Hi
I have an old Revolution Streetfinder with 7 speed Tourney quickfire shifters. Considering the cost its been a good workhorse. Now the 7 speed freewheel is worn so i was wondering if anyone knows if i can fit an 8 speed? The 7 speed shifter has an extra click after gear 7 tho it isn't marked.
Thanks
There are a couple of things you need to check. Firstly whether the wheel has a freehub that can take an 8 speed cassette (and is not a 7 speed freehub, or a screw-on hub that can only take freewheels, although 8 speed freewheels while rare do exist...). It is an 8 speed freehub if there is a c3mm spacer between a 7 speed cassette and the hub. If you want to run an 8 speed freewheel on a wheel with a 7 speed at the moment you need to check to be sure there is enough clearance between the chain and the frame when you are on the smallest sprocket - the 8 speed one would be further outboard. You can see the visual difference between a cassette freehub and freewheel hub
here.
Secondly if I were you I would check carefully that the 7th click (which is required for the 8th gear) is actually pulling at least as much cable as the other clicks. You can check this by slackening the cable by just over 3mm at the rear mech (so you would need to re-index after), and use a marker pen on an exposed bit of the cable where it meets a cable stop on the frame as you click along.
If the above checks are both positive then all you need to do is to replace the cassette, although you should try to adjust cable tension at the rear mech by centering the derailleur to a middle (4th or 5th) sprocket, to minimise differences since the amount of cable pull is a little bit different between 7 and 8 speed, as you can see from
here.
