rick99

Hi .
I was cleaning my cassette and trying to sort out a small shifting issue i have. I dismantled it and noticed that all the spacers are labelled in very small numbers as being 2.55. Now the only diagram i can find with all the spacers the same says they should be 2.6mm. This isn't the same, as in: it matters, right?

I think it is a veloce 12-27 with joined biggest sprockets, about 2013/1014 age.

Bill Kapaun

Did you calculate how much .05mm is?
Did you actually measure? 2.55mm sounds thicker than ANY spacer I'm aware of.
What's the cog thickness vs "specified"?

gregf83 

Over 9 spacers the difference is only .45mm or .017". If your derailleur was properly aligned in the middle of the cassette the smaller spacers would only contribute .2mm of offset at either end of the cassette. That's unlikely to make a difference.

I think it's unlikely that Campy built a cassette with close but slightly wrong spacers. More likely someone rounded up on a drawing.

rick99

ok Just a bit weird that their technical drawings are wrong. I mean they are quite particular about their spacers being 2.55, 2.4 etc.

Thanks anyway!

gregf83 

Rounding up isn't wrong it's just an indication of the precision required.

rick99

Normally yes but they are quite specific in that they give them a different letter. I .e. a 'K' spacer is 2.6mm whereas an 'O' spacer is 2.55.

If the measurements were quoted to a specific order of magnitude it would seem odd that they abandon that convention at different points on the same page.

The operational difference is probably negligible though, you're right.

I was kind of looking for someone with a knowledge of he mysterious world of campagnolo cassettes rather than some brut common sense, which i think i have myself. Curiosity has prompted me rather than an ignorance of measurement science.

gregf83 

You said the top couple of sprockets were attached? I believe Veloce always had separate cogs so you may have a Centaur or above cassette. What makes you think it's Veloce?

Drew Eckhardt 

Looks like Campagnolo changed to 2.6mm spacers on the 12-27 and 12-30; maybe they switched to 11-speed cog thickness on those?

Otherwise most of the spacers are 2.4mm tick although they're not all the same thickness. If some how (used parts?) you got all 2.55mm spacers you may have problems.

Centaur/Veloce cassettes have 2.4mm spacers with two exceptions:

The 6th and 7th cogs are separated by a 2.55mm spacer not 2.4mm; that's amber not black on my Veloce/Centaur 10 cog cassettes.

The final two cog cluster on Daytona/most Centaur cassettes is preceded by a 3.05mm spacer. Loose final cogs in Veloce/some Centaur cassettes are separated by a thin 1.6mm spacer.




Things are more complicated with Chorus/Record cassettes where different spacers go with different paired cog combinations.

rick99

My biggest two sprockets are joined . The smallest two separated by a flange attached to the smallest . The other 6 are 2.55mm marked and labelled.

It may be centaur. I'm not sure. Can't remember but I bought it new .

On the campag website there are various combinations for 10 speed cassettes shown and the closest to my 12/27 set up is shown with spacers and joined sprockets but with 2.6mm for all of them not 2.55.the variable width of spacer per sprocket is also there but the spacers are different shapes . I also have this version of 10 speed cassette on my cross bike .

gfk_velo

This note made for another user.

He had a specific problem apropos 12-30 cassettes and cassette spacers but without detailed checking of the 12-27 cassettes across the years, I can't say that this is exactly relevant here but it is generally relevant to all such queries & the "downstream" impacts on set-up.

I've added a couple of notes in italics.

The ages of the cassettes are important, as per the posts above which mention variation across model years. Sprocket layout is not always definitive, especially with Campagnolo's tendency to "trickle down" technology and late in the production cycle, to change parts in order to be able to continue offering a legacy product - i.e. ErgoPower lever bodies - EC-RE200/ 201 and EC-CH200 / 201 when introduced, had different spring mount rings and cable bushings. Now, we see late production EC-RE200 and 201 bodies with Chorus cable bushings (which were used in Record up until 2007 anyway) as the very last stock parts are used ...

<starts>
Spacers in the cassettes have varied slightly over the years, according to the model year - not all Centaur cassettes, for example, even where ratios have remained the same, carry the same spacers as the material used to make the sprockets themselves can vary in thickness from Model Year to Model Year. It's a question of overall process and what materials are used, for instance, in the production of other cassettes in the same Model Year. Where it becomes more economic overall, to change a product specification, all manufacturers will do so - hence the "Specifications may vary" disclaimer that one often sees.

If you check the label on the end of the box that your cassette came in, you will find a part number which will probably be CSxx-CEX20 (in 12-27 this will be CSxxCEX27) where the "xx" is the model year.

Centaur cassettes from the year of introduction of the 12-30, 2013 (IIRC, CS13-CEX20) had spacers "K" (2-CS-812). These have a width of 2.6mm.
Centaur cassettes from model year 2017 onwards (IIRC, CS17-CEX20) also have spacers "K" but you'll see in the spare parts catalogue that the quoted width has changed to 2.55mm.

