(Redirected from Wheel Sizes)
Parts of a Wheel
The first step of the process is to determine what size the wheel is. You will probably do this either by looking at visual cues or by the obvious size of the wheel, but sometimes if the wheel could be, for example, 700c or 27", you may need to check with a tire. The reason you need to check is because some wheel sizes are much more in demand than others.
Tires have two sizes, diameter and width. Diameter is more important, because for the most part tires of different widths will fit on the same rim size. Tires of different diameters never will. The major size categories on this page are diameters, but there is some discussion of width within the sections. The diameter of a tire that matters is how big it is where it fits the wheel - it doesn't matter how big it is where it rolls on the road. The diameter where it fits the wheel is called the bead seat diameter, or BSD. It is measured in millimeters, and will be a number between 200 and 650. [[need a picture to contrast the two diameters]
Why it's not easy
It sounds easy - if tires are measured by diameter and width, you can find one with the right diameter and put it on the wheel. However, years ago people who made tires didn't write the correct diameter on the tire. They wrote some number that was a little like the tire's diameter where it meets the road. But as you know, that diameter is meaningless. It's a little easier with common sizes, since manufacturers usually used the same made-up numbers for most of them. We'll concentrate on those.
- 622 - 700C, rarely 28" or 29". Although far outnumbered by 26" wheel types, these may be in high demand for both building up new fixies/SS frames and by people also try to modify their 27" bike to use 700C because of the much greater choice of new and used parts. These are a good size to start the list with, because you should essentially just make a "fair" evaluation of 700s - you don't need to be overly generous or demanding. A decent amount of rim damage to one of these wheels will usually mean that it will never ride as nicely as it should, but it might still work well enough to be a decent wheel. If you think a flat spot can be fixed well enough for safe braking, save it. All of these wheels will be aluminum and have bead hooks - if you find one that isn't, it is probably not worth saving. If spokes are corroded, up to 2 or 3 rounded/frozen nipples should be ok, at which point the wheel becomes a despoke unless the rim and hub are also completely ruined. It is very unlikely that a 700C wheel will end up in the backyard - they will almost always be repairable or have a useable part - even if it is just the aluminum rim, useable for non-bike fabrication.
- 630 - 27" wheels are always in demand, both front and rear. Steel rims are great to have around for all the people walking the door that need replacements, aluminum perhaps less so, but if you need a wheel, any will do. We need a lot of these because bike boom bikes had skinny tires and many riders succeeded in denting their rims. Because of this, your standards will be fairly low. Any aluminum 27" wheel without a decently damaged rim will be considered repairable. Steels that aren't more than a few mm out of true can be kept as well. It would be nice to have hook beads, but they usually don't. Aluminum wheels with bead hooks and moderate rim damage (a fixable flat spot or other crash damage) can be consider repairable if the spokes aren't too corroded, because they are very rare, especially if the hub is decent - and it usually will be if the rim has bead hooks..
- 559 - Modern/Cruiser 26" or "26 decimal". These wheels are also in demand, but are we have a better supply of them because they are still in production and bikes with this size wheel commonly end up getting scrapped. All steel that isn't absolutely ready to ride goes to the backyard - we may end up using them, but they can wait out there. All the aluminums should have bead hooks, and any without serious rim damage that are less than 2cm or so out of true should be considered repairable, unless there are more than one or two frozen nipples.
- 590 - Old 26" - Three speed or "26 fraction". Another size to be fair with. These are all going to be steel, and generally won't seem like anything special. Hold wheels with good three speed hubs, namely Sturmey-Archers, to a higher standard: if the rim has a decent dent, these wheels should be despoked so the hub can find a better future. Generally, keep anything around that seems trueable.
- Other sizes. Most other sizes can safely be considered "oddball". One mildly notable size is the kids mountain bike 24" size (507mm). The rules for these should be the same as 559s. Road tubular wheels are rare, and also easy to evaluate: if there is anything wrong with the wheel that prevents it from being absolutely perfect, it should be despoked; all of its parts are high quality and could be useful. Kids wheels smaller than 24" are either fine or ruined - ruined could mean a big rim dent, a broken spoke, or frozen bearings. Loose bearings, cheap bearings, out of true, and corroded spokes are not a problem. Decent 20" BMX wheels are subject to standards similar to those of 559 wheels.
- 597 - Old 26" - Similar to the "26 fraction" 590, especially in people confusing it with other 26" sizes. If you have a lot of old Schwinns passing though, you'll find that many of them do indeed use this size, and the 7mm difference vs the 590 makes life fairly difficult if you don't have 597 around. In some locations, even getting a "26 fraction" 597 tire can be difficult and special ordering will be required. If your shop can purchase new parts, you might want to stock this size - if for no other reason than to have some around if the shop needs to refurbish a donated bike. If you find that a mounted 590 tire is generating a "hop" while riding, it could be because the rim is actually sized for 597 - does that 590 actually fit that well onto the rim?
- 650b - A specialized retrofit item...
There have been many different sizes of wheels used on bicycles, but only a few of them are common at the co-op. Here is a full list of sizes. It is a good list for reference purposes, but you can learn almost all of what you need to know on this page.
