Tires and tires accessories...

[RJ]

I just went thru the manual but can't find the specs for the original tire size. 

Ed -

The OEM stock tire size for the 4106 was 11.00x20 tube-type BIAS PLY on split rims that turned 495 revs per mile. Some Greyhound divisions back then spec'd 19" wheels/tires to reduce theft, others spec'd 22.5s - but that's ONLY Greyhound.  Most other carriers simply opted for the stock size.

20" wheels & tires are almost impossible to find nowadays, everything is either 22.5" or 24.5."  Ditto for tube-type tires, let alone bias-ply construction.

As I said in my earlier post above, look for tires that turn as close to 495 revs per mile as possible for OEM performance with your 4-spd manual.  22.5" or 24.5" rims, doesn't matter except that 22.5's are the most common.  Just stick to the 495/mile number for best results.

FWIW & HTH. . .

[eddieboy]

So if I end up changing tire size, do I need to change the rims as well or just go with a smaller sidewall? Is this a good question for Luke or some other expert?
Ed

[TomC]

22.5 x 8.25 rim for tubeless tires is the most popular rim made. You can run a 10R-22.5, 11R-22.5, 12R-22.5, 255/80R-22.5, 265/75R-22.5, 275/80R-22.5, 295/75R-22.5, 295/80R-22.5 (at reduced carrying capability over a 9" wide wheel), 315/80R-22.5 (at reduced carrying capability over a 9" wide wheel. For closeness to the magical 485 rpm, which is the 12R-22.5, the 11R-22.5 is very close at 498 rpm. Good Luck, TomC

[RJ]

So if I end up changing tire size, do I need to change the rims as well or just go with a smaller sidewall?

Ed -

Simple answer:  Maybe, maybe not.

But to answer your question more intelligently, what size wheel/tire is on your coach now, front & rear?

Is this a good question for Luke or some other expert?

I think Luke will echo what's already been shared with you for wheels & tires, plus will supplement that with "make sure your wheel studs and lug nuts are in good condition, as well as the wheels themselves.  If in doubt, replace them."

For closeness to the magical 485 rpm. . .

Tom -

I believe this is a typo on your part, correct?  The magical number is 495 for GM coaches.

I've also noticed, when looking at tire spec charts, that often the same size tire (let's use the common 11R22.5) will have quite a range of revs per mile among different manufactures, and even among different tire types from the same manufacturer, such as all-purpose vs steer vs drive only.  So one has to really do their homework before plunking down their hard-earned cash when buying new shoes for their ride!

FWIW & HTH. . .

[TomC]

Most 12R-22.5's that are used on buses are 485rpm tires. 11R-22.5 drive tires are around 498rpm. The only tire faster then the 12R-22.5 is the 11R-24.5 at 476rpm.

If 495rpm was the magical number, then what tire size was that?  Good Luck, TomC

[RJ]

If 495 rpm was the magical number, then what tire size was that? 

10.00x20 tube-type bias ply. 

This was the size that the brilliant engineer Dwight Austin used when developing the revolutionary (for it's day) V-drive for the Greyhound-only Yellow Coach 719 introduced in late 1935.  Based on his 1932 patent, and originally installed in the Pickwick Nite Coach (see the Santa Fe version below), it was really the beginning of a design concept that basically is still in use today.  Granted, 99.9% of North American buses are all T-drive, but Austin's original concept paved the way.

The YC-719 used a GMC 707 cu. in inline 6 gas engine, coupled to a 4-spd manual gearbox, a 4.125:1 rear axle ratio and 10.00x20 tires.

In 1937, YC introduced the 743, which was a mild face-lift of the 719, but more importantly, introduced the venerable 6-71 Detroit Diesel and coach air conditioning.  No other changes were made to the drive line specs with the change to the Detroit, as the 707 operated w/in the same RPM range.

IIRC, the 12R22.5 (or it's bias-ply equivalent) size became the stock OEM installation when GM introduced the 40-foot 4903 in 1968, but am not sure.  All of my 4108 and 4905 sales literature indicate 12R22.5 as the stock tire.

How's that for historical GMC coach trivia?  Hehehehe. . . 

FWIW & HTH. . .

[uncle ned]

Per  RJ  the 476 tire in the 11r24.5 size was the best thing I did for huggy.

run down the highway easy now.

uncle ned
huggy bear
4104 with a 6v92 and v730

[belfert]

Is 470 to 480 RPM pretty standard for a 11R24.5 tire?  The data plate for my bus shows a metric size of some sort for the tires so I have no idea what the correct RPM should be.

[TomC]

just look up the tire size on line. Good Luck, TomC

[eddieboy]

After looking closely at my wheels, I found that I have 3 different sizes on the bus.  I called Pomps and they said any of the 3 different sizes should be ok.  He recommended the 12R22.5.  I think the 11R22.5 might be a less expensive alternative.

[RJ]

I think the 11R22.5 might be a less expensive alternative.

Ed -

Here you go:  Bridgestone all-position model R250F, size 295/80R22.5, load range G (plenty for the '06) and best of all: 499 revs/mile.

How's that for almost exactly what the powertrain was designed for?  (495)

The 295/80R22.5 is just a little bit taller than an 11R22.5, which, in the same tire, turns 503.

More food for thought!

FWIW & HTH. . .

[TomC]

Straight from the Michelin Commercial Tire site-all listed are the XZE for front axle:
11R-22.5 16ply 501rpm 13,220lb
12R-22.5 16ply 486rpm 15,780lb
275/80R-22.5 16ply 517rpm 14,320lb
295/80R-22.5 16ply 500rpm 14,600lb
315/80R-22.5 20ply 489rpm 18,000lb

Weigh your bus. Unless you are more than 13,000lb on the front, I'd stick with 11R-22.5. Easy to get on the road and used quite a bit. 275 is the most popular size (crosses also with 295/75). Good Luck, TomC