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  1. #1
    Senior Member Chacal's Avatar
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    Advice needed on mod to old road bike drivetrain

    the bike is a '86 Trek, DT friction shift, Shimano 600 RD (non index, RD 6207). It originally had a six speed 14-28 freewheel.

    I've replaced the wheel set and am running a 9 speed drivetrain. I tried a new SRAM 9 speed chain and a new Sram 12-26 9 speed cassette and all was great.

    I wanted to get a lower low for some upcoming hilly rides (I have a 53/39 up front), so I swapped in an old 11-32 mtb cassette and it seems to be working okay.

    Problem - the smaller cogs on this old cassette (which is riveted together, not discreet sprockets) are shot, and the chain skips on them. I was all set to buy a new SRAM PG-970 steel 9 speed mtb cassette, now on sale at Performance for $26.

    Advice #1 : They offer it in 11-32 and 11-34. I realize a 32 is probably pushing it with the old 600 RD, no max wrap is stamped on it but I am assuming it'd be 28t. Would I be nuts to go for a nice low 34t?

    Advice #2: I also have a gently used 10 year old Shimano Deore LX SGS M570 Rear Derailleur I could toss on the Trek - longer cage. Would you go that route, or just stick with the 600 short cage if it is working?

    Advice#3: If sticking with the old 600RD, the lower pulley is shot - almost worn down to the nubs. I would replace it with the Aluminum ones, but how do I know whether to go with 10 or 11 teeth? The original pulleys look to be 10t, but that was with the old six speed chain. Should I get 11t pulleys for the nine speed set up?

    Thanks for any words of wisdom.

  2. #2
    Senior Member Chacal's Avatar
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    btw, my original problem was described here

  3. #3
    cab horn
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    This is simple to resolve.

    Run the new cassette in whatever cog size you wish (limiting yourself because you want to run your old derailleur doesn't make any sense). If your old derailleur won't clear the bigger cogs then use the deore.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  4. #4
    Great State of Varmint Panthers007's Avatar
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    Yep. Or look into mountain-bike rear-derailleurs. 34T is usually where one must swap out the RD for mountain-sizes with Long Cage beasties.

    But do give what you got a try. Sometimes I'm pleasantly surprised to find how well somethings work that aren't supposed to.
    How do you keep an idiot in suspense?

  5. #5
    cab horn
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    Quote Originally Posted by Panthers007 View Post
    Yep. Or look into mountain-bike rear-derailleurs. 34T is usually where one must swap out the RD for mountain-sizes with Long Cage beasties.
    He already said he has a deore in his #1
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  6. #6
    Senior Member Chacal's Avatar
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    thanks guys, yeah that was my thinking too - get the 34, try it out with the old RD, and just throw the Deore on if it doesn't work....I was just wondering If I was nuts to even try this. I did not check the biggest chain ring/cog test for sufficient chain length, but I suspect it'd be fine - the chain is very slack on the 39 when you get under 20t in back. There is plenty of give in the chain with 39x32 as it is now.

    I still would like to get the new pulleys when I put in my order to Performance - any thoughts on whether to go with 10 or 11t? again, it looks like it had 10t stock originals, but that was with the old 1980s 6 speed set up. It's a narrower nine speed chain now.

  7. #7
    Senior Member johnknappcc's Avatar
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    Quote Originally Posted by Chacal View Post
    I did not check the biggest chain ring/cog test for sufficient chain length, but I suspect it'd be fine
    I would still check, it's better than finding out the hard way.

  8. #8
    Senior Member Chacal's Avatar
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    good point - i just did, an with the 53x32 the chain still seems fine. The RD is stretched but not badly.

  9. #9
    Senior Member Chacal's Avatar
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    rode it in to work this morning, worked fine...although it shifted by itself a few times in the rear. This old bike often does this (bad tension on the rd cable?), especially on the FD when standing....again, not sure if that is FD cable/shifter issues or just a flexy BB.

    But I am wondering if the large cassette is contributing to instability in the rear? I took it for a 15-20 mile ride over the weekend and it was doing the same thing, shifting in the rear, a bit more than usual I'd say....could it also be worn teeth on the old cassette?

