How Many Speeds? | Shimano Freehubs
| Sprocket Replacement
| Traditional Threaded Freewheel | Traditional Threaded Hub | Cassette Freehub ® | Cassette Cluster |
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Older multi-speed bicycles have simple rear hubs with a set of threads on the right side of the hub shell. A traditional freewheel cluster has matching threads which screw on to the hub.This is different from the more modern "Freehub ®" or "cassette hub" design, in which the freewheeling ratchet mechanism is a more-or-less integral part of the hub. See also my article on Cassette Hubs.
A standard freewheel attaches to a hub by screwing on to external threads that are part of the hub. The action of pedaling tightens the freewheel down on the threads, so no tools are required to install a freewheel.
To remove a freewheel requires a special tool, commonly called a "freewheel puller" or "freewheel extractor"
This tool is a splined unit that may be mounted in a vise or turned with a wrench. The splines engage matching splines in the interior (non-rotating) part of the freewheel body. Different brands of freewheels have used different spline patterns, but there is a recent tendency to standard on the Shimano pattern.
Older freewheels had simple notches and matching extractors with two or four "bosses" (prongs.) This obsolete system was prone to failure, and it is easy to ruin the tool and the freewheel while trying to remove the freewheel. When using a boss-type freewheel puller, the tool should be secured against the freewheel by tightening down the axle nut or quick release skewer.
Since the action of pedaling tightens the freewheel's threads onto those of the hub, the more torque is applied by the pedals, the tighter the freewheel will be on the hub. This can make it quite difficult to remove a freewheel that has been used on a tandem or any bicycle with a very low gear. The usual technique for removing a freewheel from its hub is to clamp the freewheel puller into a solidly mounted vise and unscrew the wheel from the freewheel. If your vise is suitably flexible, it works better if you clamp it so that the wheel is in a vertical position; this permits you to twist it harder without having your feet slip on the floor.
An alternate approach which I have found to work quite well for really obstinate freewheels is to use a suitable box wrench to hold the tool, and strike the wrench handle sharply with a big rubber mallet. I use a Park chain whip for this, because it has a hexagonal hole in the handle that fits Park freewheel pullers perfectly. The standard ISO. thread for freewheels is 1.375 x 24 TPI, the same as for standard ISO bottom brackets.
| Type | Thread Specification | Equivalent |
|---|---|---|
| I.S.O. | 1.375" x 24 tpi 1.370" x 24 tpi | 34.92 x 1.048 mm 34.80 x 1.058 mm |
| French | 34.7 x 1 mm | 1.366" x 25.4 tpi |
| Italian | 35 mm x 24 tpi | 1.378" x 1.058 mm |
| Metric BMX | 30 mm x 1 mm | 1.181" x 25.4 tpi |
Older European freewheels had all of the sprockets screwed on. The big ones got screwed on especially tight. The larger two sprockets had left threads, and screwed on from the back side of the freewheel, so it was impossible to remove them without removing the freewheel from the hub.In practice, you never removed all of the sprockets at the same time, because you needed a sprocket to hold the freewheel in place while you unscrewed the one you wanted to remove. (There were special vises to let you take off the last sprocket, but I never found the need to use one.) There were commonly 2 or 3 different thread sizes on the same freewheel, so sprockets made for one position wouldn't necessariyl fit on another position. Threaded sprockets also had built-in spacers, so they could only be installed in one direction.
In the mid 1970s, Sun Tour and later, Shimano took the freewheel business away from the long-established European manufacturers, such as Atom, Campagnolo, Cyclo, Everest, Maillard, Regina, TDC... They did this by virtue of greatly superior design and workmanship, even though the metallurgy of the Japanese products was not as good:
- One of the reasons that the Japanese were able to take over from the Euro manufacturers was that the larger sprockets attached to the freewheel body by splines, not threads. The splined sprockets were held on by a couple of small threaded ones. Since the only threaded sprockets were the small ones, (which don't get screwed on that tightly) it was much easier to remove and replace the sprockets.
