DanseMacabre

This Mercier came yesterday in the post from France. Looking at TonTon it is supposed to be from 1973 - 1978, though I cannot find a definitive answer. Simplex dropouts in the rear, unmarked dropouts in the front.

It has French threading. Recently I spoke a mechanic who said all French bikes in their shop get re-threaded to English thread. I was surprised, "does that work?". "Sure it does" he claimed. How does this idea fare in the BF hive mind?
I am planning to use a modern Campagnolo bottom-bracket with a cartridge. English threading makes things so much easier I would think, compared to French or Italian.

The Mercier 300 is Reynolds 531, the Mercier 100 and 200 are "Tubes Alleges Special 28 - 26". I assume the 100 and 200 differ in chroming and in parts, depending on the year. I could not find a definitive difference for the 100 and 200 series.
It does need a polish, new decals and some paint repairs.

Measurements as measured:
Seattube 54cm CC
Toptube 57cm CC
Seatpost: 25,4mm
Seattube diameter: 28mm
Toptube diameter: 26mm
No serial code to be found.

DanseMacabre

Two more photo's.

juvela

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mechanic quoted must have very low standards and/or be ill-informed

metric steerer is 25.0mm X 1.0

BSC/ISO/"english" steerer is 25.4mm X 24TPI

it is a simple matter to run a BSC steerer die over a metric steerer but you will not have adequate thread engagement to safely hold a headset adjustment of a BSC dimension headset

on the bottom bracket the metric threads have a pitch diameter of 35.0mm while British is 1 3/8" which works out to 34.85mm

so once again you can easily run a British tap through but once again will not have adequate thread engagement with British thread cups

would not recommend taking any repair work you have to this mechanic

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your dating about right

would think earliest possible date 1974 due to dropout model

frame constructed of plain gauge hi-tensile tubing (house brand is LUXTUB) so 25.4 saddle pillar size exactly what one would expect

would expect actual diameter of top tube to be 26.0mm rather than 26.4mm; perchance a bit of out-of-roundness at spot of measurement due to heat of brazing


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DanseMacabre

Thank you very much

I will hold of on English threading for the bottom-bracket. Italian should still be an option I assume.
I wasn't planning to re-thread the steerer, even to me that sounds very daring.

Myself I am from 1973, so it isn't built in my birthyear, I can stop dreaming about that

juvela

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rethreading of bottom bracket shell to Italian is somewhat limiting since you will have a 68mm width shell with Italian threads

this means you could not have a nice fit with a T.A. or a Stronglight bottom bracket assembly since they did not make spindles for 70mm shells

they handled Italian dimension by making the walls of their Italian thread bottom bracket cups one mm thicker than those of the metric, BSC or CH dimension cups

doing the job is not just a matter of running the tap through
it is necessary to also have the correct reamer to first ream out the shell to where it will accept the Italian dimension tap


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DanseMacabre

Ouch, that is very informative.
Thank you.
Maybe Campagnolo in French threading is then not the easiest option I will think about how to proceed here.

juvela

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see no reason why Campag in metric "French" dimension would not be a straightforward fit


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DanseMacabre

That is true. It will mostly be limited to cup/cone bearings with more vintage tools. I was feeling hesitant about that, but when the other option is a change of crankset, this comes back in the picture

Will require a good night sleep, or some more.

rustystrings61 

I'll throw out an option to consider - figure out which Phil Wood bottom bracket you need for your crankset. Then find a deal on a good used one, and pick up a set of the Phil French-threaded mounting rings. I wound up going that route with my '71 Gitane TdF fixed-gear conversion, and it has worked flawlessly.

I HAVE owned a Mercier 100/200 (I was never sure which variant!) that someone had hamfisted an English adjustable cup into, and left the original French fixed cup (Barden?) in place. It was a little wonky and I would agree with juvela that forcing a French bike to be English is just wrong.

DanseMacabre

Thank you, I will take a Phil Wood one into consideration. I see some are available on ebay.

