Tire Question

[Chaz]

I have a shot at some pretty good tires to replace a couple that are older. They are Goodyears 295 x 80R x 22.5. Is that something I can run?? They came off a Monaco. The price is right!!   
Thanx.......
  Chaz

[RJ]

Chaz -

Short answer:  Yes, you can run them, they're just about the same as an 11R22.5

Long answer:  The truck tire market is finally switching to metric sizing, like the automotive market did over a decade ago.  So the familiar 11R22.5, 11R24.5 and 12R22.5s most commonly used are being phased out for similar sizes but with metric markings.

Best is to go to the manufacturer's website and look up the tire model and size to be able to compare it to the above common sizes.  12R22.5 was stock on your 4108, , but a lot of busnuts run the 11 series due to lighter weight than commercial service.

Be aware that GM designed the manual gearbox powertrain around tires that turn 495 revs per mile.  The closer you are to that figure, the closer you'll be to OEM performance - with a manual gearbox.

V-730 equipped coaches suffer from a numerically lower bevel gear ratio in the transmission, thus more engine RPM for any given road speed vs the manual cars.  The tire size I've found that comes closest to providing nearly the same road speed/engine rpm combination as the manuals is with an 11R24.5 tire that turns 470 revs/mile.

Give it some thought and do a little homework, your choice.

FWIW & HTH. . .

 

[Chaz]

Wow. Thanx RJ. Good info! I was going to be using them for my steer tires for starters. He has 5. (My rears are pretty good yet.) But if he should come across 4 of the same that are in better/newer shape than mine, I may jump on them. ("He" being my cousin that manages a commercial tire company of some sort.) 

I also have a V-730 (I guess) as a tranny. So if I do find a set of 4 the same size, I guess I should be sure they have as tall a profile as I can get, correct ?

Thanx a million for doing my home work for me!!            (I love this board!) 

Chaz

[Chaz]

Just talked to my Cuz again. Seems I was mistaken: he has 8 of the tires. 
So...... I'm kinda interested in just replacing all 6 (maybe) but that pesky fuel mileage thing is bugging me.  How could I get an idea of the mileage lost by going by a little bit smaller tire?? I'm doing about 7 mpg right now and man I would like to hold that or somehow increase it, obviously. If it would be a substantial loss, I'll just bag it.
By the way, this tire place he works at is in Dayton OH. if someone would want the others. He also said he may have a deal on some new ones. I'll keep ya all posted.
Thanx,
   Chaz

[RJ]

Chaz -

Before you bite the bullet, here's some homework for you:

1. Take a look at your drive axle tires.  Determine the make, model and size.  Go on the manufacturer's website and determine the revs per mile for your current tires.

2.  Call your cuz up and ask him to look in his spec book for the revs per mile of the tires he's suggesting for you.

3.  Compare the two.  The one with the fewest rpm will get the better mileage.  Is that your current tire, or the new one?  Do the math to find out the percentage difference.  If the new tire is 1% smaller (more revs/mile), that translates to 6.9 mpg.  If it's 2%, that's 6.8 mpg.  3% = 6.7 mpg.  4% = 6.7.  5% = 6.6  OTOH, if it's 1% LARGER (fewer revs mile), then theoretically 1% = 7.1 mpg, 2% = 7.1 mpg, 3% = 7.2 mpg, 4% = 7.2 mpg, and 5% = 7.3 mpg  (all rounded approximations.)

4.  After all this, simply say "Screw it" and just buy the new tires!   

FWIW & HTH. . .

 


PS:  Don't forget the spare!!

[Stormcloud]

I agree with measuring and comparing the tires to determine approximate MPG. The next step is to figure the miles you drive per year, and figure if the .1 mpg difference in fuel mileage will impact the pocketbook MORE than passing on these tires and purchasing taller ones.

If your drives are still pretty good, leave them and replace the steer tires only.

If you are gonna replace all 6, maybe buy 7 (include a spare) and trade in your 4 good drive tires;
the steer tires will probably make decent casings for recaps for someone.

JMHO

Mark

[TomC]

Even though the low profile metric tires have taken hold in the over the road bus and truck market, there is still a demand for the 11R-22.5 (for over the road and dump truck), the 11R-24.5 (owner/operator over the road trucks, heavy haul trucks, flat bedders), and 12R-22.5 (trash trucks, municipal trucks) to the point I wouldn't worry about them disappearing anytime soon.  Especially the large 11R-24.5-that is the largest diameter high speed (75mph) tire you can buy.  They make larger tires, but are 45-55mph tires for construction or crane use.  Good Luck, TomC