djtrackie

I recently ordered an 11 tooth sprocket from you Harris Cyclery online. I was under the impression that I can swap out the 12 tooth on my dura-ace 12-25 cassette for the new 11 tooth sprocket. But it seems that the built in spacer is a bit larger than the current 12 tooth sprocket so the derailer doesn't shift quite right. The cassette is a 9 speed dura ace. I already tried adjusting the limits on the RD, but even at the max... it just won't interface right.

What else do i need to make the 11 tooth sprocket work on my dura-ace 12-25 cassette?

Below is a picture of a 9 speed dura ace 12T cog and on the right is the 11 tooth I got from Harris Cyclery. As you can see, the 11 tooth cog is about a millimeter taller than the 12T one.

Did they send me the wrong cog?

HillRider

Maybe the 11T is an 8-speed or even a 7-speed cog which have wider spacers than 9-speed.

erader

the 11-tooth cog requires a different lock ring and the cassette body of your hub must be compatible or modified.

ed rader

2_i 

Derailleur's position for the smallest sprocket is determined by the limit screw and not the shifter. Provided there are no problems with putting the sprocket on, just adjust the limit screw.

The sprocket they have sent you must have been intended for fewer speeds. Only such sprockets, to my knowledge, are available separately. What I suggest above is the standard procedure to make them work.

djtrackie

The lockring fits onto the cassette, so I can't imagine it being a lockring issue.

As for the limit screw, I already tried adjusting it, and the problem is that when the limit screw is all the way out like that, the chain interferes with the skewer.

Michel Gagnon

If you are patient, file it. I never did that with a starter cog, but I did it with lots of spacers.

2_i 

The skewer should be on non driveside.

cascade168

11 tooth cogs are not compatible with all Shimano freehubs, as is clearly pointed out on the Harris Cyclery site:

https://sheldonbrown.com/harris/k7.html#11

On that same page there is a table that shows which freehubs ARE compatible. Scroll to the "Freehub ® Bodies" section and you will see that there is a column that shows "11 tooth compatibility", or not.

Did you make sure and check this out before you purchased your "11" ?

erader was right on with his comments ;-)

Here's a section with pictures of what makes a type "C" hub different (and allows the "11"):

https://sheldonbrown.com/k7.html#hyperdrivec

Michel Gagnon

To "Cascade168":
The Hyperdrive-C freehubs allow one to install an 11 cog onto the hub. If I read the original poster correctly, his problem is not that, but rather that the cog is too thick. Either it's a cog made to go in a 13 or whatever suitable mate (I doubt it) or it is a cog made for an 8-speed cassette. The latter is more likely. Practically speaking, most cogs are interchangeable, but the starter cog isn't because it incorporates the spacer.
If he had a 9-speed cog but a non-compact Hyperdrive freehub, his cog would be of the same thickness as the 12 he is replacing... but he would nonetheless have problems inserting it far enough.

To "2_i"
I think your first message is correct. About your latest one, I think the original poster meant that the chain interfered with the right dropout. Some bikes have very tight clearances and I, for one, have seen that problem when going from an 11 to a 13 starter cog or when going 8 to 9 speeds as the cassette is a little bit wider (even though it fits on the same freehub).
As for the skewer itself (i.e. the handle itself), it's traditional to have it on the left, but it's very easy to place it on the right without interfering with the derailleur.

cascade168

Yup, I see your point. But, what does not make sense to me is that there is not enough adjustment in the "H" limit to allow for an extra mm or two. I would ask djtrackie - was the "H" limit adjust screw already at it's end with the old 12T cog?

The one other thing to look at is the lock ring. There is a special lockring required for an 11T on a Hyperglide "C" hub. Here's the quote from Sheldon Brown:

"Note, if you install an 11 tooth sprocket on an existing cassette that had a larger top gear, you must also replace the Hyperglide lockring with a Hyperglide-C lockring. The lockrings made to work with 11 tooth sprockets have a smaller outside diameter. If you use a larger lockring, the side plates of the chain will hit the edge of the lockring, and the chain will not run properly on the 11 tooth sprocket. (Hyperglide-C lockrings are compatible with all sprocket sizes.)"

So, the OP says that with the new sprocket the "derailer doesn't shift quite right". Did djtrackie replace the lockring at the same time? Since this is obviously a known problem, I'd want to know the answer to this question.

That note about Hyperdrive C hubs has to be read very carefully. It also says that a spacer may need to be added to the axle in some cases. This would definitely change the limit adjustment AND the wheel dish. Just a thought .....

Al1943

From the photo, the built-in spacer is too thick. I had the same problem with a first position 13 that I ordered from Harris cyclery. As others have pointed out it's for a cassette with fewer cogs, wider spacing. You can either grind the spacer down to the correct thickness (you'll never file it down) or send it back to Sheldon. I'll bet he'll make it right one way or another. I ground mine down with a bench grinder.
BTW, the 11t cog does require a special lockring with a smaller diameter to create enough room for the chain to fit the cog teeth. Just because your old lock ring screws in does not mean it will work.
I'd much rather have a 12 than an 11. But experimentation does make the world a fun place.

Al

cascade168

Yes, I think you've got it.

The OP never said how many cogs on his cassette.

The spacer should measure:

3.0mm - for an 8spd
2.56mm - for a 9spd
2.35mm - for a 10spd

If he can measure that spacer thickness he should be able to tell exactly what he has and if it's the correct one. Easy to do with calipers or a depth mic.

HillRider

The "spacer" for a top position cog is "built in" to the cog so you can't easily measure the spacer's thickness by itself. Do you have the overall thickness dimensions for 8, 9 and 10-speed top cogs?

cascade168

Huh? Depth measurement is one of the three basic measurements you can do with calipers (thickness, width, and depth). It's as simple as it gets. If you have access to a depth micrometer, that's exactly what they are made for.

freeranger

Rather than guess and reiterate what others have already said, why not just call, or e-mail Harris, tell them what cassette this 11T is to fit, and I'm sure they can get you up and running. Can't think of anyone better to ask than Sheldon Brown!

djtrackie

I really have come to the conclusion that the sprocket is just too thick.

I have emailed Sheldon.. several times actually (with a week or two between emails) and I haven't yet got a reply.

I guess i'll try giving them a call tomorrow. Are they pretty good with return/exchanges?

it seems is like this is what i need

https://aebike.com/site/page.cfm?PageID=30&SKU=FW4650

HillRider

OK, you make a good point. I was just pointing out that the spacers on top cogs aren't separate so measuring the over all thickness of the assembly won't give you the spacer thickness. You have to measure from the inside face of the cog to the top of the spacer and that does require a "depth" measurment, not a thickness measurement.