Do I need a new Brompton chainring (3/32 vs 1/8)?

the_hundredth_idiot
the_hundredth_idiot Posts: 813
edited February 2019 in The workshop
I'm replacing the chain and sprocket on my Brompton and I seem to be making a meal of what should be a simple task.

The Brompton is about 6 or 7 years old. It had a new chain and sprocket when I had it professionally serviced about 4 years ago, but hasn't been used much over the last couple of years.

I bought a new chain and sprocket. First problem was that the sprocket had 7 internal notches (Shimano fitting?) compared with the 3 internal notches of the old one (SA fitting?). But I returned that and bought a 3-spline sprocket which fits, albeit with a flange which the old one didn't have.

However, now the chain doesn't fit the chainring! The chain sits proud of the teeth of the chainring, which I'm assuming means the chainring is 1/8 and the chain is 3/32.

What's the easiest solution? Buy a new 3/32 chainring or buy a 1/8 chain? Would a 1/8 chain cause a problem with a 3/32 sprocket?

Thanks in advance
Never be tempted to race against a Barclays Cycle Hire bike. If you do, there are only two outcomes. Of these, by far the better is that you now have the scalp of a Boris Bike.

Comments

  • ugo.santalucia
    ugo.santalucia Posts: 28,255
    chain is always cheaper than chainring. 1/8 chain should be OK with 3/32 sprocket... its the other way round that won't work (same problem as the chainring).
    However, chain/sprocket compatibility can be black art... I had 3/32 chains that didn't work with 3/32 sprockets
    left the forum March 2023
  • the_hundredth_idiot
    the_hundredth_idiot Posts: 813
    Yeah - I suspected that's the case - new chainring £25; new chain less than £10. And I don't think the chainring is worn enough to justify changing it.
    Thanks
    Never be tempted to race against a Barclays Cycle Hire bike. If you do, there are only two outcomes. Of these, by far the better is that you now have the scalp of a Boris Bike.

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