Common tires sizes
These four are the most common tire sizes that you will encounter if you are fixing bikes at the co-op. If you have a bike, it probably has one of these tire sizes as well. Farther down the page, there is some information on less common sizes. If you can learn how to spot these, you will know everything you ever really need to know.
Known as: 26", mountain bike size, cruiser size, "26 decimal" Common sizes: 26 x 1.5", 26 x 1.75", 26 x 1.95", 26 x 2.15"
This is probably the most common size made today, since it's on almost all mountain bikes and most "cruiser" bikes. It was also the size of wheels on old American beach cruisers (the big heavy bikes with one speed - not the English-style bikes with three speeds). These are very easy to recognize - if you look at the list of common sizes, you can see that they are all known as 26 inches, and the width is given as a decimal number, like 1.5" instead of 1 1/2 inches. Any tire listed as 26 x a decimal is a 559mm. If you need to replace one, there are a lot of choices in width and tread, and you can choose one to fit the riding style - ask a key volunteer or staff member if you need advice.
Known as: 26" x 1 3/8", 3-speed tires Common size: 26" x 1 3/8"
These are found mostly on 3-speeds, the old style of city bikes with turned back handlebars, fenders, and 3-speed hubs in the rear. They are also found on similar bikes without the 3-speed hubs (sometimes single speeds, and sometimes with derailleurs). They always say 26" x 1 3/8" on the side, so they are easy to recognize. Bikes are no longer made new with this size, but we have a lot of them at the co-op. If you need to replace one, there is only one type, so the choice is easy.
Known as: 27", old road bike tires Common sizes: 27" x 1 1/8", 27" x 1 1/4", 27" x 1 3/8"
This size was used on road bikes in the United States for many decades, and there are still a lot of these bikes around. Anything with road ((handlebars)) at the co-op that is older than about 20 years will have these wheels. They will always have be labeled as one of the three common sizes, and will not be hard to recognize. Bikes are no longer made with this wheel size, but it is almost the same size as the modern road wheel size (see below), so be sure you check the tire rather than assuming any large wheel is one size or the other. If you need to replace a tire on one, you should typically use a 27 x 1 1/4" tire, although if the bike is very cheap you may wish to use a 27" x 1 3/8" for extra comfort, since people who buy the cheapest 27" bikes (e.g. $50 bikes) are not usually buying them to ride fast.
Known as: 700c, modern road wheels, hybrid, 29" Common sizes: 700 x 25mm, 700 x 38mm
This size is not found too often at the co-op, but it is very common on new bikes. It is the size on all modern road bikes, and many "comfort bikes" and "hybrids", as well as some recent mountain bikes, known as 29ers (the wheels are referred to as 29 inches when they have mountain tires). It should be very easy to recognize these wheels if they have tires on them, as almost all of them will actually say 622 on the side, and most will say 700c as well. There are a wide variety of tires available for this size, and replacements should be chosen to fit the riding requirements. Ask a key volunteer or staff member.
This is an advanced job that requires a lot of knowledge about wheels and wheel repair. However, this makes it a great opportunity for someone who doesn't have this knowledge to learn by working with someone who does. If you are going to be evaluating wheels by yourself, you should be familiar with all of these aspects of wheel repair:
- Flat spots or other impact damage and how to find them
- How to spot a bead hook on a rim
- How to quickly tell how out of true a wheel is, and see hops
- How corroded is too corroded for spokes
- Finding rounded and/or frozen nipples
- Telling the difference between wheel sizes on wheels without tires attached
- A basic knowledge of wheel sizes and what they're used for
Having these skills also implies a knowledge of basic truing. Although this process doesn't require much actual truing, it would be difficult to have a good eye for how out of true a wheel is without having trued before. There are steps of the process that anyone can do, so even if you don't have all of these skills, read on.
The main goal of wheel sorting is to determine whether a wheel should be despoked, repaired, or just put out in the backyard. Despoke wheels typically have one or more good parts, but a fatal flaw as a wheel. A good example would be a wheel with good spokes and a good hub, but a rim that was ruined in a collision with a pothole. Wheels to be repaired are the ones with no fatal flaws. Backyard wheels are ones that are either a complete loss, such as a wheel where the rim, spokes, and hub are all ruined, or cheap steel wheels which aren't in great shape but could be used as is, since the standards for steel wheels are fairly low. These wheels are free for members to take, if they need them; an individual who needs a wheel and can't find anything better may find it worthwhile to repair them although the co-op does not.
Tasks for apprentices
While an experienced volunteer can do the entire job, there are certain aspects which can provide a good learning experience for someone who is newer. One of these is lubricating nipples. After a quick initial inspection by an experienced volunteer looking for fatal flaws (mostly rim damage, but give the axle a spin as well), an apprentice can get the wheel in the truing stand and lube all of the nipples, then pick the correct spoke wrench and make sure they're all turning. The lube is necessary to check if the nipples will turn, and if they do, it will save some time for the person who trues the wheel later on. This can help educate the volunteer in the processes involved in wheel truing. If there is some confusion regarding the size of a wheel, a new volunteer can check the wheel using tires to determine its size. New volunteers can also be the ones to tag a wheel when it's finished, which will involve them in the evaluation process and show them what problems are common, both fixable and fatal.
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