[jaybert]

This is on my son's bike, a 24" transition ripcord. It has a 140mm heir crank set (HEIR Crank) from prevelo and chromag radar youth pedals (Radar). We were riding at the bike park this weekend and the drive side pedal fell off as he was about to hit a jump and he somehow saved himself (looked like superman with his belly on his seat and legs parallel to the ground).

I'd normally just say that the pedal wasn't tightened or something and it loosened itself, but we had the same thing happen to the non-drive side pedal a while back which i threaded back in, but I must have cross threaded it then where the pedal was no longer parallel to the ground. Anyways, I removed the pedal, and the threads were completely stripped. I purchased a new crankset (exact same one) and had a local shop install it since I was bringing my bike in for service anyways. This was the second day at the park after the new crankset was installed.

Anyways, the fact it happened twice makes me wonder if there is something going on funky between the crankset brand, and the pedals (i re-used the same set of pedals, as there was no damage to the threads on it at all, though I did have to take a pick to it to scrape out the aluminum threads from the 1st time around). The pedal on both sides looks/feels super tight/secure.

The threads this second time around on the crank seem fine / the shop ran a tap through to clear them out and the pedal is back on, but thinking if there is something I'm doing wrong or incompatible here I should be considering. Would some blue loctite on the threads help keep it nice and tight if its just happens to be loosening itself? Or is it just coincidence that this happened again? The shop just didnt tighten the pedals enough after installing the crank.

 

[jochribs]

Generally the threads get so buggered from the loose spindle getting to wobble in the cranks threads that the ability to torque them properly after that, and have them hold is compromised.

One thing to look at is the pedals themselves. Are the bearings allowing the pedals to rotate normally? Have they seized at all? If the pedals seize, the pedaling motion will unthread the pedal spindle from the crank arm. Quickly.

Looking back at your post, I'm doubting the pedals seized, and am wondering if the pedals just weren't torqued properly. The motion of repeated pedaling (let alone jumping) will begin to loosen a pedal that hasn't been properly tightened. If it's not caught quickly, it will wreck the cranks.

****Edit: Missed a few things from your post.

-Tapping and cleaning up the threads on a crank that a pedal stripped out of is not something I would have any faith in. Might work for a while, but the threads have been compromised, and the tapping only cleaned up what was left so to speak.

-Loctite is not necessary for pedals installation crank arms. Just some grease and proper torque.

I'm still leaning towards the pedals not being installed/torqued correctly.

 

[jochribs]

Proper torque is in the range of 350 in/lbs by the way. I've never used a torque wrench on a set of pedals in my life and time as a shop mechanic, but pedals require a good amount of force to be sufficiently tight.

 

[jaybert]

Generally the threads get so buggered from the loose spindle getting to wobble in the cranks threads that the ability to torque them properly after that, and have them hold is compromised.

One thing to look at is the pedals themselves. Are the bearings allowing the pedals to rotate normally? Have they seized at all? If the pedals seize, the pedaling motion will unthread the pedal spindle from the crank arm. Quickly.

Looking back at your post, I'm doubting the pedals seized, and am wondering if the pedals just weren't torqued properly. The motion of repeated pedaling (let alone jumping) will begin to loosen a pedal that hasn't been properly tightened. If it's not caught quickly, it will wreck the cranks.

****Edit: Missed a few things from your post.

-Tapping and cleaning up the threads on a crank that a pedal stripped out of is not something I would have any faith in. Might work for a while, but the threads have been compromised, and the tapping only cleaned up what was left so to speak.

-Loctite is not necessary for pedals installation crank arms. Just some grease and proper torque.

I'm still leaning towards the pedals not being installed/torqued correctly.

Hmm that’s interesting thought on the bearings being seized. Now you mention it, they def do not spin freely like my one up aluminum pedals, though I don’t recall them ever spinning freely even new. I just tried it out and even with some force, the pedals only do 1 full rotation when I try and spin them. I vaguely recall noticing them when I got them and figured that’s just how the pedals were / less chance of slipping or pedal strikes since they were meant for kids?

 

[jochribs]

Hmm that’s interesting thought on the bearings being seized. Now you mention it, they def do not spin freely like my one up aluminum pedals, though I don’t recall them ever spinning freely even new. I just tried it out and even with some force, the pedals only do 1 full rotation when I try and spin them. I vaguely recall noticing them when I got them and figured that’s just how the pedals were / less chance of slipping or pedal strikes since they were meant for kids?

I clicked on the link for the pedals and I feel it's a pretty low probability that the bearing seized on those pedals. You are probably feeing a good amount of seal drag from the bearings and any seal that's on the spindle to cage interface.

Since they don't have flats for a pedal wrench on the spindle, they have to be broached for either a 6 or 8mm allen. You need to put a good amount of force on the allen wrench (especially if it's a 6mm) to tighten them in properly/enough. The 6mm will bend in your hand a bit, for reference. 8mm is a bit stiffer and not as much. But don't be afraid to put some weight into them.

