So who wins what works what changes and what happens because i don't have a clue. Will everything just turn faster and accurately keep track of my miles and current speed or will all readings be totally off? Originally the truck had 20" Firestone RH-5 widow makers that had to go and were about 34" tall and my current setup is 38.3" tall.



As you can see there is a little more tread on the new tires


Samson GL274A A/P 9-22.5 Radial 14 PLY






My whole garage still smells of new tires

 

What size tires and wheels did you put on anyway? I replaced all of my 8.25x20 WM's with 9R22.5's , and they are virtually the same size.
I also noticed that you had the wheels balanced. How fast do you intend to travel?

 

What width tires were on your widow makers? That 34" you mention is more indicative of the 7.00x18" tires used on F-4s. A 7.50x20" is generally about 37", and the 8.25x20" is the 38" equal of your 9R22.5s. Below is a side by side comparison of them. Stu

 

To answer your question, with taller tires the MPH indicated will be less than actual, by about 12%. The flip side is, your engine RPM will be 12% less to go the same speed. That's as good as many axle changes.

 

Ross correctly got us back to an answer to the core question. Your F-6's speedo should now read more correctly than it did with the 34" rubber. Stu

 

Well I was hoping to do 55mph without the engine screaming. I went with clip on wheel weights because I didn't want that magnetic powder garbage. Before I couldn't roll my old tires 2 feet without them falling over, now my new ones roll with ease not toppling over. I noticed a big difference.

Apparently the old tires that were 7.50-20 front and 8.25-20 rear are too small? As previously stated the old rims were 20" Firestone RH-5 rated for 7.50" wide tires or 8.25" I'm not sure but the 8.25"s were probably rubbing on the back dually setup with a load? Before i could barely get one finger in between them. Now with 7.50" inch tires I get two fingers with plenty of room. Maybe I should pull out a tape measure and measure something. ha








Wee... were going for a ride!!!
or so they thought.


Good thing I never aired them up, i wouldn't be here right now

 

Hi all, so I'm still a bit confused i thought originally the truck came with 20" rims? So my question to you guys, the tires and rims I had previously were they the right size for the truck?

 

F-6's originally only came with 7.50 x 20's and 8.25 x 20's.

 

Correct, the standard F-6 was equipped with seven 20" x 6" wheels fitted with six 7.50" x 20" tires (8 ply rated). No spare tire on the wheel. Optional extra cost were two 7.50" x 20" (8 ply rated) on front with either four 7.50" x 20" (10 ply rated) or four 8.25" x 20" (10 ply rated) on the rear. Highest option was 8.25" x 20" (10 ply) on all six wheels.

If your tires measured 34" it can only be explained by years of deterioration or maybe under inflation. Or you measured wrong. Stu

 

Yeah some were retreads, all were worn and none had more than 8 or 12 psi. I had a big chain threw them and around a double tree when i let them loose (should have took some pictures) we unscrewed the schrader valves and then i cut them up with the sawzall. So in the end nothing spectacular happened it was more like one of those moments where your so focused on not having anything go wrong, that we were out there standing behind the tree in case one let loose so we didn't have time to think oh let's take some pictures and enjoy the crazy moment!

 

Yeah, my technique of choice is a 1/8" drill bit straight down into the middle of the tread while I'm standing off to one side. That way my hand isn't exposed unscrewing the valve. Either way they are gone and you'll have no drama out of those 22.5s. Stu

 

This is probably the best picture I have showing the space between the tire and fenders. I never thought to measure the gap as I did not originally intend to change the rims out or go with bigger tires (which in this case wound up being closer to the correct size). Given the new information and by the looks of this picture my new tires with all their tread should fit hopefully. I hope

 

You'll have tighter wheel wells than before, it's for sure. I'll speculate that if the front springs have sagged over the years you may have some rubs on the extremes of the turning radius. But that's a small price to pay. Stu

 

The truck was designed to run 8.25 x 20's. Shouldn't have any problems. I was concerned about that as well but the 9R22.5's fill the fender well nicely with no interference.