Here's one for your grey matter...mech change on kids bike.

PostieJohn

Ok chaps, try this one out.

We have just purchased a teeny weeny bike, off E-bay for Jnr PJ.
Spec:-
FRAME C -C =16.5"
TOP BAR C-C17"
S R SAKEA CHAMPION ROAD BARS C-C=14"
SACHS HURET FIVE SPEED .
PHEONIX TUBING 101 WEST BROMWICH .
20X1 3/8TYRES ,
RIGIDA RIMS.

The gear change is on the downtube.
Naturally I'd like to start Jnr how he intends to carry on, plus I'd rather he wasn't looking down to change gear.

With that in mind I have spare Campag Mirage 9 shifters and mech.
What are my chances in being able to fit them to a SACHS HURET FIVE SPEED, whatever that is.

Monty Dog

Your 5 speed transmission has a pitch of something like 6mm whereas the Mirage is 4.55mm so it won't index unless you do something to compensate. Have a look on the Highpath Engineering website, under Rear Derailleur Indexing for some tips on adjusting throw

http://www.highpath.net/

mz__jo

But if you had Shimano 6,7 or 8 speed mech and shifters they should function with your 5 speed or (even Sachs mechs) or if not fit a 6 speed freewheel and they definitely work. How old is the Huret mech (pre-Sachs)? You can also use a Shimano 9sp shifter with a Shimano 7sp freewheel or cassette (Shimano or old Sachs mech), you have to do a double click at 2nd and 6th sprockets to make it line up when changing (I have done this with an mtb, I know it works). In theory it should also be possible with a 6sp freewheel and also a 5sp but I haven't tried so I can't confirm. The 5 could pose problems because the cog spacing is a tiny bit wider. What is possible with Campag I can't say. Generally you can make indexing work on 5 and 6 speed freewheels without too much difficulty even if they were not made to index in the first place but it will not be slick like a modern system. After that just how far you want to go with a child's bike, bearing in mind that he will want it to work predictably and without need for mechanical sympathy, is up to you. My preference would be 6sp freewheel (probably enough room) with 8sp Shimano shifters and mechs.

just realised I am talking about Sachs mechs, not the same as modern SRAM. Sachs were Shimano compatible.

rolf_f

What's the point - it takes five minutes to learn how to use down tube shifters and another five minutes to learn how to use STIs.

Besides - why would he look down to change gear anyway?

mz__jo

For under a tenner Spa Cycles have some entry level Shimano 6sp indexed downtube levers which would go with your Sachs mech (if it is ARIS which most of the Sachs-Huret mechs were) and solve the problem if you could be persuaded to go that way. I think indexed downtube levers are the top, only beaten by indexed bar-ends. Never did much like Ergos!

mz__jo

Re-reading that, make sure that the Sachs mech is an ARIS one (it will be marked on it), there were some cheap and hideous Huret mechs that look like they came out of the jungle in Taiwan, but I think Sachs didn't put their name on them, just Huret. I think I have the bits of one in a box somewhere.