Carrera Vulcan Gears

[Micknal]

Rebuilding a Carrera Vulcan and wondered if anyone knows if I can reduce the size of the rear freewheel from 8 to 7 speed ???

 

[PatrickPending]

7 speed are generally freewheels and 8 speed are freehubs - you may find a 7 speed casette - i don't know - pretty rare I guess otherwise youd need a wheel designed to take a screw on frewheel

http://sheldonbrown.com/k7.html

 

[Rickshaw Phil]

7 speed are generally freewheels and 8 speed are freehubs - you may find a 7 speed casette - i don't know - pretty rare I guess otherwise youd need a wheel designed to take a screw on frewheel

http://sheldonbrown.com/k7.html

+1. Just to add, if it is a freehub and you get yourself a 7 speed cassette you may also need a spacer to get it to line up correctly.

Just out of curiosity why do you want to reduce the number of gears?

 

[RecordAceFromNew]

Rebuilding a Carrera Vulcan and wondered if anyone knows if I can reduce the size of the rear freewheel from 8 to 7 speed ???

If you want to replace the original 135mm hub mtb wheel with 8 speed cassette by another 135mm hub mtb wheel with 7 speed freewheel/cassette, or the cassette with a 7 speed cassette (which needs a 3mm spacer for an 8/9/10 speed hub), you can do so.

If you are using an 8 speed shifter (original is sram x4 shifter and rear mech) you should set cable tension to centre the rear mech on the middle sprocket (because there is a difference in 7 and 8 speed sprocket pitch of 0.2mm, it will only be 0.6mm out at the extremes).

 

[TheDoctor]

A 3mm spacer like this one is what you need. Goes on behind the cassette.
Why do you want to go from 8 speed down to 7? While an 8 speed shifter can be made to index on 7 speed, it's not ideal. 7 speed cassettes are still around, but there's more choice in 8 speed.

 

[Micknal]

Many thanks for all your answers.
Reason I was asking is that I need to replace the whole drivetrain and I have a brand new set of shimano 7 speed shifters which I could use to keep costs down on rebuild. Consesus of opinion seems to be to keep with the 8 speed.
I'll need to have a hunt around for some 8 speed shifters.

 

[TheDoctor]

Ah, I see. Well, you could use a 3mm spacer and get a 7 speed cassette, thus allowing you to use the 7 speed shifters. Or not buy the 3mm spacer and get an 8 speed shifter and an 8 speed cassette. Depends how tight money is, I suppose...

 

[Micknal]

I have now decided to replace both front and rear mechs , shifters and 8 speed cassette. I not looking for top spec but something that is fairly robust and will withstand my local riding conditions ie rough track comprising light shingle and sand, for a decent length of time ( already gone through two lots of gear on my current MTB), Once the sand gets in it wears quite quickly!!!

Look forward to your suggestions.