Hi All,

I'm in the UK and restoring a much loved but neglected Peugeot Aquitaine (c. 1991) that is a 'sentimental attachment' veteran of Land's End to John O'Groats (eight days) amongst other long charity rides. I have a couple of other newer bikes (nothing too flash, and I'm in the market for a new carbon bike: I have not ventured there yet) but my sadly neglected Aquitaine is being slowly bought back to life, retiring to a less stressful life as a permanent feature on a turbo trainer (for the moment: it could rise again if I can figure out relaxing the brakes, which look prehistoric, and unavailable.....). I'm replacing the chain rings and find that they are BCD 72mm, 50T and 40T (StrongLight) rings. I can't find anything like that as current: are my measurements likely to be out? I've replaced the rear cassette with a new Shimano 7 speed: what should I be using on the chain rings, given the 72mm BCD measurement. I'm pretty certain it is not as much as 74mm I'd rather not have to replace the whole shaft do the pedals too.

I realise that this might seem strange if the bike is to be put out to pasture on a turbo trainer, but if I can replace the brakes, the old dear may yet see the tarmac again. Restoring full shifting capacity increases the chances that I'll try to achieve that.

So, yeah, there you go. Excuse that my introduction is immediately demanding of your expertise.... and that almost inevitably this is being submitted to the wrong forum section. Thanks to the moderators for reallocation, if appropriate.

Dornfield (aka Brian)

Thread moved from Introductions to Classic & Vintage.

Welcome to the forums!

Never heard of Stronglight rings with a 72bcd, so my guess is they are likely 74bcd, which used to be fairly common. I bought some a few years ago from Spa Cycles, Harrowgate, England. They probably still have them in stock.

Most of the advice you'll get here in regards to your old brakes will be: clean them, lube them, re-cable them and most of all, get new KoolStop or similar brake pads. Do all that, and they are probably pretty good brakes.

Welcome to BF

Dear Lascauxcaveman,

So I'll order the exact replacement 50T and 40T rings then, and I'm happy to presume that there will be a bit of play in the rings fitting, or that my measurements are out.

Also thanks for responding with a username that I take to be a sign! My family are on the cusp point of booking a gite in the Dordognefor the end of July, more specifically in Montignac: your user name is therefore quite the coincidence! So I'll book the gite as well. It is likely to be a bit more expensive than the chain rings. I'll give your regards to the buffalo when I see them, or at least the exact replica of the caves that has recently opened to the public.

Dornfield

Hi [MENTION=460049]Dornfield[/MENTION] and welcome! We can help get her back on the road if that's what you want. We do like pictures, though, so that will help inspire us. Cheers from the left coast of the US.

I had to look up gite.

So I've taken delivery of the 130mm BCD rings, and they really are too big.... I calculate that the BCD of my old rings is 122.5mm (I used a url - I'm not allowed to post urls because I'm a newbie, but it's at littlemachineshop.com/mobile/bolt_circle_dia.php - ha! outwitted the net nanny!) with the distance between adjacent bolt hole being 72mm, not 74. Measure twice, cut once. I've measured a dozen times, using a steel rule. 72mm between bolts. 122.5 BCD. I can't find this anywhere - do you think it is a relic of a bygone era and I may have to resort to purchasing a whole new crank and chainring set?

I'll continue looking, but does anyone know of a source of 122.5mmm BCD chainrings, 5 bolt, ideally around 50T and 40T?

Best,

Brian

The 122mm bolt circle was used on the Stronglight 93 crank. It's not a common bolt-circle anymore. Most of the rings I see are 52T, 45T, and 42T. It may take a while for you to source the sizes you want.

Although I cannot figure how to post a link to another thread (that must be possible, right?), I found a discussion thread (about the 122mm BCD) back to 2009 that used words like 'obsolete' and 'hard to find'. So it looks like I need to replace the whole crankset. That's a shame as I'd like to have kept as much of the bike original as possible.

The crank length is 17cm. Am I fairly safe in installing anything with the same sort of tooth count? The rings were 40T and 50T. I have replaced the cassette with a Shimano MF-TZ21 Cassette, so compatibility with that would be great if anyone can advise me.

Thanks

Brian

I did a search for your difficult to find BCD on eBay and I can find the rings you're looking for, but they're about $50 USD and up per ring.

I also did a search for 170mm cranksets (searched "170 crankset") and I found many, including rings, for less than $50.

So if your bottom bracket is square taper it may be cost effective to swap the whole kitten kaboodle. As for compatibility, without knowing what derailleur you're using and its associated chain wrap I can't say if the selected replacement will work or not. Frankly, I suspect you'll be fine with most offerings so long as you keep the difference in chainrings similar to stock, so a difference of 10 teeth. Plus, you can alter the aesthetics while you're at it, which is fun.

Posting pictures motivates all sorts of answers around here. Lots of bikes are foreign or weird, but with a quick glance these C&V guys can deduce all sorts of information =) I come here mostly to see the interesting solutions to peoples' atypical problems. Good luck with yours =)

Thanks Carbomb,

I have opted to replace the whole shooting match and have ordered a new 17cm Stronglight Impact JIS (I think) 38/48, so not too different from the original kit.

I'll have a go at posting images in future (is it the paperclip to the right hand side of the emoji smiley face?). I will continue in this thread, and probably need help sourcing brake parts that look very 'frame specific' and pretty shot. If I can get those fixed, then the bike will be roadworthy again. I would not describe myself as an expert, but I regard brakes as fairly essential. Too exciting without them.....

Brian

Hilary Stone is in your area and usually has a supply of 122 BCD chain rings. Check him out.

Use the paperclip if you have the images on your computer, and if you have them hosted on someplace like Flickr or Imgur, use the button down and 2 to the right (looks like a tiny framed picture of mountains with the sun) and paste in the URL.

I suspect the brake solution will be easier than you think, but... well, you know... pics...