- The Japanese freewheels also featured better shaped sprocket teeth, which made them shift significantly better. Sun Tour sprocket teeth were beveled at the top in a direction that made it easier for the chain to seat into position as it shifted. Shimano used a "Twist-tooth" design, which placed the back corner of each tooth where it could more easily snag the passing chain during a shift.
- Japanese freewheels also had, a better, deeper, more reliable freewheel remover fitting. Sun Tour used a conventional two-prong connection, but the notches were much deeper than those on European freewheels, and the puller was designed for a superior fit to Sun Tour freewheels. Shimano was a major pioneer in the adoption of splined pullers, which were pretty much immune to the old problem of rounding off the two corners of the tool and the matching corners of the freewheel center.
Freewheels screw onto the hub without any tools, then, as you ride the bike, your pedaling effort tightens them down. A freewheel that has been ridden for a long time, especially by a strong rider with low gears, may be quite difficult to remove because the threads are so tight.Although you can screw the freewheel on by hand, just by turning the sprockets clockwise, when you want to remove it, the sprockets don't help, because the freewheel's ratchet mechanism lets it spin freely counterclockwise. You need a special wrench, called a "freewheel puller" to grab hold of the non-rotating core of the freewheel.
Older designs used a tool with two prongs, that fit into two notches in the freewheel core. The shape and spacing of these prongs would vary from one brand to another. It was very common for the prongs to get rounded off or broken, and to ruin the freewhel. Once the notches are damaged, there's no way to remove the freewheel without destroying it. (The last resort is to dissassemble the freewheel and clamp the core into a vise, then unscrew the wheel.)
Before trying to remove a freewheel using a 2 prong tool, it is very important to secure the tool against the freewheel, using either the axle nut, or the quick release skewer (with the springs left off.)
Note, once you have broken the threads free, you need to loosen the skewer or axle nut to allow the freewheel to unscrew further.
Newer freewheels use pullers with multiple splines (grooves) that give a much more positive engagement than the older 2 prong design. This type doesn't require any special measures to secure it.
| Some Popular Freewheel Tools | |||
|---|---|---|---|
| Park FR-1
| Park FR-2
Sun Tour 2 prong. | Park FR-3
Sun Tour 4 prong. | Park FR-4
Atom/Regina splined. 20 splines. (About the same outside diameter as a nickel.) |
The usual way to use a freewheel puller is to install it in a vise and unscrew the wheel from the freewheel. If you have used an axle nut or QR skewer to secure the tool, make sure to loosen it after breaking the threads loose.If you have a suitably mounted or articulated vise, it helps to install it so that the wheel is vertical (axle horizontal.) This gives you better purchase to turn the wheel. I used to work in a shop where we had a vise mounted sideways on a door frame for this purpose. My present vise has an extra pivot that permits the jaws to be rotated 360 degrees. Unfortunately, most vises lack this useful feature, so you may have to make due with a horizontal wheel orientation.
For really tight freewheels, removal by impact sometimes will succeed where the vise approach fails. I do this by attaching a long handle to the freewheel puller, and striking the handle sharply with a rubber mallet. Park Tools makes a couple of suitable handles that fit their freewheel pullers:
Whatever method you use, it is best if the wheel has a tire installed and inflated. This will improve grip and reduce the risk of damaging the rim.
If you need to remove an old freewheel and don't plan to use it again, you can remove it destructively. This is often a reasonable option if you don't have the correct puller for that brand/model, or for cases where the extractor notches have been damaged by unsuccessful removal attempts.Disassemble the freewheel as described below, then remove the pawls and clamp the core in a sturdy vise. Unscrew the wheel from the core in the usual counterclockwise direction.
Installing a freewheel is quite easy, and requires no tools at all. Basically you just screw the freewheel on as you would screw the cap onto a jar. The final tightening will occur by "foot power" as soon as you ride up your first hill.The foot power is very considerable, and that's why it can be so hard to remove a freewheel that has been used for a while, especially on a bike with low gearing.
To prevent future difficulty with removal, it is very important to grease the threads before screwing a freewheel onto your hub!
