Sunsanvil

Which DS are you looking at? The 8.6 is the only one with a 3x10 drivetrain. Believe me 10 at the back is not too much choice. I know 2x10 is all the rage right now in higher end cross country, and it sort of makes sense to have finer range at the back, but when I test rode one recently I was in the top gear and felt I could use one more on the fast flats. Wished there was that 3rd chainring.

Remember that its not really 30 speeds. You dont actually go through them sequentially like a car. Think of the chain rings (front gears) as a range choice you set based on the current riding conditions. If you are anything like me you'll spend 90% of you time on the middle chainring, and switch to the other two only when facing extended up/down hill sections.

This is an impromptu calc on my part using Sheldon's, but on the middle chainring you'll have ratios from 2.2 to 6.5. The large chain ring will literally give you a couple more (up to 8.6), same for the small one (down to 1.6).
For 700 X 35 / 35-622 tire with 175 mm cranks

With 10-speed 11-13-15-17-19-21-23-25-28-32 Cassette

[TABLE]
[TR]
[TD][/TD]
[TH="bgcolor: yellow"]48[/TH]
[TD="align: center"]33.3 %[/TD]
[TH="bgcolor: yellow"]36[/TH]
[TD="align: center"]38.5 %[/TD]
[TH="bgcolor: yellow"]26[/TH]
[/TR]
[TR]
[TH="bgcolor: yellow"]11[/TH]
[TH="bgcolor: white"]8.6[/TH]
[TD][/TD]
[TH="bgcolor: white"]6.5[/TH]
[TD][/TD]
[TH="bgcolor: white"]4.7[/TH]
[/TR]
[TR]
[TD="align: center"]18.2 %[/TD]
[/TR]
[TR]
[TH="bgcolor: yellow"]13[/TH]
[TH="bgcolor: white"]7.3[/TH]
[TD][/TD]
[TH="bgcolor: white"]5.5[/TH]
[TD][/TD]
[TH="bgcolor: white"]3.9[/TH]
[/TR]
[TR]
[TD="align: center"]15.4 %[/TD]
[/TR]
[TR]
[TH="bgcolor: yellow"]15[/TH]
[TH="bgcolor: white"]6.3[/TH]
[TD][/TD]
[TH="bgcolor: white"]4.7[/TH]
[TD][/TD]
[TH="bgcolor: white"]3.4[/TH]
[/TR]
[TR]
[TD="align: center"]13.3 %[/TD]
[/TR]
[TR]
[TH="bgcolor: yellow"]17[/TH]
[TH="bgcolor: white"]5.6[/TH]
[TD][/TD]
[TH="bgcolor: white"]4.2[/TH]
[TD][/TD]
[TH="bgcolor: white"]3.0[/TH]
[/TR]
[TR]
[TD="align: center"]11.8 %[/TD]
[/TR]
[TR]
[TH="bgcolor: yellow"]19[/TH]
[TH="bgcolor: white"]5.0[/TH]
[TD][/TD]
[TH="bgcolor: white"]3.7[/TH]
[TD][/TD]
[TH="bgcolor: white"]2.7[/TH]
[/TR]
[TR]
[TD="align: center"]10.5 %[/TD]
[/TR]
[TR]
[TH="bgcolor: yellow"]21[/TH]
[TH="bgcolor: white"]4.5[/TH]
[TD][/TD]
[TH="bgcolor: white"]3.4[/TH]
[TD][/TD]
[TH="bgcolor: white"]2.4[/TH]
[/TR]
[TR]
[TD="align: center"]9.5 %[/TD]
[/TR]
[TR]
[TH="bgcolor: yellow"]23[/TH]
[TH="bgcolor: white"]4.1[/TH]
[TD][/TD]
[TH="bgcolor: white"]3.1[/TH]
[TD][/TD]
[TH="bgcolor: white"]2.2[/TH]
[/TR]
[TR]
[TD="align: center"]8.7 %[/TD]
[/TR]
[TR]
[TH="bgcolor: yellow"]25[/TH]
[TH="bgcolor: white"]3.8[/TH]
[TD][/TD]
[TH="bgcolor: white"]2.8[/TH]
[TD][/TD]
[TH="bgcolor: white"]2.1[/TH]
[/TR]
[TR]
[TD="align: center"]12.0 %[/TD]
[/TR]
[TR]
[TH="bgcolor: yellow"]28[/TH]
[TH="bgcolor: white"]3.4[/TH]
[TD][/TD]
[TH="bgcolor: white"]2.5[/TH]
[TD][/TD]
[TH="bgcolor: white"]1.8[/TH]
[/TR]
[TR]
[TD="align: center"]14.3 %[/TD]
[/TR]
[TR]
[TH="bgcolor: yellow"]32[/TH]
[TH="bgcolor: white"]3.0[/TH]
[TD][/TD]
[TH="bgcolor: white"]2.2[/TH]
[TD][/TD]
[TH="bgcolor: white"]1.6[/TH]
[/TR]
[/TABLE]