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Front Derailleur/Gear Issues

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Front Derailleur/Gear Issues

Old 03-03-21, 12:43 PM
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MillieTheCat
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Front Derailleur/Gear Issues

Hi all,

Iím continuing my education on classic bikes by trying to install gears onto an old Peugeot that I converted into single speed years ago.

I bought some new parts and Iím having trouble with the chain rubbing on certain areas, mainly the front derailleur but also on the chainring itself.

Iíve tried adjusting the screws on the front derailleur and it rubs on either the smallest rear cog or the largest rear cog, itís one or the other but itís impossible to avoid it on both.

Also when the chain is on the smallest rear cog, and the smallest front cog, the chain contacts the largest front cog.

And finally itís incredibly difficult to move the chain to the largest rear cog with the friction shifters, Ive attached a photo of how far it has to be pulled to get there.

Iíve attached some images, the bike is a 1980s Peugeot, the new cassette is a Shimano HG500 10 speed, the front derailleur is a Sachs Huret pinched from another bike.

I appreciate your help and guidance!!

S





Does this look right? It seems too far backwards to me...


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Old 03-03-21, 12:54 PM
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It's common and normal for the chain to rub against the big ring when running in the small-to-small gearing.

Novices often use that gear because of a dislike of selecting a precise lever position while riding, or because of their failure to keep the shift lever tension screw tensioned.
So it's only the cheap bikes that typically use longer bb spindles to gain chainring clearance, at the expense of straighter chainline when running big-to-big.
I would argue that the big-to-big gearing combination is much more useful and so would say that your chainline is healthy. The rubbing would be even worse if you were using wider vintage chain, which you aren't.

It's also not uncommon for the shift lever to need to be moved to it's travel limits when using modern derailers, and wider cassettes than the bike's original freewheel.
Modern derailers, mostly starting with Shimano's first "600 SIS" derailer of the mid-1980's, require more cable and lever throw to move a given distance sideways. This is called a lower actuation ratio and makes shifting more precise (though which also can make for sluggish shifting feel until one adapts to the greater movement needed at the lever).

There are also different make/model shift levers having larger diameter cable spools that will move more cable if needed.

Consider yourself lucky if the narrower 10s chain never "skates" between the two chainrings, which are spaced for older, wider chain. It's fixable if it does, by beveling the non-drive side of the tips of the small ring's teeth, and/or by bending all the teeth slightly toward the drive side.
I will say though that steel chainring's teeth generally give better shifting than equivalent alloy chainrings of the same vintage.

Last edited by dddd; 03-03-21 at 01:03 PM.
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Old 03-03-21, 06:27 PM
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It's possible that a too-short crank axle could place the outer ring too far inward. Was the axle was changed to be correct for a single-speed?
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Old 03-03-21, 06:35 PM
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Originally Posted by oneclick View Post
It's possible that a too-short crank axle could place the outer ring too far inward. Was the axle was changed to be correct for a single-speed?
The axle is the same one from the factory I believe!
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Old 03-03-21, 07:11 PM
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I think the thing is that you installed a 10 speed rear on a bike that was not designed for it. This required spreading the rear to achieve clearance for the wider hub. This has to be done carefully so that the stays are spread the same amount on each side. The fact that your chain rubs on the big ring tells me that your alignment is off. You can check this yourself with the string test, but using the right alignment gauge, like the Park ***-2, works much better. Also, those shift levers were not designed with enough cable pull for a 10s derailleur. Take a look at the Dia-Compe ENE shifters, which will handle up to 11s. The other option is to go with bar end shifters, which will add indexing for you.

Don't get discouraged. A bit of thoughtful effort will get this all sorted out for you. This is the way we all learned.

Edit: I wondered if the Park designation for their Frame Alignment Gauge-2 would get censored. Guess so.
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Old 03-06-21, 10:42 AM
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I guess the inevitable happened...

Chain mustíve got caught either on the front derailleur itself or the chainring, snapped the chain and then destroyed the front derailleur...

back to the drawing board, and probably eBay...





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Old 03-06-21, 02:35 PM
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You probably shouldn't mix 6/7 speed cranks with 10 speed cassettes and chains. @dddd mentions it and some workarounds but this is maybe a source of your problems. The front derailleur too. Keep your drivetrain simple and as compatible as possible, otherwise it's hard to diagnose what the issues really are.
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Old 03-07-21, 08:21 AM
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Your first picture above shows the chainrings very close to the stay. It may just be the angle of the picture but if this is accurate, you may have your bottom bracket spindle reversed (assuming it is asymmetrical). The end of the spindle with the longest length after the bearing race should be on the drive side. Also the lock ring on your adjustable cup doesn't look like it's seated firmly against the shell. If the cup then becomes loose, it could contribute to the sort of problems you've described.

Looks like you have a lot of things to sort out. Work systematically.
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Old 03-07-21, 02:31 PM
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[QUOTE=MillieTheCat;21954844]I guess the inevitable happened...

Chain must’ve got caught either on the front derailleur itself or the chainring, snapped the chain and then destroyed the front derailleur...

back to the drawing board, and probably eBay.../QUOTE]


That looks symptomatic of the chain partially losing a sideplate off of a leading-side rivet head, which then caught on the outer plate of the front derailer, leaving the sharp bend there and forcing the derailer to rotate on the tube.
On occasion, I've come across same situation but before any real force was applied by pedaling hard, so fixing only the chain was still tenable.

On your derailer, both plates need to be restored to flat and parallel, which appears to still be quite possible with some judicious cold-working of the cage.

Beware that modern chain should never be re-riveted without using special pins or a proper connecting link. Modern chain's pins are peened flat against the outside of the outer side plates, and this narrow/thin ring of peening shears off completely when the pin is pushed out. So a pin is toast after breaking the chain there.

Last edited by dddd; 03-07-21 at 02:36 PM.
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