# pedal fell right off my crank arm!



## LONO100 (Jan 10, 2012)

hey all, i went on maybe my 4th or 5th ride last weekend and i was climbing a pretty long hill and right when i got to the very top my pedal just fell off. the pedal was fine, but the crank arm threads were completely blown out. i bought the bike less than a month ago, and now its sidelined in the shop. they told me they were going to talk to the owner to see if they can replace it. anyone ever have this happen to you, and if so were you able to get the shop to replace the arm?


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## TraxFactory (Sep 10, 1999)

What crank arms, what pedals? sounds like it may have been a botched install...


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## LONO100 (Jan 10, 2012)

its on a scott scale 950. the cranks are a shimano 2 piece, and the pedals were well-go m21's. how can i prove that its a botched install. they have the bike, and im pretty sure they could just deny that. 

im pretty sure i couldnt have broke it, im 177 lbs, and wasnt going super hard on it.


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## TraxFactory (Sep 10, 1999)

Well see what they say first, if its a decent shop they will make it right. Any pics?


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## eb1888 (Jan 27, 2012)

That bike needs pedals when new. Who did the install? That person is responsible.


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## perttime (Aug 26, 2005)

Pedals don't routinely fall off cranks - with destroyed threads, or otherwise.

I suppose it is possible to put out enough torque with a long pedal wrench, to strip the treads. My pedals go on the bike with fingers and a small wrench or hex key.

The one time I had a pedal fall off, it was because the pedal axle was soft. It bent and started binding.


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## TraxFactory (Sep 10, 1999)

Possibly the pedals were reversed and stripped into place. Easily done with steel spindle pedals and aluminum cranks.


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## J.B. Weld (Aug 13, 2012)

RipRoar said:


> Possibly the pedals were reversed and stripped into place. Easily done with steel spindle pedals and aluminum cranks.


I think that would be pretty difficult, and next to impossible to get them in straight that way. I think its also near impossible to strip them by over tightening, more than likely it was never tightened enough during the install. The shop should cover it.


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## burtronix (Jun 5, 2006)

J.B. Weld said:


> ....I think its also near impossible to strip them by over tightening.... The shop should cover it.


Not hard at all to strip them, but I would expect most shop employees to know better. Not only that they stripped them, but that they let the bike leave the shop without fixing it. When you strip threads it's pretty obvious. Either didn't know or didn't care. Must have been a novice. The shop better cover it.

Sent from my SCH-I535 using Tapatalk 4


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## Brockwan (Aug 6, 2013)

yeah defo sounds like they were put on too tight by the shop. dont take no BS from them, they put it together get them to fix it.


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## mack_turtle (Jan 6, 2009)

three possibilities:

1. shop did not tighten pedals enough. as the pedal worked itself loose, it wobbled around in the crank arm until it stripped the threads out. the mechanic probably threaded the pedal in with his fingers, then threaded the other pedal in with his fingers, and forgot to go back and tighten the first pedal with a wrench. this is the most likely scenario.

2. shop stripped cranks by over-tightening. you have to wail on a pedal wrench pretty darn hard to make this happen. unlikely, but possible.

3. pedals forced into the wrong side of the cranks. unlikely, the mechanic would have to be a real buffoon to do this.

regardless, the bike shop should do whatever it takes to get a new crankset on your bike asap. they should just take a crankset off another bike if they need to and slap it on your bike so you can get it back in 24 hours or less. I would have fixed that on the spot and sent you on your way.


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## shiggy (Dec 19, 1998)

J.B. Weld said:


> I think that would be pretty difficult, and next to impossible to get them in straight that way. I think its also near impossible to strip them by over tightening, more than likely it was never tightened enough during the install. The shop should cover it.


Agreed. I have never seen pedal threads stripped from overtightening.


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## ghettocop (Jul 26, 2011)

J.B. Weld said:


> I think that would be pretty difficult, and next to impossible to get them in straight that way. I think its also near impossible to strip them by over tightening, more than likely it was never tightened enough during the install. The shop should cover it.


This. The crank arm threads are ruined now because the pedal became loose and started moving around in the crank arm as you pedaled. I have never seen crank arm threads affected by "overtightening" a pedal. Hard to get off? Yes. Damage to crank arm? No. The shop should cover this if the cranks are stock. I wouldn't worry about it.


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## citiznkain (Jun 11, 2012)

mack_turtle said:


> three possibilities:
> 
> 1. shop did not tighten pedals enough. as the pedal worked itself loose, it wobbled around in the crank arm until it stripped the threads out. the mechanic probably threaded the pedal in with his fingers, then threaded the other pedal in with his fingers, and forgot to go back and tighten the first pedal with a wrench. this is the most likely scenario.


^^this. I have seen this on bikes quite a bit. Especially spin bikes (I have a part-time gig working at a local gym repairing equipment. This happens when some people bring in their own pedals and shoes and don't re-tighten the stock pedals when they switch back).

