Wheel/Tire FAQ

[Eric von Kleist]

Here is a wheel/tire FAQ that I am working on. If anyone would care to contribute/critique/input, I'd appreciate it.

Thanks!

A Wheel FAQ that started as a request for one.

I was confused about wheels. I had read many different things, but was still confused. I asked about wheels on a couple of the school bus groups, and the answers are incorporated here.

Brad Barker, Administrator of the http://www.schoolbusfleet.com fora provides these resources on the net for information about wheels and tires:

See article in back issue. June/July SBF [School Bus Fleet] magazine [www.schoolbusfleet.com], 'All wheels are not created equal'. This should give answers. Contact Accuridecorp.com. They will send you free of charge everything you need to know about all types of wheels including wall charts, training manuals and video tapes.

General Rim Types

Rims vs. Split Rims

With regard to the mounting of tires on the wheel, there are two types of rims: solid rims and split rims. Solid rims take tubeless radial tires. Split rims take tires with inner tubes, and can use either radial or bias-ply tires. (Note: it seems that most tires nowadays are radial tires, although bias-ply tires are still available – but not as good in some respects as the radials.) Rims are welcome at tire repair centers, and it is easy to mount tires on them. Split rims are a bit harder to get serviced because they require special mounting equipment and there are serious dangers with their potential "explosively" to come apart as tires are mounted. Split rims seem to have the reputation of a loosely packed cannon. Most of what I have read recommends replacing split rims with rims, if not immediately, then as soon as it is time to replace tires. Note: this dire warning regarding split rims seems to apply mainly to the very old type of split rims, although it does apply to some smaller degree modern split rims. From what I read and have been told, many, if not most, tire stores that cater to the trucking industry can, and will, handle either type – the Goodyear place down the street might not handle the split rims, but the truck center out on the interstate is likely to be able to tackle the job.

Question: How can one tell which kind of wheel is on a bus? I have seen tire sizes referred to as 9.5Rx20 or 10.5Rx22. The smaller number is the tire width. The larger number indicates the wheel diameter. The "R" indicates a Radial tire. Is it safe to assume that a bus described as having tires with an R in the tire description has rims (NOT split rims) since split rims do not work with radial tires?

ModMech at http://www.schoolbusfleet.com answers:

"20" or "22" is TUBE type, 19.5, 22.5, 24.5 would all be tubeLESS.

EDITORIAL QUESTION: I’m still not clear on this. Do radial tires ONLY go on non-split rims? I think the answer is, “yes�, but I would like verification. Sorry if I’m being dense on this.

Are split rims and rims ever mixed on the used busses that are sold? That does not seem to be a wise thing to do, from my limited experience with mixing radials and bias-ply tires on automobiles.

ModMech at http://www.schoolbusfleet.com answers:

Technically, it IS ALLOWED, but the tires must have the same rolling radius, capacity and MUST be Radial or Not (you CANNOT mix types).

Brad Barker, Administrator of the http://www.schoolbusfleet.com fora provides this information about split rim types:

There were wheels (rims) that had a manufactured split that went all the way across the wheel and had a solid locking ring that held the tire onto the rim. They were [used] prior to the 1960's. They used the Dayton style center spoke system to hold them onto the axle.

As far as so called regular wheels, or disc wheels as they are truly called, there are three main styles with some variations of the multi piece wheel and locking ring. Locking ring wheels have a solid wheel and rim and use either a two piece locking assembly which consists of a split locking ring and a solid outer ring or the single piece split locking ring. There may be even more variations than that as in the solid ring that had an oblong center cut hole.

These multi piece wheel and ring assemblies used tube type tires in sizes such as but not limited to 9.00x20, 10.00x20, etc. with smaller and larger sizes.
When manufacturers started using tubeless tires the wheels changed, as an example, 10.00x20 was equivalent to a 11.00x22.5. Each has the same or nearly the same weight rating. What Joe recommends is good. Refer to a tire data book, easily available from any tire supplier, free of charge. These will give you all of the technical data that you are requesting. Again Accuride Corporation will also give you, free of charge, all the technical data about all types of wheels. All you have to do is go on-line to accuridecorp.com and ask for them to send you the information.

