Center of seatpost to chainring.
Hello from AZ
- Thread starter Go-Rilla
- Start date
I haven't ordered a crankset yet, and I'd like to use something like these:
Big City Single Speed Crank 170x52 118 SQR JIS crankset black
Steel chainring with forged alloy crank arms and double chainguard. Compatible with 3/32` chains. 45mm chainline TECH SPECS Type Length/Teeth 170x52 Spindle Type 118 SQR JIS Color BLK Bolt Pattern N/A Weight Speed 1
bicyclewarehouse.com
PCeBiker
No-Hands No-Pedaling No-Credentials
- Region
- Canada
That single speed crank says it has a 45mm chain line, but I'm pretty sure that depends on the length of the bottom bracket.
The common bicycle BB size is usually 68mm, but an ebike is usually between 100mm and 120mm long.
That effects the offset from the center of the seatpost to the chainring.
The common bicycle BB size is usually 68mm, but an ebike is usually between 100mm and 120mm long.
That effects the offset from the center of the seatpost to the chainring.
Yep, which is why I don't want to buy a crankset that doesn't carry about a 65 chainline. The mathing here throws me a bit, since the BB number would need to be reduced by half, but there's more to it, yes?
PedalUma
Well-Known Member
- Region
- USA
- City
- Petaluma, CA
A standard BB fits a 68 to 73 frame shell. The difference between then in the length of the square taper shaft. A triple ring takes a longer shaft and you would want to balance that with the Q on the left. The shown ring should work fine. And should be the same distance from the center of the bike as the existing ring, because of the shaft length and taper.
PCeBiker
No-Hands No-Pedaling No-Credentials
- Region
- Canada
Just measure the frame shell and buy a BB with the same measurement.
The ring shown isn't really a triple ring.
It's a single chainring with a chain gaurd on either side of it.
It may have a bit more offset than a standard chainring, but not as much as a triple chainring.
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