I changed the LT245/75R16E out for LT265/75R16E tires on my truck right after I bought it. The dealer cannot change the speedo but you should have the anti-lock brakes reprogramed to the correct size. It is a simple reprograming of the ABS system and will not affect the speedo. I work for the dealer and I called the GM Tech Line to get the new calibration settings for the 265's and GM will not give them, they said the truck came with 245's and is not available with 265's. I even gave them the old "The SRW 3500 has 265's on it" but it won't work....
Gary
Gary
Delaware
2006 Chevrolet Silverado 2500HD Crew Cab Duramax
2006 Outback 30FRKS
235/85-16 and 265/75-16 tires have (practicaly) the same diamter, because the difference in aspect ratio and width just happen to coincide to the same diameters-- 75% of 265mm versus 85% of 235mm of tire width.
Here is the forumla to determine tire diameter in inches from a metric tire size-
((2 x AspectRatio x TireWidth) / 2540) + WheelDiameter = TireDiameter,
where-
-AspectRatio is expressed as a percentage of TireDiameter
-TireDiameter is expressed in millimeters
-WheelDiameter is expressed in inches
((2 x 235 x 85) / 2540) + 16 = ~31.73"
((2 x 265 x 75) / 2540) + 16 = ~31.65"
To find TireWidth in inches, use this formula-
TireWidth (mm) / 25.4
265/25.4 = ~10.43"
235/25.4 = ~9.25"
Plug in the numbers for your favorite metric tire size and see what comes up!
I' doing something similar to Bryan with my dually also, 245-75-16 on the front, 215-85-16 on the rear. Toyo has both at 30.5".
Both these two sizes I use, and the 235-85 and 265-75 seem to be in about the 3x.5 to 3x.8" in hight range. In reality, even with 4wd, assuming a non full time transfer case, on should be able to run any combo without a problem as Bryan and I am doing with duallys. I do the same with my Navistar dumptruck, only 8r19.5's on the rear, and 245-70-19.5 on the front. Personally, I find this skinny rear, fat front to work well, as I do a lot of city driving, and the fronts last twice as long with the fatter tire than the skinny tire. I believe from having duals, the fronts get pushed more on turns, the skinny tires the tread will get a bigger angle for lack of wording, as such, wear on the outside more than a fatter lower profile tire.
As far as the original question........I have used on two previous GM's, 265's along with the stock 245's. I have run 265's on stock rims, and with 8" rims. The wider rim is a better ride, handling, and carries loads better! I noticed enough difference, that I personally can not recommend using a stock 6.5" rim with 265's. If you want a taller tire, go to a 235-85-16. Frankly, tween the 245, 235 and 265 tire with a proper rim width. the best is the 265, then the 245, and lastly, the 235 for handling, trailering etc IMHO on my 88 ex cab, and 96 CC GM models.
marty
05 Chev CC D/A LS Dooley
92 Navistar dump truck, 7.3L 7 sp, 4.33 gears with a Detroit no spin
00 Chev C2500, V5700, 4L80E, 4.10, base truck, no options!
92 Red-e-haul 12K equipment trailer
3 Single axle utility trailers
I did the change as well just because I didn't like the look of the smaller tires on my truck. LT245/75R16 to LT265/75R16 (load rating "E") I also have the Hypertech Power Programmer III that could change my tire size in the pcm.
Fire44 wrote: I changed the LT245/75R16E out for LT265/75R16E tires on my truck right after I bought it. The dealer cannot change the speedo but you should have the anti-lock brakes reprogramed to the correct size. It is a simple reprograming of the ABS system and will not affect the speedo. I work for the dealer and I called the GM Tech Line to get the new calibration settings for the 265's and GM will not give them, they said the truck came with 245's and is not available with 265's. I even gave them the old "The SRW 3500 has 265's on it" but it won't work....
Gary
A couple years after I had my truck I change to the larger tires and then wen to the dealer to have them reprogram the drivetrain for the larger tires. They did it with no problem at all.
