This may seem silly but there is a true purpose behind this lengthy post:
I want a custom 9 speed SRAM ~FREEWHEEL~... Not a cassette or ~FREEHUB~ but a FREEWHEEL!
According to the spec's, this is do-able if you mod a SRAM 8-speed Freewheel.
All that is required is changing the spacing between the gears from 3,2mm to 2,54mm.
[I do have access to a machine shop to make this mod as required]
Here is the LINK
to this reference.
Why do I want to do this, you ask?
I have a Actionbent Tadpole Trike on the way and it uses the SRAM 9 speed cassette and everything else is married to the 9 speed spec's.
I want to put a Bionx 350W motorhub on this trike. The Bionx hub is still set up for a freewheel ( LINK
So obviously, I want to keep the same 9 speed bar-end shifter, same chain, etc... so I can simply change out the rear wheel for a motorless ride whenever I want without the extra 15lbs.
According to the numbers, the 9 speed cassette would be the same stackup~width as the 8 speed freewheel. This should be a no-brainer with the exception of getting the spacers thinned out.
[ (1,8*8=14,4) + (3,20*7=22,40) = 36,80mm ] or (5,00 * 7) + 1,8
[ (1,8*9=16,2) + (2,54*8=20,32) = 36,52mm ] or (4,34 * 8) + 1,8
The 0,28mm is only .011" different (well within tolerance range).
Being slightly narrower means this WILL WORK!
I believe the proper combo of sprockets is as follows:
11~13~15~17~20~23~26~30~34 (9 speed)
All of these are common 8 speed sprocket sizes
...And if you're wondering if this is a worthwile expedition?
Ask youself how many people might be searching for the same solution one their late model Bionx motorized conversion. Any bike shop worth their salt offering Bionx conversions will jump on the opportunity to buy such an upgrade. AND... it's made with common old stock parts.
Today, Bionx dealers are loosing out on sales.
I'm a great example: I won't downgrade to the 8 speed options due to the incompatability with the motorless quickchange option.
Please contact me if this opportunity interests you!
...Or I'll pay cash for clean parts to make this work