Can a Shimano 7 speed cassette hub be swapped for 9 speed hub ?

[Psycolist]

If I have a wheel with a 7 speed Shimano hub , can I remove the freehub bit and replace it with a freehub that would accept 8 and 9 speed cassettes ? Anyone know ?

 

[RecordAceFromNew]

If I have a wheel with a 7 speed Shimano hub , can I remove the freehub bit and replace it with a freehub that would accept 8 and 9 speed cassettes ? Anyone know ?

What is the model code (usually FHxxx or FH-Mxxx) of your 7 speed hub?

 

[Psycolist]

I was only curious from a theoretical viewpoint. Its not unusual to find wheels for sale that only take a 7 speed cassette, for less money than an equivalent 9 speed hub set would cost. Just 'in theory'

 

[RecordAceFromNew]

I was only curious from a theoretical viewpoint. Its not unusual to find wheels for sale that only take a 7 speed cassette, for less money than an equivalent 9 speed hub set would cost. Just 'in theory'

In practice, the vast majority can, as long as the hub is made by Shimano, not just Shimano splined.

For road wheels the fly in the ointment of your scheme is that not only will you have to introduce spacers (to achieve 130mm OLN for 8/9/10 speed, from 126mm which is usually though not always the case for 7 speed), but also to redish the wheel (because all the spacers introduced would have been on the drive side) and equalise the locknut positions in relaton to the axle. However if you are to use the wheel for a hybrid or mtb (which usually need hubs with OLN of 135mm) then you can just introduce spacers to both sides without needing to redish - but you will need a longer axle.

 

[Sterba]

Generally speaking, Shimano's 7 speed gears are not compatible with their 9 speed counterparts. The derailleur has a different parallelogram, and the shifters move it in differently spaced steps. So, in addition to the different width between the ends of the frame and the wheel-dishing issue mentioned by Record Ace above, the complete geartrain would probably all need to be swopped out. Are you sure all these changes would be worth it for just another couple of cogs? What you might want to consider instead is buying a 7 speed cassette with a wider range of cog sizes. 12 to 32 are readily available in 7 speed cassettes. The gaps in the gearing are not as bad as you might fear.

 

[Psycolist]

Many thanx for those replies. I hadnt given any thought to the dishing being affected, the axle, yes, but not the dishing. A great example of why these forums are so usefull. It seems that the theory is do-able but may simply not be a viable option in terms of expense.. Thanx again .