campag cassette query

[berty bassett]

This may be stupid question number 10 from me ,but here goes - i have put 13 - 29 veloce cassette on swapping from a 11 25 . i have done this to get ready for some hills that are going to get in my way to scotland . question is - can i swap and change cogs so i end up with a 11 - 29 as i am missing my 12 - thanks in advance

 

[jack smith]

Yes if the smaller cogs are loose as in tot pre attached to the rest just swap them out with the old ones

 

[slowmotion]

I swapped the original cassette for a 13-29 Veloce a couple of months ago for the same reason.....hills. From memory, only the three or four biggest cogs are a "block" so, as js says, you should be able to mix and switch the loose cogs on the cassette. One thing to watch out for is the total span of the teeth. I can't see a 29-11T range being a problem compared to a 11-25T but you might want to consult the Campag tech docs. The manufacturer's gear rules for rear mechs are usually pretty conservative. I think you will be fine.

 

[Graeme_FK]

The shift at the "harder" end of the cassette might not be quite as slick - the ramps that are used to help the chain go from 11 to 12, 12 to 13 and so on will lose their "timing" relative to one another. Coming up the gears, the other way from easy to hard, the spacings are slightly different on the 11-up cassettes by comparison to the 12-ups and the 13-ups, so you might get a less slick shift - it's all down to what your expectations are of shift speed and accuracy and also of the shifting under load.

slowmotion is also quite correct - 11-29 is a tooth difference of 18T and you may be running 34-50 at the front, giving a total tooth difference of 34T, two over what Campagnolo recommend for a "standard cage" rear gear. Yes, manufacturers are conservative on these numbers but whether you *really* can do it or not is dictated by the exact length of the chainstays of the bike, the angle of the chainstay to the seatube when seen from the side (as that defines exactly where you can & can't join the chain) and the length of the rear hanger from centre top pivot bolt to centre wheel spindle. If you don't have enough chain to span the biggest sprocket & the big ring and you select that gear by accident (as you should never actually need it if you can plan your shifting), the consequences vary from the "pretty expensive" to the "extremely expensive" - so you need to be darn' sure!

 

[jack smith]

If you've had an 11 on previously with the same chain and front chain rings just switch it mate no need to over complicate it, it will work I'm sure a few milliseconds longer to shift a bigger gap won't bother you

 

[Graeme_FK]

@ jack smith - you need to be careful there .... if the chain length was set by the often-recommended "big to big" method on a 25T bottom gear, there won't be enough chain. It's not a question of over-complication, it's a question of making sure that the change won't cause a very expensive problem ... we have seen a number of occasions where cassettes have been swapped like this, there has not been enough chain and in one unfortunate incident, a young lady not only came to a grinding halt in the middle of a group taking several other people down - but also demolished a rear gear, the chain, the rear wheel and damaged her carbon-fibre frame to the extent that it wasn't economic to fix it - the cause was not enough chain.

I quizzed the mechanic who built the bike originally (he was working for me at the time) and he confirmed that he had used the big-to-big method on a 12-25 to set chain length. The young lady had asked someone else to fit a 13-29 ... so pretty much a carbon copy of this scenario.

On the downshift I agree, most people won't see or feel the difference, but the upshift can occasionally hang (especially under pressure) which is a pain in the backside.

 

[slowmotion]

^^^^^^ All excellent advice! I forgot to say that I did check the chain length with one of the online calculators when I swapped.

 

[Crankarm]

Or simply fit the larger sprocket then see if there is enough chain to go big big front and back. If there is then you are ok. However there maybe far too much chain in the opposite direction i.e. small small meaning the chain is flopping around as the deraillieur is not under any tension as the chain is too long. I am sure Graeme_FK van give a more in depth analysis but these are just my lay observations. If you know anything about bikes you wouldn't knowingly select these gear combinations anyway as you are in effect twisting your chain right across the width of the cassette to the outer or inner front chain ring which is not good and if done repeatedly will lead to premature wear of both chain, sprocket and chain ring. Also as Graeme_FK states SHOULD the chain or deraillieur become jammed or break or go into the spokes because it is over stretched or zero tension because there is insufficient or too many links in the chain then the consequences don't bear thinking about as the damage could be considerable as well as the risk of injury to yourself if you come off.

But to answer the OP my gut feeling is no, as the size range in sprockets 11 min and 29 max is too great, but suck it and see. Why not go 12-25 or 13-26 which are well within safe use limits? What size are the rings of your front chain set? It is unlikely you would spin out on a 53 or 52 front ring on a 12 rear sprocket or even 13 unless you can cycle faster than 40 mph on the flat ! What's the size of the inner chain ring - 39 or 42? If there is a wide range in sprocket size in your rear cassette you have much larger jumps between gears. Perhaps the better approach would be to look at what size front chain rings you have and maybe make some changes here?

Also you should consider whether your rear deraillieur has a suitable cage length and whether you are exceeding the spec of this in what you are trying to do.

Currently I use an 11-21 9spd rear cassette with a 52/42/30 triple front with 700c wheels and I seldom get off the middle 42 chain ring as it is pretty flat although some gentle hills occasionally carrying two heavy rear panniers which slows me down so I am on the lowest 21 sprocket. I did use a 12-25 but found the 25 sprocket too low and I wanted fewer gaps in the mid range of the cassette. I seldom get higher than the 13 sprocket though at the moment, seldom use the 12 and never use the 11. The latter's use is to stop the chain coming off . I suppose if I were going down a mountain col then maybe I'd get onto the 11 sprocket and the 52 front ring, but the brake blocks would probably melt trying to stop the bike I'd being going that fast …………….

For hills I just go down onto the 30 front ring and of course I can put the 12-25 cassette back on should I feel the need.

The Sheldon Brown gear calculator is a great help.