[irablumberg]

Has anyone with a road tandem switched from a triple front crank to a compact double?

I was considering making this change to simplify front shifting and reduce weight. I am curious if anyone has tried this.

Unless I hear that this is a really terrible idea, I will probably take a flyer on it if I can find a compact that will fit my current bottom bracket (Octalink) since I can keep the existing left crank arm and simply use the new right compact crank. So far, the only Octalink compact double I have found is the Ritchey WCS, but no one has it in the required 170mm size in my area. I am hoping that the local Performance shops will get some of these.

Cheers,
Ira

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[TandemGeek]

We know of several teams who run doubles, but not with "compact" gearing.

Technically, we've got "compact" cranks on both of our road tandems... daVinci 110 bolt circle diameter (BCD) cranks: sorry, square taper only. Remember, "compact" is merely a new name for what have been known for eons known as "standard" cranks. The migration to 130 and 135 BCD "racing" cranks seems to have precipitated the redesignation of the 110's as "compact" and, at the same time, spawned a major coup for crank manufacturers.

Less I digress.... We just happen to run our "compact" cranks with 54/44/32 triple chainrings, but could just as easily throw on the smaller 50t/38t or similar "compact" chain ring combo. However, I'm not sure why I'd want to do that on a tandem. 99% of our riding is done in the big and middle ring with the "granny" available as a bail-out for very steep (>15% grade) climbs in the mountains where we're usually darn glad it's there. If we rode mostly in flatlands, I'd still probably want a larger chainring on the tandem vs. what I used on my single and would just run a triple without the granny ring installed using a 54/44 or 53/39 combo.

For reference purposes, one of my singles is fitted with Campy Chorus 135 BCD cranks sporting 53/42 chainrings & 9 speed gearing and the other has Stronglight 110 BCD standard cranks with 50/36 and 10 speed gearing... the latter is my climbing bike which runs a 13x25t cassette. My wife's road bike also has standard cranks... Centaur triple with 50/40/30 and 10 speed gearing (12x29). Of course, 20 some-odd years ago I was able to ride into the San Bernardino mountains using 110 BCD 52/39 cranks with a 13x19 corn cob / straight block freewheel... Oh to be young again. So, no bias for one vs. the other, I simply gear them according to how they will be used and what each rider might need available given their needs/riding strength which, over time, can change.

Anyway, knock yourself out... just be sure you run the gear tables to understand what you'll have in terms of steps and overlap with the various combinations of chainring sizes and cassettes you'd be using.

[ElRey]

You've already got a triple... most folks who go to COmpacts are those without the power to turn a standard double, but don't want to run a triple.

Spend the money on a wheel upgrade. The best money you can spend on a bike, more or less.

[irablumberg]

We already run the Shimano Sweet 16 wheels, so I don't think a wheel upgrade is in the cards.

I'm mostly interested in seeing if I can get 2 chainrings to do the work of 3 without giving up anything important for my riding style. The compact cranks I'm looking at are 50/34 compared to the 53/39/30 triple I now run. I don't mind giving up the high end as we are too lazy to pedal at those speeds anyway. On the low end, we'd be giving up a 30x34 gear, but I don't feel comfortable pedaling in that gear with a stoker anyway, its just too slow to feel stable.

Ira

[TandemGeek]

The compact cranks I'm looking at are 50/34 compared to the 53/39/30 triple I now run.

I would have a hard time with that big of a gearing jump from the big chain ring to the small ring with the 16t front chain ring differential. I even struggle a bit with my 50/36 but can't go to a 48t up front without a frame mod as my bike has a brazed-on front derailleur mount. 50/38 might work, but I'd have to go to a 13x27 cassette for some of the steeper climbs 'round here and I'd rather not do that on my single bike.

So, you'd have to give it a go to decide if the somehat larger than average gearing jump from the big ring to the small ring would be objectionable or not a problem; very subjective.

[irablumberg]

I would have a hard time with that big of a gearing jump from the big chain ring to the small ring with the 16t front chain ring differential. I even struggle a bit with my 50/36 but can't go to a 48t up front without a frame mod as my bike has a brazed-on front derailleur mount. 50/38 might work, but I'd have to go to a 13x27 cassette for some of the steeper climbs 'round here and I'd rather not do that on my single bike.

So, you'd have to give it a go to decide if the somehat larger than average gearing jump from the big ring to the small ring would be objectionable or not a problem; very subjective.

I made the switch from a 53/39 double to a 50/34 on my half bike while keeping the 12-27 cassette and I really like it. I did need to adjust my shifting practices, but it only took a few rides to get used to the new gearing. I can now climb fairly steep hills that previously were simply too much strain for my aging knees.

I have been assuming that a 50/34 on the tandem would feel about the same as it does on my half bike. We shall see.

Ira

[mrfish]

I really don't understand why you would want to change from a triple to a compact. Only reasons I can think of are:
a) Lower Q-factor
b) Aesthetics
c) Weight weenieness

If the gearing on the small ring is too low and therefore rarely used, a better option could be to use a tighter ratio block. For example my Trek has 11-34 which gives gaps which are bigger than I'm used to when riding on the flat. Using single road bike blocks like 12-25 or 11-23 would cover this, while still leaving a low speed uphill option.

Also if you change only the left crank, you could end up with one crank with bigger Q-factor than the other, which probably isn't great from a biomechanical point of view.

Lastly, IMO the tandem is a different beast from a single bike, and the tiddly inner ring really is necessary when you encounter steep climbs that you could power up on a single bike or just run out of energy.

[zronn]

What about just running a MTB cassette?
12 x 30 and loose the little ring?

Of course the shifting problems can be alocated to ShimaNo. Switch to Campy with the micro adjust built in.