1988 Peugeot Triathlon
05-08-22, 08:21 PM
#26
curmudgineer
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There should be upper and lower limit screws on the front derailleur. Take a close look at the mechanism and you'll see how it works. Then adjust the upper (H) screw to let the derailleur travel far enough to eliminate the rubbing in the big-small combo (but no further).
05-08-22, 08:53 PM
#27
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update - cog arrived and I installed today. In case anyone else is wondering this in the future, I can feel a substantial difference between the 13T and 12T. Satisfying to pull apart that cassette, dismantle and clean all the individual gears and spacers with a toothbrush and then reassemble. Thanks everyone for your help, I'm not sure if I'll end up keeping the cassette like it is now, switching back to the 13T small, or maybe picking up a 14 so that there isn't such a jump from 12 to 15T.
Separate question, and I think it's always done this and it's just bugged me today because I spend the whole afternoon working on the bike, the front derailer rubs just a bit, enough to be audible when it's on the big chainring and especially on the higher/harder to pedal rear gears. It almost looks like my front chainring isn't completely true as I look down while pedaling, like it goes from side to side. Any advice on this? Live with it? Get a new front chainring? Try to pry open the jaws of the derailer a tiny bit? Is this just part of the design of the biospace system?
Separate question, and I think it's always done this and it's just bugged me today because I spend the whole afternoon working on the bike, the front derailer rubs just a bit, enough to be audible when it's on the big chainring and especially on the higher/harder to pedal rear gears. It almost looks like my front chainring isn't completely true as I look down while pedaling, like it goes from side to side. Any advice on this? Live with it? Get a new front chainring? Try to pry open the jaws of the derailer a tiny bit? Is this just part of the design of the biospace system?
But most likely what has happened is that your bottom bracket has loosened over time and needs adjustment. Grab the crank arm near the pedal and pull away from the bike. Do you feel any back and forth movement? If that's the case I would pull your bottom bracket apart and repack it with new balls and grease and put it back together so there's no play but it spins smoothly.
05-08-22, 10:39 PM
#28
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There should be upper and lower limit screws on the front derailleur. Take a close look at the mechanism and you'll see how it works. Then adjust the upper (H) screw to let the derailleur travel far enough to eliminate the rubbing in the big-small combo (but no further).
05-08-22, 10:43 PM
#29
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Your crank could be loose (tighten crank bolt). It could also be that that chainring is bent. You can take it off the bike and lay it on a flat surface to check.
But most likely what has happened is that your bottom bracket has loosened over time and needs adjustment. Grab the crank arm near the pedal and pull away from the bike. Do you feel any back and forth movement? If that's the case I would pull your bottom bracket apart and repack it with new balls and grease and put it back together so there's no play but it spins smoothly.
But most likely what has happened is that your bottom bracket has loosened over time and needs adjustment. Grab the crank arm near the pedal and pull away from the bike. Do you feel any back and forth movement? If that's the case I would pull your bottom bracket apart and repack it with new balls and grease and put it back together so there's no play but it spins smoothly.
05-09-22, 05:51 AM
#30
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Given that it is a 52/12T combination that appears to be ridden at high force and low cadence, the issue could also be a combination of crankset and frame flex.
05-09-22, 06:04 AM
#31
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Yes this is also a potential. If you are spinning with low resistance in a low (easy) gear do you have the same wobble?
05-11-22, 06:04 PM
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I spent a few hours fiddling with the high low adjustments and somehow made it worse. Took in to friendly LBS who confirmed the large chainring badly bent. He advised trying to straighten while still on bike. I watched a youtube video and spent another hour trying to straighten it using a large adjustable wrench. I got it a little straighter, but after putting the chain back on and tweaking the high/low even more, I've still got the rubbing, and I'm nearly certain it happens where the chainring is warped.
There's a sante biospace 52 on ebay that looks cool for $45 or one that matches my current one perfectly that is not sante that's around the same price.
Both are NOS, which seems worth it to make sure I'm not getting another bent one. Sante a bad idea?
update - went for an actual ride and the rubbing is improved from what it was before, I guess I did manage to straighten more than I thought, so will just live with it for a while.
Both are NOS, which seems worth it to make sure I'm not getting another bent one. Sante a bad idea?
update - went for an actual ride and the rubbing is improved from what it was before, I guess I did manage to straighten more than I thought, so will just live with it for a while.
Last edited by Agfa001; 05-12-22 at 07:59 PM.