WHE8913 at http://www.schoolbusfleet.com adds some more history and information:

First, I think it is important to note that the dangerous types of split rims that no one wants to work on anymore is what Brad mentioned [as in use prior to the 1960s]. Those rims could completely blow apart if they weren't fastened securely.

The split rims that people are more familiar with today are the single rim with the locking ring type. While becoming obsolete, it has been my experience that tire shops have no problem with mounting a tire on them, but you do hear some "grumbles" from them about having to "true up" the wheel on the "Dayton" type spoke assembly.

To answer a couple of questions from the original post…

First, you should not (and I think it is illegal to) mount a spoke type, split rim and a spoke type tubeless rim ON THE SAME AXLE. I think, however (since I have seen it), that you can put split type rims on the back axle and have updated the front steer tires to tubeless rims.

Second- They DO make radial tires for split rims, though they are getting harder to find. To distinguish between a radial and a bias-ply tire, the R was put in between the wheel width and the rim size, and a dash (-) is used to denote a bias-ply split rim tire. I.E: 9.00-20 would be a tire that is made of bias- ply construction, while a tire with 9R20 is a tire made with radial construction.

A final note- they also make 20 inch split rims with a "Budd" configuration. This is the locking ring type with the 10 hole mounting, rather than the 5-6 lugs, or "dogs" as I have heard them referred to.

IMHO, the 11R22.5 "Budd" hub-piloted wheel is the most advanced in the truck and bus industry in a long time, and that is what should be ordered with new buses, finances permitting.

Spoked Wheels vs. Disk Wheels

Once past the rim style, there are to be two kinds of wheels, spoked wheels and disk wheels. Each kind uses a different hub design. In order to switch from one kind to the other the axle has to have a different hub and brake system installed, and changing hubs is not really economically practical. If you are desirous of a particular wheel type on your bus, buy the bus with that kind of wheel on it: changing wheel types would involve some costly work to change the hub and the brake system.

There are two types of disk wheels, hub piloted and stud piloted. The hub piloted wheels are more like car wheels in that they are centered on the axle by the hole that fits over the hub assembly. The stud piloted wheels fit over the hub, but are centered on the axle by the studs that attach the wheel to the hub instead of by the hub itself.

The terms "Daytons" and "Budds" are used when talking about wheel styles, and the terms refer to whether the wheels are disk or spoke wheels.

Question: What are "Daytons" and what are "Budds"?

ModMech at http://www.schoolbusfleet.com answers:

Dayton = spoke
Budd = disc


Question: If the front wheels on a bus are spoked wheels, are the back wheels spoked as well?


ModMech at http://www.schoolbusfleet.com answers:

No, not REQUIRED, but almost all are manufactured that way.



Question: How hard is it to change a spoked wheel as opposed to a disk wheel? Is the difference worth worrying about...that is, is it as big a difference in terms of service and repair as the difference between split rims and rims?

ModMech at http://www.schoolbusfleet.com answers:

In MY opinion, for Disc brake vehicles, Spoke (dayton) wheels are preferred. Also, if you do your own tire work, Dayton wheels are much lighter and are LESS of an injury problem.


Question: If one had a flat tire out in the boondocks, would it be possible to change a spoked wheel on his own? Would it be possible to change a disk wheel on his own?

ModMech at http://www.schoolbusfleet.com answers:

Definately, easier [to change a Dayton rim] than with a Budd.


Number of Wheels

How many wheels do busses need? Obviously this must vary from bus to bus, and is probably dependant on the size of the bus and its loaded weight. Some busses I have seen have 4 wheels, 2 front and 2 back. Some have 6 wheels, 2 front and 4 back (dual wheels). It appears that the longer/larger busses have dual wheels in the back.

How can one tell whether a bus has dual wheels in the back from a written advertisement that has no picture. Is there some standard to go by?

ModMech at http://www.schoolbusfleet.com answers:

All vehicles (except motorcycles) need at least 4 wheels. Most vehicles over 10,00 GVW have SIX tires.

