Did you know that derailleurs are essentially interchangeable between road bikes & mountain bikes? Yep! They work exactly the same way in both applications. Of course you still have to match up your derailleur to your shifter in make & gear sizing but you can put a Shimano XTR derailleur on a road bike and vice versa. Although I don't know why one would put an Ultegra or (godsakes) Dura-Ace derailleur on a mountain bike. But don't be too surprised to see the opposite. Mountain bike components are tougher components! So for situations requiring enhanced reliability, you might see a mountain bike derailleur, especially the rear derailleur on a cyclocross bike or a tandem bike.

adjusting the front derailleur

adjusting the rear derailleur

lubricating points on the rear derailleur

DERAILLEUR - Looks like a funny name doesn't it? It's French, ya know. (They got a different word for everything.) The job of the derailleur is to change the gear that your chain is riding on. Anywhere on the bike that you can have more than one gear, you'll have a derailleur. Most bikes will have a front and a rear derailleur.

Shimano XTR Rear Derailleur

Shimano XTR Front Derailleur

Single Speed bikes have no derailleur at all. As per their name, they have only one speed (or one gear). That lightens them as they don't have a front or rear derailleur, extra gears and shifters. These bikes are typically loved by the people who value the classic styles. Bike messengers often use single speeds. Track bikes are a special form of single speed. It's a fixed gear single speed meaning that it does not have a freewheel. This in turn means that the pedals will revolve constanly in synchronous motion with the wheels. This type of bike will definitely teach you to spin correctly on your pedals.

LUBRICATING YOUR DERAILLEUR - The picture above has red circles to point out the lubrication points of your derailleur. These are the primary hing points from which the derailleur will extend. Use a light oil like WD-40, Tri-Flo or machine oil. Motor oil will only gunk things up and so will a paraffin or wax based oil. This should be done about once a month.

If your derailleur was recently installed or if you know that you took a direct impact to your front derailleur, then the first thing you should check is the air gap between the big chainring and the bottom of the front derailleur.

The picture gives you an idea of what the spacing should look like. Of course, it shouldn't be so close as to touch the chainring and not so big that the chain can slip through the gap. Adjustment to the gap is made by adjusting the derailleur itself by moving the whole clamp up or down by loosening the clamp or bolts that affix your derailleur to the bike.

(left picture) You'll see 2 screws on the top of your front derailleur. Our first step will be to adjust the inside screw (#1). The purpose of screw #1 is to limit the inward travel of the derailleur so that your chain doesn't come off the small chainring and land on your frame. It also moves the derailleur cage so that the chain won't rub on it while you're pedaling.

Put the chain on the front small chain ring and the largest rear cog. There should be a 1/16" gap between the chain and the inner side of the derailleur cage (#2). If not, adjust screw #1. Rotate the pedals and shift the chain to the middle of the rear cassette. Now shift the front derailleur to go between the large & small chainrings a few times to watch to ensure that the chain falls down from the large chainring and down onto the smaller chainring easily & without any rubbing on the derailleur. There should still be a 1/16" gap between the inner side of the derailleur cage and the chain (#2).

(right picture) The outside screw (#1) limits the travel to the outside of the big chainring so that it doesn't fall off the chainring and controls the smoothness of the shift from the small to the large chainring.

Put the chain on the front small chainring and on the smallest rear cog. Rotate your pedals and shift your front derailleur to the large chainring watching that the chain should jump up onto the large chainring without overshooting it. If the chain is overshooting the large chainring, then tighen screw #1 and repeat your shifting obserations. When you're done, there should be a 1/8" gap between the chain and the outer side of the derailleur cage while the chain is on the front large chainring and the smallest rear cog (#2).

(left picture) This picture just serves to illustrate the gap between the chain and the side of the derailleur. The picture shows the chain on the large chainring. Basically, you want the closest gap possible wihout the chain rubbing and still allow for smooth shifting transitions. To check the potential for rubbing at the point when the chain is closest to the derailleur cage, the chain must be on the outermost front ring and rear gear and conversely the innermost front ring and rear gear.

The upper right diagram shows the derailleur in the position with no tension on the derailleur cable. If you were attaching the derailleur cable then you'd allow the derailleur to fall into this position and simply tighten down the cable with just the slighest tension. After this is done, we'll adjust the derailleur's range of movement.

The B screw is the only screw that is used to move the derailleur body closer or farther to the rear cogs. You certainly don't want the derailleur body to touch the rear cogs and you don't want so much of a gap that the chain can come off the cog. This screw hardly ever needs adjusting unless you've taken a hit to your rear derailleur. Adjust it so that your chain runs off of the

derailleur and onto the cog in a straight line without the derailleur ever touching the cog.

You can see from the upper left diagram how the derailleur cogs lines up underneath the two outermost cogs when the chain is on the two outermost cogs. This alignment is made by the use of the H screw (high gear screw) and the L screw (low gear screw). Sometimes you may actually see an "H", "L", "HI" or "LO" stamped on the derailleur near these screws, but even the markings are not there, the order of the screws are almost always the same in that the topmost screw (of the set of two screws together) is your high limit screw.

HIGH GEAR SCREW

LOW GEAR SCREW

Use the L screw to adjust the low gear's alignment

Use the H screw to adjust the high gear's alignment

On your rear cassette, the small (outermost) cog is the high gear while the largest (innermost) cog is the low gear.

ADJUSTING THE REAR DERAILLEUR

To set the high gear screw, shift the front derailleur to the large chainring and the rear derailleur to the smallest cog. Stand behind the bike and eyeball the alignment. The derailleur cogs should be in line with the smallest cog. If not, adjust the H screw so that it is in line. If you see that the top derailleur cog is in line but the bottom derailleur cog is not, now is the time to say your favorite cuss word. Your derailleur is bent! If it's not too far off, you can grasp it and bend it back (or you might want a bike shop do this for you).

To set the low gear screw, shift the front derailleur to the small chainring and the rear derailleur to the largest cog. Stand behind the bike and eyeball the alignment. The derailleur cogs should be in line with the smallest cog. If not, adjust the L screw so that it is in line.

Now rotate your cranks and shift the rear derailleur from one end of the cassette to the other. Your limit settings should prevent the chain from falling off of the rear cassette.

Be EXTRA CAREFUL when rotating the cranks if you've adjusted the L screw (low gear). If your adjustment is not

correct, the chain could fall in between the cassette and the hub/spokes. If this happens while you're still cranking, you could really lock up the chain hard, causing minor damage. You could also get the derailleur caught in the spokes which is VERY BAD. So if you did ajust the L screw, then slowly and carefully rotate the cranks while shifting to your largest cog.

ADJUSTING THE FRONT DERAILLEUR

The rear derailleur's cable barrel adjusts the tension in the derailleur cable. It is used to smooth out your shifting if you find that your shifting is too slow or grinds a bit on the cassette before it makes the jump.

Imagine the barrel as a nut screwing onto a bolt while you're standing behind the bicycle. From behind the bike, if you turn the barrel clockwise, you're tightening the barrel which shortens the barrel housing and therefore lessens the tension on the cable because the barrel will move inward towards the derailleur. This action will cause the derailleur to move towards the smallest cog.

If you turn the barrel counterclockwise then it moves away from the derailleur, elongating the barrel housing which increases the tension in the derailleur cable which in turn will cause the derailleur to move in the direction of the largest cog.

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barrel loosened

barrel tightened

adjusting the barrel on the rear derailleur