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New Cassette

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Roy:
I have just installed a new cassette. It is a campag 9 speed 14-28. My bike, a steel frame Pinarrello which I bought from new 20 years ago has always had a 13-26 cassette. I noticed when the bike was on the work stand that when the chain was on the 14 the outer plates just brush the rear drop out and that the the teeth of the sprocket were touching the end of the chain stay rendering the 14 unusable. I have put the 13 back on, that end of the cassette does n't get much use anyway. Has anyone else on here come across anything like this?

Brucey:
this kind of thing is very common. Often you need to add another spacer on the RH end of the axle to make enough room for a larger sprocket.

fig 1 here

https://www.miche.it/pub/media/productattach/m/i/miche-manuale-istruzioni_10-9-8speeds_laser.pdf

shows how much clearance is required (at the usual axle end position) when different sprocket sizes are used. This clearance is at the seatstay, and allows enough room for the chain to shift on and off the sprocket too.  The clearance at the chainstay can be as small as you like because the chain should never be on the sprocket at that point.

However since stays very in shape from one frame to another, it isn't possible to say exactly how  much extra clearance you will get if you start to add spacers on the axle.

cheers

sojournermike:
Yes! The early run Spa Steel Audax frames don’t like cassettes that start at 13, but are happy with 11 or 12.

The later ones, I think from about the second or third shipment, certainly in the small size are quite happy to start at 13.

mzjo:
It's not a new problem, I have it on a Moser 51.151 that dates from about 1987.

Brucey:
a variant on the problem is when the frame has slotted dropouts (eg old campagnolo) and the wheel is spaced so that top gear will (just) run and shift OK, yet you can't get the wheel in and out of the frame without the top sprocket chewing the inside of the RH chainstay end as the wheel is slid  forwards.   When 7s became a thing, many frames were limited in this way.

 Older frames had either a small relief on the chainstay end inside the RH dropout or none at all.  I was recently surprised to find a fairly generous relief on a frameset built in 1963; I can't think it was commonplace at that time.

cheers

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