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  1. #1
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    changing chainring on 81 Schwinn Le Tour

    I have a 81 Schwinn LeTour with a 52-39 Sugino Crankset in the front with a 5 Bolt 110 BCD. In the back, I have a 5 speed freewheel.

    I'd like to install a compact double on the front, as I am 220lb novice rider and live in a hilly area.

    Of course, I'd like to do it at as low of a cost as possible, ie with replacing as few of parts as possible, but am open more complicated approaches.

    Some of my questions

    - can I find new chainrings to attach to my existing cranks, a lot of the rings I see seem to be for 8/9 speed or higher, which I assume would require a new rear end, new chain etc

    - will I need a new front derailer, or will I just able to adjust it?

    Any advice welcome

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    For all practical purposes, you already have "compact" cranks, ie. 110bcd, (though the 39/52 chainrings make me suspect that it may in fact be a 130bcd). So if it is 110, it's imply a matter of switching to the ring sizes you want subject to a minimim size of 34t (there are 33t, but they don't work on all cranks).

    Standard 110bcd mtn chainrings will be fine.
    FB
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  3. #3
    Insane Bicycle Mechanic Jeff Wills's Avatar
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    Quote Originally Posted by FBinNY View Post
    For all practical purposes, you already have "compact" cranks, ie. 110bcd, (though the 39/52 chainrings make me suspect that it may in fact be a 130bcd). So if it is 110, it's imply a matter of switching to the ring sizes you want subject to a minimim size of 34t (there are 33t, but they don't work on all cranks).

    Standard 110bcd mtn chainrings will be fine.
    The 1981 Le Tour had Sugino Super Maxy cranks, which use 110mm BCD chainrings: http://www.trfindley.com/flschwinn_1...0/1981_09.html

    As FB says, you're just a chainring swap away from lower gears.
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    Quote Originally Posted by Jeff Wills View Post
    The 1981 Le Tour had Sugino Super Maxy cranks, which use 110mm BCD chainrings: http://www.trfindley.com/flschwinn_1...0/1981_09.html

    As FB says, you're just a chainring swap away from lower gears.

    You are correct, those are my cranks. On the new chain rings, a number of the ones I have found indicate for 8/9 speed, which makes me think that they wont work with my chain/ rear cogs. Please see link and note 8/9 speed compatible.

    http://www.nashbar.com/bikes/Product...79_-1___202345

    Also, would i have to change both the large and small chain rings, or can I run 52- 34?

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    If the rings fit, they will work with your cassette. The tooth profile is sized for 3/32" chains and that's been the case from 4s to 9s so there's no issue. What has changed is the gap between the chainrings, and that's set by the crank arm spider's tab which is between the rings.
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  6. #6
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    Quote Originally Posted by FBinNY View Post
    If the rings fit, they will work with your cassette. The tooth profile is sized for 3/32" chains and that's been the case from 4s to 9s so there's no issue. What has changed is the gap between the chainrings, and that's set by the crank arm spider's tab which is between the rings.
    Thanks, a couple more questions

    what does the vendor mean by 8/9 speed compatible, is that to distinguish from those for 9 or 10 speed, but not to distinguish from 5/6/7 speed?

    can I just add the 34 small ring, and run 52-34? I really dont care whether the large ring is 50 or 52, if the 52 will work.

    Will I need to remove chain links? I would think that if I replace both Chain rings, then I would also remove a couple of links, but if I go 52-34, then presumably I still need all the length, so will I have an issue with too much chain when in the small chainring and a small rear cog?
    Last edited by Baggins2012; 09-28-12 at 12:19 AM.

  7. #7
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    Quote Originally Posted by Baggins2012 View Post
    Thanks, a couple more questions

    what does the vendor mean by 8/9 speed compatible, is that to distinguish from those for 9 or 10 speed, but not to distinguish from 5/6/7 speed?

    can I just add the 34 small ring, and run 52-34? I really dont care whether the large ring is 50 or 52, if the 52 will work.

    Will I need to remove chain links? I would think that if I replace both Chain rings, then I would also remove a couple of links, but if I go 52-34, then presumably I still need all the length, so will I have an issue with too much chain when in the small chainring and a small rear cog?
    As far as I know, 8/9/10/whatever-speed compatible just means the chainring is designed to accept the thinner chain used to fit between all the cogs on 8, 9 or 10-speed systems, they'll still work on setups with fewer speeds.

    There's no reason why you can't just switch out one ring.

    As for chain link removal, it'll depend on how much chain slack your rear derailleur can take up.

  8. #8
    Senior Member bud16415's Avatar
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    I’m not going to say this is the right fix for you as the others here are much better mechanics than I. But here is what I did on an older Cannondale I have. It came to me with a 52,42 crank and those rings were ok for flat around town riding I was doing but I rarely used the 52. I wanted to take that bike on a trip where I knew I would see some serious hills so I tried a mountain triple I had collecting dust. There was no easy way to make it into a triple nor did I need a 22t granny gear. So I took the granny off and that gave me the clearance to fit the crank on giving me a 44,32 up front with a 13-24 (7 speed) in the back. Gear inches between 35 to 65 on the small ring and 48 to 89 on the bigger ring. It’s not a half step pattern it overlaps by 4 of the 7 gear inches. The shifters had been upgraded to index Sora type and I wasn’t sure how well that would work but it shifts fine. I’m assuming you have friction and that would be less risky I would think. I kept the old crank as is and with a different chain length it’s a few minutes to swap it back and forth if I wanted to. I thought I would because I feared the 89 GI wouldn’t be enough high gear when cruising around home, but haven’t missed the taller ones yet. I don’t know if the chain line is perfect but it doesn’t look to bad. I did lower the FD (might not be shown in photo) but I did work ok left higher.

