Need new chainset for old Peugeot (late 80's?) road bike

Discussion in 'Cycling Equipment' started by MikeyV, Mar 16, 2013.

  1. MikeyV

    MikeyV New Member

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    Hi

    I've got my old road bike out after 15 years! I've replaced a few bits and it seems to work ok. I replaced the freewheel so that I've got a larger 28 sprocket. I'm not as young as I was and want to put a smaller chain set on it to replace the original 5242. It's got an old SachHuret front mech with friction shifters and they work fine so I'm hoping I can get away without changing that if at all possible. Also I don't want to replace the bottom bracket unless I have to. Can anyone point me at a suitable chainset? I'm thinking of something like a 4836 but am open to suggestions. I don't want to spend over 100 quid - the nearer to 50 the better.

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    Thanks everyone

    Mike
     
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  2. alfeng

    alfeng Well-Known Member

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    There IS a chance that your crankset can use a 110BCD chainring. If THAT is the case, then you may simply need to buy a 36t 110BCD chainring + five (5) BMX chainring bolts (or, equivalent ... see below), and you'll be good-to-go!

    BUT, if THAT isn't the case, then the NEXT thing you may want to investigate as a possibility is to simply change the inner chainring to a 39t 130BCD chainring (presuming THAT 130mm is the Bolt Circle Diameter of your crankarm's spider) ...

    • 39t chainrings are available in a full range cost -- from a couple of Pounds to more than you want to spend for the updating of your bike
    • if you can snag one, a steel 39t chainring will usually cost a lot less ...

    • a 38t 130BCD chainring is typically a more expensive option since it is not as standard a size as a 39t 130BCD chainring

    If your Peugeot is post-1985, then it probably has an English threaded BB shell (I'm not exactly sure when Peugeot abandoned French threaded BBs ... if the frame is pre-1975, then it probably has a French threaded BB ... if it is in between those two dates then you'll have to actually look at it). If THAT is the case, then you can install ANY crankset which suits your budget & aesthetic sensibilities -- Shimano, Campagnolo, FSA ...

    • if you buy the crankset + tools (if & as necessary) via eBay, then you can certainly manage the conversion for under £60 ...

    If you are not adverse to installing a used crankset, then you can install an older (pre-1998) Shimano MTB crankset on your current BB spindle ...

    Of course, if the frame has an English threaded BB then you can install any MTB crankset ... simply choose the shortest BB spindle option ...

    • that is, if you opt to install an obsolete Octalink or ISIS crankset, then you can choose the shortest BB spindle available
    • OR, simply install any External BB & crankset whose tooth count works for you (you can remove the Granny from a MTB crankset, of course).

    If your frame has a French threaded BB shell, then your options are fewer ... the fore mentioned chainring with 39t option and/or a vintage MTB crankset ...

    • without disassembly of the BB, if you loosen the lockring on the non-driveside, then if the thread pitch appears to be 1mm then it is probably a French threaded BB
    • if the pitch appears to be coarser (I realize that this is like asking you to identify counterfeit money if you don't know what 'real money looks like, BTW, so it is a problematic way of determining the type of threading which a frame's BB shell has) then it is English threaded

    • the FIXED cup on the driveside of a French threaded BB has right hand threads
    • the FIXED cup on the driveside of an English threaded BB has left hand threads

    ---​

    ONE option (still sub-£60 cost if you DIY if you-or-a-friend have some tools to remove the old crankset) which you can implement if you are willing to implement a DIY modification is to take TWO non-driveside MegaExo or Hollowtech II or UltraTorque BB cups & remove about HALF the threads from each cup -- doing so will allow the fore mentioned cups to thread into a French threaded BB (35x1) -- Yes, I have done this!

    • Hollowtech II & MegaExo cranks are interchangeable -- both have 24mm spindles
    • Campagnolo UltraTorque & PowerTorque cranks have 25mm spindles

    Obviously, this MAY be an expensive option unless you can buy the cups separately OR if you somehow manage to muff the hand work (i.e., use hand files!). I suppose that with External BB cups that they don't even need to be threaded since the crank holds the assembly in place, so the threads on the driveside cup can be reduced to almost zero with just a remnant of the threading remaining to ensure the fit is snug -- basically, a DIY press-fit. I have NOT tried that!

    ---​

    BUT, yet another option (THIS is what I would do if the BCD is not 110mm which you may also decide is your 'first'-or-'best' option!) is to re-drill the outer chainwheel to accept a 110BCD chainring OR any other chainring (I do not recommend now-obsolete, non-standard BCD chainrings unless you are living in sub-Saharan Africa or some obscure part of Central Asia and you do not have a source for now-standard components, BTW) which normally attaches to a 5-arm spider and either DRILL new holes in the appropriate location OR simply EXTEND the existing holes by creating appropriately long notches (the latter may be easier-and-faster if the outer chainwheel is steel) -- the latter just requires a couple (?) of hours (probably, much less time) with a RAT TAIL file ...

    • simply lay the 36t 110BCD chainring over the outside of the outer chainwheel ...
    • after centering the new chainring, mark the holes with a pencil OR 'magic marker' ... BTW, I would then lay pieces of tape on the edge of the circumference on the arms closest to the center to act as visual stops ...
    • remove the current inner chainring -- it it is riveted in place, then you need to drill out the rivets OR grind off one side (on the frame side) of the rivet and then pop the rivets out & remove the chainring
    • if the inner chainring is riveted, then you want to either buy five (5) BMX-or-SS chainring bolts OR you could just use some relatively SHORT 3/8"-or-9mm dome-or-hex headed bolts + nuts & washers (a split/lock washer on the inside would probably be a good idea)
    • on the cheap, your cost would be for an 11" (?) Rat Tail file (less than £2 if made in Asia, zero cost if you already have one ... 5x-to-10x the cost if you buy a file made by Union labour ...) + 5 of the fore mentioned bolts/nuts/washers (also, less than £2) + the appropriate 110 BCD chainring (£5-to-£15 depending on how-and-where-you-source-it) + your time (a new file cuts better than an old one)... plus, whatever you need to remove the look-like-rivets of the old chainring.

    So, if you are on a tight budget AND handy AND willing to spend a little time, then your cost is just a little more than the cost of a replacement chainring.

    FYI. Now, there is one Forum member who owns a bike shop in Boulder (COLORADO) who disdains DIYers & who thinks that everyone who rides should spend as much money as he can convince them to spend at shops like his, so I am sure that if you brought your bike to his shop-OR-equivalent then the recommendation would be to buy a new bike OR to spend £100+ for components + £20+ for labour charges ...

    • bike shops like his are great for people who have deep pockets even though his actual knowledge appears to be superficial ...

    • BTW, there are a select group of people whom 'I' feel should probably not DIY -- people with arthritis or who have a debilitating upper body injury + surgeons-or-equivalent AND/OR hand models should not do the work themselves because their livelihood depends on being able to use their hands for whom a mishap could put them out of commission for a period of time (or worse, permanently).
     
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