Tire size requirement

[mhhobo1@gmail.com]

I went to a tire shop that specializes in motorhome tire replacement. The salesperson said the Toyo tires for my coach were no longer available. I was told that Goodyear made a special tire for coaches in the 12R22.5 size (G149RSA) that would replace the original Toyos. The only difference is the Goodyear tires have less rubber thickness in the tread area, making for a lighter-weight tire and better ride. The Goodyear tire is also 1/2 inch smaller in rolling diameter than the Toyo tires of the same size. This concerns me. The Allison transmission computer is programed for tires of a larger circumference.

Will these smaller tires have an adverse effect on fuel economy, performance, engine and transmission wear?

[wolfe10]

I went to a tire shop that specializes in motorhome tire replacement. The salesperson said the Toyo tires for my coach were no longer available. I was told that Goodyear made a special tire for coaches in the 12R22.5 size (G149RSA) that would replace the original Toyos. The only difference is the Goodyear tires have less rubber thickness in the tread area, making for a lighter-weight tire and better ride. The Goodyear tire is also 1/2 inch smaller in rolling diameter than the Toyo tires of the same size. This concerns me. The Allison transmission computer is programed for tires of a larger circumference.

Will these smaller tires have an adverse effect on fuel economy, performance, engine and transmission wear?

The most accurate reference when discussing "effective change in gear ratio" -- economy, performance, etc is REVOLUTIONS PER MILE. Check the tire manufacturer's websites/publications for this information. Do not rule out going to a metric replacement for the 12R's.

Brett Wolfe

[tbutler]

Talk to Allison about your concerns and see what they say. Anything that is programmed can be reprogrammed. I have had our Allison transmission reprogrammed to adjust for my driving style when we purchased a used motor home. Actually it was deprogrammed and then set to learn mode again. I'm sure they can make an adjustment for tire diameter if need be.

[wolfe10]

If what you are concerned about is engine RPM's/shift points, I BELIEVE (please confirm with the Allison number below-- I have no phone service where we are this week) that the Allison ECU makes "shift decisions" based on engine RPM. So tire size should not change shift points from an engine RPM standpoint, though of course it would be at a slightly different actual road speed.

Allison help line 800 252 5283.

Brett Wolfe

[pegandronthompson@comcast.net]

I went to a tire shop that specializes in motorhome tire replacement. The salesperson said the Toyo tires for my coach were no longer available. I was told that Goodyear made a special tire for coaches in the 12R22.5 size (G149RSA) that would replace the original Toyos. The only difference is the Goodyear tires have less rubber thickness in the tread area, making for a lighter-weight tire and better ride. The Goodyear tire is also 1/2 inch smaller in rolling diameter than the Toyo tires of the same size. This concerns me. The Allison transmission computer is programed for tires of a larger circumference.

Will these smaller tires have an adverse effect on fuel economy, performance, engine and transmission wear?

I am also in need of replacements for my Toyo 12R 22.5's. The G149RSA Goodyears seem like a direct replacement but appear to be optimized for long life truck aplication. Unlike the Goodyear G670RV which are RV specific - but only come in metric size. The 295/80R22.5 appear to be shorter (41.3 vs. 42.8 inch "outside diameter") and wider (12.1 vs 11.6 inch "Overall Width" - according to the local dealer).

I would like to go with the G670RV's but there are several questions I would appreciate any information on... Are the G670RV tires really better on my RV (Quieter? Smoother? Better handling? Something else?). Should I be concerned about the additional width, particularly on the rear where best I can tell my space between duals will be reduced to about 0.5 inch? How about the roughly 3 percent height reduction?

The tires will go on my 32' non-slide Country Coach Intrigue so the weight loading is not high. Not sure the significance but I also note that CC changed to 295/80R22.5 in the 2007 model year.

Any help or experience would be appreciated.

[pegandronthompson@comcast.net]

I am also in need of replacements for my Toyo 12R 22.5's. The G149RSA Goodyears seem like a direct replacement but appear to be optimized for long life truck aplication. Unlike the Goodyear G670RV which are RV specific - but only come in metric size. The 295/80R22.5 appear to be shorter (41.3 vs. 42.8 inch "outside diameter") and wider (12.1 vs 11.6 inch "Overall Width" - according to the local dealer).

I would like to go with the G670RV's but there are several questions I would appreciate any information on... Are the G670RV tires really better on my RV (Quieter? Smoother? Better handling? Something else?). Should I be concerned about the additional width, particularly on the rear where best I can tell my space between duals will be reduced to about 0.5 inch? How about the roughly 3 percent height reduction?

The tires will go on my 32' non-slide Country Coach Intrigue so the weight loading is not high. Not sure the significance but I also note that CC changed to 295/80R22.5 in the 2007 model year.

Any help or experience would be appreciated.

Just an update for anyone that might be interested...

Have been talking with a friend with directly applicable, first hand experience. He ordered his 2006 CC with Goodyear G670RV 295/80R22.5 tires. However, it came through with Toyo 12R 22.5's. CC was transitoning that year from the TOYO's to the G670RV's. CC, being the good company that it was, let him take delivery of the coach with the TOYO's and promised to replace the tires - which they soon did. He tells me that the G670RV's fit with no problems and the the ride was much improved (went from good to great). The TOYO's had a harsher ride than the goodyears - as you might expect a truck tire might provide vs the G670 - RV specific tire.

I was also contacted by "Tim" at Goodyear. His position was that the "dual clearence" would not be a problem and that the G670RV's would be a much better choice.

My plan is to go with the G670RV's