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Old 07-11-2014, 08:24 PM   #1
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Tire size and brand question: Move from 12R to 11R?

Hi all,
I'm in need of a new set of tires (my wallet just screamed a little). I only run about 3,000 miles a year, most is highway but some is on gravel roads.

I'm running very old Goodyear radials in front (steers) and a mix of four recaps in the rear (drive). They are all size 12R 22.5.

My first question is about moving to an 11R from the 12R. I'm thinking to keep the 12R in front as Lucinda is a transit style and I like the additional load rating. In the rear, though, I've had some dicey clearance in my wheel wells when fully loaded near my GVWR. It's not the wheel well itself, as there is actually plenty of vertical clearance, it's the side of the wheel well or outer wall of the bus that comes down within an inch or so of the tire. It would be fine if the tire were inset about an inch further, but alas it is not.

Moving to the 11R makes the tire a little cheaper, and a lot more common on the road. It increases the tire revs per mile, which I think then also increases my rpm for the same speed. I don't really know how much, though, and I've also read that smaller tires will increase speed (why? Easier to spin?). My old dealer thinks I should stick with the 12s, that I'll lose speed, won't gain much clearance, and will increase the rpm wear on the engine. The local tire shop says the 11R is what all the fleets are running here now, and says that I will gain some clearance, and will hardly notice a speed difference.

Past the size question, I'm thinking of Firestone steers (City Transport Radials or FS560) or Daytons, which is lower in the Bridgestone/Firestone/Dayton line (Radial Metro steers, Drive Radial drives). Any thoughts on these tires? Quality/Value? I also looked at Hercules L-303 drives, but with a 50 mph rating I thought the Daytons a better choice. The Dayton Drives only come in the 11R, they aren't available in 12R. I could put on Firestone FD663 drives in either size.

I don't mind putting on new radials as drives--when I do long trips they are often in harsh environments (Nevada desert in the summer, for example) so heat dissipation and endurance is key.

Thoughts appreciated!
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Old 07-12-2014, 06:58 AM   #2
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Re: Tire size and brand question: Move from 12R to 11R?

I use to work for a large tire company for a few years and managed tires for very large shipping fleets.

If it were me I would stick with the 12r. the 11r will be more common to find used for take offs and spares. You are correct it will be a smaller tire. Typically you will only see 12r on a rock hauler type trucks and trailers that need really tall clearance.

Most of the tires you list there other than the firestone are second tier tires. So their quality and longevity is not as good as Godyear, Michelin, etc….Dont want to say you get what you pay for but over the years with tires I think you do.

I would personally go with new steers and recaps on the rear for cost savings. Its what I plan to do if I can not get hooked up from my old employees.

Hope this helps
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Old 07-12-2014, 09:27 AM   #3
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Re: Tire size and brand question: Move from 12R to 11R?

You might check to see if 12Rs are original to your bus. It's not a common size. Could be someone once got a great "deal" on some tires and they just kept replacing with the same size.

I would not think that switching from 12R's to 11R's would be a big deal. You are talking about the width of the tire. Think of it like this... you are traveling down the road, you have a blow out and what are you going to do... get a common spare or sit around waiting on a tire to come in. I vote to switch over to a more commonly available tire. But we also built our bus conversion out of home improvement store to aviod having to go to specialty RV stores and/or wait for replacement parts to come in. We like the freedom allowed in using commonly available parts. Special is nice if you've got the time and money to waste.

It's your bus and your decision to make. No one else can tell you what to do. We can only make suggestions. That is my suggestion.
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Old 07-12-2014, 09:38 AM   #4
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Re: Tire size and brand question: Move from 12R to 11R?

Quote:
Originally Posted by lornaschinske
You are talking about the width of the tire
And height. 12r22.5 will have 12" tall side wall and 12" wide tread. If the ratio of side wall to tread width is different you'll see numbers like 265/75r22.5. That's probably not a real tire, by the way I just made it up.

I drove a bus with 11r22.5s in the front and 10r22.5s in the back. Surprisingly, it was easy to tell that the front was higher off of the ground.
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Old 07-12-2014, 01:03 PM   #5
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Re: Tire size and brand question: Move from 12R to 11R?

Quote:
Originally Posted by jazty
...
I drove a bus with 11r22.5s in the front and 10r22.5s in the back. Surprisingly, it was easy to tell that the front was higher off of the ground.
Good for those not so level sites?
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Old 07-24-2014, 09:58 AM   #6
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Re: Tire size and brand question: Move from 12R to 11R?

What does your ID plate say? It. Will list your tire size.
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Old 12-23-2014, 09:32 AM   #7
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My id plate says 11.00-20 for the tires but the PO has put 12r22.5 on my crown. Every shop in town has new 12r22.5 tires but no one has used in this size here in Portland.
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Old 12-23-2014, 05:29 PM   #8
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Quote:
Originally Posted by Branden View Post
I've had some dicey clearance in my wheel wells when fully loaded near my GVWR. It's not the wheel well itself, as there is actually plenty of vertical clearance, it's the side of the wheel well or outer wall of the bus that comes down within an inch or so of the tire. It would be fine if the tire were inset about an inch further, but alas it is not.
Have you thought about "rolling" your fenders? This is where they roll the inner lip of your fender up on itself for a little extra clearance. If this isn't enough you could trim them back. Might not be the entire solution, you might need some more suspension in the back, not sure how yours is configured. But it will definitely help no matter what you do.

While on the subject, can someone explain how bus tires are rated? This is all greek to me.
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Old 01-10-2015, 06:01 PM   #9
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11x20 is the same size as a 12x22.5 or 11x24.5.

11x22.5 is going to be a little small for a Crown. Itis the same as a 10x20.

I would not use a recap in any position on a bus. When a cap let's loose it will cause some real damage.

For most convertors using cheap Chinese knock offs will do the job at a big savings.

The tires will die of old age long before they wear out
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Old 01-10-2015, 09:22 PM   #10
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Quote:
Originally Posted by cowlitzcoach View Post
11x20 is the same size as a 12x22.5 or 11x24.5.

11x22.5 is going to be a little small for a Crown. Itis the same as a 10x20.

I would not use a recap in any position on a bus. When a cap let's loose it will cause some real damage.

For most convertors using cheap Chinese knock offs will do the job at a big savings.

The tires will die of old age long before they wear out
The id plate on my Crown listed 11x22.5 for tire size
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