Can an eight speed freewheel be fitted?

[ZigZagLSD3]

new to the forum. I was looking into getting a rear 1000w hub but have a few questions. the bike I am thinking of using has 8 sprockets on the current wheel is there a set up that uses 8 sprockets if not what are the options I might have short of getting a new bike.

[Andrew]

Remember that ebikes use thread on freewheels and not cassettes which slide on as you get on modern bikes.

You have two choices,  a shimano freewheel or a DNP epoch freewheel.

Shimano better quality but smallest cog is 14 tooth.
DNP lesser quality but has a small 11 tooth cog so you can still pedal at speed with the motor.

You can run an 8 speed but you will find that some fabrication will have o take place. If you have a steel frame then you can bend it out a bit at the rear drop outs. But do not do this with an aluminium frame.    You ill find that if running 1000w of power that you will only ever need the last three cogs on the freewheel.

For hassle free build get a six speed shimano.  Sometimes even a  severn speed can cause fitment issues

[Bikemad]

Hi andto the forum.

You have not specified which 1000W hub you were looking into, if it's an HBS 1000, the extra width might be a problem. However, if it is the Magic Pie III, you can fit an eight speed "thread on" freewheel, but it may require an additional washer (or even two) on the axle to provide the correct clearance between the frame and the wider freewheel unit.

It might also be necessary to spread the dropouts apart slightly, in order to get the additional spacer to fit between them.
As Andrew has already mentioned, spreading the frame is not recommended with lightweight aluminium frames as it can cause excessive stress, which can result in premature failure of the frame.

I fitted a Shimano 7 speed "Megarange" freewheel to my MPIII and did not need to fit any additional spacer washers:



You should be able to adjust your dérailleur end stop screws to set the travel limits for the seven speed unit, but if the gears do not work correctly with your indexed gear changer, you might have to fit a seven speed changer mechanism to correctly match the spacing of the sprockets on the freewheel.

I also agree with Andrew regarding the number of gears, as I typically use the highest gear in conjunction with the Magic Pie's assistance most of the time, including hill starts, and I have a 52 tooth chainwheel driving a 14 tooth rear sprocket.

Remember that ebikes use thread on freewheels and not cassettes which slide on as you get on modern bikes.

This should help to clarify the difference between freewheels and cassettes:



Alan