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Old 10-20-11, 05:07 PM   #1
mistergbrown
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Peugeot Racer Right Crank Arm Snapped

I have a 1980s Peugeot Racer bike that has a broken right crank arm that snapped today (see attached photo(apologies it is upside down))



I am complete newbie with bikes. Do I need to replace just the crank arm or will the whole chainset and crank arm need to be replaced? I am looking for the cheapest possible way of doing this. Ideally I would be looking to buy a cheap 2nd hand replacement and let someone else fit this for me.

The crank arm is 21cm or 8 inches in length and reads 'Lasco f-12b'. Any help much appreciated.

Thankyou

Gary
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Last edited by mistergbrown; 10-20-11 at 05:12 PM.
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Old 10-20-11, 05:45 PM   #2
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U need to learn how to measure the crank to start with, then get another one the same size at ebay.
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Old 10-20-11, 05:50 PM   #3
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80's stuff has to come off a donor bike, or you buy a whole new crankset.
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Old 10-20-11, 06:00 PM   #4
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Never seen one do that before. 21cm is way too long for a crank arm if measured properly (center to center). They should be between 165mm to 175mm; a men's road bike of that vintage is probably 170mm (175 for a mountain bike). The number should be stamped on the back of the arm probably near the peddle end. I can almost read the number on the unbroken arm in the picture, it looks to be 175. If you replace just the broken arm it is important the the replacement is the same length as the original.

There are a number of non profit bike shops around the country that may be able to provide used parts and assistance at a reasonable price; I volunteer at one. There is more to selecting a replacement crank then I can get into here. You need to consider crank arm length, gearing (sprocket tooth count), the type of attachment to the bottom bracket (crank spindle), the size of the peddle thread and the derailleur range if you change the gearing. Sheldon Brown provides very good information for beginners and experts on his site (http://sheldonbrown.com/cranks.html). For non profit bike shops in your area search Google for "non profit bike shops" along with your local area.

You may be able to find a cheap replacement on eBay or Craigslist, but you need to know what will fit. It's not that hard to change a crank if you have the right tools and someone to show you how. Again a non profit bike shop can provide both of these.

good luck,
paul

Last edited by deermouse; 10-20-11 at 06:07 PM.
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Old 10-21-11, 08:32 AM   #5
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I don't know for sure but that Lasco seems like a lower-quality part and not original to the bike. You could replace it with a left crank arm of any brand as long as the length is the same (I used a Specialized I had lying around on one of my Peugeots until I could find a proper Stronglight.) Or you could replace both sides - cranks from 80s Peugeots are plentiful on eBay. Here's a nice Nervar 52-42.
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Old 10-21-11, 11:41 AM   #6
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You will need to get new crank set. Preferable a good used one of the same vintage,gearing and length with axel. A older Sugino something like a Maxy should be a good match and would be a better crank than this one and a lot cheaper and easier to find than trying to find an exact replacement or crank arm for this crank.
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Old 10-21-11, 12:04 PM   #7
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You'll need to determine the length of the bottom bracket spindle you have, before you can see if compatible cranksets are available at your price point. If not, then you'll need to buy a matching BB to go with your newfound crankset. Hopefully your bike is late enough in the 80's where you won't have either French or Swiss threading. IIRC by about '82/'83 all had gone English.
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Old 10-22-11, 08:18 AM   #8
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How the heck does a crank break like that? Fatigue?
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Old 10-22-11, 09:22 AM   #9
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How the heck does a crank break like that? Fatigue?
Yep!
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Old 10-22-11, 12:54 PM   #10
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Quote:
Originally Posted by mistergbrown View Post
......I am complete newbie with bikes. Do I need to replace just the crank arm or will the whole chainset and crank arm need to be replaced? I am looking for the cheapest possible way of doing this. Ideally I would be looking to buy a cheap 2nd hand replacement and let someone else fit this for me.
...
Hi Gary;

I would suggest that you get a new crankset unless you are very concerned about being vintage correct. Something like this:
http://www.amazon.com/Sunlite-Alloy-...9309339&sr=1-2

While you are taking things apart, you should clean and re-lube your bottom bracket. Given the ago of your Peugeot; the bottom bracket maybe threaded to French standards (hopefully not), which are different from most current. http://www.sheldonbrown.com/bbsize.html#threading

If you can determine that your BB is ISO threaded, I would get something like this:
http://www.ebay.com/itm/380375142343
which includes a new bottom bracket.
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Old 10-22-11, 09:08 PM   #11
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I think I see "175" stamped on the good arm. That's the nominal crank arm length (175mm). That seems a little long for an older bike - they usually had 170 or 172.5. You should be able to pick up something used out of the junk bin at the LBS that would work. It appears this crank is integral with the large chainring, meaning you'll have to replace the whole thing. Best to have right and left sides match.
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Old 11-01-11, 05:47 PM   #12
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Crank arm french peugeot



Thanks for everybodies help with this!

Unless anyone strongly disagrees I think i am going to use a tool from a friend at work and remove the bottom bracket from the bike to see if it has been threaded to French standards or not. But what should I look out for? Is it pretty obvious?

I remeasured the crank arm and it measure 170mm (center to center) as suggested. Someone said they thought they could see a 175mm mark on the good arm in the original photo I posted which would go against the measurement I have got.

