Road Cycling - changing triple chainrings

Ah ha! I had you tricked. I'll bet that you were thinking, "not another one of these !#$@#$ing triple to double threads!

Well, you are sorely mistaken!

I'm buying a Lemond alpe d'huez with a triple crank. (hey! it gets pretty freakin' steep in MD!) I am used to a 53/39 crankset though. I was thinking, whould it be possible to simply swap out the 42 chainring for the 39? I did not notice the one tooth difference in the 53 during the test ride, but I did notice the difference in the middle ring, where I ride the most. I have asked the LBS, and they said maybe. I know that there is a DA crank with a 53/39, why not a 105?

The middle chainring of a triple has ramps and pins on the inside to help the shift up from the small ring. The rings on the double don't have them in the correct places. Also, I believe the triple front der can't lift a chain to a ring that is more than 12 teeth larger. Or it can't without a great deal of effort and/or crappy shifting.

Is there a 30/40/50 option?
If you want to brew your own ratios, consider using Specialities-TA rings. These are good enough for US-Postal team, and available in a huge range of sizes.

Shimano doesn't offer a 40t middle or a 50t outer chainring. Salsa does, as does Sugino.

I went with a double instead. I asked the LBS mech, and we considered all the options. the decsion I was closest to making was to take the bottom two rings off of a dura-ace triple, and putting them on my 105 setup, but that was an extra $80 for just the parts. The double also shifts A LOT quicker, like BAM! and you've shifted. the triple that I tried hesistated a bit. At first, I thought that all of the long cage/short cage business was all in people's heads, but it isn't!

Phatman,

I have 105 Triple... and I have the same problem. I hate the 42 tooth middle chainring. I so wish it was a 39. Unfortunately, Shimano only offers the 53/39 rings for the triple in Dura-ace. Sucks. I have actually considered going to a double quite a bit. I looked at all the gear ratios (I have a 12-27 cassette and a 52/42/30 Crankset), and the triple only gets me two lower gears than I would have if I had a double crankset (53/39).

Unfortunately, it wouldn't be super cheap to switch to a double, so I guess I'll live with it. But I'm definitely going to go with a double on my next bike.

I'm still not quite sure what the big deal with a triple is... those two lower gears are a matter of 0.33 in the gear ratio. So it's not a huge difference. If they are going to give you a triple, it really should be something like 53/39/27 or 53/39/25.

PBW

There are several companies out there that offer 48/38/26 chainrings for Shimano triples. That works pretty well for most people (except racers who actually need a 53)

One neglected format is the low-ratio double, using a small PCD crank. I used the cheapie Stronglight 80 crank, which originally came with a 36/48, then I set it up with 3 rings, 28/38/48. Specialities-TA make a lovely double with a 110mm PCD which does a similar job.
Its great for lightweight tourists who dont want to pedal hard.