Tool Tips
Cotterless Cranks

Sheldon Brown photo

(A Blast From The Past)
This is an old article, and some of the information in it is obsolete.

by Sheldon Brown

This article originally appeared in Bicycling magazine, March, 1983

[Comments in brown are second thoughts, 1998.]

Aluminum alloy cotterless cranks have replaced steel cottered cranks on all but the least expensive bicycles. The advantages of lighter weight, easier maintenance, and closer dimensional tolerances have made cotterless cranks very popular. Manufacturers have spent the last decade perfecting cost-cutting ways of making cotterless cranksets, so that the cheaper models cost barely any more than the steel cottered cranks they replace.

Unlike cottered cranks, cotterless cranks require special tools to install and especially to remove the cranks from the spindle. The need for special tools is an inconvenience, but this is more than made up for by the great ease of using them. By contrast, the un-special tools used to remove cottered cranks-a hammer, a drift pin, and a cinder block (discussed in Bicycling, January/February 1983)- require more skill (and luck) on the part of the user.

Another benefit of cotterless cranks is that the needed tools weigh only a few ounces. You can carry them with you on the road. You wouldn't want to do that with the tools for cottered cranks!

To install or tighten the cranks, you need a socket wrench. To remove a crank from its spindle, you need a cotterless crank puller to fit your brand of crank. The socket wrench and crank puller are often sold together in a small tool kit.

Tapered Square Hole

Let's look at the way that a cotterless crank is secured to its spindle. The ends of the spindle are square in cross section, and tapered so that they are slightly thinner toward the ends of the spindle. There is a corresponding tapered square hole in the crank, so the crank fits onto the end of the spindle.

Depending on the brand and model of crank you have, it is secured onto the spindle by either a bolt or a nut. The older, more traditional crank design uses a hollow, threaded spindle. A bolt, properly called the fixing bolt, threads into the spindle. A flat washer under the bolt head is an essential part. Sutherland's Handbook for Bicycle Mechanics calls this crank spindle design "Type I."

The alternate crank design uses a spindle with a small threaded boss protruding past the ends of the square tapered section. A nut threads onto this boss to secure the crank onto the spindle. Usually, the nut is a special nut with a built-in serrated lock washer, so that no separate washer is required. Sutherland calls this crank spindle design "Type II." [Some newer Shimano cranks use a splined connection between the axle and the crank.]

Remove Dustcap

The first step in removing a cotterless crank is to remove the dustcap, if any. Depending on the brand, this is un-screwed either with a five-millimeter Allen wrench or with a wide-bladed screw driver. (Don't use a small screwdriver, as you run the risk of damaging the slot--most dustcaps are soft aluminum or plastic.) If you don't have a large enough screwdriver, a cone wrench or a dime will often fit nicely. [Most newer cranks use snap-in/pry-out dust caps, rather than threaded ones.]

Next, you remove the fixing bolt or nut that holds the crank to the axle. Since the bolt or nut is recessed inside a cavity in the crank, you need a socket wrench to turn it. If a nut is used, it will be 14 millimeters. If a bolt is used, it will usually have a 15-millimeter head; [these days, 14 mm is more common] Stronglight and Zeus use 16-millimeter bolts. (A 5/8-inch socket works well on l6-mm bolts.)

Be especially careful to remove any washers that may be present, or you may easily destroy the crank in trying to push the crank puller "bolt" against the washer!

Now you are ready to use the crank puller. This tool is a joy to use, and with reasonable care will work every time with no complications.

A cotterless crank puller is made up of two parts, one of which is basically a nut and the other a bolt. (The "nut" part is actually a bolt and a nut at the same time! It has both a male and a female thread, plus flats for a wrench.) The "nut's" large male thread fits into the same threads of the crank that the dustcap screws into.

Before you screw the "nut" part of the crank puller into the dustcap threads, the "bolt" part must be screwed back out of the way (counterclockwise) so that it will not hit the end of the spindle while you are screwing the "nut" part into the crank. Otherwise, the "bolt" will keep you from screwing the "nut" all the way into the dustcap threads.

Be sure you screw the "nut" part of the tool all the way into the dustcap threads. These threads will be subjected to severe stress as the crank is removed, and aluminum threads are not noted for their durability!

But don't over tighten the "nut" of the puller. Most of the time you should not need to use a wrench on it. If you must use a wrench to fully seat the "nut," be gentle!

Once the "nut" is securely screwed into the crank, tighten the "bolt." The "bolt" will press against the end of the axle, the "nut" will pull on the crank. Usually, the crank will fall off in your hand with surprisingly little effort, because of the very high mechanical advantage of the tool. Consequently it is hard to realize how much force is being exerted. (On some cranks, most often the less expensive "melt-forged" models, you'll have to apply considerably more effort than this.)

Three Sizes

Which tool to buy depends on what brand and model of crankset you have. Although all types use the same one- thread-per-millimeter pitch, three common diameters for the dustcap threads: Campagnolo, 22 mm; T.A. 22.8 mm; and Stronglight, 23 mm. All other brands that I know of use the same size as Campagnolo.There is one small exception: early Lambert cranksets were threaded 7/8-inch by 24 threads per inch.)