(Apparently I was mistaken about seeing a bus with two single wheels on the rear end. It was a picture that I was looking at, taken from an angle.)


Wheel Size

I have seen tire sizes from 16 inches to 24 inches mentioned. Are these measurements used in the same way that car tire measurements are used, that is the size indicates the size of the wheel, or do these (particularly 22.5" and 24.5" tire sizes) fit a common wheel size and just have higher/lower sidewalls?

ModMech at http://www.schoolbusfleet.com answers:

Yes, RIM diameters.


What are the common wheel sizes for busses?

ModMech at http://www.schoolbusfleet.com answers:

10R22.5, 11R22.5 are the most common "standard" sizes on Full-size units.

Note: These are tire sizes, but the second number indicates the rim diameter. The wheel sizes are described in the answer relating to rim diameters.


Question: What are the advantages to each? (I have seen it recommended that a partial "fix" for an undesireably high geared rear end is to increase the wheel size.

ModMech at http://www.schoolbusfleet.com answers:

Smaller tires (10R22.5):
Advantages: Tighter turning cicrle, lighter, lower step-in heights, very slightly cheaper.
Disadvantages: Lower load capacity, less resistant to impact damage (potholes), wear out more quickly, less room under vehicle for servicing, no (or negative) residiual value.

Larger tires (11R22.5)
Advantages: Lots of room under vehicle, long life, durable, high residual value, most common "truck tire", high load capacity.
Disadvantages: Slightly higher cost, greater weight, higher step-in height, wider turning radius.


Is it possible to change wheel sizes on a bus?

Is it EASY to change wheel sizes on a bus?

ModMech at http://www.schoolbusfleet.com answers:

Yes. But you need to correct the speedo. On '89 up Navistars, that's EASY. Older units can be less cooperative.

Note: Changing the wheel diameter on a vehicle alters the final drive ratio of the vehicle slightly, which affects the real speed of the vehicle, but unless the speedometer is modified (by changing a part) it will reflect the speed based on the old drive-train set up.


Question: Say one found a bus that met his requirements with regard to size, engine, transmission, rear end, but it had smaller/larger wheels than he wanted.

Is changing wheel sizes on a bus as easy as changing wheel sizes on a car?

Could 20 inch wheels simply be replaced with 24 inch wheels?

ModMech at http://www.schoolbusfleet.com answers:

With "Budd" wheels, anything is "easy" and possible. With Daytons, you WILL have 20/22.5" rims (a 20" Tube-type = 22.5" tubeless, they are completely interchangeable).

EDITORIAL QUESTION: Are there ONLY 20/22.5 rims available for Daytons? Is that what this means?


I know that changing wheel sizes can raise issues of clearance within the wheel wells and with the steering gear, but are there some common "universal" changes that can be made?

ModMech at http://www.schoolbusfleet.com answers:

10.00-20.00 to 11R22.5, 9.00-20.00 to 10R22.5 are the most common.


Is it necessary to have the same sized wheels on the front and rear of the bus? Is it desireable to have the same sized wheels on the front and rear?

ModMech at http://www.schoolbusfleet.com answers:

1. No, not on a private vehicle. On a school bus, YES - mandatory in most States.
2. Without question. Tire inventory, vehicle stability.


Tire Sizes

With cars, there is some latitude in the width of tires that a given wheel can handle.

What size tires can be put on what size wheels?

ModMech at http://www.schoolbusfleet.com answers:

A 10R22.5 should have a 7.5" rim, a 11R22.5 tire should have an 8.25" rim. You *can* put a 11R on a 7.5" rim, but DO NOT put a 10R on a 8.25" rim.


Can a bus with 9.5 inch wide wheels take a 10.5 inch wide tire?

Is it possible to increase the tire width on dual wheels without running into clearance issues between the tires?

If anyone can answer some or all of these questions, it would be a big help to me (and others, I'd bet) in understanding bus wheels and evaluating busses.

Please feel free to add any information or considerations that I have left out through beginner's ignorance.

Thanks!

