7 speed hg cassette to 8/9 speed

DonOfAshford
DonOfAshford Posts: 53
edited January 2011 in Workshop
Hi, sure this is in the forums somewhere but struggled to find, I have an early 80's Giant, which has biopace double chain ring and 7 speed hyperglide shimano cassette, looking to upgrade to change the 7 speed 13/23 to an 11/28 have looked at Sheldon Brown site but lost the plot a bit, would i need to change the wheel as well, as the there is something about the 11 being an awkward fit....?


OR should I go the whole hog with STI shifters and triple chain ring plus 8/9 speed cassette do I need to match components exactly or play ebay happy shopping
Cheers Don

Comments

  • maddog 2
    maddog 2 Posts: 8,114
    8/9spd cassette won't go on your 7spd wheel*

    so you either need a 7spd cassette or
    a new rear wheel, 8/9cassette and new 8/9 shifters


    Cash is cash but I'd do the second option as decent 7spd is getting harder to source so you'll have to change eventually anyway.

    *you can fit a 8/9spd freehub to your current wheel and then re-dish the wheel, but it's a fair faff.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • simon_e
    simon_e Posts: 1,706
    Hi, sure this is in the forums somewhere but struggled to find, I have an early 80's Giant, which has biopace double chain ring and 7 speed hyperglide shimano cassette, looking to upgrade to change the 7 speed 13/23 to an 11/28 have looked at Sheldon Brown site but lost the plot a bit, would i need to change the wheel as well, as the there is something about the 11 being an awkward fit....?

    OR should I go the whole hog with STI shifters and triple chain ring plus 8/9 speed cassette do I need to match components exactly or play ebay happy shopping
    Cheers Don
    Is it definitely a cassette-compatible freehub and not a freewheel?

    You can get a Shimano 7 speed cassette, HG30 (11-28 ) or HG50 (12-28 ). I have used both and they fit and work in exactly the same way. The only thing I don't like on the 11-28 is the 3-tooth jump between 4th and 5th, the two most used ratios on my commuter.

    BTW it's a good idea to fit a new chain at the same time. SRAM PC830 or PC850 with Powerlink would be ideal.

    IMHO buying STI's (and maybe rear mech too) could end up being a rather expensive option. I don't think you'll find the extra gear(s) warrant the expense. Better to save the money for a new bike or a decent jacket.
    Aspire not to have more, but to be more.
  • Back in the day i upgraded my stumpjumper from 7 to 8 (and later 9) speed.
    To go from 7 to 8 speed you need an 8 speed freehub, because the 8 speed cassette is wide than 7 speed. This is the bit that the cassette fits over. These can be replaced by unbolting using a 10mm allen key after you have removed the axle and bearings.
    Once you have replaced the freehub you need to respace the axle and redish the wheel to bring it back to the centre of the frame. This is the most technically difficult process and might be further complicated on old wheels where the spoke nipples are tight.
    A nine speed cassette is a straight replacement for 8 speed but needs different shifters.
    On a MTB with thumbshifters it was possible to get an 'extra click' so they could handle the 8th gear when going 7 to 8, but i had to get new shifters for 9 speed.
    On a road bike you will need compatible shifters which might be the most expensive part of this whole process.