Replacing Shimano 100GS Biopace - Need advice please


New Member
Sep 24, 2013

This is my first post and I'm something of a noob when it comes to cycling, so please forgive my innocence.

I have a Ridgeback 602 GS of around 1991 vintage which has very worn out gears and chain of the Shimano 100GS BioPace variety, 21 speed. The rest of the bike is nigh on perfect so I'm looking to use it on the road for commuting once repaired. I don't have much free cash so I'm trying to avoid bike shop repairs and I am reasonably capable with the spanners.

The real question is: Can I replace the gears with a current product? If so, how much do I need to change as the BioPace stuff says that it must be used with a narrow chain ( I guess that means 1/2 x 3/32?)?

I realise that I'll need to change the chain up to 1/2 x 1/8, rear cassette and chainrings, but which of the following, if any, can I keep?

Crank set.
Rear derailleur mechanism.
Front derailleur mechanism.
Rear hub (and hence wheel).

Any advice welcomed!




Well-Known Member
Jul 23, 2005
FYI. 1/8" chains are typically used on SINGLE SPEED bikes ...

And, most bikes which have multiple gears will use a 3/32" inch chain ...
So, your best bet is probably an 8-speed SHIMANO chain, or equivalent.

If you need a new Freewheel, then I recommend a 7-speed SunRace Freewheel.

If you happen to need a Cassette, then just ensure that it has RAMPED Cogs (most will, some NOS may be so old that they won't have ramping on the Cogs).

You do NOT have to change anything else UNLESS they are physically worn out or in bad repair ...

If-or-when the time comes to change your Chainrings, you can opt for ROUND Chainrings if you want ...

  • I had a BioPace crank whose spider had the "standard" 130BCD