[Doc]

Hi,
I'm brand new here and didn't find an answer to my particular situation in the excellent story about tires and rims.
We just acquired an '85 Ford B700, which our family intends to use as a hurricane evacuation vehicle. All six wheels are of the split rim type.
The four rear tires are in good condition and I suppose, at least for the time being, that we'll leave those alone. The two front tires need replacement and since I need to do that, I thought it might be a good move to replace the split rims with modern one piece wheels.
Can anyone tell me exactly what wheels I should look for as a direct, bolt-on replacement? This is an "economy" project, so I'll need to look for junkyard wheels, BTW.
Any help greatly appreciated.

Best regards
Doc

[Steve]

I recently went from 8.25x20 to 10R22.5 on my IHC Loadstar w/ 345. The information I have found that if you want to keep the same size of tire when moving to radials you should go with 9.00R22.5 however the 10R22.5 fit under there just fine with lots of room, look great, and will increase your top speed a bit.

If you have a six lug wheel like I did it will be expensive for a new wheel mine where $150 each. But I got all the tires for free from the local bus barn.

[Jarlaxle]

My B-700 went from 9.00-20's to 11R22.5's in front. It's a bit tight at the leaf springs & mud flap bolts, but they clear. I have the standard 10-lug Budd wheels, & took my steer wheels & tires off a junked Ford L8000 semi tractor. In back, I bouight the bus with old 10-22.5 bias-plys on it. Right now, I have 10R22.5's from a junkyard, but they're pretty worn. I plan to replace them with Bandag-recapped 11R22.5's when I get everything roadworthy.

If you have 10-lug Budds, 99% of class 7 and 8 trucks will have the right wheels. 11R22.5 is the industry standard for tractor trailers, & dirt-common. 295/75R22.5 is the metric "equivilant", but is ~1" shorter. 10R22.5 is less common, but used on some MDT's & long-nose school buses. A 265/75R22.5 is, again, ~1" shorter, but "equivilant". 12R22.5's are less common, essentially being highway coach tires that I also see used on many 10-wheel trash trucks. A B315/70R22.5 is equal to a 12R22.5 tire.

You may also run across an oddball--likely either a 305/70R22.5, a 12.75R22.5, or a B305/85R22.5 size. These are usually city-bus tires (Firestone City Transit and Goodyear Metro Milers are the most common I see), with super-thick sidewalls. However, they are low-speed, being limited to <55MPH.

Lastly, there is nothing wrong with tube tires. There are 2 wreckers at work that have them: A 1972 Ford F-800 rollback with 10.00R20's on split-ring Daytons, & a 1979 International S1700 hoist with 9.00-20's on 10-lug split-rim Budds. If you have the more-common 9.00-20's, you can get 9.00R20 radials from several companies, as well as Bandag retreads. The 10.00-20 is even more common, still used extensively as a trailer tire. 10.00R20's are also available (IIRC, the F-800 has Goodyears), first-run and retreaded. Radials will ride better than bias-plys.

[Steve]

I agree there is nothing wrong with bias ply but I was not able to find anyone in the state who would put tires on a budd type split rim. These are only held together with friction so if you have this type of wheel you will want to change them out because you might not be able to find a place who would fit a new tire if you were on the road.

[Jarlaxle]

Most truck stops can still deal with split rims.

[1964_Superior_Skoolie]

From the previous posting:

Question: How hard is it to change a spoked wheel as opposed to a disk wheel? Is the difference worth worrying about...that is, is it as big a difference in terms of service and repair as the difference between split rims and rims?

My rambling answer:

I know this is an old posting but here are my thoughts since I’m new to this site. Split rims are great if you are a do-it-your selfer since they can be repaired with a lot of elbow grease and without a lot of fancy equipment. However, with everything there are drawbacks. I probably repaired a few thousand tires in my time and the split rims were always a lot of work. First you made sure the tire was fully deflated and then you broke the seal by taking a tire iron and taking of the retainer ring. This was actually fairly simple unless it was an old tire. The nice thing about split rims over more conventional tires is that that they lift off quite easy over the wheel once the split rim retainer is removed.

Then it is simply a matter of finding what punctured the wheel and then repairing the inner tube.