Most shops can drill out the crank and insert a threaded sleeve. then you can just put your pedal back on. costs around $13 for my LBS to do this. I've done this a couple of times to repair stripped cranks. so far the fixes are holding with no issue.


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## goodmojo (Sep 12, 2011)

i have straightline amps and there is a thread about these pedals having a tendency to work themselves out even when you tighten them hard. I did have this happen to me and it only stripped the very end of the crank threads. I put them in from the other side to fix the thread then I was able to put them on the correct way. 

I stopped pedaling when the pedal started to feel loose.


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## Surly29 (Jun 8, 2009)

mack_turtle said:


> 1. shop did not tighten pedals enough. as the pedal worked itself loose, it wobbled around in the crank arm until it stripped the threads out. the mechanic probably threaded the pedal in with his fingers, then threaded the other pedal in with his fingers, and forgot to go back and tighten the first pedal with a wrench. this is the most likely scenario.


+1 on this. I had always been under the impression that pedals tighten while riding so I never tightened mine more than finger tight (and I switch one set of pedals between two bikes all the time). One day a pedal worked its way loose, fell off the crank, and buggered up the threads pretty bad. Couldn't get the pedal back in on the trail. Now I always give the pedals a little snug with a wrench before riding.


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## mack_turtle (Jan 6, 2009)

I would give your pedal more than "a little snug." Park recommends 307 in/lbs minimum. if you have ever torqued something to 26 fl/lbs, that's a pretty hefty amount of torque. you really need to lean into the wrench to get that much torque.

Park Tool Co. » Torque Specifications and Concepts


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## Ricko (Jan 14, 2004)

RipRoar said:


> Possibly the pedals were reversed and stripped into place. Easily done with steel spindle pedals and aluminum cranks.


...and an installer with no brains:madman:


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## .WestCoastHucker. (Jan 14, 2004)

RipRoar said:


> Possibly the pedals were reversed and stripped into place. Easily done with steel spindle pedals and aluminum cranks.


considering that the threads go in opposite directions, this is almost impossible to do. you can spin the axles for the rest of your life and they will never get a beginning bite to even continue threading...


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## mack_turtle (Jan 6, 2009)

^nope, it happens more often than you might think. I have seen a lot of big box store bikes come in assembled this way, despite the big "left" and "right" stickers that come with them. people start to thread them in there and just ram the wrong pedals into the softer aluminum.


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## J.B. Weld (Aug 13, 2012)

burtronix said:


> Not hard at all to strip them, but I would expect most shop employees to know better.
> Sent from my SCH-I535 using Tapatalk 4


It has got to be pretty dang hard to strip them by over-tightening because I've never seen it, and I've worked along side some real bruisers.

I have seen plenty of threads butchered using various other methods however.


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## Mr5150 (Dec 20, 2011)

mack_turtle said:


> I would give your pedal more than "a little snug." Park recommends 307 in/lbs minimum. if you have ever torqued something to 26 fl/lbs, that's a pretty hefty amount of torque. you really need to lean into the wrench to get that much torque.
> 
> Park Tool Co. » Torque Specifications and Concepts


Wow, please don't ever do that to my bike. I finger tighten mine then hand tighten with an 8mm allen. Even then, the pedals are a little hard to take off. Never had an issue with my pedals unscrewing themselves (been riding for 21 years). Of course Park might be covering itself

My guess is the shop put the pedals on the wrong sides of the crank.


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## HitmenOnlyInc (Jul 20, 2012)

I agree, I find it hard to believe they were stripped from over-tightening. More likely scenario is like stated above, finger tight then worked themselves loose, which in turn stripped said crank arm.

I am also in agreement about how tight pedals should be. I just snug them after finger tightening and never had a pedal work itself loose. 

One other scenario is that the damaged pedal could have been cross-threaded in the correct side and with the constant pressure of the OP's first several rides, stripped the crank. Although OP may have felt the pedal slightly off center.


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## .WestCoastHucker. (Jan 14, 2004)

i'm more baffled by the fact that you didn't even notice the massive amounts of play in the pedal before it was anywhere close to even falling off. or the fact that it was almost a half inch away from where it's supposed to be without you even noticing...


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## J.B. Weld (Aug 13, 2012)

In threads gone by it has been proven time and time again that major problems can occur when pedals are under tightened. I have yet to come across any catastrophic issues due to over tightening. What on earth is the purpose of getting them just "snug"? Why not just tighten the damn things and be done with it?


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## mack_turtle (Jan 6, 2009)

Mr5150 said:


> Wow, please don't ever do that to my bike.


I am just going by the manufacturer's specifications and the decades of experience and scientific research by mechanics and geeks. Shimano recommends up to 39.75 foot pounds of torque. Crank Bros are supposed to be torqued to 25-30 Nm (22 ft/lbs). The Barnett Manual recommends about 30 ft/lbs. if you want to under-torque your pedals, that is fine.


