11R22.5 vs. 295/75R22.5 tires - School Bus Conversion Resources (2024)

porkchopsandwiches

Join Date: Jul 2013

Location: Maryland / Boulder

Posts: 347

Year: 1999

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Chassis: Saf-T-Liner MVP ER

Engine: CAT 3126b Rotella-Chugger

Rated Cap: 72

Hi,

So the tires on my bus are aging. They are old and the rears are almost at illegal tread. I came upon an opportunity for some free 11R22.5 tires off a dump truck from a construction company. I will check the date codes, but they said they are at most 3 years old with about a half inch of tread left. Not sure what brand. They may be recaps.

Currently my drive tires are Goodyear G622RTD (retread i think?) and the fronts are G622RSD, low profile 295/75R22.5 size. After looking at this table: https://www.fleet.ford.com/truckbbas...bb_pdf/233.pdf

I determined that the 11R22.5 tires are about 15mm narrower, and about 1.2 inches taller sidewall diameter. The taller sidewall will have the effect of gearing the bus up slightly, and making the speedo inaccurate (which it already is, I use my GPS for speed anyway). With the way this bus rides, I could use more sidewall, so that should not be a problem.

Assuming the tires are good and recent, do I take this deal, or is there some reason I shouldn't?

Thanks!

retiredChemist

Join Date: Jul 2016

Posts: 56

The 11r is usually a much cheaper tyre. If it will fit without issue, same speed index and within the weight window. I'd say use the cheapest tyre for the job.

The 11r usually has a better weight rating which will mean less pressure to carry the same weight. Giving a longer footprint and more sidewall flex. Which hurts mileage but gains traction. Less prone to breakage on severe corrugation too.

Also means it'll sink into the campground fractionally less.
The sidewalls on 11r can be two different ply ratings, the stiff ones can really hurt mileage if they're <90psi trying to inflate them to the right pressure for weight, if the front is very light.

But ultimately it's your decision what to do with your bus.

porkchopsandwiches

Join Date: Jul 2013

Location: Maryland / Boulder

Posts: 347

Year: 1999

Coachwork: Thomas Built

Chassis: Saf-T-Liner MVP ER

Engine: CAT 3126b Rotella-Chugger

Rated Cap: 72

Awesome, thanks for the pointers. The way my bus rides, it could use more sidewall. I picked up 4 tires, for FREE yesterday.

They all have about 1/2" of tread left, much more than I have currently. The tread patterns do not match, but I do not think that should be a problem. One is open shoulder and three are closed, I will see if I can trade the open shoulder one for a closed one at a tire shop, as the open shoulder one is almost new.

Only issue now is steer tires - they are in decent shape and from 2011, so not too old, but they are the low profile ones, and I dont know if that RPM difference would cause a problem with the ABS wheel speed sensors.

Thanks!

retiredChemist

Join Date: Jul 2016

Posts: 56

I'd suggest having one tyre size all round. Keep it simple.

The open shoulder will wear quickly on asphalt, won't grip well in the wet either.
the closed pattern is similar to a on/off road steer tyre that bridgestone make.

Don't skimp on steer tyres.

superdave

Join Date: Mar 2015

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I that dry rot on the sidewall

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Tango

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porkchopsandwiches

Join Date: Jul 2013

Location: Maryland / Boulder

Posts: 347

Year: 1999

Coachwork: Thomas Built

Chassis: Saf-T-Liner MVP ER

Engine: CAT 3126b Rotella-Chugger

Rated Cap: 72

That's the one retread tire dated 2011. The other three are virgin tires dated 2015. It looks more to me like curb rash than dry rot, but I'll have the shop check it out. These are all for the drive tires, getting new or good used non retread steers.

Thanks!

Versatile

Join Date: Jun 2011

Location: KANSAS CITY

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cadillackid

Join Date: May 2009

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'only last a year or two' is of course relative.. if they are on a semi thats running 100,000 miles / year thats about average for drive tires....

-Christopher

retiredChemist

Join Date: Jul 2016

Posts: 56

The Chinese tyres are generally different sidewall construction usually 2 generations behind the name brands. They're also a different compound which runs fractionally hotter.

They do narrow the pressure window between under inflated and comfortable but again not by much. The sidewalls will generate more heat than the name brands and cost a little bit of mileage. But unless you're doing big miles the extra burn isn't worth the extra tyre spend.