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Rear cassette change

steve1978steve1978 Posts: 29
edited July 2018 in Workshop
Hi,
I really struggle on the hilly stuff, I know this is mainly down to the engine but in order to make life easier I have been considering changing my gears.. here is my current spec.
Ribble cgr
Full hydrolic 105 5800 groupset

105 Black 5800 11Spd Chainset Compact 172.5 34/50
11 Spd 105 5800 Cassette 11-28
105 Black (5800) 11Spd Rear Gear Short (SS)
5800 (HG600 105 Chain) - 11 Speed

A look at a gear ratio call tells me that in my lowest (highest?) gear I travel 2.54 meter. I can see that the 105 comes with a 32t option which would travel 2.22m but I am looking for even more assistance!

What would I need to do to get maybe a 42t? Could I disconnect my front 50t in effect giving me a 1x11? Then swap out the cassette for a sram xg 1150 which would give me a 10-42t, I would loose about 2m at top speed but the 34t42t climbing gear would do 1.7m per turn, this would really help me on the hills! I believe the rear derailier will catch on the larger sprocket, so is it possible to fit a hanger extension like the wolf tooth?

Failing this, what if I bought a full mountain bike groupset, would that fit to the road bike?

Posts

  • whyamiherewhyamihere Posts: 7,599
    You can do it with a few new parts.

    First, get a long cage (SGS) Shimano MTB derailleur. It looks like Shimano have only made XT M8000 with the SGS cage. Next, a Shift Mate 8a - https://www.sjscycles.co.uk/cables/0-jtek-shiftmate-8a/ - This converts the cable pull of a road shifter to work with an MTB mech. For the cassette, only 11-40 is officially supported, but you could experiment with 11-42. The Sram 10-42 cassettes require an XD freehub body, which, depending on the hubs you have, could mean a new rear wheel. Obviously, a longer chain is required as well. To get it around the 50-42 combo, you may actually have to buy 2 chains and join a portion of the second onto the first.
  • steve1978steve1978 Posts: 29
    whyamihere wrote:
    You can do it with a few new parts.

    First, get a long cage (SGS) Shimano MTB derailleur. It looks like Shimano have only made XT M8000 with the SGS cage. Next, a Shift Mate 8a - https://www.sjscycles.co.uk/cables/0-jtek-shiftmate-8a/ - This converts the cable pull of a road shifter to work with an MTB mech. For the cassette, only 11-40 is officially supported, but you could experiment with 11-42. The Sram 10-42 cassettes require an XD freehub body, which, depending on the hubs you have, could mean a new rear wheel. Obviously, a longer chain is required as well. To get it around the 50-42 combo, you may actually have to buy 2 chains and join a portion of the second onto the first.

    Thanks, looks like a decent little project, what skill level would you say this is? I am a novice
  • whyamiherewhyamihere Posts: 7,599
    It's all pretty simple. There's millions of videos on Youtube of how to index gears, set the correct chain length etc. All of the cogs on the cassette can only go on in one direction, so the only thing you have to make sure of there is not to misplace a spacer. It's probably worth replacing the gear cable, again, instructions on Youtube.

    The tools you'll need:
    Cassette lockring tool
    Chain whip (needed to remove the old cassette)
    5mm hex key (for removing/refitting the mech, securing the cable)
    Screwdriver for the limit screws - Shimano officially use JIS screws, Philips work ok
    Cable cutters for the new cable
    Chain tool
  • For what it's worth, a simpler and cheaper way of getting a little bit more assistance is to use a long cage 105 mech with an 11-34 Ultegra cassette, rather than a 11-32 105 cassette.

    I haven't bothered to work out the ratios that 34/42 will give you v's the 1:1 drive of 34/34 but you may find that you've got a ratio so low that you can't actually use it.
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