To service a T.A. crankset, you need a T.A. puller. For Stronglight, ideally, you should have a Stronglight puller, but the T.A. is usable (although it fits a bit more loosely than it should). For any other brand, you have a wider choice available. Here are some things to keep in mind as you shop among the alternatives:

[The above two paragraphs are out-of-date; all modern cranks use the 22 mm "Campagnolo size.] Pullers made primarily for Type I cranksets usually have a rotating collar on the end of the "bolt." This collar is the part that actually pushes against the end of the axle to pull the crank off. If you use this type of tool on a Type ll. spindle, it will work, but the threaded end of the spindle may damage the pivot of the tool's collar. Also, some Type I pullers simply don't fit on Type II cranksets: the puller's "nut" may interfere with the threaded boss on the spindle.

Of the tools intended for Type II spindles, the Sugino Maxy crank puller is particularly nice; it includes its own socket wrench. It can be used with a six-inch or larger adjustable wrench, or a 16 mm open end wrench if you happen to have one. The Maxy puller has a dome-shaped end to push against the male threaded end of Type II spindles intended for nuts. When this tool is used with a Type I female threaded spindle, the sides of the "bolt" of the puller rub against the edges of the spindle threads that the crank bolts screw into. There is a slight possibility that the spindle threads could be damaged by this, but bottom bracket spindles are made of such very hard steel that the risk is small.

Park's Universal Puller

The closest thing to a universal crank puller is made by Park. This has a reversible, double-ended "nut," with T.A. threads on one end and Campagnolo threads on the other end. The wrench flats are in the middle. The "bolt" of this tool is even more unusual than the "nut." It has its own wrench welded onto one end, and the other end has a special contour so that it works well with either male or female threaded spindles.

If you want to be able to service the greatest variety of cranksets with the minimum of tools, the Park puller is the one to buy. If you are concerned only with being able to service the particular type on your own bicycle, the tool made by the crank manufacturer is probably better, and is lighter than the Park tool. The threads may also be a better fit.

There are several types of socket wrenches suitable for removing and re- installing the crank fixing bolt (or nut). The crank manufacturers all make small, easily carried single-size socket wrenches to fit their fixing bolts.

Park makes a very well-thought-out "universal" crank wrench with 14-, 15-, and 16-mm sockets on a handle that is just short enough to clear the pedal on most cranksets. One end of this wrench is designed to serve as a screwdriver for the dustcaps, and there is also a short 5- mm Allen wrench built in for those dust- caps that require one. This wrench is also very handy for general use-for axle nuts, seatpost bolts, etc. Unfortunately, Park's quality control is less than 100 percent- on my Park socket wrench, there were burrs that made both the 14- and the 16- mm sockets unusable. If you buy one, check the fit carefully first.

Don't Ovetighten

For shop use, many mechanics prefer to use an automotive-type socket wrench, usually with a ratchet handle. This works very well.

If you wish to use this type of wrench, you may have some difficulty finding sockets that are the right size for the bolt but have a small enough outside diameter to fit inside the dustcap threads. This will not be a problem for a 14-mm socket, but many 15- and 1 6-mm sockets are too thick to fit in. (It's legendarily difficult to get the 16-mm bolt out of the smaller Campagnolo-sized dustcap hole on a Zeus crankset. The Zeus tool works, but very few other tools do. The Bicycling shop solved this problem by turning a socket down on a lathe. A less elaborate solution is to beg or borrow a Zeus tool long enough to get the bolt out, and then replace it with a more-easily-removed 15- mm bolt.)

Usually the better quality sockets will have thinner walls-cheap sockets try to make up for poor quality steel by using more of it. Sockets come in six-point and 12-point types. Six-point sockets tend to have slightly thinner walls, so they are more likely to fit. For use with ratchets, six-point sockets are generally preferable anyway. The 3/8-inch drive sockets tend to be thinner than 1/2-inch drive sockets.

Needs No Puller

One promising development is the crankset which needs no puller. Shimano introduced the first such crankset several years ago with its One-Key-Release system. More recently, Excel and Sugino began offering similar units. All work the same way.

Instead of the customary 15-mm bolt, these cranksets use a bolt with a 6-mm Allen head. [Newer ones use 8 mm or, occasionally, 7 mm] This has two advantages: the necessary tool is small and practically weightless, and the Allen head can be exposed through a small hole in the dustcap.

The steel dustcap functions as the "nut" in a standard crank puller, and when you're removing the crank, the fixing bolt functions as the crank puller's "bolt." As you loosen the fixing bolt, the head of the bolt pushes against the inside of the dustcap, pulling the crank from the spindle.

This system is particularly well-suited for touring and for air travel when you need to remove either the pedals or the cranks to put your bicycle into a box. You can adapt other brands of cranks to this system by replacing the dustcaps and fixing bolts. Shimano, Excel, and Sugino all offer retrofit kits. They will work with all Type I cranks (that use a bolt to hold the crank to the spindle) with Campagnolo size (22-mm) dustcap threads.

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