I want to add to your thinking about speedometer differences when going from a 245/75/16 to a 265/75/16 tire. The actual difference is truly 3.9% when the 265's and the 245's are new. Zero miles on either of them. The speedometer will read 3.9% slow now because of the 265's are 1.1 inch greater diameter. There's a little more than 1/2" tread depth on these 2 tires which means that the well worn 245 is about another inch smaller in diameter than a new 265 tire. As there's a 2.1 inch diameter difference now, the percentage is 7.5% instead of the 3.9% you were expecting. That's an actual speed difference of 4.15 MPH at 60 MPH indicated over the old 245's. It will give you quite a difference in your sense of speed vs tach reading with the new tires and your fuel mileage DIC will drop approx 7.5% as will your low end torque from the old 245's. Your 3.73 rear ratio will immediately act like it's a 3.45 ratio as compared to when the well worn 245's were on the truck. As the new tires wear down, the differences shrink back to the actual 3.9%. Yes, the actual difference is the 3.9% but measurable difference is 7.5% when the 265's are new as compared to the worn 245's. The traffic your in will seem to be driving slower than they normally did but you'll get used to it. Unfortunately, the cop's radar won't know you just put on bigger tires so you'll have to keep reminding yourself of your true speed so you don't earn those coupons the cops love to give out. They aren't "money off" coupons!
I can assure you I was a weird feeling when we first changed our worn 245's to the 265's.
2004 Chev 2500HD D/A crew cab LB 4X4 - Air Bags - Loaded
915 Lance Camper with 2'X 8' rear porch (my own design n build)
29 ft Carri-lite 5th wheel - 1 large slide - specially built
36 ft Carriage - 3 axle 5'er -NOW SOLD- Looking at some new 5'ers
travelnutz wrote: I want to add to your thinking about speedometer differences when going from a 245/75/16 to a 265/75/16 tire. The actual difference is truly 3.9% when the 265's and the 245's are new. Zero miles on either of them. The speedometer will read 3.9% slow now because of the 265's are 1.1 inch greater diameter. There's a little more than 1/2" tread depth on these 2 tires which means that the well worn 245 is about another inch smaller in diameter than a new 265 tire. As there's a 2.1 inch diameter difference now, the percentage is 7.5% instead of the 3.9% you were expecting. That's an actual speed difference of 4.15 MPH at 60 MPH indicated over the old 245's. It will give you quite a difference in your sense of speed vs tach reading with the new tires and your fuel mileage DIC will drop approx 7.5% as will your low end torque from the old 245's. Your 3.73 rear ratio will immediately act like it's a 3.45 ratio as compared to when the well worn 245's were on the truck. As the new tires wear down, the differences shrink back to the actual 3.9%. Yes, the actual difference is the 3.9% but measurable difference is 7.5% when the 265's are new as compared to the worn 245's. The traffic your in will seem to be driving slower than they normally did but you'll get used to it. Unfortunately, the cop's radar won't know you just put on bigger tires so you'll have to keep reminding yourself of your true speed so you don't earn those coupons the cops love to give out. They aren't "money off" coupons!
I can assure you I was a weird feeling when we first changed our worn 245's to the 265's.
I had forgotten about this topic.
I found out about the speedometer difference with tire height when I was a kid with my first 4x4 (Bronco in my sig, which I still have after all these years). The cops pulled me over for doing '90'mph in a 55. I couldn't believe it. They were probly right, as the Bronco had 31" tires in place of the stock 27" tires it was designed with. A speedometer test at Dick's Speed-o-Tach revealed the percent difference and it was quite significant. Due to the speeding and alchohol tickets I got that day, I have kept that tire size/speedometer reading error in mind ever since.
Vehicle computers use their look up tables for the tire size and it is in dia.
BUT...that same computer calculates MPH based on rev's per mile from the sensor
in the tranny.
I use rev's per mile listed for all tires I'm looking at. Much more accurate
but note the wackiness of how they do it (not just GM, but all of them).
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...
I went from245's to 265's as well. To be certain about the speedo, and to get the most current updates, I sent the computer back to "wait4meperformance" and Jesse corrected all!!!
'07 Chevy 2500HD Classic 8.1L/Alli /4.10's, Tow Pkg,Factory Camper Mirrors. Equal-i-zer, Prodigy
'07 Homestead 292RKS All Options! (34' Trailer overall!)
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