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 Post subject: changing gearing
PostPosted: Thu Apr 14, 2011 2:48 pm 
Dirt Disciple
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Joined: Sun May 09, 2010 10:28 pm
Posts: 61
Location: Exmoor
I've got a slight issue with my old 1980s Bianchi. Its a bit hilly round here to say the least and when I get out of the saddle the darned thing jumps down a gear making life a good deal harder than it needs to be.

Suspecting its a worn chain I had a quick measure using the 12 links theory and its between 1/8 and 1/16" long so it needs changing I reckon.

The old bike runs an Ofmega front chainset and Simplex SX610 rear deraillier, I can't see any markings stating what the (6sp)freewheel is or what the hubs are.

I was thinking I'd just swan into a bike shop and buy a new freewheel and chain but oh no, its not that simple as its 'old' and everything now is 10sp and more.

So...Help! Where do I get a new chain and freewheel? I don't have an issue with changing the number of gears but would like something a tickle lower than the 24tooth biggest at the moment, its friction shift so indexing isn't a problem.

Will :)


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 Post subject:
PostPosted: Thu Apr 14, 2011 3:17 pm 
Retro Guru

Joined: Sun Aug 03, 2008 12:31 am
Posts: 585
Location: London
Try a new chain first, most bike shops should have a 7 or 8 speed chain which should work.

If the new chain jumps then the sprockets are also worn. I gather new freewheels are still made but I don't think most bike shops stock them.


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 Post subject:
PostPosted: Thu Apr 14, 2011 4:08 pm 
Retro Guru

Joined: Wed Dec 10, 2008 9:19 am
Posts: 2093
Location: Sheffield, top city
these guys will have wht you need ...
http://www.spacycles.co.uk/products.php ... 0s112p2333


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 Post subject:
PostPosted: Thu Apr 14, 2011 5:05 pm 
Dirt Disciple
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Joined: Sun May 09, 2010 10:28 pm
Posts: 61
Location: Exmoor
Cheers, are all freewheels the same thread, no difference between Shimano and Campag etc?

Will :)


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 Post subject:
PostPosted: Thu Apr 14, 2011 5:19 pm 
rider | rBoTM Winner
rider | rBoTM Winner
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Joined: Fri Jan 25, 2008 1:42 pm
Posts: 5131
Location: Wakefield, Yorkshire
How about these -

http://www.retrobike.co.uk/forum/viewtopic.php?t=145536


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 Post subject:
PostPosted: Thu Apr 14, 2011 8:59 pm 
Retro Guru

Joined: Sun Aug 22, 2010 7:07 pm
Posts: 1321
Location: Cotswolds
Will, first make sure you haven't got a tight link.
If your worn chain had lived its life with the same freewheel I would not expect it to slip, and surely not on the larger cogs.
If you mean it jumps on to the next smaller cog then first get some tension on the chain, and make sure you change gear far enough.
A worn chain will run on new cogs, but a new chain will not run on worn cogs.

I used to reckon 10 minutes to change a freewheel and chain on any bike, did literally thousands.


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 Post subject:
PostPosted: Fri Apr 15, 2011 10:36 am 
Dirt Disciple
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Joined: Sun May 09, 2010 10:28 pm
Posts: 61
Location: Exmoor
Thanks Keith
It does jump to the next gear down, I've adjusted the stops so the chain just jumps spoke side then eased it back a tickle to stop it going spoke side.

I've no idea if the freewheel and chain are original but I suspect they both are, theres virtually no wear on the wheel rims and they are correct for the bike as far as I can find out.

As I said before the chain has stretched a bit going by the 12 link Sheldon Brown theory. I haven't checked for stiff links, I'll do that next.

I do want to change the gearing a tad so I guess changing the freewheel and chain at the same time would be sensible anyway.

Cheers for the advice chaps 8)

Will :)


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