Replacing crank and bearing on cheap Murray Murray Cross Canyon. The pedal crank is all one piece with regular bearings. What would I use to upgrade this? Is there a bottom bracket that i can use. The outside diameter of the bearing is 43mm.
I'm converting this to an e=bike so it doesn't need to be high end, just better than the junk it came with.
There are many levels of &quot;upgrade&quot;. To be &quot;better than the junk it came with&quot; there are at least two options with many shades of quality level.
1. One piece crank upgrade
There are different qualities of one piece cranks / bearings / cones / races. Murry, Huffy etc. come with the lowest quality.
Back when Schwinn bicycles were made in the U.S. Schwinn bicycles with one piece cranks came with good quality crank parts. &quot;New Old Stock&quot; (NOS) Schwinn bearings, races, cones, and crank would be an upgrade to the parts you removed and they will fit your bike. Other sources for quality one piece crank parts would be made by Tioga, Tange or some other name brand maker.
As with anything there are advantages and disadvantages to a one piece crank. They are easy to maintain, they are very strong - they are also very heavy. This would be the least expensive upgrade.
Sheldon Brown has a nice over view of one piece crank types and interchangeability.
2. Three piece crank
The video Argenti has posted demonstrates how to replace a one piece crank with a very nice three piece crank and sealed bearing setup. There are a variety of solutions offered by different companies to accomplish this with a wide range of quality and prices. They will reduce weight but I would argue that a good three piece crank is no stronger than a good forged chromoly one piece crank.
As you convert your Murry into an e-bike remember that the quality of crank parts you removed are relatively equal to the quality of parts on the rest of the bike - including the frame.
Murry designed the bike to be affordable and to do that they compromised on the durability of the entire bike, not just the crank parts.
Adding an electric motor to a bicycle introduces forces the bicycle was not designed for. Using a low quality bicycle as the basis for an e-bike is especially problematic and could be dangerous.