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Up through the mid 1980s, derailer-equipped bicycles used "friction" shifting. The shifter was a simple lever held in place by friction, and the rider was expected to learn to judge how far to move it for each shift. If the lever was moved the wrong amount, the deailer might shift the chain too far, or not shift at all. It might also shift to the desired gear, but not line up quite right with the sprocket, so the chain would run rough and noisy. The rider was expected to correct this by feel and by ear.
Friction shifting required a fair amount of skill and practice even when the parts were new. With older bikes, where the parts are often worn, friction shifting is often even harder to use smoothly.
After various false starts, the industry perfected "indexed" shifting in the mid 1980s. With indexed shifting, there are click stops in the shifter so that the rider has a tactile guide as to how far to move the shifter to shift from one gear to the next.
Indexed shifting is one of the most popular upgrades to older bikes, and balky friction shifting is one of the most common reasons for discarding older bikes.
Indexed rear shifting is a very worthwhile feature. Indexed front shifting, however is of much more questionalble value, especially
Depending on what parts your bike currently has, you may have to replace many of these parts, but often not nearly as many as you might think.
|Old-style Friction Shifters||Shifters for Drop Handlebars||Shifters for Upright Handlebars|
|Down Tube Shifters||Stem Shifters||Bar-End Shifters||Combined Brake/Shifters (STI/Ergo)||Thumb Shifters||Twist-Shifters||Below-Bar Shifters|
Down tube shifters were the original type of shifter for derailer bikes, and were common through the early 1990s. It really makes a lot more sense to put all rider controls on the handlebars, but the poor performance of older derailers and the friction of older shift cables caused this frame mounted type to be preferable in the old days. They still have their fans, who tout their light weight and simplicity, but they're pretty close to extinct. Once you get used to having the shift controls on the handlebars, you're unlikely to ever want to go back.
Many bikes from the mid '70s through the mid '80s had shift levers mounted on the handlebar stem. This was more convenient to reach than the traditional down tube location, especially for riders who were poorly fitted to their bikes so that they would spend most of their riding time holding the top part of their drop handlebars. Stem shifters, along with brake extension levers, encouraged riding using only the top of drop handlebars. This riding style was popular at the time, because many casual cyclists bought bicycles with drop bars for reasons of fashion and style, even though drop bars were not suited to their low-intensity riding style.
Unfortunately, this riding position gives rather poor control of the bike, mainly because the hands are too close together for good steering control.
Stem shifters also present a danger in a collision. Depending on what gear you have selected, stem shifters can be like having a dull knife aimed at your groin!
Up until the introduction of combined brake/shifters by Campagnolo and Shimano in the early 1990s, bar-end shifters were the only satisfactory way to mount shift controls on a drop-style handlebar. Bar-end shifters fit into the ends of the handlebars, replacing the handlebar plugs.
Bar-end shifters are the most versatile of handlebar-mounted shift options for use with drop handlebars. Modern ones are indexed for the rear derailer, but use friction shifting for the front. As a result, they are compatible with all front derailers and all chainrings.
Bar-end shifters work particularly nicely when used with a "low-normal " derailer.
There are two main varieties:
To shift to smaller sprockets, there is button/lever on the inside of the brake hood, which is normally operated by the rider's thumb.
(An exception is the Sora model, which uses a thumb button similar to the Campagnolo Ergo system.)
Almost all upright handlebars have a diameter of 22.2 mm (7/8") and the shifters below are designed to fit that size only.
From the earliest days of mountain bikes through the late 1980s, top-mount "thumb" shifters were the norm. These are basically similar to down tube shifters, except that they mount on the handlebars.
In the late 1980s, Shimano introduced "RapidFire" below the bar shifters. The first version had two buttons below the bar, intended to be operated by the rider's thumb. (This caused confusion, because the older top mount units were known at "thumb shifters" but that name actually would have been more appropriate for the RapidFires, since the thumb was used for both upshifts and downshifts.
The first RapidFires were not well received, in part because the upshift and downshift actions were done with the same digit, going the same direction. Riders found this confusing.
Shimano soon introduced "RapidFire Plus" shifters that used a similar thumb button to shift to larger sprockets, but a small "trigger" operated by the rider's index finger to select smaller sprockets. This version was much more successful commercially, and remains the norm for most Shimano upright bar stystems.
