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Home » Cycling » The FSA Pro Compact Crank – the answer to the triple. Kind of.

The FSA Pro Compact Crank – the answer to the triple. Kind of.

August 2013
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IMG_3038My new ride presented an interesting opportunity for a fun little foray into “cycling geek mode”, so I decided to take advantage of it.  I have a new type of double on my Venge.  It’s billed as a “Pro Compact Double” and is somewhere between the compact and standard double.  There are several types of standard doubles:  52/42 is the racing double, 52 (or 53)/39 is another.  The compact double is typically 50/34 which is fantastic for climbing, especially with the 11-28 cassettes, but it leaves a little to be desired for top end speed.

My new Pro double, however, gets the best of both worlds at 52/36 – and it shifts excellently, no hang-ups or slow shifts which I thought would present a problem with such a large jump (from the 36 tooth chain ring to the 52).  The extra two teeth don’t really hurt the climbing gears either.

I went over to Sheldon Brown’s gear ratio calculator and entered in my chain rings and cassette sprockets and this is what it spit back out:

52-36 ratiosThe numbers corresponding with the chain rings (at the top) and the gears (to the left) are speeds at a 90 cadence.  Now I compared the Venge to the Ultegra triple (52/42/30) on my 5200:

52-42-30 I’m gaining 2.8 mph of top-end speed and only losing six tenths on the low-end…  What’s really interesting though is all of the overlap in gears with the triple!  But, and this is where it gets important, with the triple I can’t access the low two gears in the big ring or the top two gears in the small ring because of severe cross chaining…  Not without wearing out the chain rings.  The end result is a lot of shifting any time I come up on a decent hill just to get into a decent climbing gear.  By contrast, I only lose the 28 tooth sprocket in the big ring and the 11 tooth sprocket in the small ring with the modified double…  In short, with the modified double, I can climb a steeper hill more comfortably without having to touch the front derailleur.  Now that works great in Michigan.  Where this will get tricky is my mountain climbing vacations.  It appears I’ll be getting a little stronger for next year.  Losing four tenths on the low-end may not sound like much – until you’re looking up at a 20% grade.

On the other hand, it is plausible that last gear was a little bit too easy for my main climb (and that would explain why my legs could take the effort but my lungs couldn’t) but I was to chicken to shift up a gear for fear I couldn’t get the crank around at the 25% sections.  It’ll be interesting to test this out next year.

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6 Comments

  1. bikevcar says:

    I found the jump was too big on a compact crank when shifting from the big to the little ring. Always killed my momentum on a climb. So I’ve opted for standard 53/39 on my bikes. But 52/36 sounds like a good compromise

  2. The large touring-inspired triple chainsets that were standard on nearly all bikes were replaced with smaller, compact versions that provided greater clearance. Wider ranging cassettes with more sprockets were introduced, not only to provide higher and lower gears, but to reduce the gap to the adjacent gear for more precise cadence control. Harder hitting bikes often lost the front shifting altogether or used a double ring crank and guard for powering down hills with rock clearing confidence.

  3. fizzhogg says:

    You know what I can’t wait for? The post next July when you tell us about the Venge roaring up that mountain road by your vacation place and what it feels like to finally summit the thing!

    No way Cavelo Rossa doesn’t destroy that climb!

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