speedo change with larger tires

[bigdog]

Can anyone tell me how much the difference is when changing from one size tires to a larger one makes on the odo and speedo?I noticed that the original tires on my LTS are 235X80X22.5 and the actual tires are 255X80X22.5,so what would be the difference and is there a way to change the 'puter for this.
I was told that it raises the front axle gross to 11,000# and the rear to 22,000#,but don't know what it makes to total.33K# ??. I do know that when we went out on the first trip last week,we had full fuel,full propane approx 20gals water and mebbee 10 gallons grey and black and not a heck of a lot in the bay and food and clothes for a week and according to the wall plaque with 235's I was 500# overweight on the scales??? Not much room for play there...

[DriVer]

Quote:

Originally Posted by bigdog I was told that it raises the front axle gross to 11,000# and the rear to 22,000#,but don't know what it makes to total.33K# ??....

bigdog, I would be cautious with what you were told until I could verify that. Normally tires alone are not going to increase the load carrying capacity of an axle. The GAWRs are set by the suspension and powertrain.

In my case I have 23,500 worth of axles on paper (GAWR) however I still only have 22,000 pounds of GVWR. I believe that since both tires that you are using are 80 series that a spedo gear change may not be critical but I'm not exactly 100% certain about that.

[Hooligan]

Bigdog- The tire manufacturers website will give the specs for each tire. The 235/80 is 37.1 in. diameter and does 556 turns per mile. The 255/80 is 38.5 in and 538 revs per mile. About a 3% change or less than 2 mph faster at 60mph indicated. Also check that the larger diameter tire will fit in the wheel well...
Weight rating are based on the weakest link. A 10,000 lb axle can only support 10,000 lbs, a tire can't make the axle stronger, but a lower rated tire could limit that axle to less than 10,000 lbs.

My MH came with 235/80 22.5 tires, I went to G670 Goodyear, 275/70R22.5 only 1/2inch bigger diameter and less than 1mph change at 60mph, but load range H instead of G tires, that can carry much more weight. (Or in my case the same weight at lower tire pressure)
My axle rating (GAWR) remained the same....
Hope this helps...

[bigdog]

My rig had the Michelin 255's on it when I got it used and they are the load range G and I'm running them at the suggested 110#s.So,I would imagine that being as they are about 1/2 the new tread the mileage would be about normal..

[GA Cajun]

You can recalibrate the speedo - or rather a Cat or Cummins shop can recalibrate it. I changed tires, too and had the Cat tech recalibrate the engine computer to the circumference of the new tires compared to the old. As someone posted above, you can get the specs from the tire manufacturer.