mschwett 

replaced my rear chain at 3,000 miles - although it wasn’t measuring as “elongated” i thought i’d be preserving cassette life by doing so.

on the new chain, the small cog on my 11-34 very occasionally (twice on a 25 mile ride this afternoon) skips. i don’t remember if the tooth pattern was as varied as this when it was new. the rest of the cassette looks really clean. is it possible the new chain and old 11t will wear into each other a bit?

Badger6

Cassette is finished...even if the chain wasn't worn, it was worn. That 11t is pretty worn, along with the next two cogs. But, based on the DruaAce lock ring, is that a DuraAce cassette? Maybe you can get away with just replacing the worn cogs, though, IMO, it's wiser and far less issue prone to simply start with a new chain on a new cassette...as per the general cycling wisdom handed down to us since Napoleon rode a bike to Moscow in 1812.

mschwett 

bummer. thanks for the input … new cassette en route. the chain has only been ridden for about 40 miles on the old cassette… would like to avoid changing it again too!

MudPie

That's the prudent way to extend the life of the cassette.
How did you measure the chain? Most commercial chain checkers are inaccurate.

bikeme

You probably haven't damaged the chain yet. I went thru a similar thing on my mtb with SRAM--chain wasn't worn to the .5mm gauge so I just switched the cassette which was worn only in certain gears. Skipped like mad, so I ended up changing the chain anyway--runs like butter now. A week later I changed the chainring too after comparing it to a new one--it was cooked--no shark toothed or chipped, just very thin. Even smoother than the first fixes.

Troul 

That 11t is worn out. I have yet to find those a la carte for a cost effective replacement solution, so as I come across free cassettes [rare] , I'll inspect the assembly & retain them. Currently the spares I had are now on service duty.

HillRider

Small cogs wear faster and are less tolerant of being matched with a new chain than larger ones, particularly if you use them a lot. Your experience is common.

cxwrench

Do you only ride in the 11?

mschwett 

thats what’s surprising to me. i don’t spend that much time in the 11 except on descents. in fact i doubt i’m ever in it except on fast descents or rollers holding speed after a descent.

3,000 miles with probably a tiny fraction of it in the 11 isn’t impressive life.

CliffordK

I agree that cassette looks a bit battered, but I'd really go by symptoms. With a new chain, can you force the chain to skip? Standing on the pedals?

If I have mild skipping on one sprocket, I'll often continue using for one more chain.

Keep in mind that one has the pulling side of the teeth and the non pulling side of the teeth.



So, on the top of the cassette, the left side of a tooth would be pulling, and the right side would be the non-pulling side.

So, if that non-pulling side looks completely smashed, that may well have been how it was from the factory.

I tend to look more at the shape of the valleys. So, just the opposite, the right side of the valley is pulling, and the left is non-pulling.

Looking for elongation of the valleys, or less crisp verticals on the left side of the teeth. Also smashing of the face of the teeth.

Anyway, if the cassette shifts fine and doesn't skip, I'd probably keep riding.

Also, as the chain wears a little bit, it may start shifting better.

CliffordK

One note.

SRAM specifically lists using hardened steel on their RED models of cassettes. I've been meaning to try one out, but haven't had a chance. Still hoping for more longevity.

Use the above cassette until it dies, but it is worth exploring other brands too.

Yan 

Yes that 11t small cog is toast.

Iride01 

While a chain slipping on the cogs might be a indication that they are worn, it's not a done deal. Are you certain that your DR is fully shifting to the 11 tooth cog? Other things like a ever so slightly bent hangar or such might need to be looked at. Or just swap with a friend or a friendly LBS mechanic that probably has one or two laying around already that he/she has been using. Then you might know better if that's the reason.

The teeth don't look that much different than the picture of a new CS-R9200.

mschwett 

thanks!

i can't consistently force it to skip, but it does skip (with the new chain) occasionally on the 11t. shifts very smoothly and crisply, and if i stand on it in the 11 it won't be a guaranteed skip - the situation which seems more likely to trigger is a quick bang start from coasting at speed. skips once or twice then stays tight, even for fairly hard pulls from there. it does seem to have improved in the last 20 miles.

good point - the cassette appears to have two oddly shaped teeth out of the box, both of which have their leading edges beveled and scalloped out in profile. pretty sure the RD is still aligned and working well, the shifts are super quick and smooth in and out of every cog and it doesn't look bent in any way. no contact with the ground lately!

i'm going to switch to a new cassette tomorrow, and if it still skips occasionally, i'll put the old one back on and keep the new one in reserve for when it's really worn. i wanted to have one in reserve anyway since they've occasionally been very hard to find in the 11-34.

