Over the years I have noticed that when adjusting their bicycle derailluers quite often people get confused about the high and low gears and how the relation changes depending if you are adjusting the front or rear derailluer.

L stands for low gear, the one that is lighter to pedal which you use for climbing and H stands for high gear, the one that is heavier to pedal which you use to gain more speed. Another way to look at it is that L stands for Lighter, Low speed gears and H for Heavier, High speed gears.

In the case of the front shifter the low (lighter) gear is the small chainring and the large chainring is the high (heavier) gear. On the other hand in the case of the rear shifter the low (lighter) gears are the larger cogs while the smaller cogs are the high (heavier) gears.

Related Topic: Limit Screws.

The low-limit screw on the front derailluers is usually the one farther from the frame, but the limit screw position varies on a lot of bikes and some have an H or an L next to the screws.

The low limit screw on the rear derailluers is usually the lower one, but it also varies on a lot of bikes and most have an H and L next to the screws.

Hope this helps.
Rodge

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What do you think?
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Most bicycles have derailluers to shift gears.
Have you ever taken a close look at how derailluers work?

Obviously gear shifting works by pushing the chain from one chainring to another or one sprocket to another… but how does that happen?

The front derailluer is a fairly simple mechanism which consists of a cage that can move back and forth and from side to side. It pushes the chain sideway until it can’t run on the chainring it has been sitting on, at that point the chain falls and lands on the next chainring.

The rear derailluer consists of a cage too that can move back and forth and from side to side but it has an additional arm with a spring-loaded pulleys which adjusts the tension and slack of the chain when it moves to smaller sprockets.

Both derailluers push the chain sideways and at an angle onto the sprocket. When the chain can no longer mesh with the sprocket, it falls off of the sprocket and lands on the next one in line.

It is different when the chain is being shifted from a smaller sprocket to a larger one.

In this case the chain is forced to rub against the side of the larger sprocket which has specially shaped teeth and ramps on the side which help the chain to make a smooth transition to the one it is sitting on. Eventually, the chain gets snagged against the sides of the larger sprocket, and the teeth grab the chain and make it jump up onto the larger sprocket.

This is something I would have never thought I was going to see…
some of the newest derailluers are electric and they go as far as using wireless technology. They incorporate a servo motor, a 7.4-volt lithium-ion battery pack and the wiring harness that connects everything.

The mechanic principles applied are the same but the hi-tech design is soooo cool!

I know for some of you this is elementary stuff, but as a bicycle mechanic I have had customers who after years of riding did not understand how derailluers work.

So, hope this helped and if you have any specific problem using or calibrating your derailluer… use the comment box to let me know, I might have a solution for ya.

Rodge

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