The type of grease used is not all that important, but you must use something.
Also, make very sure that the freewheel is going on straight. Freewheel threads are unusually fine for their diameter, and the aluminum threads on the hub are soft, easily damaged if you cross-thread the freewheel.
Freewheels should be oiled from time to time with a medium-weight oil. This is easy to do, and generally requires no disassembly.The bike should be held with the rear wheel off the ground, and leaning to the left at about a 45 degree angle. An assistant may be helpful for this. Turn the pedals around a couple of times to get the wheel spinning fast, then let it coast (helps to be in high gear for this.)
Look inside the smallest sprocket. The sprocket will be stationary, since the wheel is coasting, but you'll see an inner part of the freewheel that is spinning with the wheel. Drip oil onto the crack between the turning part and the stationary part. Gravity and capillary action will help work oil into the freewheel.
Repeat this a few times, until you hear a change in the sound of the clicking pawls (they'll generally get quieter when the oil reaches them.)
This should be done every year or so, or any time that coasting sounds loud and gritty.
Most multi-speed freewheels have replaceable, interchangeable sprockets. It used to be a common bike-shop service to assemble custom freewheels with any desired combination of sprocket sizes. Unfortunately, with the general decline in freewheels, replacement sprockets are no longer as readiliy available as they once were.To remove sprockets from a freewheel, you normally use two chain whips: one to unscrew the sprocket, the other to prevent the freewheel from rotating backwards. If you have one, you can use a special freewheel vise in place of the second chain whip.
Older European freewheels mostly used all threaded sprockets. Usually the two largest would have left threading, and would have to be removed/replaced at the wide end of the freewheel. Because of the low gearing provided by the larger sprockets, they would usually be screwed on very, very tight, and could require a considerable amount of effort to unscrew. The smaller sprockets would screw on from the outside, using normal right threading. For this type of freewheel, it is impossible to remove all of the sprockets at the same time without a special vise, but it is never necessary to remove all of the sprockets at once.
When the Japanese took over the freewheel market, starting in the mid 1970s, one of the chief advantages they offered was that only one or two of the smallest sprockets screwed on, the others simply slipped onto the freewheel body. The sprockets had splines fitting into matching grooves in the freewheel body. Since only the smallest one or two sprockets need to be unscrewed, this style is much easier to service.
Shimano Hyperglide freewheels use all splined sprockets, with a threaded lockring, similar to the system used on Hyperglide cassette hubs.
Customizing
Back in the days of 4-, 5-, even 6-speed freewheels, it used to be common to customize the ratios. When there were so few positions available, it was more important to provide the specific sizes desired to match a given rider's style and riding conditions.As gears proliferated through 7-, 8-, 9- and now 10-speed cassettes, this became less of an issue. As a result, custom gearing is now much less common than formerly.
Many older cyclists assume that this is because it is harder to customize cassette-type clusters than it was with the old thread-on freewheels. In fact, the opposite is the case! Cassettes are much easier to customize, because all of the sprockets use the same spline pattern, so any of the sprockets (except the smallest one) can be used at any position on the Freehub body. With thread-on freewheels, the body is "stepped" so that sprockets for different positions will attach with different spline or thread patterns. Back in the day, better bike shops would have a big "sprocket board" with dozens of hooks to stock all of the various permutations of tooth count and attachment size needed to create custom freewheels. Generally each different manufacturer would require a different sprocket board, because each manufacturer would have its own proprietary design.
Note: I advise against doing this, because it is generally not worth the trouble. The freewheel is the least important bearing on a bicycle, since it only turns when it is not carrying any load.Nevertheless, some people will ignore my advice and try to service freewheels, so here's how to do it:
Screw the freewheel onto a wheel so that you will have something to hold it with.
You should see a ring with two holes in it for a pin spanner to fit into. This is usually the ring which has the brand name of the freewheel marked, and may also have an arrow pointing clockwise, and the word "remove" in one language or another.
