Freewheel / freehub cassette question

[4F]

I am currently riding a 531 80's double 6 speed however my cheap rear wheel is currently breaking spokes at an alarming rate.

My question is how pratical would it be to replace the rear wheel with a more modern freehub with say a 7 or 8 geared cassette ? I already have a spare second hand 105 rear mech (RD 1055) that I could replace at the same time but would I also need to replace the BB and front chainrings at the same time?

 

[Landslide]

7/8spd should be fine. It'll use the same width chain as 6spd. I'd be surprised if your current BB and chainset gave you any serious issues. Shifters? Friction shifters should be fine, and indexed downtube levers normally stretch to an extra gear (6spd will do 7, 7 will do 8).

Dropout spacing may be an issue - IIRC 6spd tends to be spaced at 126mm, 7/8spd upwards is set at 130mm. Your frame will spring apart, but it's a bit of a faff every time you take the wheel out/put it back in. Might be worth getting a local framebuilder to cold set (bend) the rear end.

 

[4F]

7/8spd should be fine. It'll use the same width chain as 6spd. I'd be surprised if your current BB and chainset gave you any serious issues. Shifters? Friction shifters should be fine, and indexed downtube levers normally stretch to an extra gear (6spd will do 7, 7 will do 8).

Dropout spacing may be an issue - IIRC 6spd tends to be spaced at 126mm, 7/8spd upwards is set at 130mm. Your frame will spring apart, but it's a bit of a faff every time you take the wheel out/put it back in. Might be worth getting a local framebuilder to cold set (bend) the rear end.

Cheers, I currently have downtube friction shifters (sachs huret) but as part of the second hand 105 set I got some 105 down tube shifters that can be set on either friction or index mode so should be able to cope with 8. I will check the dropout spacing, would I be able to "cold set" this myself with a bit of brute force ?

 

[PpPete]

Cold-setting - check this out:
http://www.sheldonbrown.com/frame-spacing.html

but proceed very gently, is my advice. I have an even older 531 frame (70's is my guess from the lovely brown colour scheme) and it was very easy to go too far, even though it did not feel as if it was moving at all.

 

[4F]

Cold-setting - check this out:
http://www.sheldonbrown.com/frame-spacing.html

but proceed very gently, is my advice. I have an even older 531 frame (70's is my guess from the lovely brown colour scheme) and it was very easy to go too far, even though it did not feel as if it was moving at all.

Nice link, thanks

 

[e-rider]

I would get another 'old' wheel and keep the same set-up OR save up and buy a new bike - you can get something NEW and reasonable for £400 (much better then what you have I would guess)