Koyote

Does the cassette only have 3,000 miles, too? If so, then something else is going on. It wouldn't be worn out already. Or is it on its second or third chain?

Yes, true. But this is odd, since a rider should spend sooo little time on the 11t. Do you cross-chain the bike much? Was the skipping happening while cross-chained?

Troul 

x2

Unless you're treating the bicycle as a fixie or amming rocks & sticks in the particular cog while riding, it should last a few more thousands of miles under typical use.

mschwett 

the cassette, bike, chain all have/had 3,000 miles.

it's 12 speed di2, it doesn't even allow cross chaining into the 11t. big/little, abrupt start from coasting generates the skip. i'm a middling rider, 185lb and FTP in the 225-250w range, rarely put out more than 500w even for 30 seconds.

looking more closely at it it, it really doesn't look like the profiles are any different than new. it's just a bit worn around the edges:

CliffordK

Here is the parts diagram.
https://dassets.shimano.com/content/...R9200-4808.pdf

Part Number:
Y0MV11000 - 11T
Y0MV12000 - 12T
Y0MV13000 - 13T

It looks like the parts are all over the Europe and the UK... perhaps big piles of them. And pretty cheap at that.

https://www.bike24.com/p2185946.html?sku=794754
https://r2-bike.com/SHIMANO-Sprocket...ettes-11-Teeth

Unfortunately Shimano won't let them ship to the USA.



This one is apparently Switzerland. I'm not seeing anything saying they won't ship it.

https://www.velofactory.ch/Shimano-s...in-spacer-type

You can also take the part numbers/diagram to your LBS or favorite retailer and see if they can get the parts.

If it is only the one sprocket, and not your favorite gear, I'd probably ignore it. But, with some luck you could get just that one bad sprocket.

SoSmellyAir

mschwett The cassette lock ring looks quite marked up; does the chain fall off the 11T cog and get wedged or dragged between the lock ring and the frame?

Koyote

Thanks, that was my next question. When I pull off a worn cassette after way more than 3,000 miles, the lockring still looks like new. Why is this one all beat up?

mschwett : Hopefully you bought the bike from a shop...Because if it is only 3,000 miles old, you should take it in for a free tuneup -- and tell them that it runs poorly on the 11t cog. No way should that be happening after so few miles, and it does appear (correct me if I'm wrong) that, as SoSmellyAir suggests, the chain is dropping off the cassette.

mschwett 

25 miles later, definitely still skips on the 11t under full force. not constantly but enough.

i actually don’t remember losing the chain on the back - but looking at the lock ring it clearly happened at least once, but i have no idea when. it’s definitely not common at all. i had one low speed fall on the bike from a sudden rear flat and abrupt clipped-in stop, which scratched the RD a tiny bit and i think the chain dropped. but that was 2,000 miles ago and it hadn’t skipped even once until the new chain. or dropped, that i can remember… and i think i’d remember !

mschwett 

that’s a good suggestion - i didn’t find anything locally suggesting the 11t cog was available by itself. thank you.

Dave Mayer

The Dura-Ace 12 cassette has 5 or 6 larger cogs with titanium sprockets. This is the expensive part, as Ti as a material is expensive and very difficult to machine. The smaller 6 cogs are relatively standard steel.

Since the bigger cogs spread wear over a larger number of teeth, all things being equal, they should wear slower; mine do. So being cheap and creative, when my expensive cassettes wear, then I replace the smaller cogs from an Ebay or Alibaba cassette that can be had for cheap. Of course with the same cog counts and number of cogs in the cassette. A few minutes of searching on Ebay reveals a ZRACE 11-34 12-speed cassette for $40. So I'd mate the smaller new cogs with the larger spidered cogs. I've done this with several cassettes with no apparent deterioration in shift quality.

CliffordK

As far as hacking together a mishmash... I've mated a 9 speed Capreo to a 11 speed Dura Ace cassette. A few adjustments to get it all to work. The outer Capreo sprockets had enough redundancy that I was able to thin the built in spacer part slightly to get it to fit. 1.78mm sprocket thickness (Capreo) vs 1.6mm (Dura Ace 11) didn't seem to be a problem.

Anyway, for 11s to 12s, it may be possible to grind the outer 11s sprocket so that it would fit on 12s.

tFUnK

You say that it only skipped after the new chain; I'm wondering if there might be a stiff link somewhere (for whatever reason) causing the issue?