Tripple crankset, useable gears ?

[hmronnow]

I got a cervelo soloist team with dura ace 10 speed and fsa crankset.
Since I often cycle alpine trips in my wife's tempo, I thought a triple crankset would be useful. Of course the small front-chainring, cannot work with the smaller rear-chainrings. But which gear-combination should work with proper adjustment?

At the moment, this works without chain touching front- or rear-deraileur:
Front (1 is smallest) -Back (1 is largest)
1-1 to 1-2
2-1 to 2-8
3-3 to 3-10

Thanks
Henrik

 

[RussB]

Your center chainring should work with all the rear gears. When you shift the front derailer, you probably noticed it clicks once going from small to meduim, and clicks twice from medium to large. You'll see something similar when down shifting as well.

This double click is refered to as "trim". After shifting into the middle gear, this "trim" will allow you to reach each end of the back gears. One position will run smooth in the lower gears, but will rub when in higher gears. Shift the front derailer just the one click, and the rub in the higher gears will go away. When you go back to the lower gears you will have to shift the trim back down again.

 

[hmronnow]

Thanks for fast response. Yes, with the 'trim' I can get center front-ring to work with all rear gears, except the last two feel non optimal.

My main question is which rear-gears should work with the smallest front chainring?

Henrik

 

[John M]

Thanks for fast response. Yes, with the 'trim' I can get center front-ring to work with all rear gears, except the last two feel non optimal.

My main question is which rear-gears should work with the smallest front chainring?

Henrik

I think that there is not a real need to use the middle chainring with the smallest rear cogs. When I am needing those ratios, I go to the large chainring plus the chainline is better. I only use the small chainring with the largest rear cogs for steep climbs.

Your little table is about what I use, although your inner chainring should work well with more than just the two largest cogs with proper FD trimming.

 

[RussB]

I agree, The center chainring should work with all gears if it is the dreailer is properly adjusted and using the trim. As for the other two chainrings. One should work well in the top 8 gears, the other with the bottom 8 gears. You just need to anticipate when shift the front derailer depending on what type of terrain is up ahead. IE: big hill up ahead, switch to the smaller chain ring as soon as your speed is right for 8th gear or lower. You don't want to be starting up the hill and have to shift both derailers, you'll lose too much speed. Also never shift both at the same time. cascade them shift the second right after the first completes. Both at once and you stand a higher chance of the chain coming off.

 

[sogood]

Reading elsewhere and double checking the chainline geometry, I try to follow the following.

30 - Largest 3-4 cogs
42 - Smallest to 2rd largest cogs
52 - Smallest 3-4 cogs

Seemed to work but trimming is still useful. Bottomline, that 42 chainring really is a very nice workhorse on my rides when paired with 12-25.