The danger is putting it all back together. A large tire shop would usually have something called a tire cage where there could inflate the tire and not be worried if the split rim retainer should separate. I heard of horror stories where the rim separated when somebody inflated the tire and the split rim did severe damage to the person inflating it. Some shops would even point to the roof where there would be a good impression of a tire ring embedded in it.

I still was a bit skeptical but would lean toward the conservative side. Our cheap solution was to turn the tire over and have the split rim retainer pointed downward. Then we would inflate it. If the retainer ring wasn’t properly sealed (never happened in over 20 tires I repaired) then the force would be deflected downward and because of the weight of the tire it would probably only lift up a few inches.

So my opinion – If your wheels will allow it go with radials. Don’t ever mix radial with bias ply or bad results will occur. If you have to go with split rims (such as in my case) they are not that big of a headache and if you are a true outdoorsman they can be actually repaired out in the rough.

Just my opinion – not that I am young enough to take on that challenge again.

Ken

[the_experience03]

I have radial rears and bias ply fronts. I have no complaints and I really don't see how you would have a difference so long as you had the same type on the same axle.

A spoked rim will weigh a lot less, but is harder to true up on the hub. That would be my only complaint.

[Elliot Naess]

I have been lucky enough to learn what the deal really is about mixing radial and bias tires. Of course, this is on cars; on buses all bets are off, but the underlying physics still apply.
Here goes: It's about oversteer and understeer. Or, in currently fashionable NASCAR lingo: being loose or tight. The key is SLIP ANGLE. Every tire slips a little bit sideways while turning, mostly from the flex in the sidewall. Bias tires slip more. For safe handling, you do NOT want the rear to slip more than the front, because then the car will be "loose", that is it will oversteer. That means you will be sawing at the steering wheel to keep it straight and it may spin out.
So radials on the front and bias on the rear is out.
Radials on the rear and bias on the front is OK. This makes the car understeers a little; it is "tight" or "pushes". This is the universally accepted safe condition for highway use.
Even just mixing tire brands and sizes can cause the same effect. My Mazda Miata became undrivable when I put new tires of a different brand and one step larger size on the back. I switched them to the front and it became wonderfully stable. Two more of the new tires and it was normal again.
On my Dodge Dakota, I also put bigger tires on the back, and it became twitchy. I solved that by keeping the front tire pressures low for more slip, and the rear pressures high for less slip. Wore out the middle of the rear tires, though.
Oh, buses. My first bus drove really steady and straight on the petrified 9:00x20s it came with. I then put new 295x22.5s on it, and it lost that good directional stability. So tires do affect handling, oh yes.

[the_experience03]

I have a hard time wrapping my head around the idea of oversteer and understeer on a bus. It just doesn't seem like something we should have to deal with. Nice write up and explanation, Elliott.

For the record, I know all about the bias ply understeer from my super swampers on the truck. It's one of those things that I've gotten used to, but when other people drive it they comment on the fact that it feels like they have to move the wheel excessively to get it to turn. I have to explain that the steering is actually QUITE solid in the it has over-the-top true crossover steering with massive rod ends....everything is tight. But with the way a bias ply tends to roll on the sidewall in a turn combined with the high void pattern not giving much traction on the pavement combined yet again with tall sidewalls such that the rim can actually move within the tire without affecting the tread surface...yadda yadda yadda. I just don't pretend that it's a Miata and it seems to handle just fine for me

[Elliot Naess]

Right, a bus does not have a whole lot in common with a sports car! Except... the laws of physics.
Thank you for the kind words! I figure everything helps when we are trying to figure out what the... uh... hoot we are doing with these big silly yellow things.

[the_experience03]

Yellow? Mine is currently International Tractor White (it's actually a beige color) and covered in Sharpie graffeti from the people at all the places it has been this summer.

[Elliot Naess]

Heh, heh... Yes of course. My new bus is not painted yet, but the old one was white with a red stripe. Colors are funny things -- that bus was 95% white and 5% red, yet several people referred to it as the red bus. That stripe was what they noticed.