    Before


    After



    On a different project I rebuilt a LeTour right around the same age as yours for a friend and they loved it except the gears were too tall for them similar to what your problem is. On that bike I tried a triple off a junk Schwinn I had ready to be scrapped just to see if it would work or maybe to do something similar to what I did on the Cannondale. I can’t remember now if it was a mountain bike or a hybrid or what. The triple (JUST) made it on the leTour without changing the BB out to something longer. Mostly luck I think but I hooked it up and the friction shifter with some tweaking handled the triple. As did the RD just barely. I don’t have photos of that bike after the transplant unfortunately. But the owner is really liking the overall lower gears and really loves that granny ring. So it can be done.
    What's not in your legs needs to be in your gears.

  9. #9
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    "As for chain link removal, it'll depend on how much chain slack your rear derailleur can take up."

    Always make sure the chain is long enough to safely engage the big chainring-big cog combination; if there is slack in the small-small combinations avoid them (you shouldn't be using them anyway) or change the derailleur to one which will take up the slack.

    If you decide to go with a smaller big ring you should lower the front derailleur for best shifting performance although as bud16415 mentions it may shft OK as is.

    The only hitch you may run into with a much smaller small ring is whether the tail of the front derailleur will clear the chain on that small ring. Should that arise going with a smaller large ring and lowering the derailleur may help it clear.

  10. #10
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    Quote Originally Posted by dsbrantjr View Post

    Always make sure the chain is long enough to safely engage the big chainring-big cog combination; if there is slack in the small-small combinations avoid them (you shouldn't be using them anyway) or change the derailleur to one which will take up the slack.
    As the OP probably isn't replacing the big ring or getting a larger sprocket on the rear, I didn't think that was an issue.

    If the bike's got a really short rear derailleur cage and a close-range freewheel on the back, I should think it's entirely possible to produce slack when the small chainring is used regardless of which rear sprocket the chain is on.

  11. #11
    7-speed doomsday prepper ThermionicScott's Avatar
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    I would be interested to see if the FD can handle the 52/34 (18-tooth) jump... Since rings can be found relatively cheap, you might consider a 48/36 double, which gives a nice 35-94" range if you're still using 27x1-1/4" tires.

    P.S. My work shown here: http://www.gear-calculator.com/#KB=3...0&UF=2180&SL=2
    Last edited by ThermionicScott; 09-28-12 at 09:26 AM.
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  12. #12
    Senior Member bud16415's Avatar
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    Quote Originally Posted by Airburst View Post
    As the OP probably isn't replacing the big ring or getting a larger sprocket on the rear, I didn't think that was an issue.

    If the bike's got a really short rear derailleur cage and a close-range freewheel on the back, I should think it's entirely possible to produce slack when the small chainring is used regardless of which rear sprocket the chain is on.
    That was my thought when going to a whole new crank vs small ring change when wanting a climbing setup. On my touring bike with a triple I have a big jump dropping down to the granny ring and I’m ok with that because that’s not a shift that you are doing all the time and it requires a soft pedal shift. But with a double or the two biggest rings on a triple you want to flip them back and forth a lot I would think and want a smaller tooth count difference. He’s already dropping 13t and going to a 34 would be an 18t drop. IMHO that’s getting into a harder shift. If you are going to change them both the cost of a crank assembly like I used is about the same cost. I think that crank I used was around $35. That 12t jump is effortless in my case almost like shifting the cassette. The down side would be spinning out on the top end sooner. In the case of the OP he’s just getting into riding and mentioned his weight to strength ratio so he might be ok with coasting out some hills.

    He needs to put in some ideas into a gear calculator like this one and make some guesses based on the gears he has now he likes and the ones he doesn’t and go from there.

    http://home.earthlink.net/~mike.sherman/shift.html


    Original LeTour 39,52 14-17-20-24-28 13t drop 37-99 GI

    http://home.earthlink.net/~mike.sher...no&TITLE=&HL=1

    Mod 1 34,52 14-17-20-24-28 (one new ring) 18t drop 32-99 GI

    http://home.earthlink.net/~mike.sher...no&TITLE=&HL=1

    Mod 2 36,48 14-17-20-24-28 (two new rings) 12t drop 34-91 GI

    http://home.earthlink.net/~mike.sher...no&TITLE=&HL=1

    Mod 3 32,44 14-17-20-24-28 (mtn crank –granny) 12t drop 30-84 GI

    http://home.earthlink.net/~mike.sher...no&TITLE=&HL=1


    I put in a cadence of 90 RPM and if the OP looks down at the output speeds at the bottom of the screen for each gear selection and adjusts that along with whatever tire size he has he can get a feel for what each gear will give him as to speed. For a new rider a top of around 20 MPH I think would be ok and try and get the best low gear for the least amount of cost.

    .
    Last edited by bud16415; 09-28-12 at 11:45 AM.
    What's not in your legs needs to be in your gears.

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