Sprocket doesn't fit need help

[Bronson]

I'm converting a bmx bike to electric and I'm trying to move the old bmx 13t sprocket onto the new hub motor but the threads on the motor are bigger than the ones on the sprocket, What do I do? Can I get an adapter? The cassette the motor came with has a 14t sprocket on it, Can I use this instead? Do I have to buy a 13t that will fit the threads? Am I better off just going full electric and not using pedals at all?

 

[glennb]

No adapters that I'm aware of.

The only 14t freewheels you can use are poor quality, I'd strongly recommend spending $15-50 on a good quality 16T one. If you prefer a larger gear, you can use a larger chainring.

 

[Apartunis]

Normal freewheel threads that use multi speed freewheels or singles with 16 or more teeth are 1.37 inches diameter. 13 to 15 tooth freewheels require 30mm threads, which only exist on a few BMX hubs.

You can find 14t and 12t freewheels that fit the larger diameter thread, but they are wider overall and may not fit if there is only enough room for a single freewheel.

 

[glennb]

Yep.

You can use the 14-28 freewheel supplied with the hub.

The advantages to 16t single speed are the options for quality freewheels, achieving better chainline, and the ability to centre the hub in the dropouts so that it doesn't require dish, which results in a vastly more robust wheel. Everything overall will be stronger, quieter, neater, and longer lasting.

There's no disadvantage as such, merely the upfront effort to respace the wheel and disc caliper, and undish the wheel.

 

[Bronson]

No adapters that I'm aware of.

The only 14t freewheels you can use are poor quality, I'd strongly recommend spending $15-50 on a good quality 16T one. If you prefer a larger gear, you can use a larger chainring.

Normal freewheel threads that use multi speed freewheels or singles with 16 or more teeth are 1.37 inches diameter. 13 to 15 tooth freewheels require 30mm threads, which only exist on a few BMX hubs.

You can find 14t and 12t freewheels that fit the larger diameter thread, but they are wider overall and may not fit if there is only enough room for a single freewheel.

I don't have any extra links for my chain, would the 14t or 12t freewheel fit with my current chain that worked with the 13t or am I better off getting a new chain and a nice 16t freewheel

 

[Apartunis]

I don't have any extra links for my chain, would the 14t or 12t freewheel fit my current chain

Smaller sprocket might require you to remove links but will not require you to add links.

 

[99t4]

I don't have any extra links for my chain, would the 14t or 12t freewheel fit with my current chain that worked with the 13t or am I better off getting a new chain and a nice 16t freewheel

How long is the adjustment slot and where was the axle positioned with the 13t?

 

[glennb]

Forgot you're using a BMX rear end, meaning it's too narrow for the multi-speed freewheel. You will need to run single-speed and mess with spacing and dish. If it's 110mm rear end you won't be able to use the <16t freewheels. If it's 120mm, they should fit.

Either way, you need to take some measurements before proceeding, to see what your options are.