carleeno
Advanced Member
https://tiresize.com/comparison/ can help you to visualize the difference. The tires he put on are 16% wider and 6% taller.
Normal tire sizes are expressed as:
[width in mm] / [aspect ratio in %] R [rim diameter in inches]
(the R just stands for radial btw)
Aspect ratio is the sidewall / width expressed as %. So your old tires were 255 mm wide (10 inches), 70% of that is 178mm (7 inches), that's your sidewall height. Add 2x that to the rim diameter (7 * 2 + 22.5) and you get your overall diameter (36.5) (there are some rounding errors converting from mm to inches)
For truck tire sizes like 10R22.5, it's [width in inches] R [rim diameter in inches]. The aspect ratio is always 88%, so if you want to plug in those sizes to the calculator above, just multiply the width by 25.4 to get mm for the first number, and use 88 as the second number.
10R22.5 would have been even taller at 9.8% larger than your originals, but the same width. So assuming that the tires he installed are sufficiently rated for the rear axle weight limit (or less if you're willing to sacrifice load capacity compared to the sticker in the bus) then you're good.
There are probably other sizes in-between like 255/80R22.5 that have a slightly smaller increase in height and without adding to the width compared to the originals. However truck tires generally are skinnier and run a much higher pressure to compensate for the heavy load (skinnier means better fuel economy). So the reason your guy might have increased the width is to ensure it can handle the weight of your bus at a lower pressure, or that was the smallest he had that had sufficient load rating to match the sticker on your bus. Or it could just be what he had in stock at the warehouse.
As for clearance to the fender, you want to consider worst case of going over a big bump and hitting bump stops when the suspension is fully compressed for a moment. The biggest question is does your bus have air ride in the rear or leaf springs?
If air ride, it mostly will have the same ride height when empty as well as loaded. Just make sure you're not overloaded once you've added all your materials, water tanks, batteries, solar, and people inside. While it's empty, take it to a CAT scale and get a weight slip so you know how much weight is on each axle, compare that to the sticker inside so you know how much you can add, and try to stay well below that. These buses can take a LOT of weight...but I've seen people create dangerous situations by putting all their water in the rear for example, putting too much weight on the rear axle and making the front light.
Anyway, if it's air ride, don't expect it to sit much lower when loaded...but regardless you need to check that it doesn't rub when going over bumps, which you won't know until you have some load in it. So my advice is to wait and see, but definitely don't forget to check! As for a small lift, there may have been others on here doing that but I don't know the first thing about axle geometry except that it's black magic :wink1:
If you're really only adding 2000 lbs (that's light!) then my gut feeling is that it'll be fine, especially with leaf springs as they're going to be made for much more weight, so it'll ride very stiff without much weight. even with air ride it'll still feel kinda stiff when empty because the shocks are tuned for more load (the shocks determine how fast the suspension can respond to bumps).
All that to say: the only way to know if it'll rub is to see if it rubs. Just keep watching for scrapes/grooves on the sidewall and tread where it might be meeting metal when hitting bumps. Other's here might have more experience with knowing how much suspension travel to expect in practice and you might be able to judge how much it "might" move.
Anyway, I'm looking forward to see this come to life!
