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Broken crank arm please help!

Old 10-10-12, 01:58 AM
  #1  
groshmo
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Broken crank arm please help!

I've got a 1983-84 Lotus Eclair and to my misfortune I found out that the crank arm is completely wrecked the allen socket has been wrecked (imagine riding on a bike for many miles with a loose crank arm). Should I just get a whole new crank set or is there anything I can do to fix it?




I've attached a picture its the inner socket of that crank arm that is messed up.
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Old 10-10-12, 02:59 AM
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Greenfieldja
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Can you provide a closeup picture as well please. It is hard to make out any specific details such as make/model/mechanism for removal of the crank from your posted pic.

-j
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Old 10-10-12, 04:04 AM
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Perhaps you can replace just the damaged part. As mentioned, more info needed.
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Old 10-10-12, 06:16 AM
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You can often get a complete crankset for not much more than just a crank arm. This is especially true if it's a right arm. So, if the right is damaged, definitely consider shopping for a new crankset. If it's the left check prices both ways, then consider the condition of your chainrings, and decide if you want to spend the difference for an upgrade.
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Old 10-10-12, 07:50 AM
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It sounds like you've ridden the bike with a loose crank, which generally results from the crank not having been put on tightly enough in the first place and NOT from failure to tighten the crank arm up at intervals.

It is rather unlikely that the crank has an allen socket to attach it to the bike, one that age will probably be a square taper crank, which has a square hole, as the name suggests. Allen sockets are hexagonal (or sometimes 12-sided) and are generally used on bolts as a means of tightening them up rather than as a permanent fitting.

I agree with the others, we'd be a lot more use if we could see pictures.

Last edited by Airburst; 10-10-12 at 07:55 AM.
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Old 10-10-12, 07:55 AM
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You realise the pic you posted is next to useless, right?

We knew that was the bit you were referring to, and we can't tell anything else from it except that seems to be quite an interesting old bike.

So put up a closeup of the bit in question, and while you're at it, a bunch more pics would be good too (including the drive side); consider it payment for services to be rendered.
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Old 10-10-12, 08:10 AM
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Originally Posted by FBinNY View Post
You can often get a complete crankset for not much more than just a crank arm. This is especially true if it's a right arm. So, if the right is damaged, definitely consider shopping for a new crankset. If it's the left check prices both ways, then consider the condition of your chainrings, and decide if you want to spend the difference for an upgrade.
That's what I think too.

Boogering a left crankarm is such a common problem that bike shops that specialize in repairs will have spares in stock. If you aren't picky about having an exact match, that's the cheap dirty fix. It's about a $20.00 part. Make sure you get the correct interface and length.

Replacing the whole crank would definitely be a more elegant fix and it's what I would probably do. If you go that route you'll probably have to replace the BB too and the total parts bill will probably be north of $100.00. If you live somewhere where there's a convenient bike co-op, you might luck into a more economical replacement.
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Old 10-10-12, 09:56 AM
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Some decent cranksets on amazon that run from cheap on up...

https://www.amazon.com/crankarm-alloy...words=crankset

is one example. A simple sort for Crankset provides pages of replacement left side arms starting at $9.99 so should be simple to click on a few of them to find one that looks the most right. If you don't find the exact arm, then look read further for a full crankset... many starting at $18. Be sure to get a bottom bracket and the required tools also so you can get back on the saddle promptly...

Noting also that sorting the crankset search by Price "lowest to highest" not only finds arms but also lot of ads for the crank bolts and caps and tools...all of which can quickly let you figure out what yours actually is since most adds have hi-res photos and text descriptions that you can match up to your bike to make sure you make a knowledgable buy.
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Old 10-10-12, 08:16 PM
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Could always use it an excuse to get a new bike?
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Old 10-10-12, 08:57 PM
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groshmo, while you're out getting a new crankset, consider getting new tires. Your sidewalls are all cracked.
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Old 10-11-12, 07:59 PM
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Find a Torx bit that will fit the 8mm allen head (T45 I think), then hammer it into the allen head. You should be able to get enough bite to remove the crank bolt.
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Old 10-18-12, 10:23 PM
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That's a beautiful vintage Lotus. Not only is it a 1983 model (less common than 1984), but it's an uncommon color combination that was only used in 1983, (Burgundy replaced the Bronze in 1984). It also has the original racks, bottle cages and all that good stuff.

The Shimano Deore crank uses a proprietary pedal thread so if you replace the crank with something different you'll also need pedals.

Deore crank parts show up quite frequently on ebay, there is one there now, with pedals, for $55.00 or best offer. I'd strike up an offer and keep the bike original.
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Old 10-18-12, 10:39 PM
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That is a Shimano AX series crank, with a larger hole for the pedals. May not be able to find spare crank arms. Anyway you could use this as an excuse to fix on a crank that uses the standard 9/16" pedals.

The earlier adamas ax series uses a groved spline, while the later 600 ax and dura-ace ax uses square taper bottom bracket. Both feature a one-key release. ie. you do not need a crank puller to remove the crank. It works quite similar to the Syncros Crank-o-Matic. However if the allen key bolt is rounded. you could still remove the crank, by removing the outer ring (the one with two small pin holes) with the Shimano Peg spanner (TL-FC21). When this is removed, then proceed to remove the allen key bolt. Once that is removed, you can use the cotterless crank arm extractor (TL-FC11) to remove the crank.

Last edited by TiBikeGuy; 10-18-12 at 10:56 PM.
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Old 10-19-12, 08:11 AM
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Hard to tell by the photo, but it may just be the dust cap that is damaged. THose dust caps were often made of chromed plastic or similar extra-soft cheese based material and whatever tool was intended for removal only worked under the most ideal conditions.

Do you know for sure the crank is damaged or is it just the fastener (whatever it is) circled in the pic?
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