Loose pedal crank/drive section?

Chris007

I've recently noticed that pedal cranks and drive section (unsure of the techical name for this part but i've attatched a picture) is loose and will wiggle from side to side. I can still cycle with it but it's worrying. As a novice cyclist I find it difficult to explain the problem but can anyone shed some light on the situation as of how to repair it?

Any advice is much appreciated!

kenmc

Should be just a case of tighten the bolt - i'd suspect it's a square taper BB and the bolt is just loose.

Ryaner

Depending on the brand, it is as Ken says, just a case of tightening the bolt. My FSA one comes loose every now and then. I loosen the crank (pedal bar), push things together, tighten the internal bolt and then retighten everything else.

rob1891

If only one side is loose, i.e. one crank arm and not the other, then you need to tighten the bolt at the centre of the loose arm. If on the other hand, both crank arms are loose and move with eachother, your bottom bracket is totally worn out. Expect to pay maybe 50 euro to have it fixed in a shop (20 for the part, 30 for labour ... guesstimates).

rottenhat

kenmc wrote: »

Should be just a case of tighten the bolt - i'd suspect it's a square taper BB and the bolt is just loose.

However...if the OP has been riding with it loose for a while, the bb taper will have messed up the hole in the crankarm irreparably and the OP will need to replace the cranks. This can happen surprisingly quickly.

seamus

rottenhat wrote: »

However...if the OP has been riding with it loose for a while, the bb taper will have messed up the hole in the crankarm irreparably and the OP will need to replace the cranks. This can happen surprisingly quickly.

Aye, if you've done any kind of forceful riding on a loose crank arm, then it's irreparably boned, I'm afraid. Best way to check is to remove the bolt and the crank arm and inspect the hole. It should be a smooth, uniform square hole (with slightly rounded corners). If anything looks deformed or any of the edges aren't dead straight, the arm is screwed.
You'll also find out pretty quickly because the arm will feel weird or will continue to come loose even when you've tightened the bolt.

I have entirely the opposite problem. I sheared the threads off a crank (despite putting the extractor in correctly, long story) and spent about an hour battering the arm with a claw hammer and gently riding around on it and it still refused to come off. Going to try the boiling water trick tonight.

fixyfiend

If both crank arms moving as rob1891 suggests and the bike is fairly new then it should be easily repaired. Your bike has a "cup and cone" bottom bracket which is adjustable and has probably loosened off. This can happen if it was not assembled correctly. As long as there is no wear on the bearings it can be regreased and tightened.

Húrin

seamus wrote: »

I have entirely the opposite problem. I sheared the threads off a crank (despite putting the extractor in correctly, long story) and spent about an hour battering the arm with a claw hammer and gently riding around on it and it still refused to come off. Going to try the boiling water trick tonight.

What is the boiling water trick? Is the idea to loosen the crank arm by applying heat to make is expand? My friend's bike has the same problem.

seamus

Húrin wrote: »

What is the boiling water trick? Is the idea to loosen the crank arm by applying heat to make is expand? My friend's bike has the same problem.

Yeah, it's the same principle, but you're not putting a naked flame to it. Sounds like a long shot to me, but I'll let you know how I get on.

seamus

...yeah that didn't work. Though either did cycling around on it for 20 minutes. It's stuck pretty fast.

Chris007

If on the other hand, both crank arms are loose and move with eachother, your bottom bracket is totally worn out.

From that description it sounds like the bottom bracket is worn out. Both the crank arms move with each other as well as the chainsets part. However the movement isn't that much, its only a 'wiggle' for want of a better word.
Any more suggestions? Thanks for all previous advice

seamus

If they both move together, i.e. the whole thing has "play" in it, which is what it sounds like, then your bottom bracket is worn out and needs replacing.

If you're happy to do it yourself, you'll need a medium-large adjustable spanner, a good quality crank extractor and a bottom bracket tool (as well as a new bottom bracket).

Tbh, there are a couple of things you could do wrong which would turn your bike into scrap metal, so if you're not very comfortable doing bike maintenance, I'd hand it into a professional.

kenmc

seamus wrote: »

...yeah that didn't work. Though either did cycling around on it for 20 minutes. It's stuck pretty fast.

Can you take the other one off? If so I'd suggest doing so, rotate it 180 degrees so both pedals are facing the same way (i.e. both are hanging down when the bike is standing upright) and reattach the bolt on this pedal.
You should now be able to get a car jack between the pedals (put it as close to the axle as possible) and jack the stubborn one off.
And next time use grease when putting on the crank

seamus

kenmc wrote: »

And next time use grease when putting on the crank

No, the lesson here is to not thread them. I've never actually taken them off since I got the bike. Which probably explains why it won't come off.

I like that jack trick. At this point, I'm not too concerned if I screw up the crank...always a good excuse for a new one

kenmc

seamus wrote: »

No, the lesson here is to not thread them. I've never actually taken them off since I got the bike. Which probably explains why it won't come off.

I like that jack trick. At this point, I'm not too concerned if I screw up the crank...always a good excuse for a new one

Sounds like it's already screwed - best to have it off quick sharp!

trad

Seamus, you need a bearing puller, pour plenty of Wd40 or simular onto the crank area, attach the bearing puller, wind it up and be careful at they can release very suddenly. If it doesn't move, hit the end centre shaft in the bearing puller a sharp rap with a decent hammer, it should shift.

JMJR

seamus wrote: »

I have entirely the opposite problem. I sheared the threads off a crank (despite putting the extractor in correctly, long story) and spent about an hour battering the arm with a claw hammer and gently riding around on it and it still refused to come off. Going to try the boiling water trick tonight.

You could try on of these
http://www.toolking.com/otc(divisionofspxcorp.)_otc1042.aspx
Goughs of Little Mary St are selling a two arm one for I think 10 euro at the moment. This type will pull off the crank which has the chain ring arms. For the (other) single crank you can get away with this type from a motor factors
http://www.choiceful.com/choiceful-id-1723-Ball-Joint-Splitter.html
southsite motor factors in kylemore stock a draper branded one
John

seamus

Yeah, so after getting a gear puller from Gough's (a fiver, nice one JMJR), doing irreparable damage to the crank arm and taking a not insignificant amount of skin off my knuckles, I'm calling defeat on this one.

Can anyone recommend a good LBS in south dublin who'd be able to sort this?

New crank time though....

seamus

Never mind. I just realised that a hacksaw will do the job. This should be fun