Retrofit Gears to Single Speed Kids Bike

DisoGaza

Hopefully I'm posting this in the correct forum.

My son has a Trek Jet 20 single speed bike. After many failed attempts he managed to ride without stabilisers a couple of weeks ago and is now charging about like he has been riding for years.

The only issue he has is tackling inclines. He struggles with all but the smallest. He is a big strong lad (5.5 years old and 125 cm tall) and plays mini rugby and skis so it shouldn't come down to strength.

We were possibly a little shortsighted last year in buying a bike without gears but as it is likely to last him a couple of years more I'm considering retrofitting gears. I'm reasonably technically/mechanically minded so could tackle the job myself if it is not too difficult. The questions I have are:-

1. Is it an easy job for an amatuer?
2. What parts would I need to fit a 7/8/9 speed gears set?
3. Would I only fit a rear derailleur?
4. Is it cost efective?

supersonic

If there is no cable stops for derailer, or derailer hanger for the rear mech, then this is going to be hard.

However you could use a full length outer, and a derailer with the 'claw' fitting such as:

http://www.amazon.co.uk/dp/B008DTGHP2/r ... wo=&hvqmt=

You'll also need a new rear wheel (if it fits).

The upshot of this is I'd sell the bike and get a new one ;-)

The Rookie

+1, the cost of doing it outweighs the benefits....if it's overgeared you could fit a larger rear cog though....

bikaholic

I would start by measuring the dropout spacing - this will give a rough indication of the number of sprockets (ie number of speeds) that will fit onto the current hub. A 3-speed freewheel can be used in place of the single speed freewheel, but is there enough room for more.

Small children have very weak fingers and thumbs so the choice of shifter is limited to either gripshift (Shimano's is called revoshift), or some other type of big lever friction shifter (like a downtube friction shifter but mounted elsewhere).

The 20inch wheels are small so the RD has to be a short cage version otherwise you risk striking small bumps on the ground.

As noted, there is no hanger but you can buy or make bolt-on hangers.

1. Fairly difficult.
2. Dropout spacing may limit the maximum number of speeds you could have. Freewheels are available in 1,2,3,4,5,6,7,8-speeds. Nine speeds would require a hub change (or new wheel with freehub).
If it were possible, you would need a shifter, gear inner cable, gear outer cable, a rear derailleur, a bolt-on hanger (if not part of a really cheap RD), a longer chain, zip ties, a cable cutter, a big adjustable spanner, Allen keys, flat bladed screwdriver, grease and probably a freewheel removal tool.
3. No.
4. It can be done for under £20 if you already have some of the tools at hand. If you have lots of spares like I do then cost is negligible.

DisoGaza

Thank's all. It looks as though the best option will be to change the bike for one with gears. Hopefully, I'll be able to sell on his current bike for a reasonable price.