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## Bruce in SoCal (Apr 21, 2013)

For as many threads as there are on a crank arm, you'd need an incredible amount of torque to strip the threads by over tightening it. You'd need a huge cheater bar on the wrench.

If the pedal was on the wrong side, you will have the wrong pedal on the other side, too. Plus, it will be visually obvious.

If the whole thing was lose, it is unlikely that more than the outermost one or two turns of the thread are damaged. Four rotations should hold the pedal firmly enough to ride without excessive play. Only when you are down to two or three turns will it be lose enough that peddling hard could damage the threads - and then it will only be the outtermost one or two. In that event, once the one or two are cleared, the pedal ought to thread in tightly and firmly.

Based on this, I'd go with the pedal having been cross-threaded when first installed - or with a manufacturing defect.


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## Ladmo (Jan 11, 2013)

I have had this happen before. I then found out my multi tool wasn't multi enough as it did not have an allen wrench large enough for the pedal. I now carry a loose allen wrench - an 8 I think - in addition to my multi tool in case it ever happens again. Looking at the pedals before every ride is now also a part of my pre-ride routine. Similar to the previous post, I threaded the pedal in from the other side to "fix" the arm threads, and then re-installed the pedal.


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## LONO100 (Jan 10, 2012)

im happy to report that the bike shop left me a message late yesterday that my bike was repaired and ready to pick up. im not sure what they did to it, or what was the cause, but i should find out today when i pick it up.


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## net wurker (Sep 13, 2007)

As far as "did they put th ewrong pedal on th ewrong side?", was the other side stripped? It would have to be unless soemhow it came with 2 left or 2 right pedals.


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## LONO100 (Jan 10, 2012)

when i first got it home, i checked the pedals and they were in fact on the correct arms. im going to find out this afternoon what they think happened.


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## big_papa_nuts (Mar 29, 2010)

Little late I know, but how deep was the damage? If it was just the last few threads it's likely the pedal came loose. If it was more then that chances are it was properly stripped or cross threaded. Either way the shop should take care of you, but use this as a learing experince and in the future try to pay attention to what's going on with your bike. Chances are the pedal started to feel loose before it fell off and the problem may have been avoided with a turn of your multi-tool.

And for the record, damaged crank threads are actually fairly common. I have seen every type of situation discribed in this thread.


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## LONO100 (Jan 10, 2012)

ive felt pedals come loose before, but i didnt see or feel this one coming at all. it went from spinning freely to falling off it seemed like.


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## citiznkain (Jun 11, 2012)

.WestCoastHucker. said:


> i'm more baffled by the fact that you didn't even notice the massive amounts of play in the pedal before it was anywhere close to even falling off. or the fact that it was almost a half inch away from where it's supposed to be without you even noticing...


In most cases, you don't feel any play. the pedal feels tight, but the spindle does not feel perpendicular the crank. If the spindle is not snug against the crank, the damage will start.

For me the easiest way to check is visual, and then pedal the crank backwards. for some reason I can feel this better when i pedal backwards than pedaling forwards.


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## LONO100 (Jan 10, 2012)

so i picked up my bike this evening, and what they told me was that the pedal most likely wasnt torqued down properly, and that it stripped out on the last few threads. they were able to re-tap it and it looks good as new. they didnt charge me either. good service, good people out at that shop.


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## HitmenOnlyInc (Jul 20, 2012)

LONO100 said:


> so i picked up my bike this evening, and what they told me was that the pedal most likely wasnt torqued down properly, and that it stripped out on the last few threads. they were able to re-tap it and it looks good as new. they didnt charge me either. good service, good people out at that shop.


I am glad this worked out for you!! That's the difference between a good and bad shop. These guys owned the problem, fixed it and got you on your way! Well done!


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## LONO100 (Jan 10, 2012)

thanks, im pretty happy too. im going to give them a really good yelp review for sure. they have been pleasant and helpful since i first walked in there looking for a bike. 

im still interested in how they were able to re-tap it. after it broke, i was able to slide the entire pedal through the eye of the crank. did they use some sort of sleeve?


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## J.B. Weld (Aug 13, 2012)

LONO100 said:


> im still interested in how they were able to re-tap it. after it broke, i was able to slide the entire pedal through the eye of the crank. did they use some sort of sleeve?


If the pedal would slide in as you say then they had to have used some type of helical repair kit. The crankarm is tapped out to a larger size and an insert is threaded in, the pedal then threads into this. You should be able to see this if that was done.

I'm glad that you found a good shop that is taking care of you but if they did this repair I would keep a sharp eye on it as I have had some bad luck in the past using that method. I would rather have had them replace the crankarm.


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## big_papa_nuts (Mar 29, 2010)

The Golden Wrench: Repairing a Stripped Pedal Thread

Common repair but in this case I feel like I'd rather see a new crank arm.


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