Older front derailer cables used a short length of housing running from a stop near the bottom of the down tube, looping down just above the left side of the bottom bracket shell, then up the back of the seat tube to the derailer. The down-tube stop was sometimes a braze-on, sometimes a clamped-on accessory.
Older front derailers incorporated a downward-facing housing stop to terminate this loop of housing.
Newer front derailers don't use housing in this area. Instead, they run bare cable under the bottom bracket shell, then up behind the seat tube to the derailer. There's usually a plastic guide of some sort underneath the shell, which guides both the front and rear derailer cables below the bottom bracket.
Newer front derailers work a lot better than older designs, but they lack the housing stop to make them work with the old-style cable routing. This is not a difficult problem, however. All you need to do is ignore the down-tube housing stop and run the bare cable under the bottom bracket shell.
If you want to protect the paint of the bottom bracket shell, you can cut a short length, maybe 2 inches (50 mm) or so of housing to slide over the cable where it runs below the bottom bracket. This length of housing won't be working in compression as with most housing installations, since neither end will be up against a housing stop, but it will protect the paint and reduce cable friction.
You might expect the "floating" bit of housing to shift out of position over time, but this tends not to happen in practice.
Shimano STI brifters and Below-the-bar MTB shifters are indexed for the front as well as the rear. So are many of the twist grips supplied as original equipment on new bicycles.
Bar-end, down-tube and Campagnolo Ergo brifters are indexed for the rear, but use friction for the front. This is also true of most aftermarket twist-grip shifters. Older front derailers will generally be compatible with any friction shift system, but you do need to consider the chainrings to be used.
If your bike uses a double chainring, front indexing is generally not an issue, since there are only two basic positions to be used.
If your bike has a triple chainring, things get interesting! Although rear indexing is consisten with a brand, Shimano's front indexing is different between their so-called "road" and "mountain" lines. Here's what that means in practice:
Shimano does make one front derailer, the R440 model, that is designed to work with upright bar shifters and a crankset with a 52-53 tooth big ring.
The no longer make any front derailer that is compatible between drop-bar shifters and smaller chainrings.
Front derailers are designed to work with a particular-size of big ring, and the bottom edge of the outer cage plate should follow the curvature of the big chainring.
Good front shifting depends on getting the cage low and close to the chainrings, but a mismatch in curvature will make this impossible.
Older rear derailers are generally much inferior to modern ones, even quite expensive older rear derailers don't work as well as the cheapest newer designs.
Modern rear derailers will handle more sprockets, than those originally made for, say, 5-speed freewheels. They will also allow you to upgrade to indexed shifting.
Generally, modern derailers are completely compatible with older shift levers and freewheels, so there's no need to look for a "period" replacement even if you aren't immediately upgrading the rest of the shifting system.
The adaptor claws included with older derailers are sometimes an integral part of the derailer, other times they're detachable and interchangeable. If you want to mount a modern derailer on a frame without a built-in hanger, you can simply buy an adaptor claw...it's a standard repair part.
|Plain Dropoout||Adaptor Claw||Dropout with hanger|
When frames began to be built specifically for derailer use, with built-in hangers, each derailer manufacturer had its own proprietary attachment system, generally not interchangeable with other brands. Benelux, Campagnolo, Hurét and Simplex, among others, had their own systems. As time went by, the Campagnolo style (shown above) became the de facto standard, and this is what all modern derailer-type frames use. It features a 10 mm thread (sometimes 26 threads per inch, sometimes 1 mm thread, which works out to 25.4 threds per inch. This pitch difference is so small as to be insignificant in this application.)
The Simplex style dropout is fairly common on older, higher-quality French bikes, including the Peugeut PX-10, Gitane Tour De France, Mercier 300, etc. Although the Simplex hanger looks similar to the Campagnolo type, it differs in two important ways: it is not threaded, and it lacks the locating notch on the bottom.
It is not difficult to convert a Simplex hanger to work with a modern derailer. All that is required is to thread it with an appropriate tap, and file a notch into the bottom of it for the "B Tension" screw to bear against.
With some derailers, the B tensions screw will undershoot the notch. This can often be corrected by reversing the B tension screw, so that the screw head is bearing on the notch. That makes adjustment a bit more awkward, but this is not an adjustment that needs to be made often.
|Articles by Sheldon Brown and others|
Last Updated: by Harriet Fell