How does tire size affect your RPM's?

@Rideandrepair

 

If you go onto the road Ranger site and put in the search box road speed calculator that should give you an idea. There are some other road speed calculators if you Google them also.

I think it will probably drop your RPMs maybe by a couple hundred. It is not a huge difference.

 

Keep what you have ... If you go bigger, you will lose probably .5mpg in rolling resistance. And that 1500 at 70 will turn into 1325 with the truck lugging and getting even poorer economy and no power for the smallest of hills. I went up from lp 24.5s to tall 24.5s with a built cat. 13spd, and 3.55s ... anything less than 70 if its hilly I now run a higher rpm in 12th. I dropped nearly a mpg ... but I also went hwy tread to winter knobbys.

I only learn by expensive mistakes. In my defense ... I couldnt find low pro 24.5s when I needed tires.

 

the difference in rotations/mile is 505.7 to 489 so 96.7%
therefore you will drop to 1450 rpm @ 70mph or 73mph @1500rpm

 

I’m not sure I used the right tire sizes. 40” and 42”. 11Rs 22.5 are very close to 295/75/24.5, which seems to be the most common size for 13/355’s. I considered going from lo pro 24.5s to Lo pro 22.5’s. As I recall it would be a bigger difference than changing the rears from 3.55 to 3.70. I’ve been told 13/3.70s/24.5 lo pro are ideal in the hills of Ky and Tn. Maybe someone can chime in on proper tire diameter sizes. Mine runs out now @1500 rpm at 67 mph. I can’t say if my Tach is accurate though. Speedo is off by .04% Truck gets terrible mpg. Good on flat land, light loads. 1375rpm @ 62 mph. Use the calculator. My #s never match up right.

 

If you can get actually to the road Ranger Road speed calculator if they still have that, that one was pretty accurate. I used it to see what my truck would do and it was exactly right on.

Yes Lo pro 24.5 tires are very similar to 11R22.5 in diameter.

 

285/75 24.5 and 11r22.5 are the same size (40.8” iirc) 12r22.5 are like 41.5 and I believe 11r24.5 are almost 43”, unless you need a little more clearance off road or need the weight rating for heavy hauling id just leave it since low pro 22.5s are the most common tire you should be able to find one if need be even though taller rubber does ride a smidge better and last a little longer, probably be about 100 rpm lower in any given gear though making the switch