    I am set to pull the trigger on the new cassette, am gonna go for the 34t. Just hoping for guidance on whether to go with the 10 or 11 tooth jockey and tension pulleys with a nine speed chain.

  10. #10
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    With friction shifting the "auto-shifting" is due to insufficient friction in the shifters. There should be an adjustment on the shifter, in some cases this is a "D" ring.
    I think you'll need the Deore RD to work with the 34.

    Al

  11. #11
    Senior Member Chacal's Avatar
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    Thanks Al. I have messed with the d ring but it is pretty much as tight as it will go - according to Sheldon Brown's site the front der. auto shift is probably due to friction in the cable guide under the BB (sounds right, as the FD shifts when I stand up to hammer).

    As far as the rear, I dunno...it'll just randomly jump a cog while I am taking it easy...

    So, maybe i should stick with the 32....I could really use the 34t, I am just being lazy about swapping the derailleurs

    After more online research, I did find that pretty much every Shimano and SRAM 9 speed pulleys use 11t so I am going with that.

  12. #12
    Senior Member Homebrew01's Avatar
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    compact ?
    Bikes: Old steel race bikes, old Cannondale race bikes, less old Cannondale race bike, crappy old mtn bike

  13. #13
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    Quote Originally Posted by Chacal View Post
    - according to Sheldon Brown's site the front der. auto shift is probably due to friction in the cable guide under the BB (sounds right, as the FD shifts when I stand up to hammer).
    That could be true for indexed shifting. Cable friction is not much of an issue with friction shifters.
    I would see if there is a way to improve or replace the shifters. There may be a creative way to increase friction within the shifters.

  14. #14
    Senior Member Chacal's Avatar
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    Quote Originally Posted by Homebrew01 View Post
    compact ?
    That'd be the obvious remedy for lower gears, but I am not interested in spending $100+ on a new crank for this old bike...it is not a super high end ride.

    Quote Originally Posted by Al1943 View Post
    That could be true for indexed shifting. Cable friction is not much of an issue with friction shifters.
    I would see if there is a way to improve or replace the shifters. There may be a creative way to increase friction within the shifters.
    I also have the original rapid fire 9 speed shifters for the Deore RD....I planned to swap both the shifters and the RD in eventually (I run a flat bar on this bike so I can commute with it when needed), but have been lazy about that too....any time I need to run new cables I get queasy. Especially with this bike - it has that nasty routing through the chainstay....ugh.

    Maybe instead of getting new pulleys for the old friction RD, it's more worth just ordering a DT cable stop, new cable and just going indexed with the 34t cassette, Deore RD and rapid fire shifter? Is that what you'd do, being you have the parts laying around anyway?

  15. #15
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    Quote Originally Posted by Chacal View Post
    I also have the original rapid fire 9 speed shifters for the Deore RD....I planned to swap both the shifters and the RD in eventually (I run a flat bar on this bike so I can commute with it when needed), but have been lazy about that too....any time I need to run new cables I get queasy. Especially with this bike - it has that nasty routing through the chainstay....ugh.

    Maybe instead of getting new pulleys for the old friction RD, it's more worth just ordering a DT cable stop, new cable and just going indexed with the 34t cassette, Deore RD and rapid fire shifter? Is that what you'd do, being you have the parts laying around anyway?
    That should work and it sounds like you know what you are doing. You know what they say about cutting housing- you can always cut it shorter but you can never cut it longer.

    Al

  16. #16
    Senior Member Chacal's Avatar
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    Hmm...coming home I have a subtle hill the entire last mile of my commute. I did it in 53x32. Aside from some slight cross chain noise (believe me, I've heard worse) it worked just fine.

    Here's how the RD and chain hang in the big x big combo:



    And in the 39t chain ring with 32t rear cog:




    A closer look at the gap between the jockey pulley and the 32t cog, when on the big ring:




    view from the rear, now on the 39t in front ...noticeably closer gap, and a much slacker chain:


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