1977 Mack CF600 Wheel/Tire Questions

[rjmcfarland]

Hey everyone, I have owned a 1977 Mack CF600 for about a year now, and I think its about time I start addressing some of its "problems" and getting it into better shape.

In service in rural Kansas only a couple of years ago, it was retired and sold to a private party who addressed some long term issues it had, and it was later resold again to the person I purchased it from. This is an older photo and I have since removed the business decals as they were from the previous owner. It's also sporting a mix of different lights that the last department installed, something else I will probably try and correct eventually.

I am in contact with the Mack Museum for more information about it's history, manuals, etc. but I am still waiting to get anything.

The biggest thing I want to get sorted a the current moment are the wheels and tires. Like most other Mack apparatus at this time, it has 20 inch Daytons which now sport a very outdated and hard to find tire size. All of them are currently 11.00-20. Tread is getting low and they are starting hairline to crack. Searching around me for used options brings up a lot of old and worn out tires that I wouldn't feel safe putting on this rig.

Through my research it seems as though I can have a shop swap out the 20 inch rims to 22.5 inch rims while keeping the cast spoke center, opening myself up to more tires and going tubeless as well.

Anything I'm missing here information-wise? Is it as "easy" as swapping for the 22.5 inch rims and finding 11.00-22.5 tires?

Thanks for any help, this style of wheel is completely new to me as our modern apparatus don't sport Daytons (obviously).

 

[Geoff Weeks]

12x 22.5 would give you the same tire size (circumference, load and rev/mile) as 11.00 x20)  Likely need 9" width rim to run that size.  11x 22.5 would be one step down in size and load capacity.

 Going to be expensive buying rims and tires. Neither are all that common either, but still easier to come by than 11x 20's.

[rjmcfarland]

2 hours ago, Geoff Weeks said:

12x 22.5 would give you the same tire size (circumference, load and rev/mile) as 11.00 x20)  Likely need 9" width rim to run that size.  11x 22.5 would be one step down in size and load capacity.

 Going to be expensive buying rims and tires. Neither are all that common either, but still easier to come by than 11x 20's.

Thanks for your help. Considering the price of all new rims and tires, would it be more worthwhile to convert to hub pilot?

[BOBWhite]

Looks like a sharp truck! What are your plans with it? If it's only going to be used in parades and slow speed stuff I would just keep the original rims and tires, when kept out of the sun these old tires can last a long time. If you're planning on working it then new tires and rims are probably a good idea, just be ready for the bill. 

Do you know what town/district this truck originally served in? 

 

[Brocky]

10 hours ago, rjmcfarland said:

Thanks for your help. Considering the price of all new rims and tires, would it be more worthwhile to convert to hub pilot?

Converting to Hub Pilot rims will be VERY expensive as you would have to change the spoke hubs to Bud style hubs. Check out the local trucking companies as they may have a pile of 22.5 rims in the back corner as they replaced equipment with disc style wheels. If you have a friendly local tire store check with them on finding you some reasonable radial "take offs" with decent tread especially if you are only going to use it as a hobby truck with NO water load... The radials will give you better ride and handling.. Take your time and ask around locally before you jump into all new.

[mowerman]

Yeah, it looks good. Thanks for the post and good luck.bob 

[rjmcfarland]

12 hours ago, BOBWhite said:

Looks like a sharp truck! What are your plans with it? If it's only going to be used in parades and slow speed stuff I would just keep the original rims and tires, when kept out of the sun these old tires can last a long time. If you're planning on working it then new tires and rims are probably a good idea, just be ready for the bill. 

Do you know what town/district this truck originally served in? 

 

Thanks! I’m not 100% sure what I’m going to do with it yet, but it likely won’t be all slow speed parades, so I want to be safe, especially if I have passengers.

 

This rig served Arcadia Kansas for nearly 20 years.

[609albert]

Hi , just like so of the other guys mentioned  go for the dayton rims ( the split rims are dangerous) , I had a steer tire rim fail cut the tube ,the rim was rusted out at the locking ring on inside which you could not see ,luckly was turning  slow in front of my firehouse and had spare at my garage and a large floor jack inside the station.

6 new rims and 6 new radials (chinese) tubless on my 54 L Mack 1100 x 22.5 and what a difference in ride and no split rims even they where so called 'Safety Rims'

[CF-Firefighter]

Hey brother,

fulltime company officer in a metro department and also a CF700 owner. I havent seen Daytons on a front line rig in a long time. My truck has the daytons and originally had the 11-20’s. Now it has 11r22.5’s on daytons. Not sure if they are the original wheels adapted. But if you need pictures I can post some of the wheel tire set up. 

Edited March 16 by CF-Firefighter

[Geoff Weeks]

Again, when changing from tube type to tubeless, you add one to the "size" so 11 tube type becomes a 12 tubeless and you add 2.5 to the rim diameter. So a 11x 20 becomes 12 x 22.5 to remain the same.

