30t cog with SRAM rival rear mech

raymond82
raymond82 Posts: 330
edited August 2013 in Workshop
Couple of years I tried fitting a 30t cog with a rival rear mech but I didn't get it to work, the cog kept touching the pulley. Now with a bit more experience in bike mechanics I would like to try again, it should be possible right? At least that's what I read here and there on the internet. I'm wondering though, would I need to replace the B screw with a longer one to make it fit?

Comments

  • Yossie
    Yossie Posts: 2,600
    If you need a 30 I think its time to give up and buy a scooter. Sorry.
  • owenlars
    owenlars Posts: 719
    Have you a long or short cage derailleur? If the latter you may need to change it to a long cage in order to make room for the 30t
  • spearmint_wino
    spearmint_wino Posts: 109
    You might be able to get a short cage to work with 30t but it will be close close to the biggest sprocket (i know someone who's done it with sc ultegra). If its a route you definitely want to go down then give it a try, if you can't get it to work then go buy the medium cage derailleur. After the last hour of pain of this year's Etape 30t is something I'll be definitely be investigating before next years.
  • robbo2011
    robbo2011 Posts: 1,017
    Yossie wrote:
    If you need a 30 I think its time to give up and buy a scooter. Sorry.

    Stupid comment.

    Perhaps the OP wants to go riding in the mountains, where at the end of a long, hot day, a 30T gear would provide welcome relief.
  • freddiegrubb
    freddiegrubb Posts: 448
    Now then Yossie, we don't know the persons age- state of health- or what they want to climb, sorry old son consider yourself reprimanded . My study at 4 pm.where punishment will be THWACKED out, oooh matron!!!!
  • Monty Dog
    Monty Dog Posts: 20,614
    SRAM recommended maximum sprocket for short cage mech is 28 - it's down to the distance between the top jockey wheel and sprocket - so unless you've fitted a longer mech hanger, no amount of mechanical tweaking will make it fit. You need to fit the long-cage mech to make it work reliably.
    Make mine an Italian, with Campagnolo on the side..
  • raymond82
    raymond82 Posts: 330
    If you need a 30 I think its time to give up and buy a scooter. Sorry.

    I'd say that depends on what chainrings I run in the front! I could say I'm 80 years old and planning on going up Angliru three times on hot day but I'd be lying. The truth is that I'm planning on going to the mountains and with a 36t in the front I thought a 30 would be nice to have, especially to keep the cadence reasonably high on segments higher than 9%.

    Thanks for all your input, it doesn't sound too easy from what I read here... I thought I understood that the long cage is mainly necessary for accommodating the increase in chain length, not so much the distance between the pulley and the cog. So a longer B screw wouldn't work to push the pulley away from the cog?

    Otherwise I might have to go for a smaller chainring, I was hoping to have both a smaller chainring and a 30 in case I ride the Marmotte again next year.
  • robbo2011
    robbo2011 Posts: 1,017
    Raymond, I am with you, you definitely would find a 30 nice to have in the mountains, especially if you run a 36T front chainring. But you'll need a new rear mech. A Rival mid cage mech is not that expensive though.

    The strongest cyclist I know spends most of his summer time in the mountains and he uses a 34-29 combo as a lowest gear. I suspect he'd blow the legs off most people on this forum! so forget about all that MTFU nonsense and get the lower gears.

    I use a 34-32 as a bottom gear and I'm not ashamed to say I use it on long passes at 10% gradient or more.
  • raymond82
    raymond82 Posts: 330
    Thanks for the support! Now that we're confessing, I actually ran a 28x28 during the Marmotte this year, I didn't use that gear too often but was happy to have it on a couple of occasions during the ride! Being less fit than now I used to manage with 34x28 when I did one mountain a day in the Alps but for longer rides I definitely prefer lighter gears, also because I prefer climbing with a higher cadence. I was hoping to have for 33x30 without having to buy a new mech but I guess I have to go for a new mech then.

    I just found the exact same question asked recently in another forum, also regarding a Rival mech. Although some people say it's possible the outcome was that it probably won't work as well with a Sram mech as it could with Shimano one.
  • wishitwasallflat
    wishitwasallflat Posts: 2,927
    Get yourself a WiFLi mech and you can run a 32t SRAM cassette - you won't wear out your cardiovascular system spinning up those hills but you will wear your knees grinding up em!
  • raymond82
    raymond82 Posts: 330
    I guess I'll go for that, for now I ordered a 33t chainring which will be fine with a 28 cog for whatever hills I'll still ride this year. Next year I'll look for a second hand WiFli rear mech for whatever cyclo I'll participate in, just adding a 30t chainring would have been a cheap option but I'm convinced now it's not a good idea with the Sram rear mech I have. Unless of course next year I'm so fit I can handle everything with a 33x28!!
  • Yossie
    Yossie Posts: 2,600
    Nah - its time for a scooter I think.
  • raymond82
    raymond82 Posts: 330
    I realized yesterday that I'll be quite close to Mont Ventoux while on holiday next week and since I can't fit my scooter in the car I decided to go for the 30t with the mid-cage derailleur. Just out of curiosity I tried fitting the 30t with the short cage derailleur and I think it's absolutely impossible, the space between the cog and the pulley is way too small. I did find stories from people who managed but I guess it can only be done with Shimano derailleurs or on bikes that have very long derailleur hangers.

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