Bicycle Mechanics - Can I make a custom cassette?

I noticed I have a box full of cassette cogs -- all Shimano 9-10 speed.

Right now I'm running a 12-23 that is way too burly for the more intense hill exercises here. I need relief before next weekend (a century) and a grannier cassette I ordered some time ago online still hasn't shown up yet. Is it possible for me to cobble together a 12-30 out my current cassette parts? Would it all fit together?

Joe

As far as I know yes, since I've done it. I don't know if you can mix cogs of different speeds though because everything I have are 9s. You can try it and see (thats how I did it), or wait for someone more informed to post.

Oh, and just makes sure those pins (actually bolts) and spacers will fit.

Since it's Shimano Sheldon has a table of the combinations that are designed to work and shift smoothly: http://sheldonbrown.com/k7.html

Note the 9 & 10's have a different thickness.
Now maybe you could "fudge" 1 near the end(s?) of the "stack", and live with a bit of "roughness" (for lack of a better word),

The 9's and 10's should work together if you use the correct spacers between them. I've customized a 9-speed cassettes with one 8-speed cog but used the 9-speed spacer and it works fine.

As an expedient, you could remove one of the loose cogs from your current cassette and add an appropiate spacer and a 30T cog behind the 23T. This would give a big jump from 23 to 30 but would give a bail-out gear for the times you need it.

I haved done this so many time with 7, 8 and 9 speed gears. The major thing is the spacers between the gears. They must stay the same thoughout the cage and be specific to your 7,8 or 9 speed shifting system. I know nothing about 10 speed.

The 9's and 10's should work together if you use the correct spacers between them. I've customized a 9-speed cassettes with one 8-speed cog but used the 9-speed spacer and it works fine.

As an expedient, you could remove one of the loose cogs from your current cassette and add an appropiate spacer and a 30T cog behind the 23T. This would give a big jump from 23 to 30 but would give a bail-out gear for the times you need it.

Would the big jump negatively affect ease of shifting? I thought close gears aided in shifting. If not, I'll probably do something like this. I have a broad cadence tolerance on hills.

Some of the cheaper Mega-Range FW's go from a 34 to a 24.
Of course your shift won't be as "pretty" as a closely spaced gear. It certainly shouldn't be "intolerable".

Would the big jump negatively affect ease of shifting? I thought close gears aided in shifting.
It's possible. HG (HyperGlide) cassettes use different tooth shapes to encourage the chain to move between cogs. The relative location of teeth between adjacent cogs is important to smooth shifting, which is why the position of the cog is fixed on the hub. With larger tooth count differentials, some of the teeth won't be in optimum alignment.

Chances are you'll be alright, but don't be surprised if the chain sometimes hesitates or jumps crossing the larger gaps.

Would the big jump negatively affect ease of shifting? I thought close gears aided in shifting. If not, I'll probably do something like this. I have a broad cadence tolerance on hills.

Yes, it probably will to a small degree and you're going to want to anticipate the 23 to 30 shift as it won't be the smoothest under load. Closer gears are better but this is an expedient and it will work.

The thought of shifting from a 30 to a 23 makes my knees hurt.

Al

As Sheldon Brown says, the Hyperglide cogs are shaped to facilitate shifting to upper cogs. In theory, you can't mix and match cogs that easily because they should be related to eachother. In practice, that's true if you like to stand and shift while standing and applying pressure on the pedals. But if you ease up pressure, shifting between "incompatible" gears is not problematic and happens faster than it did on a 1970-1980 bike.

As for a large jump, it's not a problem, as long as you are ready for it. My touring bike has a custom cassette: 12-14-15-16-17-19-21-25-34, and all the shifts are easy. Of course the jump from 25 to 34 or 34 to 25 is a steep one, just like the jump between the middle and small chainrings (34 and 22), but I adapt my riding style accordingly. I should add that the 34 is a bail-out gear, not one that I use that often.

The thought of shifting from a 30 to a 23 makes my knees hurt.

Al
The thought of grinding up a steep grade in the 23T with no alternative should also make them hurt.:)

As I said above, I'm proposing this to the OP as an expedient for one ride but, as Michel confirms, a large gearing gap can be made to work routinely and provides a good bail-out gear with out compromising the rest of the ratios.