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1980s Peugeot to singlespeed?

keef66keef66 Posts: 13,123
edited January 2018 in The workshop
Have a 1980s Peugeot (Triathlon I think) that my son bodged / tarted up, got into road cycling, then bought a new bike. Younger son now needs a cheap commuter. It's London, so chances are it'll be nicked at some point, so don't want to spend much on it.

Can I cheaply convert it from drop bar 5 speed freewheel to flat bar singlespeed? I have some straight bars off a mid 80s MTB; will they fit in a quill stem?

Can I just lose the 53 chainring and mount the 39 on the outside?

What's the most cost effective singlespeed freewheel? Sturmey Archer look OK for £15

3/16 or 1/8 chain / freewheel

Will it need a chain tensioner?

Posts

  • whyamiherewhyamihere Posts: 7,570
    Quick answers in order:
    1. Probably not, MTB bars had a 25.4mm clamp, road bars had 26mm, before everything moved to 31.8. You can make a shim with a coke can though.
    2. Yes, but you'll either need shorter chainring bolts or suitable washers to take up the space previously taken by the other chainring.
    3. Around that price there's likely little difference, they probably all come out the same factory anyway.
    4. 3/32 stuff tends to be cheaper, and you may be able to reuse the chain it already has if it isn't too rusty.
    5. Maybe. If it has some horizontal movement in the dropouts where the wheel is mounted you can probably use that movement to take up the slack, otherwise you'll need a tensioner. The cheapest option is to reuse the old derailleur with the limit screws wound in.
  • keef66keef66 Posts: 13,123
    Many thanks! I'll give it a go then.

    The seat tube already has a coke can shim to take the wrong size seatpost, and I had to do something similar for one of the headset cups, so another round the bars will be entirely in keeping :D

    Liking the idea of using the RD as a tensioner if I'm unlucky with the chain length / cog sizes.

    Might get away with just having to buy the single speed freewheel and the brake levers. Bargain!

    Actually he's coming home at the weekend so we can help him with his tax return, so I'll take the opportunity to try him on the bike and choose a gear he's comfortable with. Peckham's not at all mountainous is it?
  • crakercraker Posts: 1,739
    What sort of ratio are you after? With a 39 tooth chainring you'd need a 15 tooth freewheel for 68" or so. Is that just a screw on replacement for a 5 speed block? That's a bit outside my experience but I wonder if you _might_ have chain line issues.

    My first go at hacking an old Raleigh to SS reused the chainring and chain off a 7 speed, it was mostly fine but as the teeth of the chainring have got ramps to help shifting and the chain is flexible, I did get the chain coming off. It was much improved when I bought a single speed chain (£5 or so).

    You'll probably get away without a tensioner if it's got semi horizontal drop outs; think carefully before removing chain links!
  • keef66keef66 Posts: 13,123
    I dunno about the ratio till I take him for a ride on it and ask him to pick a gear. He's 27, lean and pretty fit. Not cycling fit though, just gym and football. He's always hated cycling but one of his flatmates commutes by bike and he needs every penny to live where he is.

    Yes, it was originally a screw-on 5 speed freewheel. Think I put a 6 speed one on when we did it up as a road bike.

    Chainline is the only thing that I think might scupper it. I'll have a squint tonight to see where the big chainring lines up with the block. Suppose I could always run it with just the 39 mounted inside the spider. Would look a bit weird but possibly even less attractive to a thief. A SS chain is only another few quid so I might chuck one in the basket when buying the other bits.
  • fenixfenix Posts: 5,437
    Why spend money to make it singlespeed when you could just spend nothing and leave it in one gear ?
  • timothywtimothyw Posts: 2,482
    Yeah, bit confused why you need to do anything to it to use it as a commuter? Are the old gears completely knackered/bent?

    The existing components are not going to make the difference between it being nicked or not.

    Funnily enough I bought an old road bike as a hack a few years back, thinking I might convert it to single speed.

    I never bothered. Friction shifters on the downtube are pretty much indestructible, and basically immune to neglect. There's hardly any cable run to gunk up, and lack of indexing means you can always finesse them into gear.

    The brakes on the other hand were terrifying. I was very glad when I replaced them!
  • keef66keef66 Posts: 13,123
    If it was for me I'd stick with the drop bars and the friction shifters. The bars are the original engraved Cinellis and the shifters are NOS Shimano R600 and look nicely retro. I grew up with friction shifters in the early 70s; I love their simplicity and on the fly tuneability, I could shift nearly perfectly every time. And a gear cable would last 15 years.

    Son on the other hand isn't a confident rider, so flat bars with familiar brake levers, and no faffing with stuff on the downtube.

    I suppose I could always do the bars + brake levers and he can just leave it in whatever gear he likes.

    I was just trying to make it as mechanically simple as possible so there's less to go wrong. Older son was forever dropping the chain and coming back covered in grease, a feat I never managed when I rode it, but something I could never eliminate using the FD limit screws.
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