Out of pure curiosity, wondering what's happening to your crank set and pedals that's causing you to replace them?
Is it just the pedals causing the issue? I'm a little under 300lbs when fully decked out for work commuting with winter gear and commuter backpack. Seems like the aluminum crank seems pretty standard for a lot bike and ebikes? I upgraded my pedals to BC extra wide platform MTB pedals. I found the Radrover pedals were too small for my size 14 feet and they sometimes slip off when trail riding (especially in wetter conditions). Zero issues with slipping, solid aluminum design, and I have plenty of grip with any type of shoes I wearing at the time. Most I have to do with these pedals is apply a little touch-up paint every once in while.
About $80 on Amazon: https://www.amazon.com/Platform-Mou...r=8-2-fkmr1&keywords=bc+mtb+extra+wide+pedals
I found for around $62 on eBay: (Link Removed - No Longer Exists)
Those pedals are severely cross threaded. You started them crooked, and all those metal bits you see there are the threads torn out. When they are crooked to the face of the crank, you did it wrong and they are destroyed. You should be able to thread the pedals nearly all the way in WITHOUT a wrench and with little effort. If it takes effort and a wrench to get them started, it's crooked! I'd suggest you take it to a bicycle shop for the repair if you've done this twice already.
True...the very idea of pedals loosening against their threading seems not possible. I've got road pedals coming with toe clips, and I just unthreaded mine to be sure they weren't too tight. They weren't, and of course I had greased them. Never-Seez next time, as on the crank bolts.The most common cause of crank's pedal thread stripping is over-tightening. Pedals should be tightened very lightly as you may want to change them from time to time. It is safe to tighten them lightly as the directional thread tightens naturally with your pedaling.
The pedal axle/spindle is steel and the crank is usually aluminum alloy...much softer so it is also a good idea to put a little grease on the threads before threading them in.
Yes, they cannot be put on wrong.One side is right thread, one side is left thread, is that the problem? Pedals are made for a certain side.
Yes, crank arms are shot...Since they're aluminum, they get the damage. I'd never trust a repair, if it's even possible...replace...they're cheap enough.Somehow the threads keep stripping. I mean, they only thread in one way and I cranked them down flush. Take a look.
Those threads will never be trustworthy.I don't think I'd order an extra set of arms. Pretty unusual for you to need the fist set....