Different tire sizes

[Spaznaut]

So my bus doesn't seem to have any one brand of tire on it. But what is bothering me is that the front are 9R22.5 and the back is 10R22.5. My sticker for tire sizes inside the bus is faded to the point you can't see what size is recommended for it. This is a '95 Int 3800 shorty 5 window. I know my speedo seems to be pretty accurate as my friend following me home said I was doing 55 and I'm limited to 55 (2,300 rpm ) One of the front steers has some really weird cupping on the inside edge so I'll be replacing them first. Will an 11inch or 295/75-22.5 bother anything? It seems the back is a little higher anyway. One side of the back has dry rotting so they'll have to be replaced later on. I'd like to go to the 11R22.5 to get a little more speed on this machine as it seems the rpm's are about maxed for cruising at top governed speed.

[plfking]

I've got 11R 22.5s on mine all around. I've got the majority of my build done weight-wise, with no clearance issues at all.

[rossvtaylor]

I've owned 4 of the same bus...1995 IH 3800...but in a 7-window size. They all had/have 11R22.5 tires on them. The popular (with semi trucks) "low pro" is about the same size. Either of those should be a good choice for your bus.

[TheHubbardBus]

As long as you've accounted for other important parameters (tire-to-chassis clearance, ground clearance, etc), tire height can be chosen to optimize your final drive ratio. It can also negatively impact your gearing if you choose a tire size without considering the impact it will have on gearing. So that might be something you'll want to consider.

Also, your wheel size will determine what range of tire sizes you can mount. You definitely don't want to mount tires that are too big or too small for the wheel. In general it's a pretty narrow range of tire sizes allowed for a particular wheel size. Within that range, the 'measuring rim' size, or 'design wheel' size, will be what's considered optimimum for that tire. It's also what measurements like tire height will be based on. If you mount a tire on a wheel that's a bit smaller or larger than the measuring rim size - but still within the acceptable range - it will change the aspect ratio of the mounted tire and therefore change, to a small extent, both the contact patch width & tire height.