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Pedal Thread on bike looks like its broke off

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Pedal Thread on bike looks like its broke off

Old 12-29-20, 11:54 AM
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Pedal Thread on bike looks like its broke off

Recently I bought a bike for my little boy a cube rookie pro 240 hybrid I put the pedals on with no problem but while he was out riding the bike the pedal fell off when I checked the pedal arm the tread on the inside of the arm has broken off but the tread on the pedal is fine what could cause this anyone help??
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Old 12-29-20, 12:07 PM
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I think you mean thread, not tread. If so. it sounds like the the thread in the crank arm is stripped. This could have been caused by over torqueing or miss-aligning the pedal and as the pedal thread is steel and the crank is likely aluminium the crank thread will strip before the pedal thread.

The other thing is if you installed the pedals on the wrong side as the RH pedal has RH thread and the LH pedal has LH thread. Doing this will definitely damage the threads and if so it is likely the other side is damaged too.

Fixing it by yourself is dependant on you mechanical skills. If you can't do it yourself you will need to go to a bike shop. The fix will either be 1) re-tapping the threads IF there is enough material left, or 2) replacing the crank arms.
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Old 12-29-20, 12:15 PM
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Hi thanks for your reply the bike was from Germany and it usually says on pedal left or right pedal but it didn't say so I put them on with no resistance I was able to use my fingers till I had to use a spanner to tighten it there is no damage to the pedal but the pedal arm has half of the thread missing the bike is only 4 days old how would I know if the pedals are on the wrong side if it doesn't say on the pedal??
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Old 12-29-20, 12:22 PM
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There's this thing called "punctuation."
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Old 12-29-20, 12:22 PM
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Hi I have just found where it says left and right it was on the end of the pedal by the thread they were on the wright side so I never put them on wrong few but its still broken off the thread on the pedal arm and I put it on with my fingers till I needed I spanner to tighten it up what could of cause this to happen
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Old 12-29-20, 12:27 PM
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Originally Posted by Tom12345
... I put it on with my fingers till I needed I spanner to tighten it up what could of cause this to happen
Could you have over-tightened it? Even with aluminum cranks, it seems it would take a lot of muscle to strip the threads and most people would stop by then, but who knows, you might be a lot stronger that I realize.
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Old 12-29-20, 12:32 PM
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No I don't think so I use my fingers till a had to use a spanner. So I don't think I over tighten it, its a ebike could that have anything to do with it??
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Old 12-29-20, 12:40 PM
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Is what you are calling the "pedal arm" the crank arm shown (without attached pedals) in this picture:

https://cube-bikes.ca/2021/acid-240-...00-kids-ebike/

If the threads are stripped from the crank arm, they would have to replace the crank arm (or whole crank) which, on an E-bike, might be an expensive proposition.

Since the axle of the pedal is steel, and the threads on the crank are are aluminum, my guess is that it is the crank arm that needs to be replaced.

However, if the thread is stripped from the pedal axle, then a new set of pedals will fix the problem.
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Old 12-29-20, 12:52 PM
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Yes it is the crank arm when I got the bike it said make sure the pedals are put on the wright sides or you loose your warranty. I have put them on the wright way and I haven't over tighten them so could that be a manufacturers problem the bike is only 4 days??
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Old 12-29-20, 12:56 PM
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You have nothing to lose by trying.
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Old 12-29-20, 01:05 PM
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Definitely talk to the manufacturer or whoever you bought it through and see if they will replace it under warranty or at least give you a break on the price of a replacement part as you bought the bike new.
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Old 12-29-20, 01:25 PM
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NIce bike and at 1,754.00,someone can easily put on a new pedal arm if you bring more money. I always found it hard to see how people break off pedals at their axles, but if the threads inside the arm are still good, new pedals will solve it. I take it you didn't buy from a shop if they made you assemble the pedals?

https://www.cube.eu/en/2021/e-bikes/...rookie-hybrid/
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Old 12-29-20, 01:28 PM
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A 24" wheel kids eMTB. Why?
Regardless, yeah ask for it to be replaced. Perhaps call them instead of emailing though...
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Old 12-30-20, 10:00 AM
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Manufacturing defect ?

P.S. Fixed thread title.
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Old 12-30-20, 09:34 PM
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Originally Posted by Tom12345
Yes it is the crank arm when I got the bike it said make sure the pedals are put on the wright sides or you loose your warranty. I have put them on the wright way and I haven't over tighten them so could that be a manufacturers problem the bike is only 4 days??
Was the bike at a local bike shop before you bought it? If so perhaps someone put pedals on to try it out and stripped the threads in the arm?
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Old 01-02-21, 02:48 PM
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Which way did you turn the pedal to tighten it? Clockwise or counterclockwise?
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Old 01-02-21, 07:18 PM
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Originally Posted by Tom12345
Yes it is the crank arm when I got the bike it said make sure the pedals are put on the wright sides or you loose your warranty. I have put them on the wright way and I haven't over tighten them so could that be a manufacturers problem the bike is only 4 days??
The 'right' way. You may have put them on the correct side but who knows if you put them on 'correctly'.
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Old 01-04-21, 06:15 PM
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Originally Posted by mstateglfr
A 24" wheel kids eMTB. Why?
Regardless, yeah ask for it to be replaced. Perhaps call them instead of emailing though...
knew this was going to come up...

ours is not to question why, ours is to...something something and i forget the rest.
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Old 01-05-21, 08:06 AM
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Originally Posted by mstateglfr
a 24" wheel kids emtb. Why?
omfg ikr?
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Old 01-05-21, 08:11 AM
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THis is typically, but probably not always, caused by not properly tightening the pedals. Many a bike has been completely assembled but the assembler forgot to tighten both pedals with the wrench. THe obvious sign is usually the depth at which the threads are damaged - if the pedal threads are fully engaged into the crankarm threads then the missing threads should be approximately the same depth as the threads on the pedal spindle.

If a new arm is not readily available, a skilled mechanic can drill out the damaged threads and install a 'Helicoil', which is generally considered to be stronger than the original threads.
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