Pedal crank will not stay tight

[wbmkk]

My daughter has a mountain bike but has been having problems with her left pedal.

The pedal will not stay tight. She has tightened it a few times and it seems to work for a few weeks, but then it works itself loose again.

I'll be seeing her (and the bike no doubt too) over the weekend. However, i may as well get some background information here before I go. Somebody has suggested to me that maybe the thread is a bit worn on the actual crank.

If this is the case, is the only option then to buy a new crank ?

Do pedals come already attached, or can the pedal be removed from the crank and fitted on to a new one.

Would she (or maybe Me) have to buy a pair of cranks, with one having chain rings too.

thank you for any advice !

 

[helston90]

Sounds like the square has rounded slightly on the arm.

The arm is made from softer material than the square taper of the bottom bracket so that the arm will wear first- the last time i replaced one it cost £7 from halfords.

Stick a new one on and swap the pedal over and you'll be fine. Once it has wriggled loose once it's too late and it has lost its shape.

 

[Citius]

What bike, what crank, what pedal ?

 

[helston90]

^D'oh didn't read your description properly- sorry- I thought the crank itself kept coming loose from the bike.

 

[wbmkk]

Sounds like the square has rounded slightly on the arm.

The arm is made from softer material than the square taper of the bottom bracket so that the arm will wear first- the last time i replaced one it cost £7 from halfords.

Stick a new one on and swap the pedal over and you'll be fine. Once it has wriggled loose once it's too late and it has lost its shape.

Thank you for that

I think you are probably spot on .. there's a Halfords near her and maybe even a local bike shop, so I can take the old crank and get a new one.

Regards !

 

[Yellow Saddle]

If it is an expensive aluminium crank it can be repaired using a Cyclus crank repair tool and threaded insert. If it is a cheap crank, buy a new one. The tool and it's operator is expensive by cheap bike standards.

 

[gbb]

My daughter has a mountain bike but has been having problems with her left pedal.

The pedal will not stay tight. She has tightened it a few times and it seems to work for a few weeks, but then it works itself loose again.

I'll be seeing her (and the bike no doubt too) over the weekend. However, i may as well get some background information here before I go. Somebody has suggested to me that maybe the thread is a bit worn on the actual crank.

If this is the case, is the only option then to buy a new crank ?

Do pedals come already attached, or can the pedal be removed from the crank and fitted on to a new one.

Would she (or maybe Me) have to buy a pair of cranks, with one having chain rings too.

thank you for any advice !

You can sometimes buy just a non drive side crank. BUT, first you have to find one, a LBS may have one, they'd be your best bet because they'll reproduce the size etc of yours.
You can usually get one from ebay but you'll need to be sure about the pedal thread size...and more importantly, what position the square is...at 90 degrees to the crank or 45 degrees. Get it wrong, fit the crank and it wont be opposite to your other crank, it'll be at an odd angle.
Pedals don't come with them.
If you fit the old pedal, make absolutely sure the threads on the pedals are spotless. Inspect very carefully to make sure there are no metal bits in the old threads, if there are, when you wind the old pedals into the new crank, you'll immediately damage the new threads, possibly ruin them .