The 0.05mm variation is relevant, although small. You could probably get away with one spacer being 0.05mm "out" but across a stack of spacers the error is cumulative and it affects not only the distance that the RD has to move but also the compression on the spring that drives the derailleur back towards the smallest sprocket. Hook's Law states that the force exerted by a spring is directly proportional to the compression / extension of the spring until the elastic limit is reached - hence, since, sprocket to sprocket, in setting an index system up, you are balancing one spring (the one in the RD) against another (the tension in the gear cable), a move away from the intended spacings in any part of the cassette can throw indexing out as the amount of extension / compression is varied. This is why you can't just change the cable tension and get an 11s lever to shift a 10s cassette with a "spare" click.

(Note specific to original user)
I'd guess that the cassette you have is the later type, since product generally doesn't sit very long at a wholesaler or at a retailer these days - weeks rather than months and seldom, if ever, years, in the case of a common consumable like a cassette.
(ends)

The user had a shift problem between sprockets 4 and 5 when counted from the wheel towards the smallest sprocket)

More likely causes of indexing problems around the middle of the cassette are (working from fundamentals through the set up routine) are as below.
Problems usually show in mid-cassette first as this is where the chain has to pass through the smallest arc to go from sprocket to sprocket and it's also, especially on wider range cassettes, where the top jockey is furthest from the sprockets so can control the chain least accurately ... so small error show most noticeably in this part of the derailleur's movement. This is true of all derailleur systems, not just Campagnolo, although a couple of the notes below are Campagnolo-specific, Shimano and SRAM have differing specs ...

• Frame rear triangle misaligned to BB (so offset left or right) - very uncommon on frames these days but a check we always do before commencing assembly, esp on older steel frames or frames we don't know the history of.
• BB to wheel centre dimension too short (less than 405mm) or chainline error (wrong BB axle length). Some TT frames like Cervelo P3, P5 and occasionally very short chainstay roadframes like Cervelo R3 or some Quintana Roo models, can be a problem as chainstays can be as short as 395mm. Some very old-skool TT frames, built with very short chainstays can be problematic as can "Flying Gate" designs since their whole design ethos is around very short chainstays.
• Any mismatch in components ie 10s RD designed for PowerShift or Escape with full ErgoPower or UltraShift (this is quite common), hanger too long (rare on a frame used as-is but often a problem with hanger extenders).
• Mismatched chain (KMC, YBN and Connex 10s "compatible" chains - and others - can all give odd shift characteristics sometimes because of variations in width and lateral flex versus the chain the system is designed for).
• Chain incorrect length (should be sized small-to-small, lenth maximised so that the RD is tensioning the chain but no part of the chain should touch any other, for instance, at the RD itself - the idler run should not touch the part of the chain that passes around the upper jockey wheel as it "passes" - the gap here should be 5 - 20mm. The Campag tech docs actually give a smaller range than this but practical experience shows that 5mm is definitely the min and 20mm is definitely the max.
• Worn top jockey wheel.
• Cassette lockring tightness (40nm is "tight", approx 12kg of weight on the end of a 30cm spanner would generate that approx torque at the lockring) ... changes the sprocket-to-sprocket spacing.
• Cassette body-to-wheel "float" (worn bearings) and / or tightness of fixing nut.
• Wheel not in dead straight (often one of the QR springs in back to front or wheel put in with the bike in the workstand, not on the ground) - causes the same issues as a mis-aligned derailleur hanger or derailleur not hanging within the expected tolerance of "straight down".
• Hanger-to-dropout tightness
• Hanger alignment. (In through-axle frames, occasionally the tightness of the through axle can affect this, esp where the through-axle threads into a combined hanger and dropout).
• Won top pivot bolt o-rings in the RD meaning that it "hangs" mis-aligned.
• Worn outer cable casing (adds friction).
• "California Cross" cable installation - adds friction unless the gear tunnels are designed for it.
• Worn under-braket gear tunnels (add friction).
• Plastic ferrules on the outer gear cable casing (these tend to compress and / or bend which can cause drag on the cable - usually shows first in the mid-cassette shifting).
• Start point of the RD's travel (high limit screw) slightly mis-set - this should be set without the gear cable attached to the RD otherwise the movement towards the smallest sprockets may not be being limited by the screw but by the cable - so leading to unintentional slight pre-loading of the cable.
• "H" Screw mis-set, so that when on the small chainring and the biggest sprocket at the rear, the gap between the tops of the teeth on the upper jockey and the tops of the teeth on the buggest sprocket, is too great or not enough. In the former case, the chain control is compromised, in the latter,it can lead to the derailleur cage "clipping" the bigger sprockets (usually the 30, 27 and occasionally the 24) as you upshift - so leading to inaccurate cable tension being set to get a clean upshift to a smaller sprocket in these gears). In the latter case, theres too much "free chain" from where the chain "exits" the top jockey and "enters" the sprocket, so the shift isn't accurate - typically the user will have to set a little too much gear cable tension to get a good downshift from a small a sprocket to a bigger one - most noticeable in the middle of the cassette where the top jockey is furthest away from the sprockets anyway.

If you work systematically through that list top to bottom, so long as no liberties have been taken with component choices / compatibility, and wear and tear in the RD and / or lever is not excessive, you should find the issue and fix it.