 20" spokes can have 20" tube type (flat based) rims or 22.5 tubeless drop center rims.

 

[mowerman]

Personally, I’m going to look into some used takeoffs container chassis use a lot of them. You might be able to find a full set of good used tires with the rims  used. I’m thinking of doing the same thing. Also, I noticed a lot of guys nowadays are just changing the front rims to tubeless since the fronts have the lock ring sticking out which is the dangerous set , just another couple of ideas. I’m going to be looking for tires myself here pretty quick. I also have 20 inch tube type split rims plus as . geoff says taller, rubber means more top end….. good luck … bob

[Geoff Weeks]

No, what I am saying is to go from tube type to tubeless and STAY THE SAME, in terms of size in every measure, you must add 1 to the size and 2.5" to the rim diameter

 SO a 11x 20 is equivalent to a 12x 22.5, not a 11x 22.5, which is the same as a 10x 20.  If you downsize make sure the load capacity of the tire can handle the load, it will also throw off the speedo.

[mowerman]

OK, let me get this straight at 22-5  is the same outside diameter as a 1020 correct??? I wasn’t really looking for a taller rubber, but I thought they were bigger

[CF-Firefighter]

55 minutes ago, Geoff Weeks said:

No, what I am saying is to go from tube type to tubeless and STAY THE SAME, in terms of size in every measure, you must add 1 to the size and 2.5" to the rim diameter

 SO a 11x 20 is equivalent to a 12x 22.5, not a 11x 22.5, which is the same as a 10x 20.  If you downsize make sure the load capacity of the tire can handle the load, it will also throw off the speedo.

You are correct, I had it mixed up. My truck had 10 20’s and now has 11r’s. 

[mowerman]

Now I’m confused all our work trucks I 1100-22-5 but they appear to me to be a lot taller than my tires. Maybe just an optical illusion at any rate I’m getting ready to open the wallet wide ha ha hopefully not too wide.bob 

[Geoff Weeks]

10x20 is equal to a 11x 22.5, 11x 20 is equal to a 12x 22.5

3 hours ago, mowerman said:

OK, let me get this straight at 22-5  is the same outside diameter as a 1020 correct??? I wasn’t really looking for a taller rubber, but I thought they were bigger

Not sure what you are asking, 22.5 tubeless rim fits a 20" spoke. So a 11x 22.5 and a 10x 20 both have the same outside diameter, width and load carrying capacity (assuming the same load range or ply rating).  The sidewall on a 20" tube type is taller, the outside diameter of the tubeless and tube type are the same.

Tubeless require a drop center rim, (unlike the flat base of a tube type) so the rim is larger in diameter to allow for the "gutter" in the center of the drop center rim.

 On a tube type the rim comes apart to slide the tire and tube into place, a tubeless doesn't come apart so there must be a gutter to allow the beads to be forced over the rim.

[mowerman]

OK, thanks for that. That’s exactly what I was looking for.

[rjmcfarland]

On 3/13/2024 at 4:36 PM, Geoff Weeks said:

12x 22.5 would give you the same tire size (circumference, load and rev/mile) as 11.00 x20)  Likely need 9" width rim to run that size.  11x 22.5 would be one step down in size and load capacity.

 Going to be expensive buying rims and tires. Neither are all that common either, but still easier to come by than 11x 20's.

I found a shop near me that keeps the 22.5 inch Dayton rims 8.25 width in stock and they should be getting more in about 2 weeks. I found a chart online that says a 12x22.5 tire is approved for mounting on a 8.25 width rim, but I'm curious why you think it would need to be a 9 to fit. Don't want to get the wrong rim and not be able to keep the same tire "size".

Thanks for all your help on this thread.

[Geoff Weeks]

8.25 rims are generally limited to 7k lbs, so if you want the full weight capacity of the tire size, you need the wider rim.  Most often tires have a "spec" rim size and "acceptable" rim size which is often 1 size narrower or wider than the spec rim. So if you aren't going to load the rim above its limit, then 8.25 is fine if it is shown as an acceptable rim.

 I ran 295/80 22.5 steer tires, they are the same size (diameter) and just a hair wider, then a 11r x 22.5 and can be placed next to them in a set of duals, but have a higher weight capacity and to use that extra weight, you need to use 9" rims.

 Before someone says "those aren't the same , they are low pro 22.5," look up the tire size exactly as I wrote it.  They aren't the more common 295/75 x 22.5

[Geoff Weeks]

On 3/13/2024 at 1:11 PM, rjmcfarland said:

 

BTW you front hubs have the correct large "wedges" to be used on wide rims, 8" flat based (tube type) or 9" 22.5 tubeless rim. The wide rims need the long triangle wedges to keep the rim from breaking the studs.