My chevy 2500hd has gotten stuck in pismo a few times and now its time to change the tires. I'm looking at Goodyear Wrangler All Terrains in a 265 size. My stock tires were 245. I'm not making a big change because i've heard that the bigger the tire, the less you can tow. my question is will the jump from 245 to 265 make a difference in the sand, and also will it reduce towing power by much?

 

The size of the tire won't make a difference in how much you can tow, it's the load rating that matters. You may lose some power because of the rotating mass though. As for the size of the tire I'm not sure about your question. I don't think changing the height of the tire will make much of a difference but it could. If you go to a wider tire it will help as long as you air down. You want to increase as much of the contact patch as possible so you float on top of the sand, not sink. All Terrain tires will be much better in the sand then say a mud tire, mud tires tend to move too much sand. I like the Nitto Terra Grapplers. Great all around tire!! They're quiet, last alot of miles, aren't too expensive and look good. I run mine at Dumont, Pismo and alot of desert driving with a bunch of towing mixed in. Mine are a "little" larger( 37" ) then what you are looking for but I would think they would work about the same. The key is airing down all the tires, including the trailer, before you get stuck!! I take mine down to about 15-17lbs from 65lbs.

Also, you didn't say if it was a 4x4, but I assume not if your getting stuck alot.

 

actually it is a 4x4 which is what makes it pathetic. I got stuck once in pismo and once in glamis, i think my trailer is just really heavy and those stock street tires weren't getting nearly enough traction.

 

Did you air down all the tires? How big and heavy is your trailer? Just curious what motor you have, not that it makes much difference besides weight. What ever tire you decide on make sure that if most of your driving is highway and sand stay away from tires with big lugs. They don't work too well in sand and are noisy on the street!!
You can kinda see my tires in my gallery. But like I said they are pretty big, 355/65/18.

 

I love these techie type questions.... WARNING MATH BELOW!

A wider tire with the same aspect ratio on the same rim will be slightly taller. The tire being taller changes the gear ratio.

Let's take LTZ's tire size: 355/65/18

The tread (not the tire completely) is 355mm wide.

The aspect ratio is 65%. The aspect ratio is the sidewall height.

And of course the 18 is the rim size.

The actual sidewall height is: 230.75mm (make sure to double that result when figuring).

The rim is 457.2mm

So the total tire height is 457.2+(230.75x2) = 918.7mm = 36" and change.

Not knowing what your aspect ratio is, I'm gonna take a guess at 65% as that seems to be popular in a standard profile tire.

Numbers are in milimeters, unless marked otherwise.

Stock height (assuming your tire is 245/65/16):

Wheel: 406.4
Tire: 159.25
Total: 406.4+(159.25x2)=724.9 = 28.54"
Circumfrance: 724.9*3.14=2275.2126 = 89.58 = 707 RPM (Rev./mile, 1 mile = 63,360")

265/65/16:

Wheel: 406.4
Tire: 172.25
Total: 406.4+(172.25x2)=750.9 = 29.56"
Circumfrance: 750.9*3.14=2357.826 = 92.83" = 683 RPM

The tire change is about a half step in a gear swap between 4.10 and 3.73 (those are Ford sizes, I think GM is 4.11 and 3.73). It would be about a 3.95 is such a thing existed. That's one of the reasons you lose some power with a larger tire. It will hurt your towing some as the engine will be working harder as it's turning slower at a given speed, again, decreasing MPG. Going to a 31" tire will be about one gear size. You could them swap out the gears and be close to the gear ratio, but you'll still be down on power, a little at least, because of the tire weight. Gear will probably run you a couple grand (since you're 4x4), if done right. You can also drop in a locker or two.

You could also go to the 265, swap gears and gain power for towing. Your unloaded highway mileage would probably go down. City mileage might increase, and towing could even increase. You can spin an engine faster, and still use less fuel. Especially with todays rev happy truck motors.

I'll affirm the airing down. Get down under 20lbs. As long as the rim isn't pinching the sidewall, and you don't try to cut sharply, you won't have a problem.

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I'm speechless ^^^^^ Nice!!!!!!!!!! [img]i/expressions/face-icon-small-happy.gif[/img]

 

Thank you, thank you.

<takes a bow>

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Showoff!!!!LOL

 

Good information. I just went through a situation along those lines. Last year I bought a new 2005 F350. It had straight ribbed tires on it, 18" wheels. The bad weather was about finished so I figured I'd run them until this past fall and put all-terrains on it. Then, nothing in any of the catalogs for an all-terrain for 18" wheels, GVW, etc.

1. Anyone is fortunate to find a tire guy, or lady, who knows their stuff. If it isn't in the catalog, they don't have it. I'm sure you're out there, but you're few and far between and I know you really don't have time to cater to **** people like me.

2. There are some excellent Internet tire sites with tire size calculators that use speedometer MPH as a final calculation. I emailed a racer buddy who's up on final drive/tires/rpm calculations and he said use it. As he correctly pointed out, modern speedometers are calculated on optimal original equipment combinations of components for the vehicle.

3. There are so many combinations of tire height, width, tread and sidewall design that I'm glad I found those websites. I got within 1 mph and a few hundred pounds of GVW. It took me awhile to put in all the possibilities, but it was worth it. I like technology.

 

Just replaced the 245's on my Duramax to 265's and dealer told me his computer could not re-program my speedometer for the that size. At highway speeds, the speedo seems slow and I figure that the mileage readings are now off too. Is there a programmer available that you can use to recalibrate the speedo and get accurate fuel economy readings?