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hindsight
19.02.2011, 09:36 AM
Posting this here, because I know there are a few pedal bike enthusiasts and professionals on the forum ;)

We bought our daughter a pedal bike for christmas - she's seven, and it's her first bike with gears (six speed). There isn't anything wrong with the bike, but my daughter hasn't got the strength (due to a medical condition that affects her right arm and leg..) to change up gears using the twistgrip gear selector (the spring in the rear derailleur is quite strong), and she isn't likely to be able to do so in the near future.

I think it would probably be easier if it was a shimano style rapidfire shifter with pushbutton up/down - this would allow her to brace her hand against the bar, giving more leverage to change gear.

Question: Would I likely need to change both the gearshift and the rear derailleur, or can I just swap out the gear selector twistgrip.

Any recommendations on a six-speed selector to install?


Thanks,
Mike

hindsight
19.02.2011, 09:42 AM
Just spotted this. Would this work, or would I likely need to match it up with an appropriately matching shimano rear mech?


Linky (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=360342924315&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en)

Gizmo
19.02.2011, 10:02 AM
its unlikely you can simply mix and match shifters as they all have different amounts of cable pull and throw, at times it works, at times it doesn't so it would be trial and error.

Shimano tech manual is a big book and they rarely recommend mis matched parts in their compatibility tables but their are over 10000 sku's on my MTB OEM price list and with that kind of number of parts its impossible to know what may or may not work :(

Try popping into your local bike shop, they should be able to look and check whats currently on and might even have an old rapid fire to test with, either that or change shifter and mech but it also links to sprocket spacing which might mean that needs changing and that might mean a new hub depending upon whats fitted now :(

Cycling shoots itself in the foot at times when it comes to compatibility and ease of customer understanding :(

rendo
19.02.2011, 10:06 AM
Twist shift can be difficult for kids to use, my kids struggle with them too.
Rear derailleurs tend to be mechanical only with indexing done in the shifter, certainly for road bikes anyway. That shifter should work, indexing is linked to the cassette spacing which will probably be shimano compatible.
you might want to check how it mounts on the bars and that there is space for it.
I can recommend a good shop in campsie Glen near lennoxtown, very accommodating and knowledgable

rockjock620
19.02.2011, 10:27 AM
Gizmo is technically correct - but in practice any old @@@@ will fit - so long as it's a six speed. It's only a kid's bike after all. Most of the problem could be set up, poor cable runs and friction therein.

hindsight
19.02.2011, 10:46 AM
Thanks guys.. Have just checked, and the rear cassette appears to be the same spacing as my wifes' old MTB, which has a Shimano 6-speed rear.

Will order up that thumb shifter (and a set of new grips) and see how I go with that.


It's only a kid's bike after all. Most of the problem could be set up, poor cable runs and friction therein.


..and a cheap bike at that. Everything is new and lubed - and the cable runs are good.

Thinking about it, I see from the datasheet for that shifter that it recommends one of these (http://cgi.ebay.co.uk/Shimano-Tourney-TY-RD-FT30-13-99-/370422531445?pt=UK_sportsleisure_cycling_bikeparts_SR&hash=item563ee74575)on the rear. Might just order one of those too, in case it does lighten the shifting action.

I'm all in support of LBS for the appropriate things (and indeed I do send my own roadbike off to the LBS once a year for a tune-up to make sure that the gears are absolutely spot-on), but as the sort of person that does his own motorbike servicing for fun, I'm unlikely to be taking the kids pedal bikes to a bicycle mechanic :)

PhilLew
19.02.2011, 12:42 PM
if all else fails you could try swapping it to the left hand side of the handle bar so she can use her other hand:)
(it will have to be twisted the opposite direction to normal to change up or down but if this is her first bike with gears she'll be none the wiser)
Good luck :-)

Scotty
19.02.2011, 09:34 PM
you say its new and cheap , it could well be worth a re-lube of the cables etc and some sort of running in to loosen it up a bit

I've no idea about your daughters condition, but I find the grip shift less force to move back up the cassette - this might just be bigger hands like, she might be able to push the quick-fire type shifters with palm of hand, rather than just thumb, defiantly worth a try :D

hindsight
20.02.2011, 11:16 AM
I find the grip shift less force to move back up the cassette

You're quite correct, going up the gears is relatively easy, but going back is pretty tough. This usually leaves her in the highest gear, meaning that I've got to jump on the wee pink bicycle with 16" wheels, and shift it back to first for her. :lol2:



if all else fails you could try swapping it to the left hand side of the handle bar so she can use her other hand
Y'know - this is a suggestion so obvious that I hadn't even considered it :). That said, the condition is very, very mild - I'm keen to keep the bike as standard as possible.

