Changing from 7-speed to 10-speed cassette?

I stand corrected: as Hamster writes, chains have the same internal width, but the external width decreases to accommodate more gears.

You might get away with using a narrower chain than you should have, ie ten speed on a nine speed set-up, but there is no advantage in doing this.

You can't use a wider chain though: it won't fit between the sprockets.

Ten speed chainrings are also offset to the right, so others might not shift as smoothly.

How did you get on Newman?

Thanks for asking... Not got on at all yet!
Trying to coordinate all the bike jobs to happen at the same time: (1) strip, (2) respray & (3) put back together with almost entirely new (2nd-hand-but-new-to-me!) bits (so new wheels back in box for now).
Have slipped a little behind schedule & a little over budget, but the main problem is that I really can't manage being without my bike for my commute for the time being & I reckon I'll need to put about a month aside for the whole painting process.
Will test with new & old rear mechs & post results & also post respray/chroming results ASAP - June hopefully!!!
Cheers,
Robert
PS. How good is it to actually have a bit of sunshine to ride in this week?!

Very old thread this now! But for anyone interested, all that needed changing was the chain.

Downtube shifters (in FRICTION mode) were certainly not too much of a problem: The cable pull certainly covers the range of the cassette. I must admit, I found it harder to consistently get clean changes - maybe because the sprockets are a tad closer - or maybe just need a little more practice(?!).

Given the fact that Ergos & STI's seem to have very limited compatibility, I was very tempted to stick with the old shifters, but after much deliberation, have decided to try some 10-spd Veloce Ergos. (along with some new matching brakes - makes it pretty much a full Veloce set now).

See new thread for more specific questions - re - shamal 8-spd to 10-spd.

By the way - seems obvious - but more speeds doesn't mean a bigger range of gears - you just have smaller jumps from one gear to the next.
(Personally, that doesn't really bother me - just seems that finding a choice of cassettes with big ratios, or big largest cog, is only easy to do when shopping for 10-spd).

Thanks for the update on this. I was wondering how friction with such close spacing would be. As you say may get slicker as you get used to it as it used to with all friction set ups....

One thing I didn't see mentioned is the front derailleur, if it is any less than a 9 speed, you may have issues throwing the chain off, both inside and outside. The inside of the front derailleur cage will be too wide if it is an 8 speed or below. By the time you get the chain onto the big ring, there will be so much space between the outer plate of the cage and the outer face of the chainring, the chain can drop off. If you adjust it to not throw the chain off, then it will likely not climb onto the big ring at all. The same thing will happen on the inside, for the same reasons. I ran into this countless times at the bike shop, when customers were trying to 10 speed on the cheap.

Was a 10-speed front mech anyway (Veloce) & rear mech in question was a shimano 105. Never tested with any older front mechs. I've got matching front & rear now but actually that combination worked fine together. (all the time in friction - no STI's or ergos).

Cool deal! You got it