Spoonrobot 

So I'm putting together a custom 9 speed cassette and need 21, 24, and 28 cogs. I have all three but they're 10 speed cogs. Looking at Sheldon's crib sheet I see the 9/10 speed cog difference is 0.18-0.20mm.

Is this large enough to make a difference for the three cogs I plan on using? I'm going to use 9 speed spacers so it looks like the cassette would end up being 0.6ishmm too narrow? In addition to shifting issues with the narrower cogs?

Anyone have any experience running 10-speed cogs in a mixed 9-speed cassette?

Cassette will be a 9-speed 12-14-16-18-21-24-28-30-34

HerrKaLeun

I'm a noob, so take this as you may. But 10-speed are thinner and so are their chains. Also a 10-speed de-railer will have different movement steps. It may work, but will shift hard.
Why not buy a cassette? Or did you have the sprockets just laying around and want to use them?

Spoonrobot 

Let me clarify.

I am using 9-speed derailleurs, 9-speed shifters, 9-speed chain and a 9-speed cassette. I want to remove three 9-speed cogs from the 9-speed cassette that are not in the toothways I need and replace them with three 10-speed cogs in the right toothway. 9-speed cassette spacers for everything.

L134 

My attitude towards this stuff is, try it. If it works for you the answer is yes. If not, no. I find sometimes things work for me that others say can't be done.

nfmisso

Yes, true - but it is the spacing not the overall width that will cause issues, narrower cogs will not cause an issue - center to center spacing will.

You need to find some shims, or 9 speed cogs, or go with friction shifting.

CliffordK

I think you have your width calculations off a bit.

Counting from the small end, you're changing out #7,#8,&#9.

#7 will be essentially in the right spot. Slightly thin so you might say the center of the sprocket should be 0.09mm to the left.

#8 will be off by about 0.27mm (to the center of the sprocket)

And #9 will be off by about 0.45mm (to the center).

Try it out. You'll probably be just fine. Off by < 1/2 mm total. If the cassette isn't tight, add a 1mm spacer behind the cassette.

8s spacers are supposed to be 3mm thick.

The 9s are 2.56mm.

You could add a single 8s spacer between sprockets #8 & #9 to bring it back close to the correct spot.

Or, try to shave the 8s spacers to be special 9s.

#6-#7 spacer +0.09 (2.56+0.09 = 2.65)
#7-#8 spacer +0.18 (2.56+0.18 = 2.74)
#8-#9 spacer +0.18 (2.56+0.18 = 2.74)

The actual sprocket width shouldn't be a problem.

headasunder

I haven't come across a ten speed road cassette that doesn't have an alloy carrier for the first 3 cogs, if you have individual cogs and the correct spacers and the smallest cog is still proud of the freehub then your only issue maybe shift quality as the "shimano wave" will be out of sync I've had mixed results doing similar things.

CliffordK

Awww, heck, the OP didn't want sequential sprockets. That will reduce shifting accuracy slightly.

Digging into my old notes:

CS-HG400, 9s All loose (riveted) sprockets
● ar-group sprocket teeth combination: 11-12-14-16-18-21-24-28-32T
● au-group sprocket teeth combination: 11-13-15-17-20-23-26-30-34T
● bg-group sprocket teeth combination: 11-12-13-14-16-18-21-24-28T
● bh-group sprocket teeth combination: 12-14-16-18-21-24-28-32-36T

That should give you cassette options, or donate the 21, 24, and 28 sprockets..

CS-HG500, 10s All loose (riveted) sprockets
11-25T: 11 - 12 - 13 - 14 - 15 - 17 - 19 - 21 - 23 - 25 T
11-32T: 11 - 12 - 14 - 16 - 18 - 20 - 22 - 25 - 28 - 32 T
11-34T: 11 - 13 - 15 - 17 - 19 - 21 - 23 - 26 - 30 - 34 T
12-28T: 12 - 13 - 14 - 15 - 17 - 19 - 21 - 23 - 25 - 28 T

cs-4600, 10s All loose (riveted) sprockets
11-25, 11-28, and 12-30 options

CS-HG50-9 Also riveted 9s

Anyway, I'm not quite sure which cassettes the OP has, but the CS-HG400-9 11-32, or 12-36 should donate the sprockets he wants. It never hurts to try the parts on hand, but the "right" parts are available for $20 to $30.

Looking at the intended cassette:
12-14-16-18-21-24-28-30-34

The progression is a bit odd.
2-2-2-3-3-2-2-4

Generally with the larger sprockets, one can slowly increase the tooth gap to keep the percent change about the same.
The jump from 12 to 14T, (2T) for example, is about a 15% change in effort.
The jump from 28 to 30T, (2T) is about a 7% change, or about half of above.
The jump from 30 to 34T, (4T) is about a 12.5% change, or just a little less than the 12 to 14.

Spoonrobot 

Thanks for the responses everyone. I figured I'd ask before getting out the tools and trying it myself. Save those 15 minutes for more posting I guess

Basically I have a narrow(er) range 9-speed cassette designed for road riding that is new and a partially worn 10-speed mountain cassette where the final 4 cogs are essentially unused. Figured I could combine them and save myself the $20 for a new cassette.

It's for a drop bar mountain bike that I plan on using for gravel racing/singletrack. I'm trying to find a good range of gearing that will work equally poorly for both types of riding.

Previously I was using a Shimano HG50 11-30 and the spacing was too tight for singletrack without a low enough gear for the climb-focused gravel events I ride.

If the rain holds off this afternoon I will try it and report back.

Retro Grouch 

My basic philosophy is that, if I already OWN parts, I'll try almost anything and see if I can tune it to my satisfaction. If I'm BUYING parts, I'll hold out for stuff that's known to work together.

rccardr 

I've done exactly this and it worked just fine using 9 speed spacers.