Lance 1025 on 3/4 ton diesel Silverado

Redsky wrote:
I switched to 285 tires from the factory 245 tires and in theory the gearing should have been 4% taller but in reality with the weight of a heavy camper in the bed the tires squat down and the speedometer is dead on accurate with the larger tires as a result. Without the camper the truck is going about 2-3 MPH faster than the speedometer indicates which is not enough to worry about.

X2 on speedometer change.

I still am glad I went with the Nitto Durra 285/75r/17s high load index on my forged Aluminum rims from stock 265 Michelins E tires after they wore out. Heavy camper with 3970 lbs. a piece at 80 psi. Will never go back to Stock tire. They always looked to small on my Dodge.

Redsky,

Going from 245 tires to 285 tires is just under 8% difference not 4% if both sizes were 75/16's "E" range and inflated to 80 psi. Here's a quick calculator for tire size differences:

http://tire-size-conversion.com/tire-size-calculator/

There are many others that give more info on tires and tire differences and the effects.

I switched to 285 tires from the factory 245 tires and in theory the gearing should have been 4% taller but in reality with the weight of a heavy camper in the bed the tires squat down and the speedometer is dead on accurate with the larger tires as a result. Without the camper the truck is going about 2-3 MPH faster than the speedometer indicates which is not enough to worry about.

Yes 7"+ are the recomended however, since 1997 I've had 265 Michelins on the stock OEM 6.5" wheels on 2 Chevy pickups and they have worked perfectly and have worn very even. Total of approx 260,000 miles with 265's on the two Chevy 2500's. One was gas and the other is diesel. I never corner fast as it wears tire edges quick and I also keep my tires at 80 psi at all times loaded or not. GM HD pickups ride quality is fine at 80 psi unloaded but others ride like buckboards. I do drop the airbags to 5-10 psi when unloaded as that makes a world of difference. Takes 2 minutes max to re-inflate them back to about 65 psi for carrying a load.

Just one little possible caution on tires. At least some 2006 2500HD wheels are only 6.5" wide, and all tire manufacturers that I know off recommend at least 7" wheels for 265/75R16 tires and above. Which is why (I suspect) that 3500 base wheels are 7" and why I upgraded to the 3500 wheels when I changed to 265/75R16 tires right after I bought the truck new.

woodchuck1,

Some info for you if you don't already know it.

Your 2500 came with 245's OEM at 3042 lbs capacity with 80 psi each tire. 2 times the 3042 is where your 6084 rear axle capacity comes from. Your axle stand alone is rated at over 10,000 by it's manufacturer. Your rear axle is identical to the 3500 SRW rear axle which has a 6800 - 6900 rear axle, depending on the truck's model year, as the 3500 SRW came OEM with 265's at 3415 lbs capacity with 80 psi each tire. The very same axle/dia is used on the 3500 DRW trucks with a different wheel mounting plate welded on the end for attaching the dual wheels. Your axle is very strong!

Tire dia's, widths, and circuference (Distance for one revolution) for your 2006 truck:

245's = 30.47" high, 9.65" wide, 95.72 circumference

265's = 31.65" high, 10.43" wide, 99.43" circumference

285's = 32.83" high, 11.23" wide, 103.13" circumference - 3750 capacity -(don't use as it hits and is more "wallowy"/"wandering" due the the greater distance from the tire bead to the tread surface giving more flexing) A couple of the reasons why few keep the 285's on when carrying a heavy TC!

Speedometer and shift points changes from 245's to 265's is 3.9% or you will be going faster than indicated and will shift/lockup/overdrive at a higher speed by 3.9%

good point, yes, it's a 4x4 extended cab.

OP, Whoa! I'm assuming your truck is a 4X4 since you are in Minnesota. If so, ALL 4 tires MUST be the same diameter or don't ever use your 4 wheel drive because you'll ruin the transfer case (very expensive repair). Because the smaller wheels will be turning faster than the larger dia ones and your locked in 4 wheel drive transfer case won't be happy at all and will puke!

Thiis is great. Thank you for all the feedback. This is what makes the RV forum so darn great. I have lots to chew on and decide now.