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.

 

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?

 

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.

 

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.

 

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.

 

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.

 

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.

 

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.

 

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?

 

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

 

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.

 

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.

 

You should not have to torque the crap out of pedals for them to stay put. any normal hex wrench is plenty long enough to give you all the leverage you need.

The reason for them being threaded in oposite directions on each side is to that the pedals self tighten if there is any movement.

The reason for the massive pedal wrenches is to get them OFF.

 

You should not have to torque the crap out of pedals for them to stay put. any normal hex wrench is plenty long enough to give you all the leverage you need.

Torquing "the crap out of" is not the same as torquing properly. They still need to be tightened sufficiently.

The reason for them being threaded in oposite directions on each side is to that the pedals self tighten if there is any movement.


The reason for the massive pedal wrenches is to get them OFF

What you're referring to here is 'precession' where the bearings rotation lends to a tightening influence during pedaling, save for the situation where your bearings seize...then they're coming out as if a pedal wrench was on them. However, precession is not a cure for under-tightening. Hence the situations shared above, and fubared crank arms.

Put them in tight enough and they don't loosen. At all.

I would argue as well that the reason for pedal wrenches size is not to just get them "OFF" (as you say), but to also aid in applying the leverage to put them in easily.

Could a hamfisted moron mechanic do damage with one? 'Spose it could happen. Haven't seen it yet, but I have seen morons strip their cranks with loose pedals they didn't install correctly 😁. A good mechanic knows how tight is right.

 

I may missed interpreted some of the above replies but I think your problem is the pedals.
1st pedals loosen if the bearing are not spinning smooth enough.
2nd if you can thread the pedal in by hand and snug it, not crank it tight, with a pedal wrench or allen
Your threads are fine. If it will not thread, make sure left and right are correct, or if the pedal will not snug,
ie keeps spinning, then your threads are toast.
Get new pedals that spin freely