Tempo fa scrissi a Sjscycles in proposito. La risposta in sintesi fu la seguente: questo 9 speed può essere avvitato a un mozzo a ruota libera ma bisogna controllare bene la larghezza fra i forcellini del telaio: il Sunrace MFEX9 infatti è largo 41mm.
Can It Be Put In Place Of A Shimano 6 Speed Freewheel?
By Giovanni - 22nd September 2015
does a freewheel hub that takes the MFTZ20 Shimano frewheel accept this 9 speed freewheel too?
Reply from SJS Cycles - 22nd September 2015
Hi, Although the threading will be the same so you will be able to screw this freewheel onto you hub its quite unlikely it will work though as your frame will probably have been designed around 6spd freewheels and may not be able to fit a 9spd in its place. This freewheel is 41mm in width, it may be worth checking if you have room within your frame to fit this. Thanks.