If you don't see such a ring, you may need to remove the smallest sprocket to gain access to it. This is common on freewheels with 13 tooth or smaller sprockets. You will need two chain whips, one to unscrew the smallest sprocket, another hold the freewheel so that it doesn't spin backward while you unscrew the top sprocket.Use a hammer and punch (or an old flat-blade screwdriver) to drive the ring in a clockwise direction. This ring is actually a bearing cone with a left ("reverse") thread, and once you have removed it you will see a row of 1/8" bearing balls and a stack of very thin washers surrounding the threads that the cone threaded on to. These are shim washers, and you can remove one or more of them to make the bearing tighter, if the freewheel has too much play.
If you want to disassemble it further, just lift off the cluster at this point and the innards will be revealed to you, including another row of 1/8" balls at the base of the freewheel, and two or three spring-loaded pawls which make the ratchet work.
For re-assembly, you can use thickish grease to stick the balls in place while you reassemble the unit, but the tricky part is the pawls. In days of yore, there were special bobby-pin-like clips to hold the pawls compressed against their springs while you re-assembled the freewheel. These are no longer available.
Instead of the special clips, you can use a rubber band with a piece of thread looped though it. Assemble the pawls to the freewheel core, then wrap the rubber band around them to hold them against their springs.
Once the outer part of the freewheel is more-or-less in place, use the thread to pull the rubber band out through the middle of the freewheel.
These may be serviced in the same way as conventional freewheels. You'll need a fairly hard-to-find old-style Shimano special tool (TL-FH 40) to unscrew the cup, which is also the cone for the main bearings.
The first multiple-speed freewheels had 3 sprockets, using the traditional 1/8" chain.In the 1950s, narrower 3/32" sprockets and chains were introduced, permitting the move to 4-sprocket freewheels within the then-standard 114 mm frame spacingn
5 Speeds
In the late 1950s, spacing was widened to 120 mm to permit the use of 5-speed freewheels. This required adding spacers to the right-hand end of the axle to keep the chain from rubbing on the frame. The added spacers requried additional dish to the spokes, causing wheels to become somewhat weaker.6 Speeds
In the 1970s, there was a move toward 6-speed freewheels. These were of two types:
- "Standard" spaced 6 speeds had sprocket to sprocket spacing the same as the existing 5 speeds, around 5.3 mm
Standard spaced 6-speeds required increasing the frame spacing to 126 mm, aggravating the problems introduced with the move to 5-speed, but still providing satisfactory service in most cases.
- "Ultra Six ®" spaced 6 speeds used a closer spacing, arond 5 mm. This permitted an Ultra Six ® freewheel to directly replace a standard 5-speed unit on a 120 mm hub.
The key to making this work was the use of a narrower chain. The interior width of the chain was the same as always, but the new narrower chains used shorter rivets, so the ends of the rivets didn't protroude past the outer chain plates, as the rivets in traditional chains did.
7 Speeds
In the 1980s, these two approaches were combined to create 7-speed freewheels, with 5 mm ("Ultra") spacing that would fit the same 126 mm hubs as "standard" 6-speeds.8 Speeds
In the early 1990s, the industry moved to 8-speed clusters with 130 mm spacing. 8-speeds were available in both freewheel and cassette hubs. As with the move from 4- to 5-speed, and from 5-speed to 6-speed, this required adding spacers to the right-hand end of the axle to keep the chain from rubbing on the frame.As it turned out, the increased length of un-supported axle sticking out from the right side of the hub was just too long for traditional 10 mm threaded axles. 8-speed freewheels were sold for several years, but a very large percentage of the riders who bought them wound up having problems with axle breakage/bendage. As a result, 8-speed freewheels eventually pretty much disappeared from the market.
This also coincided with the increasing popularity of the cassette Freehub ® which didn't have the problem of axle protrusionn. As the number of sprockets has continued to increase to 9 and now to 10, thread-on freewheels have become obsolete for high-end applications. 9- or 10-speeds have never been produced, as all modern derailer bikes of decent quality use the much superior cassette Freehub system.
| Freewheels for sale at Harris Cyclery |
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