24.5 or 22.5 tires, help me decide?

Just a thought .. If you find a truck you really like with 24:5.. try use it to your advantage .. tell them you really like the truck but your sceptical of the 24:5 because they are not popular and getting hard to find and it reduces the value of the truck ..hopefully it gives you leverage to negotiate a better price

 

Michelin 24.5’s are pretty much nonexistent these days, but plenty of other brands still make them. The one positive to running lo-pro 22.5’s is that’s what most fleets run so you can almost always find one if you have problems out on the road, and you stand a decent chance of being able to match up a used one if the bad tire is on a drive axle.

 

You got 2 different rim sizes. 22.5 and 24.5. With tires, you got 2 different sidewall sizes, Lo pro are usually called 285/75/22.5 or 285/75R24.5 and regular ( commonly called “Tall tires”) are 11R22.5 or 11R24.5. The tall tires are overall taller than the lo pro, due to a wider sidewall. 22.5 lo pro being the smallest overall outside diameter ( overall height) and 11R24.5 being the largest. 285/75/24.5 lo pro tires are almost the same outside diameter (overall height) as 11R22.5 tires. So as @Judge mentioned, you can most likely swap from one to the other without having to re calibrate your speedometer. I’ve seen them ran side by side on a trailer, they’re that close. Back when oil got very expensive, about 15-20 years ago, 24.5 lo pros became less popular. Fleets and even some O/O started specing 22.5 lo pros to save money. Now it’s hard to find anything except 22.5 lo pros and even 11R 22.5 aren’t as common. 24.5 lo pro and 11R24.5’s are scarce at all the major Truckstops. Loves for instance only keeps a couple at each store. I still prefer 24.5 lo pro on my Truck. Most Trailers are 22.5 lo pro. I have 11R22.5 on my Trailer. There’s an obvious advantage to having all the same size, usually 22.5 lo pro on Truck and Trailer. Using old, especially steers for Trailer tires. Overall it adds up to savings, especially with a fleet. The lo pro having less sidewall = less flex = less rolling resistance = better fuel economy. As a comparison, Sport cars have lo pro tires. They grip the road and don’t flex while cornering. Luxury cars have taller touring type tires, providing a much smoother ride.

 

There was a time when every big rigger had "big rubber", like it was a right of passage of some sort. I heard years ago, there was a shortage of big rubber, some say no. Big rubber had one purpose, to go faster. Why we just didn't go with 2:50 gears, I'll never know. One of those things, I guess.

 

Because back then motors were mechanical they like the higher RPM s other wise you burned them down .. the trick was gearing & transmissions 2;50 gears weren't even heard of then

 

11r 22.5 and 11r 24.5’s have the same exact sidewall size. 11”. The height difference is made in the wheel size. These sizes are built more square because tread caps run from 9.5” to 11.5” The sidewall flex between the two is the same. 24.5’s because they have more mass due to wheel size also have higher weight carrying capacities. Look at the ratings on the same brand and model tire between the two sizes and you will see 24.5’s will be rated higher at same cold air psi. All the ####### European “metric” sizes are all over the place. Production practices by all the different makes make the size variances in them hard to match between makes. A 285/75r22.5 will have the same size sidewall as a 285/75r24.5. 285 is the width from sidewall to sidewall in millimeters. However the tread cap itself my be made narrower or wider depending on make and model. 75 means the sidewall height is 75% of the first width number. Keep in mind DOT standards dictate that manufacturers have a 10% size variance scale to work with. So makes like Mich and BFS generally build on the high side of that scale while GDY and Conti build on the middle. Most chinese brands build on the low. All that means is a china tire will be much smaller then a
Mich in the same exact size when paired together.
“R” in the size designation means radial not rim. A bias ply tire will not have an “R” in size or will have a “D”. A special built for trailer only tire will have “ST” in size. 11r24.5 means radial 11-24.5 means bias.

 

The 4 trucks I’ve owned have all had low 22’s on them. 3 of them because that’s what they had when I bought them and this last one because I ordered them. My old flatbed job we ran tall 24’s because he swore they handled the heat better and there might be something to that because we rarely had tire issues running 105k gross.

My useless opinion is that unless you’re doing something specialized whatever tire size you choose is probably going to be fine. I don’t think I’d go to the expense of switching from low 24’s to low 22’s unless 24’s get really hard to find and I don’t see that happening. There are lots of other brands besides Michelin.

One thing to consider is if you’re pulling for a place that does drop and hook. You’ll probably encounter trailers you can’t get under if you’re taller than the rest. I have a taller 5th wheel because of my fenders and there are times I have to crank a trailer up to get under it, but we also have guys with tall tires and sometimes I have to crank a trailer down to get under. All trivial things really, but buying 10 wheels just to switch sizes wouldn’t be cheap either.

 

24.5 for me…

 

Another thing worth mentioning is that smaller tires with their smaller rims weigh less.

This particular weight is both unsprung weight and rotating mass, and both can have an outsized effect on efficiency. If you can reduce these two types of weight you will generally be better off (all else being equal).

Another lesser concern is that when switching from one to the other, you will have to resize/replace your tire chains, and perhaps consider the difference in your 5th wheel height (though slight).

Lastly, while I know that today's experts attribute the gains in efficiency to sidewall flex, the experts from yesteryear pointed to the LENGTH of the tire contact patch as being equally if not more important. Taller tire = longer contact patch, giving more traction at the expense of more friction, and vice versa.