Author Topic: chain ring to freewheel sizing ? (Read 541 times)

BENDYCAT ELEVENTEEN · « **on:** September 03, 2012, 02:19 PM »

A 39 tooth chain ring - what size freewheel ?

i know you can have a fast start feel or more pace with a bigger size

just wondered what size do what ?

cheers B

oldschoolace · « **Reply #1 on:** September 03, 2012, 02:21 PM »

15? $:-\$

Jon The Bassist · « **Reply #2 on:** September 03, 2012, 02:37 PM »

On a 20" BMX you want a chainring to freewheel ratio of about 2.75, eg 44/16, 39/14 etc.
Anything that makes the ratio bigger gives more top speed.
Anything that makes the ratio smaller gives more acceleration.

BENDYCAT ELEVENTEEN · « **Reply #3 on:** September 03, 2012, 03:02 PM »

so does a 14t fit on a normal hub or is it the double sided hub it needs ?

mattuknc · « **Reply #4 on:** September 03, 2012, 03:11 PM »

Quote from: BENDYCAT ELEVENTEEN on September 03, 2012, 03:02 PM

so does a 14t fit on a normal hub or is it the double sided hub it needs ?

Yep, you'll need a flip flop hub or whatever they're called for a 14t.

Spen69 · « **Reply #5 on:** September 04, 2012, 11:13 AM »

Yep, you need a flip-flop hub.

I run an Odyssey 13T freewheel on my Badlander as it's the smallest you can get for a 30mm metric side on a flip-flop which let's me run a 36T chainring on a 110mm BCD powerdisc. Any smaller will clip the chain and you will need a small 110mm BCD spider to avoid this which wasn't an option on a park bike.