 

[jaybert]

I clicked on the link for the pedals and I feel it's a pretty low probability that the bearing seized on those pedals. You are probably feeing a good amount of seal drag from the bearings and any seal that's on the spindle to cage interface.

Since they don't have flats for a pedal wrench on the spindle, they have to be broached for either a 6 or 8mm allen. You need to put a good amount of force on the allen wrench (especially if it's a 6mm) to tighten them in properly/enough. The 6mm will bend in your hand a bit, for reference. 8mm is a bit stiffer and not as much. But don't be afraid to put some weight into them.

Thanks, very helpful. The pedals (the second time around on the new cranks) was put on by the shop but I wouldn’t be surprised if I didn’t tighten it enough the first time around. I know when I brought it to the shop at the bike park after the pedal fell off over the weekend they noticed the other pedal was a little loose (like 1/2 a turn) and they really cranked both of them tight for me.

 

[jochribs]

Thanks, very helpful. The pedals (the second time around on the new cranks) was put on by the shop but I wouldn’t be surprised if I didn’t tighten it enough the first time around. I know when I brought it to the shop at the bike park after the pedal fell off over the weekend they noticed the other pedal was a little loose (like 1/2 a turn) and they really cranked both of them tight for me.

No problem. This is what I've been somewhat suspecting...installer error. The concern you have now is if the new cranks were damaged from the pedals not being tightened enough and ridden. Keep a close eye on them. If they start feeling loose or wobbling at all, it's new crank time, again. And in that case, have the shop foot the bill, come on here and we'll walk you through removal and install. Easy stuff, and a good project to get your feet wet on bike repair/maintenance.

Is it different shops doing the install and the subsequent tightening?

 

[jaybert]

No problem. This is what I've been somewhat suspecting...installer error. The concern you have now is if the new cranks were damaged from the pedals not being tightened enough and ridden. Keep a close eye on them. If they start feeling loose or wobbling at all, it's new crank time, again. And in that case, have the shop foot the bill, come on here and we'll walk you through removal and install. Easy stuff, and a good project to get your feet wet on bike repair/maintenance.

Is it different shops doing the install and the subsequent tightening?

Yea different shops. The shop that replaced the crank set (and installed the pedals) is a local'ish one where I was bringing my bike for my last free service so I brought my son's bike at the same time to get the crank set replaced since I was being lazy / in a hurry to get the bike fixed before going to the bike park the next week. The second one was at the bike park. The mechanic there looked at the threads before running the tap through/reinstalling and said it looked fine. I also looked and other than a bit of the thread being messed up at the very edge (I assume where it eventually snapped/fell off after it kept unthreading) it looked fine, but a bit hard to know for sure without comparing it to a "good one". I'll def. keep an eye out on it before every ride, and if I need to replace the crank again, I may just do it myself (put the original crank set on with the help of youtube videos a couple years ago) or will bring it to a different shop in the area I trust (this free serivice may really end up costing me!).

 

[speedygz]

You shouldn't need Loctite on pedal spindles, but, because they've come loose, I'd be washing the threads with a solvent, and adding a bit of thread locker. As they've more than likely fretted in the threads, and lost the correct tolerance. They get a hard time, they're being loaded in a direction that threads aren't really meant for, and they're only threading into soft aluminium. You're not going to damage anything with a couple of drops of Loctite, pedals coming loose again, more trashed parts.

 

[wschruba]

6mm hex key broaches require excellent quality keys (Bondhus, Wera, are two brands that are reasonably priced) to tighten to an acceptable amount. Most pedals that have 6mm broaches also have flats, but not all of them.

Pedal thread taps need to be used carefully. Some of them are standard taps that simply taper to the final 9/16 diameter...but some, like the Hozan variety, taper from the front to the back, effectively creating oversized threads. Without knowing that, someone who is otherwise competent could cause some damage to cranks. That would be compounded by the fact that it is typical to pass a tap through a hole completely if that is possible.

Finally, if you were inclined, there are pedal thread repair kits that better shops will stock. They require quite a bit of care to install without fixturing machinery, since you can wind up with a pedal that is wobbly if the reamed hole isn't perpendicular to the crank face. This is typically not a repair that is performed except to exceptionally expensive/rare crank arms, since it is a process-and-a-half.

 

[jochribs]

OP, if you need loctite to hold pedals in to NEW cranks that were stripped due to poor pedal installation, or have a shop drill out your crank arm and install a helicoil to hold pedals into NEW cranks due to a shops poor pedal installation, it is time for new cranks.

Those fixes are bodges that the mechanic/shop/manager can do with them on their own kids bike if they so choose to after the fact. It's not your problem. If the cranks don't hold pedals properly anymore, it's time for new cranks. And not on your dime.

 

[jaybert]

OP, if you need loctite to hold pedals in to NEW cranks that were stripped due to poor pedal installation, or have a shop drill out your crank arm and install a helicoil to hold pedals into NEW cranks due to a shops poor pedal installation, it is time for new cranks.

