Chains and Chain Rings

[Leveraction35]

I installed a Bafang 1000W kit on my fat tire bike. The kit came with a 46T chain ring. I would like a little bit more torque for the terrain that I bike so How much difference would I see if I buy a 40T?

As far as chains, is there truly a difference from an e-bike chain and a regular chain? If so, can you recommend a good chain for my seven speed set up? I very rarely shift the bike if that matters.

 

[steve_sordy]

The move from a 46T chainring to a 40T will increase your torque by 13% and drop your spin out speed by the same amount.

A typical 7-speed cassette is 12-32 and has an average 17.7% change between gears. Therefore, one shift on your gears will be more than the effect of changing your front ring.

Unless of course you are already riding on the big ring on the cassette!

The only e-bike chain that I am aware of is the Sram 9-speed set up, but I don't believe that the chain itself is any stronger than a regular 9-speed chain. If you want strength, maybe stick with the 7-speed; they are certainly chunkier.

What the hell are you carrying up that hill that needs all that torque?

 

[Leveraction35]

I do currently ride on the big ring of the cassette only. My bike build was focused around the idea of using it to access hunting locations without sweating on the way in. So 80% of my usage is throttle only. My bike is definitely capable of tackling the hills in my area with some peddling to supplement, but then I would be back to the issue of potentially sweating during the ride in, which would result in me getting cold quickly once I’m stationary

 

[Kootbiker]

If you switch to a 40 tooth make sure it’s dished the same as your 46 tooth. If not the chainline will be excessive when peddling in the biggest cog on the rear cassette. I have a Bafang setup with the 42 Lekkie and recently bought a 38 Gustavo chainring and it doesn’t have enough dish. The chainline is so bad now the chain pulls itself off the chainring when you roll the bike backwards. I put the 42 tooth Lekkie back on.

 

[steve_sordy]

@Leveraction35 Ah, not sweating in a cold climate. I get it.

 

[Leveraction35]

The move from a 46T chainring to a 40T will increase your torque by 13% and drop your spin out speed by the same amount.

A typical 7-speed cassette is 12-32 and has an average 17.7% change between gears. Therefore, one shift on your gears will be more than the effect of changing your front ring.

based on your math, it sounds like a 36T might work best, then I could ride the middle gear on the cassette a majority of the time, biggest gear for the real grunt, and still half decent cruise speed on the small gear, sound about right??

 

[Leveraction35]

As far as chains, should I focus on link count or listed speed (8 speed)

 

[steve_sordy]

based on your math, it sounds like a 36T might work best, then I could ride the middle gear on the cassette a majority of the time, biggest gear for the real grunt, and still half decent cruise speed on the small gear, sound about right??

I will assume that your 7-speed cassette is a typical 12-32 (12, 14, 17, 20, 23, 27, 32; there may be a tooth difference either way on some cassettes).
You have a 46T chainring, and were considering a 40T and are now looking at a 36T?
If you currently only ride on the 46T, moving to a 36T will feel a lot different.

Currently: You have a 46T driving a 32T, which is a 46/32 = 1.4375 ratio
What gear on the cassette will give you that ratio with a 36T ring?
Answer is 32/1.4375 = 25T, which you don't have, but you have close to it with either a 23T or a 27 T. You still have the 32T to get it even easier!

This should give you the flexibility that you were after, if at the expense of spin out speed.

Your 46T give you your best top speed, but you felt that it didn't give you an easy enough gear.

The 36T driving your 32T on the cassette will give you a 22% lower top speed but 22% easier gear.
If you use the gears instead of "rarely shifting the bike", then a 36T ring driving a 22T gear on the cassette will give you almost the same top speed as your 46T driving the 32T on the cassette.

If you use the 36T to drive the smallest gear on the cassette, the 12T that will be equivalent to the 46T driving a cassette gear of 15.33. You have the 14T or 17T to choose from.

As your concern is getting up steep hills as sweat-free as possible and not that of top speed, then you are right to go for a smaller front ring and use the gears on the cassette to give you some flexibility. Don't forget to reduce the chain length.