Please find attached a more detailed picture of the crank. Im not sure if this will give anyone a stronger idea to what part I will need to get?
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Old 11-02-11, 11:02 AM   #13
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Originally Posted by Sirrus Rider View Post
Yep!
Agree...since it's high and near the axial center point.

Also, if a break is near the pedal threads - that'll usually be caused by too many instances of jamming the pedal into the ground while leaning and pedaling through a turn.

=8-)
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Old 11-09-11, 03:46 PM   #14
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Quote:
Originally Posted by mistergbrown View Post

I remeasured the crank arm and it measure 170mm (center to center) as suggested. Someone said they thought they could see a 175mm mark on the good arm in the original photo I posted which would go against the measurement I have got.
This last picture is clearly stamped 175, but what do you see. You can look at the back of the arm. It should be stamped on both arms near the pedal hole. If you replace both arms they don't have to be the same length as the originals. I would suggest something between 170 - 175. Unless you are big and strong I would suggest 170 - 172.5.

Depending on the year (not sure when or if Peugeot changed) it should be either French of English thread. Both of these use a 68mm BB shell, so there is nothing different that you can measure. The difference is in the threading. On a British BB the fixed cup (right hand side) will be reverse thread. On a French BB the fixed cup is not reverse thread. The BB may have the thread stamped on it. If it does you can see Sheldon Brown's page for the specific thread for each. The English thread will be in inches and the French thread will be metric. This site lists the specific threads:
http://www.sheldonbrown.com/velos.html

If the BB isn't damaged or worn out, you probably won't need to replace it. It may be difficult to find a new French BB. Harris Cyclery claims to have French parts, but they are expensive. Ebay has a few, but they really are very expensive. See this page for Harris Cyclery:
http://sheldonbrown.com/harris/french-cranks.html

Last edited by deermouse; 11-09-11 at 03:57 PM.
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Old 11-09-11, 03:47 PM   #15
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Crank removal tool wont fit in hole



Ok so I managed to get the crank bolt off but the Crank Removal Tool wont fit in the hole. (http://www.evanscycles.com/products/...andle-ec006782).

I now have no idea what to do. Any help much appreciated.

Gary
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Old 11-09-11, 03:57 PM   #16
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Do you have a bike shop in your town, tools there will do the job.
There are 3 different crank arm extraction thread patterns.
French Companies came up with 2 of them.
[my guess: Stronglight supplied that part.]

Quote:
But what should I look out for? Is it pretty obvious?
French thread standard for BB shells is 35mm , both are right hand threaded.
british 1.37"Rh/lh , italian 36 rh/rh

Last edited by fietsbob; 11-09-11 at 04:16 PM. Reason: silly mm
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Old 11-09-11, 04:06 PM   #17
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Originally Posted by fietsbob View Post
Do you have a bike shop in your town, tools there will do the job.
There are 3 different crank arm extraction thread patterns.
French Companies came up with 2 of them.


If your LBSs have either or both of the French 23mm / 23.35mm crank extractors your town is better than mine.

And by not fitting, we're assuming you mean the tool is too small. If it's too large, I have no idea what you need.

Last edited by Ex Pres; 11-09-11 at 10:22 PM.
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Old 11-09-11, 05:18 PM   #18
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"Lasco" what the heck brand is that?? Most Peugeots in the 80s were built with either Stronglight or Nervar French cranks with some Campy or Mavic on the highest spec models. They mioved on to mostly Shimano in the 90's. I dunno where Lasco comes into the picture but that crank does look to be a lower model swaged crank. Any crankset can crack from either a stress riser type nick on the surface that develpos into a crack after many miles of use or a defect in the casting/forging process like unseen voids under the surface which also propagates into cracks later. I think you should just get something like a Shimano 600 or 105 of the bike's era, instead of looking for the same obscure brand and low model quality/construction of the originals and they will most likely last longer because of better production quality control.

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Old 11-10-11, 02:24 PM   #19
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Your current chainrings (sprockets) have a bolt-hole pattern that's not current, it's 122mm and the smaller sprocket is 42 teeth. This part of your crankset is worth money on Ebay that might offset the cost of a complete new crankset. I might have a basic crankset for you, but there is no certainty that your existing bottom bracket (spindle that goes thru frame) would be the correct length/taper, so a new bottom bracke might also be needed to get everything back together.
There is at least some possibility that your frame's threading requires a French or Swiss-threaded bottom bracket, this would have to be checked also.
Best bet would be to find a similar right crankarm. Otherwise, someone will have to do some fiddling to get everything fitting and working correctly with the spindle length and bb threading.

Good luck.
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Old 11-14-11, 01:46 PM   #20
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Originally Posted by mistergbrown View Post
Ok so I managed to get the crank bolt off but the Crank Removal Tool wont fit in the hole.
Sounds like you have a French crank with (probably) a French thread BB .

Harris Cyclery has both size French threaded pullers, though they aren't cheap. They want $50 each for them http://sheldonbrown.com/harris/french.html. I think I have old ones , but I'm not willing to sell them. If you're anywhere near Boulder CO, you could borrow them, or I could help you with the project.

A more likely solution would be to use an angle grinder with a 1/16th inch cutting disk to cut the arms off. If you can't do that, maybe the LBS can. There is a good chance of damaging the BB spindle if you're not careful. You need to cut most of the way through and then use a large chisel to break the last of the arm . If you do damage the spindle, most any standard English of French spindle should fit.

Are you sure the bike is worth that much effort? You can often find very good deals on older bikes on Craigslist.
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