DKK

Hello, I have a 1970s Mercier. It has triple chainrings with a short cage simplex rear derailleur that cannot handle this very well, so I have a long cage SX410 coming in a few days.
As I will be riding Eroica in October, I am thinking about getting lower gearing. I currently have 32T small chain ring and 28T largest freewheel cog. I believe the SX410 GT supports up to 36T cog, so am looking for a replacement freewheel - to 36T or 34T, but have been unable to find anything on-line. Can anyone offer any advice on a suitable alternative and where I can find? Or do I just need to be patient on eBay? Or alternatively, should I consider changing the front chain ring?

Btw, the bike is fitted with Normandy hubs, Stronglight crank, Mavic racer brakes, retrofriction levers and 28mm clinchers (I will see if I can fit 32mm for the white gravel roads).

JaccoW

What Stronglight crank do you have? If you can fit a smaller chainring up front that 28T in the rear could be more than enough.

DKK

I just took a couple of photos of the crank, but the forum won't let me post as a new joiner. The rear of the left crank arm is marked "K7 170 Made in France 14x125", the right arm "H7" instead. The rear of the chain rings - smallest is marked "32", the other two are marked "Z". The outside of the arms is just marked "STRONGLIGHT" along with a logo. I hope that can help identify!

non-fixie 

Pic assist:

bikemig 

That's an 86 bcd crank and you can get a chainring as small as 28 teeth.

Freewheels are widely available as well but we will need to know whether the Normandy hubs are french threaded or not and spacing of the drop outs (this would have been set at 120 originally but it may have been spread to 126).

If you upload pics of the bike from the drive side and a close up of the freewheel, we can give you a bit better advice.

Are you in France?

DKK

Thank you all. I was allowed to upload two photos of the hub to my gallery, but am still not allowed to post them here. Sorry.
28T chainring would be an improvement, but only a ratio of 1. Changing the freewheel will have a bigger impact - .94 for 34T, 0.89 for 36T (which is attractive for me) so any advice on criteria for deciding to change chainring vs freewheel also appreciated.
I assume this will have French threads, but cannot be certain. Assumption is based on all the components being French and the bike is in France

DKK

..except I guess that means the bottom bracket thread for the crank has been converted from the original French thread.

pastorbobnlnh 

While challenging to find in the US, Suntour made the Perfect/ProCompe freewheels marked "Metric" to fit French threaded hubs. Finding a 30T, 32T, or 34T sprocket for this model is easy in that even the silver sprockets from the Winner, Alpha, and Accu Shift freewheel families will fit.

Your next option is to find Maillard Course or Atom 77 freewheels with French threads. Either had sprockets as large as 32T (IIRC they did not come in a larger tooth count).

Finally, finding a French threaded Regina or Atom 5 speed is a possibility. IIRC a 31T is the largest sprocket for these.

DKK

That's great. I can get a NOS Stronglight 28T quite easily here. Out of interest, what identifies my crank as 86 BCD?

I didn't know about the Suntour option, so will keep that on my list, although if I use a Maillard 32 in combination with the Stronglight 28T ring, I get 0.87 ratio which is good. It also means all parts stay original French, even though they are not from St Etienne ;-)
Looks like I need to keep a close eye on eBay for the latter.

Thanks for the help!

John E

28/28 is a very noticeable 14 percent lower than 32/28.

non-fixie 

DKK , we are talking about Gaiole, right? First time? What distance?

The reason I ask, is that I have been there a few times. I am permanently overweight and under-trained, but I am also somewhat vain, so showing up there on a vintage racing bike with MTB gearing is a definite no-no for me. I've always made do with short cage derailleurs, which means 28T in the back and a double up front with no more than a 28T chain wrap.

And it was never a problem. Sure, there has been huffin' and puffin', and I was walking now and then, but then so were many - if not most - of the the others. All part of being heroic.

For reference: in 2019 I brought my Jacques Anquetil, with 52/37 up front and 14-28 in the rear. I rode it up to Brolio castle, which is what I like to be able to do. Anything worse than that, and I'll just walk.

Just something to think about, and please, feel free to totally ignore me. I'm not that vain.

JohnDThompson 

That's a Stronglight "100" crank, 86mm BCD with smallest ring 28T. Sakae Ringyo also made a couple 86mm BCD cranks whose rings would fit the model 100. I also note that the arms use metric ("French") thread pedals ("14x125"), unless they've been re-tapped to English. Something to keep in mind should you ever decide to use different pedals.

bikemig 

The OP is in France so metric threaded pedals and freewheels shouldn't be hard to come by.

bikemig 

It's a common size for stronglight cranks (86 bcd) and it's a very good design since it lets you run a vintage "compact" crank. I like this design a lot.

JaccoW

Cranks from Stronglight at that time are a bit weird on those points. Sometimes they use Stronglight's own special threading for the crankpuller, sometimes the standard 22mm and the same goes for the pedal threads. It's a bit of a crapshoot.

I have an unknown pair of Stronglight cranks that use the same size and a beautiful Stronglight 107 triple.
The former unfortunately has a crack on the NDS crank arm but maybe I will put if for sale some day for parts.

DKK

Thank you for all the advice. I just ordered a NOS Stronglight 28T from a local supplier. I will try that out with my new dérailleur and see how I get on.
Yes, I have French thread pedals. No need to change. Currently have Lyotard installed.

Non-fixie - I would also class myself as "overweight and under-trained”, but I guess you are a much tougher man (or woman?) than me. Well done. Anyway, point noted, thank you, I will give the new chain ring a good test over the coming weeks. In the Alps, which is a bit different to Holland ;-)
Btw, it will be my first Eroica. How long did it take you to cover the 200km?

oneclick 

Which Lyotards? A recent thread here suggests strongly that the built-up ones are NOT to be trusted; spindles break without warning (they're inside, you can't see the crack developing).

oneclick 

Normandy hubs are marked with a groove around the section just outboard the flange, under the freewheel - if they are BSC. Metric ones have no groove. This can be difficult to see, especially if there is a spoke-protector in the way.

Suntour made at least one version of their Winner series with french threads, and from what I remember you can build it as wide as 12-34 with some Alpha sprockets at the big end; but good luck finding one.

pastorbobnlnh 

Actually, Suntour made a 38T sprocket which fits on Perfect, ProCompe, Winner (series), Alpha, and Accushift freewheel bodies. As oneclick mentions, it is very difficult to find. 34T Suntour sprockets, on the other hand, are more common.

The Suntours which fit French hubs are marked "METRIC" on the outward flat face curve between the two notches for the removal tool. I've had these in the past in the Perfect and ProCompe models.