[sportyrick]

I have 2 vehicles with split rims and have changed them all myself (probably a dozen) and all I can say is pay real close attention to the ring and if it is seating properly when filling, get some air in it and turn it over to finish. The 2 piece wheels are the deadly ones and get rid of them no matter what! My steel wheels are all Firestone 3 piece and I am not scared of them now that I have experience with them. Most any truck stop or farm tire supply will work on them. Also, if you look at my bus pictures in the gallery (page 14) I have 20"ALLOY SPLIT RIMS. Alcoa made them a few decades ago and I was lucky enough to find 4 of them (lug centered). They looked like crap and I even had to fix a couple of cracks (lifetime welder) but they are polished up and looking good on the old bus. I have real good 20" tires and didn't want to sell them and try and buy a set of 22.5's with wheels. If you are a real good scrounger I bet you can round up a set and make that bus stand out. Good luck! Sportyrick

[bigkkarl_k1]

Hello to all. I am new to all of this so hopefully my question hasn't already been answered and I overlooked it. Anyway, I have 8.25x20 10 lug tires on split rims (size 20x7.50-currently on the bus. It came with a set (6) extra rims size 22.5x8.25 What size tire can I put on the 22.5 rims that will be the closest match and not affect my speedometer. I tried finding a tire size calculator to answer my own question but couldn't find one that had the same size tires and rim combos.

How do you add a picture?

[davido]

I have old buses. I found some 10 lug Alcoa Budd Wheels with Michelin XRV 255/80R22.5 tires on them. I was wondering if anyond definitively knows if these will work on my 1964 GMC/Wayne School Bus. I know the front hubs only actually have 5 studs, but there are 10 studs in the back axle and the wheels are all 10 hole interchangeable. I really want some aluminum wheels, but I'm not sure if anything or what will fit. Any advice is much appreciated.

Here are a few pictures of what I have: (neither are closeups. I can get some if needed.)

http://www.skoolie.net/gallery2/v/Skooli ... 5.jpg.html
http://www.skoolie.net/gallery2/v/Skooli ... 8.jpg.html


EDIT: I found this on the forum. I guess I'll just have to measure them both and see.

"WRONG Wrong wrong, all 10 hole wheels are not the same. I found this out in buying the alloy wheels for my bus. There are 2 kinds of wheels, HUB centered and LUG centered and they WILL NOT INTERCHANGE! Take a tape measure and find out for yourself. The older ones (sometime pre 90's) are lug centered and later ones are hub centered. You can look at the lug nuts and figure out which is which. If you see a lug nut that has a flange that is holding the wheel on then it's hub centered. If you see no flange on the nut and a tapered lug nut like on a car then it's lug centered. Also you don't need to change the inner rears out unless you want to, steels work fine, the only difference is weight savings."

[davido]

I found a good link that was really helpful.

http://www.accuridewheels.com/completeversion.pdf

I took a screenshot of the type of wheels I have. Now I just need to find them in the material I want.

[timbuk]

thanks davido thats what im looking for also i found some from an 80's bus and they are the same as my 65 chevy bus are you gonna go to 22.5? alums would be nice but havent seen anything like that yet timbuk

[davido]

I'm not sure. I've been talking to a guy that has some. I'm not sure if they'll fit. Ultimately I would like to have some aluminum ones. Depends on what I can find. I'd go up to the 22.5s if that was required. I only have 20s now. We don't drive it very far, just locally for tailgating. I also read this which may be an alternative:

"The center hole on the new metric wheels are larger and will not hold the wheel centered. However you can have the stud holes beveled and change to bud style lug nuts this will hold the wheel centered. It is done all the time with big truck wheels when guys find good deals on hub piloted wheels and have a truck that uses buds."

[junkyardkid]

Its split rims and wheels, Split rims have a rim on them and a lock ring, together they form a wheel that splits, or split rims. one piece Wheels bolt directly to the hub and are one piece and are in no way shape or form a rim, they do however have a rim on them but all round things do, just cause a glass has a rim on it doesnt mean that we sould call it a rim. A rim is just that a rim like on a spoked wheel, the rim is the outer bit, the whole shabang is a wheel. International and some trailers and such use a sort of rim that attaches to a hub. We need to stop this confusion of calling all things round that we put tires on rims.