7spd refers only to the rear end of the bike. The
crank is unrelated and will work with any speed from
five on up. The chainwheels however may need changing to narrower versions, but 7 to 8spd likely
will not be a big deal, and the width change is
accomodated by the chain relatively well. The cassette may be a bit more demanding. On the other hand if you
swap cassettes, the chain wear may be such that a new chain is advisable also so you can get the appropriate one on that basis.
Square taper is "old tech", splined is "new tech".
You will notice little difference from a practical point
of view when riding the bike. If there is a choice go with splined. Steve
Don't think it will work with the chain rings on the front, since the chainrings on an 8/9 spped setup are thinner, even on the front, so if you try it, the chain would bee too loose side to side, and the chain would never be tensioned properly. If you get gears that are made for 7 speed and attach them to the crankset, then it can be done. Not all chain rings are equal.
'97 Gary Fischer XC hardtail, '98 Bianchi Campione, '02 Ellsworth Specialist, '01 Brisa B20, old Trek 2000 stripped down and single speeded, '70 Huffy tandem
I don't believe that you can put an 8/9 speed cassette on a 7 speed hub. I am pretty sure that the 7 speed hubs are more narrow.
I would just put the crank on as is and try it. I think it will work. If you have the problem that danka24 was talking about, I would just get a narrower 8 or 9 speed chain. It will work with the 7 speed cassette just fine.