The lowest cassette Shimano has is 12-27. It seems that if you want to go lower than this, then the "oficial" solution is that you use a triple.

That does not make sense to me. Knowing that (some) cyclists are a bit reluctant to use triples, why limit the low gears to 27? It's not like their main market is pro racers who hardy ever need it. There's plenty of people out there who could use a 29 or larger.

I want to have some low gears on my 10 speed and basically my options are:

- Triple
- Use 9 speed mtb cassette, change chain, derrailleur, maybe levers as well
- custom cassette
- train some more and get a 12-27

It's such a simple thing....Campy has a 13-29 cassette. Why can't Shimano?.

Although I am certainly far from an expert - I believe it has to do with the rear derailleur's capacity to handle only up to a 27 tooth cog....

I think they do a short cage and a long cage RD for that reason....

Now you've got a good excuse to switch to Campy!

There are some other alternatives you've failed to mention. A 50/36 compact crank will produce about the same range with a 12-27 as a standard 53/39 with a 13-29. A 50/34 would provide another low gear.

The downside to wider spaced cassettes is the big jumps between gears. Although it may be tolerable for MTB use, on the road the big jumps will leave you forever hunting for the right gear, which isn't there.

Another point about the switch to a triple. Although it's looked down upon by young and fit riders, it's often the best choice for many as we get older and/or ride demanding terrain. I rode in the Kansas City area where there of plenty of moderate hills and never used any gear lower than a 39/21 until Campy 10 speed came out in 2000 (at age 47). I first switched to an 11-23 but found little use for the 11, so I switched to a 12-25 the next year.

When I moved to Denver at age 50, I knew before the move that a triple would most likely be the wise choice and built one up ahead of the move. I first used a 53/39/30 with a 12-25 and later switched the little ring to a 28. In the early season, I don't want to avoid the steep mountains, so I use a 13-29 with the triple, until my fitness improves. I give up the 53/12 that I use a lot on descents, but in the early season, the roads are too dirty for high speed descents, to it's no big deal.

The biggest complaints about using a triple are largely unfounded. The first is additional weight, that only amounts to 1/4 to 1/2 pound. You'll lose a lot more time when climbing with inadequate gearing than with the small amount of extra weight. The other complaint is the vague "complicated shifting" excuse. While it has more truth with Shimano shifters that have vague "soft" shifts to trim the FD, it's not true with Campy. The left shifter uses 7 identical clicks to move the FD wherever needed. Setting up the FD is simple and only slightly different than a double FD. The shifting pattern with the little ring is the same and any other - make the shift to the smaller ring, then shift 2-3 cogs smaller to resume the progression.

The lowest cassette Shimano has is 12-27. It seems that if you want to go lower than this, then the "oficial" solution is that you use a triple.

That does not make sense to me. Knowing that (some) cyclists are a bit reluctant to use triples, why limit the low gears to 27? It's not like their main market is pro racers who hardy ever need it. There's plenty of people out there who could use a 29 or larger.

I want to have some low gears on my 10 speed and basically my options are:

- Triple
- Use 9 speed mtb cassette, change chain, derrailleur, maybe levers as well
- custom cassette
- train some more and get a 12-27

It's such a simple thing....Campy has a 13-29 cassette. Why can't Shimano?.
Evidently the Japanese just cannot imagine the absurd things we will do to avoid the disgrace of riding a triple. Note also their extremely late entry into the compact crankset market. The Italians, on the other hand, completely understand what we will sacrifice and pay for fashion. - TF

"Campy has a 13-29 cassette. Why can't Shimano"
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It's because Shimano refuses to prostitute themselves to the unfit who wish to use their top of the line racing group. They feel that if these unfit riders are compelled to ride Dura Ace, they must wear the stigma of a triple. This is the same reason that there isn't a compact Dura Ace crank.
There are other companies that are quite willing to prostitute themselves. You might want to look at them. One of these companies once had a motto of " If you want something lower than a 42, go suck an egg".