straightening a bent crank arm
 

I was pretty disappointed last night to remember that my MTB has a bent crank arm. I guess It wasn't a big problem with the old pedals when used it last in 2006? But it was darn obvious and annoying last night in the parking lot with the new pedals.

I'm hoping I can take it off and whack it a bit back into a close enough position to work adequately. I got the nut off but the arm didn't come off easily. I imagine that will take some muscle or taps or leverage.

Any comments about straightening a bent crank arm?

Here's a picture showing how the pedal is not perpendicular to the line of travel, so-to-speak.

FYI: I'm not the original owner, I picked it up many years ago in a trash heap in Harvard Square.

If it's a standard square taper you'll need a crank puller to get it off.

If its aluminum, I wouldn't recommend bending it back. Aluminum is likely to crack. In fact, if it is indeed bent, there probably are already small cracks. Steel, you can bend.

Left side cranks arms are inexpensive and plentiful. Much more safer and prudent just to replace it then risk injury. A bike shop may have one or thirty laying around that they will give you.

You can never straighten a bent al crankarm safely and accurately. It is FUBAR and needs replacing. Continuing to ride with a pedal that tilts up and down on every revolution will lead to knee problems.
You need a crank extractor tool, see parktools for illustrated instructions.

AGHAGHAGH!!!!!!!! :crash:

OK thanks

Uh wait, can I replace just the left crank? Should both sides be done? (seems to me)

That looks a little like a Shimano MC12 crank... if it is they were recalled and you can still get it replaced by Shimano -- albeit with a pretty crappy set.

crank recall

Breaking a crank arm can seriously ruin an otherwise nice day.

Replace.

just found these on ebay - this a generic item - are all these interchangeable or does somethign have to be measured?

http://cgi.ebay.com/VINTAGE-SUGINO-A...3A1|240%3A1318

http://cgi.ebay.com/NEW-ORIGIN-8-BLA...3A1|240%3A1318

http://cgi.ebay.com/Shimano-Acera-17...3A1|240%3A1318

http://cgi.ebay.com/NEW-Raceface-Rid...3A1|240%3A1318

hope those links work

how can i confirm my crank is the recalled one - for anyone else here is some info about the recall from another forum:



"Here's the skinny. I called Shimano at 800-353-4719. They said they replace the chain, front derailleur, and crankset (which I assume includes the bottom bracket). It's a complete set. I didn't think to ask what the component level is.

However, the CSR said they only deal with a Shimano dealer. They weren't interested in dealing directly with me. They said I should just take the bike to the shop and they would do the warrentee work and keep the old parts. I assume this has something to do with ensuring that the defective parts stay out of the used parts stream.

LBS didn't know about this, but you can't blame them for not knowing about a 11 year old recall.

Edit: After they got in touch with Shimano, LBS offered to take care of everything. They said the components are similar to what was there originally. The biggest issue for me is that Shimano must be shipping the components on the slow boat though the panama canal. It takes 2-3 weeks for them to ship the kit from coast to coast. Sigh, summer will be half over by then. I guess there really is no free lunch."

Your question was answered already in this forum- when Herbie mentioned the recall, he included a link to the US govt website that shows how to tell if you have an affected crank arm.

From the linked site:

http://www.cpsc.gov/cpscpub/prerel/prhtml97/97149.jpg

For future reference, there is a Recall Announcements forum here on BF.

If you go to an LBS that is a Shimano-authorized repair center, it takes about a week to get the new parts and have them installed, all free-of-charge to the bike owner.

I have the recalled cranks on one of my bikes; it will be replaced by my LBS eventually but until then I'm not riding that bike. The hangup in my case is that my LBS is a newer shop and never got authorized by Shimano. They've submitted their paperwork and now they're just waiting to get approved. If this was my only bike I'd take it somewhere else- many shops are Shimano-authorized- but one of the owners is a friend of mine and I said I'd wait until they got authorized.

Thanks

Hahahaha, i hate those things. I actually saw a pair of those mc-12's for sale in a shop once. I spotted that dog-bone profile pos in the case and couldn't help but laugh. Asked the sales person what he thought about them and he said they were decent mid-range stuff.. LOL


Left cranks are a dime a dozen, you'll need a puller but that may cost as much as the crank or more.
Your LBS will swap it quick and cheap and may even have a used one laying around.

Good luck..

problem solved
 

Problem solved. My crank wasn't part of the recall. My LBS installed a new left crank for $20. It's black so I might paint the right one which is still silver, but maybe not.

Good- I'm glad you got it resolved.

Wow, are you sure those cranks weren't part of the recall? They sure look like the ones..
What's the #, 291?

Anyhow good deal, you might ask the same shop if they have new springs for your brakes too. Shimano sent out a whole bunch of those as the gray plastic covers were cracking, making the brakes drag. They should be free.


Oh, do some cleaning will ya'?:p

Nice test drive today - crank works fine. Don't care about the color. Next up for this ride - I ordered a new set of twist shifters, so those cables will be new. Gotta get some housing. I was looking at the brake cables today and I wonder if they have little balls on each end. Gotta get a close up picture - just did my old 10-speed cables but this MTB looks like a different deal.