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Gearing question

rajdavrajdav Posts: 42
edited March 2012 in Workshop

My road bike has the following gearing,

(50-34) & (25-12)

I am about to do a couple of hilly rides (The Chiltern 100) and I have been given a compatible cassette which is (28-11).

This to my rather basic knowledge seems like a no-brainer, I'll get a bigger range at both ends, won't I?

Is it as simple as that?
Will I notice a significant difference for climbing?
Is it a straightforward job?

Thanks for any thoughts.
Cannondale Supersix Ultegra
Genesis iO


  • keef66keef66 Posts: 13,123
    You'll get a bigger range, but logic says you'll also get some bigger jumps between sprockets.

    The 28t should be a significantly easier climbing gear than the 25t

    Swapping a cassette is a simple job with the correct tools.

    Chain whip, cassette lockring tool* + adjustable spanner to remove it. Same to fit the new one but you don't need the chain whip.

    * Shimano or Campag as appropriate

    Check the old cassette to see if a spacer was fitted and do the same for the replacement.

    Only thing to be aware of is if the old cassette / chain is significantly worn, you'd be best to fit a new chain with the new cassette
  • andy_wrxandy_wrx Posts: 3,396
    Like he says, you'll have a higher 'top gear' and a lower 'bottom gear', but also bigger gaps between.

    10sp 12-25 is : 12-13-14-15-16-17-19-21-23-25
    10sp 11-28 is : 11-12-13-14-15-17-19-21-24-28 (Shimano Ultegra 6700) or 11-12-13-14-15-17-19-22-25-28 (SRAM PG1050)

    If you spend a lot of time in the middle of the block, you might notice the lack of the 16
    You'll certainly notice the bigger gaps at the low-gear end, but whether they bother you...

    As well as possibly needing a new chain if your existing chain and cassette are worn, another issue you could get is chain length.
    Try (bike on workstand or upside down on the garage floor, not out on the road) the bike in the new lowest gear 50 x 28 and check that the chain is still long enough : if it's not, you could rip the rear mech off...
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