Bicycle repairs

Bicycle gears seem to be a cyclists biggest fear / nightmare when they go wrong. People panic and start unscrewing things and end up snapping a spoke on the wheel or worse snapping the gear selector (Rear mech / derailleur).

Bicycle gears look extremely complicated when you look at them and people tend to  take one look and phone their local bike mechanic. This blog has been put together to try and make sense of all the teeth, chains and levers so that the next time your gears go wrong you will calmly get off your bike and adjust then continue on you way (tools allowing).

Ok here we go, bicycles have all sorts of different gear set ups the most common is the deraillleur type with either a handle twist shifter or a thumb shifter on the handle bars with which to change gear.If possible ensure that you always carry a multitool of some description so that these minor "adjustments" can be easily done.

First ensure that the bicycle is turned with the right hand side of the bike facing you. (look at the back wheel of the bike) if it's a derailleur type then there should be a dog leg shaped arm hanging down with the chain running through it.Turn the bicycle upside down or if you have one use a bike repair stand. Pedal the bike and using the selector to change the front gears to the biggest cog at the front and use the other shifter to select the smallest cog at the back, if this is not possible then select as small or large cogs as possible, the idea here is not to "cross" the chain. Loosen the gear cable and allow the rear gear changer to move if needed.

Press or twist the shifter several times to allow the front and rear gear changers to do their job whilst you pedal.Making sure that the shifters show as high a gear as possible say 7, 8 or 9

So looking at the Derailleur hanging by the back wheel, there should be two little screws next to each other with "L" and "H" printed by them. make sure that the gear selector is hanging below the smallest cog on the back wheel if it isn't turn the "H" screw until the gear selector moves directly in line with the smallest cog this is called "Indexing" Now reconnect the gear cable pull the cable to ensure it is taught and ensure that first gear was selected. Once this is done and you are happy push or twist the shifter to make the gear selector arm move to the biggest cog on the back and then use the other shifter to change the front to the smallest cog.

Look at the gear changer again and check the position of the changer it should be under the first or biggest cog on the back wheel, if it isn't turn the "L" screw until it aligns correctly.

Once this is done change gear using your shifter and all being well you should have a full range of gears, if minor adjustment is required then use the barrel screws on the gear shifters to adjust.