclosed trailer with a higher tw compared to a open trailer with a lower tw. Not sure what type of trailer you will be towing.

 

Are you sure the stock tires were a 75 series? Look at the drivers door tag to verify. I was trying to look up overall height to compare the two sizes and most sites list your stock tire as a 265/70 for a 17" rim.

 

As for what size to go with, what area do you live in, and plan on doing most of your towing (99+%)? As mentioned, larger tires will change your gear ratio for the worse when towing. IF you go up slightly you should be fine, but I think your at the edge with the current tire size (pending where you live).

 

As a comparison, I went from the stock 265/65/18's on our '10-1500 to a 275/65/18 and didn't notice any change, but the 275's were just over 1/2" taller than stock. That was towing both our 6500lb tt and our new (to us) ~7300lb tt.

[GMmaniac]

Appreciate all the comments, I traded my 2010 1500 for new 2015 2500HD with Michelin AT2 18 inch tires. Needed the bigger payload.

 

Thank you

 

Ken