replacing a few bits on a hotrock 20

danlightbulb

Hi all,

Need a bit of shopping advice for a 2nd hand Specialized Hotrock 20" I picked up for my son.

I need to replace:
1. The tektro v-brake levers. Need some ones designed for kids hands.
2. The saddle. Need something suitable for a 6 year old.
3. The pedals. Are kids pedals the same as adults?
4. The grips. Need a shorter grip suitable for the grip shift gears on the right hand side of the bars. Not sure on bar diameter.
5. The rear mech. Its a shimano tourney 6 speed. I assume short cage but I don't know if I need a special type for a kids bike.

Anyone know where I can find suitable kids stuff? I've had a look on chain reaction but they don't seem to have an easy way of searching for kids bike bits.

Thanks

The Rookie

danlightbulb wrote:

1. The tektro v-brake levers. Need some ones designed for kids hands.

Can you not use the reach adjust?

danlightbulb wrote:

3. The pedals. Are kids pedals the same as adults?

As far as I am aware, same, just get the smallest you can find with the right thread (may be older 1/2")

danlightbulb wrote:

4. The grips. Need a shorter grip suitable for the grip shift gears on the right hand side of the bars. Not sure on bar diameter.

On ebay or just take a stanley knife to any normal grip, check first though, many kids struggle with the twist loads on grip shifts.

danlightbulb wrote:

5. The rear mech. Its a shimano tourney 6 speed. I assume short cage but I don't know if I need a special type for a kids bike.

Not special, cage length depends on capacity required not bike size.

danlightbulb

The grip shift doesn't feel too bad (its a shimano revoshift 6 speed shifter). However if there is a recommendation for a standard thumb shifter i would consider swapping it. I need something with a lightweight action. The tourney rear mech is (I think) an older version of the TX55 which has a wheel on it to help shifter leverage. I'll be getting the new TX55 as a direct replacement.

The Rookie

Personally I find the lightest action on the old fashioned index thumb shifter rather than triggers.

danlightbulb

Well the existing revoshift stopped working when I removed it from the bike so have ordered a direct replacement.

I bought this mech http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_948677_langId_-1_categoryId_165694 but its a medium cage. I think the one I should have bought is this one: http://www.tredz.co.uk/.Shimano-Tourney-Short-Cage-Rear-Derailleur-RD-FT30_33356.htm. Will it be an issue putting a medium cage mech on a 20" wheel? Will it make the shifting any harder or easier?

Thanks

The Rookie

Cage length is all to do with it's capacity to accomodate the capacity (chain length change) between the 2 extreme gears (big-big to little-little) nothing else. It won't affect shifting.

What is the gear range front and rear?

danlightbulb

Hi.

The tourney rear mech (TX55) turned out not to be as short cage as it looked in the picture online.

In the lowest gear it is at about the same diameter as the wheel rim:



Is this acceptable?


This is the one orginally off the bike but its bent really bad. I cant find another one like it. I think its an FT30 but the hanger is at 90 degrees not straight, can't find another like it.

97th choice

The Rookie wrote:

Cage length is all to do with it's capacity to accomodate the capacity (chain length change) between the 2 extreme gears (big-big to little-little) nothing else. It won't affect shifting.

What is the gear range front and rear?

If its the hot rock 20 it will be single front chainring.

OP will need a short cage mech due I the 20" wheel size.

97th choice

Ft30 mech

http://www.tredz.co.uk/.Shimano-Tourney ... _33356.htm

danlightbulb

97th choice wrote:

Ft30 mech

http://www.tredz.co.uk/.Shimano-Tourney ... _33356.htm

Yeah but that is different. My version has a hangar which is at 90 degrees bent. That one is straight. Will that still fit ok?

The TX55 looked to be short cage in the photo online but it turned up and was bigger (everything bigger in scale).

I don't have time now to put the right mech on so it will have to stay like this until after his birthday. Fairly pleased with it, changed the saddle, brakes, grips, mech, revoshifter, tyres. Looks like new again apart from a few scratches on the frame. When I had the bike stripped I was impressed by the frame, felt really light, however not impressed by the whole bike weight at 11kg its a bit heavy.




Having some trouble with the v-brakes (as usual - I hate those things). Im trying to get the lever travel as small as possible to better suit his smaller hands, but its too fine a line between the brakes dragging when off and the brake lever pulling all the way to the grip.

danlightbulb

Does anyone know where I can get some solid forks for 20" wheel? Need 1 1/8" steerer. Not looking for anything expensive.

cooldad

That mech will be toast very quickly.

danlightbulb

cooldad wrote:

That mech will be toast very quickly.

It looks worse than it is. That's in the lowest gear, so its better in the other gears.

I noticed this bike on evans whilst looking for mech's, it's just as bad in the 4th cog down!



It shifts well, so if it breaks I'll get the short cage one then.

bikaholic

Use a super short cage road or mtb RD to overcome the clearance problem. Older models are more desirable as they have weaker springs so the shifting action will be very light, to the point of being vague.

You need to focus more attention on the shifter and the shifter cable (ie thoroughly lubricate) if the older RDs are not available.

This kids bike was a rusty mess and barely working before it was completely stripped down and rebuilt:





The other alternative is to use internal gear hubs like the old Sturmey Archer 7 speeds (cheap option) or newer Shimano Nexus/Alfine offerings, but the bike can end up being very heavy as a result.


For 20inch forks, look towards BMX or foldable multi modal bikes. If the steerer is 1inch, then just pad it out to 1.1/8inch with some home-made shims.