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I am commuting and training on an old Peugeot road bike. I really like it but as training rides are getting to be 100km or more, I need to add shorter cranks and clipless pedals.

Problem is these old pugs have French threaded bottom brackets and it doesn't make sense to put a Phil Wood BB on a cheapo bike!

Have any of you managed to make a modern hollow tech/press fit BB work with French threading?

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    I vaguely recall seeing pressfit BBs that screw together in the middle forming one unit. But the BB shell tolerances could be an issue. There may be a bit of filing required, potentially ruining your classy bike.
    – Criggie
    Jul 4 '17 at 9:49
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You're stuck with square taper bottom brackets. But there are plenty of good square taper cranksets still on the market (new and used).

You have a few options though:

  • Velo Orange sells a french threaded bottom bracket under their Grand Cru line for about 50 USD (For comparison, the usual Shimano BB-UN55 is about 15 USD)

  • Phil Wood sells french threaded bottom brackets for far more than 50 USD

  • Use a universal (threadless) bottom bracket (Velo Orange also makes one under their Grand Cru line for around 70 USD; Mavic also used to make them)

You'll never be able to make a Pressfit bottom bracket work in this frame, or ISO threading expecting things like Hollowtech.

As for shorter cranks, make sure you actually want them (and you're not looking for adjustments elsewhere); most people who aren't too far from average size will be fine with 165-175 mm cranks.

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    On their website the Velo Orange french threaded bottom bracket is 50 USD. I remember it being 35 USD six or so years ago.
    – itfuwub
    Jul 6 '17 at 17:15
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    @itfuwub - thanks, updated. I guess I was looking at their english threaded ones.
    – Batman
    Jul 6 '17 at 19:10
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Can't be done, sorry.

A French BB shell is about 0.2 mm larger than ISO, so there's no way to make an ISO BB stay put in there.

Forget about press-fit; those are typically several mm larger. Even if you had the tools to bore out the hole and remove the threads (while keeping the hole straight), there isn't enough metal in the shell to make the hole of the size you need.

You can try to find a BB with French threading (sounds like you already tried that); you can buy square-taper cranks (if they were good enough for Eddy Mercx and Greg LeMond, they'll be good enough for you); or you can buy a new frame. Those are your options.

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  • Thanks everybody for the input! As this is my commute/training beater I would rather avoid spending 10x the value on a Phil Wood BB. I did a lot more research and found a few square taper cranksets which fit my needs. For anyone who may face the same problem, check out eBay of course for a used bargain otherwise this looks like the best option: sunxcd.net/cranks
    – Tim O'C
    Jul 9 '17 at 18:30
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I have managed to convert the bottom bracket to work with three piece cranks on my early 1970s UO-8. It originally had cottered cranks. All I had to do was find a square taper bottom bracket spindle that had roughly the same spacing with regard to the bearings as the original. I reused the bottom bracket cups and used loose bearings. I had problems with unthreading on the driveside bottom bracket cup (it's not reverse threaded) so I used thread locker.

It works okay. The quality of the only spindle I found at a reasonable price was not great, so it's not the smoothest (there may also be a slight mismatch in the bearing surfaces).

Any of the more specific modern cranksets will probably require one of the more expensive bottom brackets with interchangable cups, such as the Phil Wood. However, if you're considering an outboard bottom bracket you will need to think about whether you need to face the bottom bracket shell. I am only familiar with using the Park Tool bottom bracket tapping and facing set for this purpose, which normally is used to face the bottom bracket shell after tapping. Looking at available tools, it should be possible to face the bottom bracket shell with a headtube facing tool if you find it necessary to do so.

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  • Thanks, the bike has a square taper BB already and I'm hoping to switch to a more modern crankset. Can't find any 165 three piece cracks, even in square taper!
    – Tim O'C
    Jul 4 '17 at 7:08
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    Interestingly enough I have 165 cranks on the Peugeot. They seem to be available through Ebay in the USA, but depending on your location that may not be the case for you. Another (terrible idea really) is to tap the bottom bracket with English threads and install a modern English-threaded bottom bracket in place with thread locker. It will probably work, but you risk destroying the bottom bracket shell and you need access to a bottom bracket tap.
    – itfuwub
    Jul 4 '17 at 15:29
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    @itfuwub - I doubt you have enough material and stuff to make that work reliably (and the labor would be quite a lot).
    – Batman
    Jul 5 '17 at 21:26
  • That's a good point. I am thinking more of a gap-filling threadlocker, so not the standard threadlocker. However, if you don't have inexpensive access to a bottom bracket tap it's just as cost effective to buy the Phil Wood with French Cups. I wouldn't worry so much about the cost if you can afford it because the only cost specific to this bicycle with the Phil Wood would be the French threaded cups. You could always move the Phil Wood to another bicycle later. The only issue will be facing the bottom bracket shell for an outboard bottom bracket.
    – itfuwub
    Jul 6 '17 at 14:19
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What ever you do under no circumstances re-tap a bottom bracket from French to English. Sugino makes reasonably priced 165 cranks I'm using them now and I have over 10,000 miles on them. They should fit on your old bottom bracket with no issues. Compass cycles sells SKS BB but like the Phil Wood, they are pricey, I upgraded the cottered cranks on an old Peugeot UO8 with a cheap set of traditional cups with bearings($5) and an old spindle I had. The spindle is available online for $10-15. you might need a new front derailleur which can be a issue as French tubing was 28mm instead of the 28.8 of English and most others. Problem solvers sells a 28mm clamp that you can mount a derailleur designed for a braze on derailleur, very inexpensive! Of course French threaded Bottom bracket shells are right hand threaded on both sides and you will need a specific crank puller for your cranks if they are Stronglight or TA, they are available online.

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