Choosing chainring size

[adamjs16@gmail.com]

I currently have the stock 46T chainring on my BBSHD. I want to replace it with a Lekkie Bling ring, as the chain keeps falling off the stock ring.

The bike is a Montague Paratrooper Pro with a 11-34T rear cassette and 26 inch wheels.

I'm unsure whether to get a 46T or a different size. It seems like I have plenty of Torque and I could use a larger chain ring, but I'm unsure if the motor would run more efficiently with a smaller chain ring. My current top speed is about 30MPH.

 

[MoneyPit]

The motor is going to be a LOT happier spinning faster. That usually means you want a smaller chainring, but not always.

I typically use a 42T Lekkie ring, partly because of its max available offset (the Luna Eclipse has the most offset available but usually its too much for me). But I am also a pedaler, not a throttler, so I want good cadence suited to my terrain, which is flat for the following example:

Thats a 52T front Lekkie ring. Why did I go that big on something like a cargo bike (thats a LvH Bullitt)? Chain alignment. The 52T has the same offset as the 42T, but with the 42T I needed to be on the 11T to keep from clown pedaling, and if I did that the chain was skewed outboard to the rear cluster, which is bad. Chain alignment on that bike is perfect about 3 cogs in. But then I am spinning like a hamster on a wheel. The solution (after I first tried a 46T and not being quite satisfied running one cog down) was to go full size and use the 52T. That cog is oversized, no two ways about it. But given how I want to keep a cadence of around 75-80 rpms, and the chain goes straight back in the cog that lets me do that, the too-big chainring was perfect.

You may have to play around some with your bike to figure out whats best for you. But just picking the ring size is only part of the issue.

I wrote up some of what I did on earlier bikes here:

https://talesontwowheels.com/2020/05/03/mongoose-bbshd-update-musical-chainrings/