Thanks,
Mike

Gizmo
20.02.2011, 11:34 AM
just read the tech manual, all Shimano 6 speed shifters pull the same ratio, they should work with all Shimano rear mechs apart for a couple of anomalies on older Dura Ace and earlier Shimano (pre 87) (1.7 v's 1.9 ratio) sprocket spacing should be 5.5mm.


Only one I didn't check was shifters designed for hubs gear systems and I'm not sure any hub gear 6 sp exists anyway.

So in theory you can buy any shifter but as Pete says check cables, one of the places companies save money on kids bikes is using cheaper cables, try and get a shifter sets that comes with genuine Shimano cables.

HTH

hindsight
20.02.2011, 01:19 PM
sprocket spacing should be 5.5mm.

So in theory you can buy any shifter but as Pete says check cables, one of the places companies save money on kids bikes is using cheaper cables, try and get a shifter sets that comes with genuine Shimano cables.

HTH

Perfect - thanks Gizmo - appreciated. Sprocket spacing is definately 5.5mm, and the shifter comes with a cable, presumably a shimano one, but I'll compare them when they arrive to be sure.

hindsight
24.02.2011, 09:58 PM
Sorted - as it turned out I couldn't use the Shimano deraileur - it wouldn't clear the larger sprockets, and only had H/L adjustment. The pushbutton shift with the original deraileur works just fine though.

Thanks all, we'll see how she gets on with it at the weekend :)

rockjock620
25.02.2011, 09:28 AM
Sorted - as it turned out I couldn't use the Shimano deraileur - it wouldn't clear the larger sprockets, and only had H/L adjustment. The pushbutton shift with the original deraileur works just fine though.

Thanks all, we'll see how she gets on with it at the weekend :)

Thye all have H/L adjusters, cable tensioner and usually a screw to set up the preload at the dropout.

BTW - common misuse of terminology here - shifting "down" the cassette to the smaller sprockets is in fact "changing "up" the GEARS - think about it.

The "mech" as we call it in the trade (derailleur to you lot :)) normally uses the spring assist in the mech to take it DOWN the cassette, these are classified as "high normal" (high being the gear ratio) set up. That's why the "upchange is much easier - the spring is doing the work. This means you have to physically lift the chain and mech back up the cassette by pulling the cable, hence the hard work sometimes needed.

There are many mechs around now where the spring sits the opposite way across the parallelogram linkage plates in the mech and the spring assist is UP the cassette to the lower ratios. These are called "low normal" mechs. The cheapest one IIRC is about 50 and will not match the six speed set up you are running. But for future reference it may be of note. For more experienced riders it offers mnay advantages, the ability to make "down" changes mid-climb and quickly being the most obvious one.

So there :)

rendo
25.02.2011, 12:00 PM
There are many mechs around now where the spring sits the opposite way across the parallelogram linkage plates in the mech and the spring assist is UP the cassette to the lower ratios. These are called "low normal" mechs. The cheapest one IIRC is about 50 and will not match the six speed set up you are running. But for future reference it may be of note. For more experienced riders it offers mnay advantages, the ability to make "down" changes mid-climb and quickly being the most obvious one.

So there :)

i always thought the 'low normal' mechs were introduced in the mtb scene wher in the event of the cable breaking the mech would spring back to the large sprocket and easiest gear to pedal, but i suppose it would aid shifting efficiency too.

Gizmo
25.02.2011, 01:10 PM
i always thought the 'low normal' mechs were introduced in the mtb scene wher in the event of the cable breaking the mech would spring back to the large sprocket and easiest gear to pedal, but i suppose it would aid shifting efficiency too.

they were introduced for use with dual control STi where rapid rise gave a smoother shift on the lever moving up. Personally I prefer that on an XC bike, once it gets longer travel and rockier terrain dual control has its downsides in that its too easy to shift as you brake. I've still got one bike set up the original XTR dual control/Rapid Rise setup but most are now on conventional shifting.

hindsight
03.05.2011, 08:14 AM
Update on this, with thanks to those who contributed. The swap to a thumbshifter has made a world of difference, it took her a little while to master the technique (and no doubt, build up the strength in her hand), but she now has full use of the gears on her bicycle, something I think would have been a lot more difficult, and taken much longer with the twistgrip selector.

I didn't use the rear mech, so if anyone has a use for a six speed shimano rear mech let me know (free to a good home).