brocki Report post Posted March 5, 2018 When we purchased our '07 Tiffin Phaeton in '12, it came with a 1 year old set of Roadmaster 11R22.5 sized tires. The placard in the coach calls for 275/80R22.5 size. The current tires have performed well without problems until a year ago when due to a blister in one of the fronts, I had to buy a new pair of tires for the steer axle. I could get Good Year Marathon brand in the 11R size and have been very satisfied with the handling and ride. My question is this: We are due to replace the rear 4 tires this year. I have had very good service from the 11R22.5 sized tires but would like to know the actual size difference between before I would make up my mind which tire size to pursue. Does anyone know of any tire size charts that give actual physical dimensions? This coach tends to sit a little nose down and if the 11Rs are slightly bigger than the 275s, I might mix the sizes to level the coach out. Share this post Link to post Share on other sites
f442485 Report post Posted March 5, 2018 It's really not recommended to run two different tire sizes. the nose low looks might be just the way the body is hung. you can check frame heights with a tape measure to check if it's tires or body. you also might want to check your air bags. I would definitely would use what the manufacture recommends. Check with your local tire service writer and he can answer all your questions. Share this post Link to post Share on other sites
richard5933 Report post Posted March 5, 2018 Even between two different brands of tires it's possible to get slight differences how the coach will sit due to manufacturing and material variations. Even more so between tires made according to two different size standards. You'll also find variances in 'revs per mile' for each tire. This comes into play with things like gear ratios, speedometer function, etc. (Rev per mile is usually on the spec sheet for each tire model/size/brand) Always best to stick with the manufacturer's recommended tire size. If for some reason it's necessary to switch from metric sizing to the old style I'd be consistent all around, if it were my vehicle. Share this post Link to post Share on other sites
manholt Report post Posted March 5, 2018 brocki. Our tire expert is Rodger "Tireman", click on any of his links, and you will find chart's and answer's to most of your questions. That's how Richard learned so much about rims/tires! You can also send Rodger a PM. I will say this, my coach came with 295R80, I had a bad steer tire in 2014, so I got 2 new 315R80 and 6 new 295R80's. The 315 are heavier than the 295's and my mpg, dropped from 6.8 to 6.4 ! Share this post Link to post Share on other sites
tireman9 Report post Posted March 5, 2018 18 hours ago, brocki said: When we purchased our '07 Tiffin Phaeton in '12, it came with a 1 year old set of Roadmaster 11R22.5 sized tires. The placard in the coach calls for 275/80R22.5 size. The current tires have performed well without problems until a year ago when due to a blister in one of the fronts, I had to buy a new pair of tires for the steer axle. I could get Good Year Marathon brand in the 11R size and have been very satisfied with the handling and ride. My question is this: We are due to replace the rear 4 tires this year. I have had very good service from the 11R22.5 sized tires but would like to know the actual size difference between before I would make up my mind which tire size to pursue. Does anyone know of any tire size charts that give actual physical dimensions? This coach tends to sit a little nose down and if the 11Rs are slightly bigger than the 275s, I might mix the sizes to level the coach out. 2 I suggest you look at the published dimensions for the tires you are considering from the manufacturer you are considering. While tire companies generally follow the same guidelines, there are variations. You mentioned Goodyear brand. You could check HERE and HERE There are alternatives Dayton brand HERE Continental Firestone Goodrich Roadmaster Share this post Link to post Share on other sites
brocki Report post Posted March 7, 2018 On 3/5/2018 at 4:24 PM, tireman9 said: I suggest you look at the published dimensions for the tires you are considering from the manufacturer you are considering. While tire companies generally follow the same guidelines, there are variations. You mentioned Goodyear brand. You could check HERE and HERE There are alternatives Dayton brand HERE Continental Firestone Goodrich Roadmaster Thanks tireman9, that is a great start for me. I used the "bus and coach" for the type selection. But interesting, the only brand that I could find a chart that listed dimensions, Firestone, those lines were all blanked out. I guess I will give up on figuring that out. I also noticed something else. I''m sure I knew this at one time but have forgotten, the OEM requirements for the tire size is a G rated tire. All the ones that re currently on here are H rated. So I am certainly not slighting my load capability. At this point, I will probably lean toward Good Year Marathon in 11R22.5. The 2 I have in front ride and handle wonderfully. That way dimensions are not a factor. Another thing in their favor is the fact that a tire inflation chart is right up front. Something I insist on for any tire I buy. Thanks again to all who responded. Share this post Link to post Share on other sites
tireman9 Report post Posted March 7, 2018 In general if you are happy with the ires you have already used I see little reason to change unless there is some significant reason. Share this post Link to post Share on other sites
