marrac

Hey, I've recently finishing up my Peugeot build with modern components, but problem with front derailleur appeared at the end. I've got Shimano Claris groupset, but the original crankset. The problem is that I don't know if that's because of derailleur clamp size (the clamp is for 34,9mm but I got adapter to 28,6mm) or just the crankset (original Nervar 52/42), I can shift to the large chainring with no problem, but downshifting to small chainring makes the chain get stuck between chainrings, like the chain can't land the chainring teeth. Also I feels like the derailleur don't have enough space for high and low limit screws, when I set up the low limit screw 1mm from the chain, then I can't do any adjustment for the high limit screw because the movement between low and high is too small.

Bill Kapaun

Crank was designed for how many rear cogs?
FDER designed for how many "speeds"?
Chain width? (speeds)

marrac

I don't really have information for the crankset, it's original set from 1986 6 speed Peugeot, but the front derailleur is for 2 speed (on Shimano site is that derailleur is compatible up to 46-52), and chain is for 8 speed. That's my first build like this and I'm doing everything by myself. Sometimes the problem was even with the original configuration of 6 speed rear, and original derailleurs.

Bill Kapaun

It sounds like the rings are simply spaced too wide for 8 speed.
Back then, that crank used a wider chain and most likely, friction shifting. Much less fussy then newer stuff.

Without other useful info, one has no idea if you have other issues involved, such as BB spindle length etc.

dedhed

Bills question was in regard to what rear the front was designed for. As speed numbers increased the chainring spacing became narrower (chains as well) and the FD doesn't move as much between "clicks" allowing the chain to drop between the rings.

icemilkcoffee 

Just get the Claris crankset/ Chain rings that go along with the rest of your groupset. That will make your life much easier in general.

marrac

Okay thanks for the information guys, so it's better if I also change the crankset, and btw if I get Claris crankset, can I just replace the crank arms or do I need to replace whole BB for that? I don't have tools for that and I want to finally drive that bike, I already lost so much time with this project that I'm done doing anything more.

Bill Kapaun

It's unlikely the BB length will be correct.
Generally speaking, cranks from that era used a much longer BB.

IS you BB French or BSA threaded?
IF French, your can of worms just got bigger.

70sSanO

One simple question…

Does the front derailleur not travel far enough inward to shift to the small chainring?

John

Edit added: I only ask because people have been using cranks that came with 6 speed freewheels with 8 speed chains for decades. 9 speed chains were more of an issue, but the fix was to swap the inner chainring, not the crank.

But a 34.9 derailleur clamp on a 28.6 seat tube can be the kiss of death because the cage can’t move far enough inward. If that is the case, there is no crank with “same”chainline that will work. You need a different FD.

marrac

@Bill Kapaun
Sorry but I don't know what type of BB I've got.
@70sSanO
Yeah that's why I don't know where the problem is. I've checked cable tension, position of derailleur, even was trying with that weird "converter pin" that you can switch around. Maybe that's the clamp problem, but then why Shimano are selling 28.6mm adapters for FD? It shifts pretty easily to the large chainring, but get stuck when shift down. It looks like this. That's the model of the FD https://bike.shimano.com/en-US/produ...D-R2000-B.html

70sSanO

Second simple question...

If you disconnect the cable and turn the low limit screw out, can you get the chain make it to the inner chainring or does the inner FD cage stop against the clamp/seat tube/??? before the chain drops on the inner chainring?

John

marrac

70sSanO It got plenty of room to move on the low limit side, the problem is only when shifting down to the small chainring, the chain doesn't go on the teeths.

Crankycrank

I think Bill's post #4 is most likely the problem. Too much space between chainrings that were (maybe?) designed for a wider 6 speed chain and crank and the 8 speed chain gets stuck between them. 6 speed chains are generally about .7mm wider than 8 speed which is a pretty big difference in bike chain terms.

icemilkcoffee 

You need to find out which BB you have. If you have BSA BB (usually on late model Peugeots), you could switch to a Claris crankset with hollowtech BB. If you have an older french or swiss BB you can switch to a square taper crankset meant for 8 speed (105 FC1056, Ultegra 600 FC6401, RX100 FCA551 ...)

70sSanO

Just change your inner chainring. Get a 9 speed, or even 10 speed, chainring and call it a day.

John

Edit added: Depending on whether the teeth are centered or slightly offset, you might be able to flip the chainring around. Did that once, but can’t remember if it is was inner or outer. It’s better if you can gain some with the inner.

marrac

Little update, so I take off the old crankset after a little battle with it, and also bought the new one Shimano FC-RS200 for square taper. My question is, can I just put the new crankset on the old bottom bracket if the new crankset is for square taper also, or I need to replace the BB also for the new crankset?

Bill Kapaun

Already answered in post #8

marrac

Sorry Bill Kapaun I forgot about that post, my bad. I managed today to unscrew the bottom bracket, and I think I've got a ton of luck because on the drive side the cup is tightens to the left side, so it's English BB right? It's weird because the guy from this forum told me from the serial number on the frame seems like the bike is from 1986. Now the question is, do I need the same lenght of the axle if I changed from 6 speed to 8 speed, or do I need to look up for BB recommended by Shimano on their site (it's probably 110mm from what I can see), also I tried to put the BB that I got with crankset inside, but it seems like the screw from cable guide under the shell is stops the BB to go through. It's a normal thing?

Crankycrank

I'm guessing the black slotted piece that the cable guide screws into is plastic and can be removed by squeezing the sides of the cap together and then just push it out.

marrac

Crankycrank Yeah but the question is, does it gonna fit when I put the BB inside? On the other side it's old bike and I'm affraid that plastic thing just gonna broke lol.

Crankycrank

I forgot to ask, is there another screw that threads into the black slotted part? It may be this is a push on type of guide and the only thing holding it on is the plastic nub so no screw necessary. If so you can just file down the slotted head until the BB can fit and the remaining stub will be enough to hold it in place as the cable tension will keep it from falling off but remove it from the shell before doing any sanding/filing. If it breaks, cable guides are cheap and easy to find and just find one like it or get one that screws in with the proper length screw.

marrac

Yes that's probably the push on type, because on the bottom it's just flat with little hole. Okay so I'll try to file down the plastic thing and try to fit in the BB.

partyanimal

I just had the same issue with a 1987 Peugeot rebuild, except mine was metal, holding on the shift cable guides- it was a rivet so I couldn't just unscrew it. I just filed it down and my BB fit fine.