A derailleur is a variable-ratio bicycle gearing system consisting of a chain, multiple sprockets of different sizes, and a mechanism to move the chain from one sprocket to another.
What is derailleur used for?
The derailleur is the device that changes gears by moving the chain from one sprocket to another. There are two derailleurs: one on the rear and one on the front. The highest ratio (when the bike can go fastest) is produced when the chain is on the biggest sprocket in the front and the smallest in back.
How do I identify my Shimano derailleur?
Shimano stamps the rear derailleur model number on the underside/lower plate of the parallelogram. All models for the last several decades.
What's the difference between derailleur and shifter?
The right hand shifter is on the right of your handlebars (as you look forward whilst on the bike) and controls the rear derailleur, which moves the chain between the sprockets on your rear wheel.
How do I know what derailleur I need?
If you are replacing an existing derailleur on a bike, simply count the number of cogs on your cassette and you're good to go. If your drivetrain's speed is an unknown quantity, you can count the number of steps that your shifter runs through and add 'one' to determine the number of gears your drivetrain has.
25 related questions foundCan I use any derailleur for my bike?
A derailleur for your mountain bike should match the specifications on the original derailleur. That is, while it doesn't need to be the same model of derailleur, it does need to be the same brand, in almost every case. It also needs to match the number of gears, or have more intended.
Can I use Shimano cassette with SRAM derailleur?
SRAM's cassettes and chains are compatible with all of Shimano's groupsets, and vice versa. Likewise, Shimano and SRAM buyers have the freedom to mix different levels of chains and cassettes so long as they are designed for the same kind of transmission.
How do I know if I have a short cage or long cage derailleur?
To find out the derailleur's rated capacity (T) we apply a simple formula: add up teeth on the biggest chainring and sprocket and then deduct the sum of the smallest chainring and smallest sprocket. According to Shimano, their derailleur's rated capacities are 45T for long cages and 30T for short cages.
How much does a derailleur cost?
If you take your MTB into a local bike shop the average price to replace a rear derailleur is going to be $110. If you DIY replacing a derailleur will cost about $50 (plus your time) This price will depend a lot on the actual derailleur needed. Usually a bike shop will also take care of other problems.
Do you need a front derailleur?
Are Front Derailleurs Necessary? These days front derailleurs are essentially not necessary, on mountain bikes at least. Now even high-end road bikes are starting to lose their front derailleurs. With a larger rear cassette, it's possible to get the same number of gears without the need for a front derailleur.
When should I replace my derailleur?
Derailleurs will last almost indefinitely. The jockey wheels will wear out in time (tens of thousands of km) but the rest of the mechanism shouldn't see significant wear. It could be that the spring will break at some point due to material fatigue, but that is also a relatively easy to replace part on most derailleurs.
Why is my derailleur clicking?
If you hear a constant clicking (especially in certain gears), it could mean that your shifter cables have stretched enough to pull your derailleur out of alignment, causing your chain to ride between gears or rub on the derailleur cage. First, make sure your derailleur is aligned and that the hanger isn't bent.
What is a derailleur cage?
The derailleur cage is a swinging link, with two pulleys. As the chain moves between different size sprockets (front and rear), the amount of chain required changes. The derailleur cage picks up this slack.
Can I use any shifter with Shimano derailleur?
Combining with various RDs:
Shimano shifters, whether for 6, 7, 8, or 9 speeds are compatible with all the Shimano RDs for 6 to 9 speeds, and with Shimano 10 speed road RDs (not with 10 speed MTB RDs). Update: a new exception are Shimano Tiagra 4700 road 10-speed shifters, and Shimano GRX gravel series shifters.
Are all Shimano cassettes compatible?
SRAM and Shimano cassettes, on either road or mountain bike, are interchangeable with each other as the spacing is the same between the sprockets.
Can you mix Shimano and SRAM components?
Most importantly, YOU CANNOT mix Shimano and SRAM hydraulic brake parts. It's more than a performance issue — it's a safety issue. Shimano brakes employ mineral oil as hydraulic fluid, whereas SRAM uses DOT brake fluid. Those are incompatible — one is insoluble in water, and the other is water soluble.
Can I change derailleur cage length?
Its not just the tooth capacity, the maximum sprocket size the derailleur is rated for can also change with the cage size in the same product line (i.e. they're not just changing the cage), with the maximum sprocket size going up with cage length.
What is the difference between long cage and medium cage derailleur?
If you are in-between the capacity ranges of the two, which is often the case with mountain bikes, then note the following: long cage derailleurs will accommodate a wider gear range and deliver a better chain line, while medium cage derailleurs are less likely to be hit by rocks on the trail.
What is difference between SS and GS derailleur?
For your particular gearing range (50/34 compact double and 12-25 cassette), an SS will work. GS is for wider gearing ranges that will result in more chain slack when the drivetrain is crosschained small-small, like on triples or if you are running a very large cassette on a double.
Can I use any front derailleur?
In addition, front derailleurs are made for either 7, 8, 9 or 10-speed chains, but they can often be used interchangeably. If you are using a different chain than your derailleur was made to work with, the degree of adjustment you can expect will be lower than with a matched set.
What is front derailleur capacity?
A front derailleur's capacity is simply the difference between the number of teeth on your largest and smallest chain ring. For example if you have a 39/53 chain ring combo, (53 - 39 = 14), you will need a front derailleur with a capacity of 14 teeth or more.