Those fixes are bodges that the mechanic/shop/manager can do with them on their own kids bike if they so choose to after the fact. It's not your problem. If the cranks don't hold pedals properly anymore, it's time for new cranks. And not on your dime.

Thanks. They seem to hold fine (rode rest of day after it was cranked down) and there doesn’t seem to be any wobble at all. Just wasn’t sure if it was worth it to put some loctite to lower the risk of it unthreading again in case the issue just isnt that it wasnt tightened properly by the shop. I def wouldn’t be looking for the loctite to hold the pedals in because the threads got stripped and it wouldn’t hold otherwise.

 

[jochribs]

Thanks. They seem to hold fine (rode rest of day after it was cranked down) and there doesn’t seem to be any wobble at all. Just wasn’t sure if it was worth it to put some loctite to lower the risk of it unthreading again in case the issue just isnt that it wasnt tightened properly by the shop. I def wouldn’t be looking for the loctite to hold the pedals in because the threads got stripped and it wouldn’t hold otherwise.

Totally hear you. Just don't want you feeling like a repair of these cranks if they're damaged enough to require either suggested approach is on you to take care of in this case.

 

[jaybert]

6mm hex key broaches require excellent quality keys (Bondhus, Wera, are two brands that are reasonably priced) to tighten to an acceptable amount. Most pedals that have 6mm broaches also have flats, but not all of them.

Pedal thread taps need to be used carefully. Some of them are standard taps that simply taper to the final 9/16 diameter...but some, like the Hozan variety, taper from the front to the back, effectively creating oversized threads. Without knowing that, someone who is otherwise competent could cause some damage to cranks. That would be compounded by the fact that it is typical to pass a tap through a hole completely if that is possible.

Finally, if you were inclined, there are pedal thread repair kits that better shops will stock. They require quite a bit of care to install without fixturing machinery, since you can wind up with a pedal that is wobbly if the reamed hole isn't perpendicular to the crank face. This is typically not a repair that is performed except to exceptionally expensive/rare crank arms, since it is a process-and-a-half.

Thanks for the advice. I believe the shop used a park tools pedal tap / generally I've found this shop to be knowledgable on the few times we've needed quick repairs while riding, but given they are a shop at a bike park, they do focus on getting bikes in and out quickly.

Do you have any views on the Park Tools p-handle hex wrench for pedals? my son's pedals are 6mm, and mine are 8mm, so I was thinking of just buying 1 of each size and keeping it in the tool box. This was what the shop used to tighten the pedals and seemed super convienent given the long shaft to be able to tighten through the bike frame vs. trying to work around the frame with a shorter allen key, though I just looked into them and it seems the long end is a ball end, which I'm not sure if that is ideal or not for tightening pedals.

 

[wschruba]

The Park hex keys are fine; they're made by Bondhus, so are good quality.

You can use the ball-end to run the fasteners in, but you wouldn't use it to tighten anything.

 

[EatsDirt]

You mentioned park so this might be relative.

I had a random issue with pedals loosening (6C cranks/xt pedals) after multiple chainless runs. Installation definitely not being the issue as I have always installed pedals "automotive tight" and they had been on the bike for over a year. Both pedals came loose at the same time. It's also happened to a lesser extent riding a lot of park, not necessarily becoming loose per se... but they break free with much less force then they were installed/last checked.

My theory is it's due to vigorous pumping (that's what she said) and slightly backpedaling while doing so... coupled with near zero normal/forward crank rotation.

My .02

 

[jaybert]

You mentioned park so this might be relative.

I had a random issue with pedals loosening (6C cranks/xt pedals) after multiple chainless runs. Installation definitely not being the issue as I have always installed pedals "automotive tight" and they had been on the bike for over a year. Both pedals came loose at the same time. It's also happened to a lesser extent riding a lot of park, not necessarily becoming loose per se... but they break free with much less force then they were installed/last checked.

My theory is it's due to vigorous pumping (that's what she said) and slightly backpedaling while doing so... coupled with near zero normal/forward crank rotation.

My .02

Yea its possible, we pretty much only ride park and lots of flow trails/pumping/jumping involved. Whats the fix? Just be sure to check them periodically and re-tighten I'm guessing?

 

[EatsDirt]

Yep, I just occasionally check after park days. If it was happening frequently I'd no doubt be using blue loctite.

 

[Rodmunch]

My experience with pedals is:

1. I haven't ever used a torque wrench, just an Allen wrench, my calibrated hands, my body weight and plenty of grease.
2. My pedals will always come loose after that first ride. So I tighten them again.
3. Then I tighten them again after every ride until they stop coming loose.
4. Then I check them about every few rides just in case.

I find they are the one (two?) component that will always come loose somehow. They take a beating so I'm not surprised.

 

[jochribs]

I have literally never had pedals come loose. Ever. They literally come out with a snap. I'm not sure many here are tightening their pedals enough.