1simplexnut

Embrace the "Frenchness" !!!
Working with what you have will be far easier -ish .

Look forward to pics of the build .

John E

I have force-threaded an aluminum English/ISO (LH threaded) fixed cup into a Swiss-threaded (like French, but, critically, LH threaded) BB, and it has held up nicely for 10 years or more. I would not recommend cross-threading into a French (RH threaded) BB, although I have a friend who built a crossover tandem crankset out of three regular Sugino Mighty sets, by cross-threading the pedal bores of the two RH crank arms he used on the left side of the bike. Seemed to work OK.

rustystrings61 

One other option occurs to me - using Phil French mounting rings with whichever of the older Shimano cartridge bottom brackets used two separate mount rings - UN71, perhaps?

There's also this - https://www.universalcycles.com/shop...IaAixoEALw_wcB

Hondo6

Assuming you're talking square taper, two other options exist.

First would be to use a Velo Orange French BB. They're currently available from VO in 103/107/110/113/116/118/122mm spindle lengths (presumably symmetric).

Second option would be to use a YST/Sunlite threadless (repair) bottom bracket. These clamp from the inside via expansion sleeve, and are designed for use on frames with mangled threads. (Can't say for sure, but I don't think they would mangle steel threads on a good frame.) Since your frame uses a nominally 68mm shell, this should work. They're available in 68mm shell width only and in multiple spindle lengths also; I've seen listings for 110/113/118/122mm (also presumed to be symmetric). Reputedly not the greatest BBs, but they do work.

If you're using a Campagnolo (or other ISO) crank, either of these would very likely have an issue: taper-mismatce. The VO unit is JIS only. Most listings for the Sunlite/YST unit are JIS, but I've seen precisely one that claimed to have one with an ISO taper. (I'd personally take that claim with a grain or two of salt, but it might be accurate.) Per multiple sources this mismatch affects spindle length needed between 4 and 5 mm total (split equally per side). You'd need to consult the late Sheldon Brown's or Rene Hearse Cycle's websites for further guidance if you were to go that route to calculate the spindle length you'll need.

Best of luck.

DanseMacabre

The Mercier was finished mostly, this afternoon. Now it is waiting for good weather that should come next week.



The seatpost might be a bit high
It's a Frankenstein build, I prefer my bikes cheap and functional. Campagnolo Centaur 9-speed shifters and rear derailer. Soma Highway One handlebar in 38cm. Grand Bois Papillon rims. Shimano FC-B124 crankset.




First time I used cloth tape with shellac. I had no clue that the electrical tape in green/yellow would shine through. It's done now, I will see if it annoys me enough to change it.
The Compact Soma handlebar is really nice and wants a 26mm clamp. I resorted to a 3ttt stem, grinded and polished it from 22.2 to 22.0mm for the French steerer. That went faster and easier than I expected.
For some reason the bottom ring of the headset didn't fit the fork steerer. The fork steerer seemed to have way too much material. I hope I wasn't too destructive, but it fits now, though it did give me a headache, and I still don't understand why it didn't fit.
The head badge is supposed to carry the serial number, but on this Mercier it is gone.



The bolt for the seatpost was a bit too long in 19mm, I suppose because the bike came with centerpulls and the bracket would take the space of 2 of these rings. I had a shorter one laying around, but that was too thick.




Many things are happening here

There is a 9-speed chain running on the 7-speed crankset, which seems to run fine. I hope changing gears will work fine too on the road.

Going for a bottom-bracket with Campagnolo triple and French threading was a bit too costly for me, so the Campa crankset is going. I resorted to a bottom-bracket without threading. I thought it was quite a non-destructive way to do it. No idea where to find better dustcaps for the Shimano FC-B124 crankset cheaply. I might need to go to a vintage fair for that.

The frame expects a front derailer with cable stop, but the Deore DX doesn't have one. The loose hanging cable does the trick, though it's not how things are supposed to be done.