thekauz

I have a 1980's era Peugeot that I saved out of my brothers basement. I have rebuilt everything and its running fine except for one problem I can't seem to fix.
It shift fine into and runs great in every gear except when I shift to the smallest cog (it doesn't matter which chainring) , it "skips" like its trying to shift up to the next cog?

Which adjustment am I getting wrong?

Thanks folks

Wordbiker

Most likely the High limit screw.

aesmith

If its not the limit screw, maybe worn chain and sprocket. The smallest sprocket is likely to be most worn. Does it skip more under load?

Tony S

Bobby Lex

Whenever I have a shifting problem that can't be fixed by fiddling with the barrel adjuster, I go back to square-one by loosening the cable and following these instructions:

https://www.parktool.com/repair/readhowto.asp?id=64

Bob

geo8rge

I had a problem like that on my Birdy when I installed a new wipperman chain.

I flipped the bike upside down. I rotated the crank while pressing on the rear wheel with a gloved hand. Rotating quickly at the very same point I noticed the derailer jumped and then I heard a click. Slowing things down if found it was the removable link not meshing with the rear cog. I replaced the removable link and the problem when away. Later I put the link back and replaced the cassette. A cautionary tale, the Birdy was used when I bought it.

It is possible you have a single link that is elongated.

thekauz

It does skip only under load. I'll try the recommendations and let you know what happens

Al1943

If it acts like it's trying to shift to the next larger cog that's usually a sign that the shift cable has too much tension or that for some other reason the cable is not able to move far enough out (away from the shifter) and that could be the high limit screw.

Al

Cadfael

I agree, this should be your first point of elimination... back of the limiting screw on the rear Dérailleur. The chain dropping down to the smallest ring is usually nothing to do with cable tension. I agree that it can happen that a cable can be so overtight it will not allow the chain to drop, but this should be the second thing you look at, first... back off the limiting screw on the Derailleur unit. Just a quarter of a turn may make the difference.

Okay, if this is not the problem release the cable clamp and let some cable out, ideally... when you then turn the cranks and shift up the next highest sprocket the chain should NOT move up... it is the barrel adjuster on the Derailleur you need to use turn to accomplish this.

thekauz

Now I'm getting frustrated. I followed the Park Tool procedure to no avail. Just cannot get the small cog to run correctly. I'm going to have to start from the beginning if not I may have to do something I haven't done in years...pay for help......unless I get some other ideas...not to worry I haven't given up yet.

trhouse

Here are a few additional thoughts. The photo shows a typical rear derailleur with the chain on the smallest cog. The "H" adjustment moves the chain left and right as shown at B. Are the guide and tension wheels directly below the smallest cog as marked by the arrows at C?

If not there could be several reasons. If this cannot be achieved with the "H" adjustment screw, the gap marked A which is set by spacers and the locknut on the axle could be too small so the "H" adjustment runs out of room. One way to determine this condition is to release the derailleur cable and remove the "H" adjustment screw. Under these conditions, the spring in the derailleur will cause the derailleur to move to the right in the photo as far as it can.

If the guide and tension wheels do not line up, the derailleur hanger marked D could be bent causing the derailleur assembly to be too far to the left.

Bobby Lex

The Park Tool procedure IS starting from the beginning. Don't skip any steps.

Bob

P.S. Make sure you have routed and clamped the shifter cable correctly to the derailleur. On my Shimano Ultegra derailleur, simply routing the cable along the wrong side of the clamping bolt (a difference of only a few millimeters) makes it impossible to dial in perfect shifting, even if you follow the Park Tool procedure exactly.

aesmith

You only have a problem with one gear, so lets focus on that. I suggest the following:

Change onto the small cog
Slack the cable right off, or disconnect, whatever's easiest
Follow the Park Tools instructions for setting the "H" limit screw, but don't go any further for the moment.

Once you're sure that's right, try the pedalling under load (still with the cable slackened off). If the chain skips, then I'm pretty certain its wear on the chain and/or the cog,

If it runs fine, then move onto the next stages.

Tony S

thekauz

I'll get on it tonight and let you guys know what happens.

thekauz

Hi All,

I followed aesmith's suggestion. With the tension released it still tried to shift up one cog. Even with additional adjustment to the H screw it did the same thing. I couldn't find my chain gauge, borrowed by a friend I'm sure, but I measured the chain and it is 12 1/16". So its a little stretched. Its an old chain so I might replace it and see what happens. Also I have a buddy with some tools that I can use to make sure the brackets are square and lined up.
Other than that I am still entertaining suggestions.
BTW, you folks have been great, I owe you all a beer

mike

mark9950

I will never own a bike with more than one speed anymore.If I want to change speeds I will change the cog.

thekauz

I released the cable and the "H" screw and it did swing to the right. It does line up under the cogs and pulleys. I'm stumped????
Maybe its one of those gear combinations you shouldn't ride in?

trhouse

I had the exact same problem with a mountain bike with a Sram indexing derailleur two weeks ago. The cause was the derailleur hanger which was not a separate part. It was difficult to see because the hanger had been bent in more than one dimension.

First, the hanger was pushed in towards the spokes. Ordinarily, this would have been easy to spot since the tension and guide pulleys would not lie under the cog but tilt to the left viewed from behind. The hanger had also been twisted for and aft so that the front of the derailleur pointed slightly inboard. The result was that the guide pulley was slightly inboard while the tension pulley looked correct because the bend in was cancelled by the twist, but two wrongs did not make it right.

The effect of the twist was not so noticeable on other cogs because the guide and tension pulleys tend to be more up and down relative to each other but on the smallest cog, the tension pulley has to take up the most chain so it moves to a position well behind the guide pulley giving the twist its maximum effect.

aesmith

Are you really sure its trying to shift, and not just riding up on the sprocket and jumping?

Try this, preferably with the bike on a stand, or hanging. With the cable slack, and the H screw slacked off, push the derailleur by hand onto the next gear (second smallest). Turn the pedals, then let go of the derailleur while still turning the pedals. Does the chain shift promptly onto the small cog? If so, I find it hard to believe it wants to jump back again,

raleighrider75

It sounds more like there isn't enough tension on the chain when in high gear.The chain could be just skipping and not trying to shift on you.
You can try taking a couple of links out of the chain and see where that gets you.Or try swapping out the derailleur for one you know works.
Is it a Simplex derailleur?

thekauz

You are correct it is riding up the sprocket and jumping back to the small cog.

I did as you suggusted and it does shift back to the small cog nicely.

It is an 80's era suntour seven derailleur I guess the spring could be weak. I'll check and make sure the hanger isn't bent and look around for a derailleur to swap it out.

I'm still at it and mot quitting till I fiqure it out.

trhouse

The photo provided above is a mid 80's SunTour Honor derailleur. Does the chain ever rub against the next larger cog? You should be able to place a piece of paper between the chain and the next larger cog and they should not touch.

aesmith

Good for you.

Have you checked for wear on the chain and sprocket?

Pepper Grinder

Thanks, that was super helpful!

thekauz

The chain is rubbing evr so slightly on the next sprocket up. The hanger WAS a little bent and I fixed that, it still rubs and skips but not as hard.

thekauz

Chain wear is a little over .50 on the Park Tool gauge. I think I might try a new chain, Nashbar has one for 12 bucks.
When the chain is on the smallest sprocket the pins on the chain rub the forward section of the sprocket ever so slightly but enough to make it skip. In all other gears there is plenty of room between the chain and the next gear up.