When outfitting my new Ritchey Break Away travel bike, I decided that I wanted to go with a compact crank. Desiring a bit of "bling," and having heard good things about FSA ("Full Speed Ahead"), I decided to try out the carbon SL-K compact crank.

If you want a long explanation for why I went with compact, see the bottom of this review. Warning - it's kind of geeky.

Current street price on this baby is about $399. Mine was a $100 upgrade when I swapped out the DA7700 (2004 9speed) cranks, which I thought was a pretty good deal (the Dura Ace cranks and BB together runs about $270 currently).

Design
Cranks
The SL-K compact has compression-molded composite (carbon) crank arms. The right side crankarm is formed in one-piece with the spider (110mm bolt circle diameter - BCD). The arms are black carbon finish with a high-gloss clear epoxy coating and relatively subdued (for FSA) decals. The arms take standard-sized pedals, with a washer between the pedal and crank that you don't want to lose.

Rings
The SL-K compact is available only with 50/34T aluminum alloy rings, though any 110mm BCD rings will fit, should you want a different setup. The rings are black with silver teeth and bolts.

Bottom Bracket
The Mega-EXO bottom bracket is included in the package. It won't work with other "stock" or aftermarket BB's. The "Mega-EXO" refers to the oversized cartridge bearings (bigger than the BB shell) that are mounted external to the BB shell. Placing the bearings that far outboard makes the crank significantly stiffer, since the BB axle is supported at the ends. Shimano's latest Dura Ace crankset uses the same idea.

The larger bearings (40% larger than before) also mean greater durability, according to FSA.

The problem with this design is that it forces the crank-to-axle connection outboard also, which has the potential of increasing the "Q-factor" (how far apart the pedals are). To avoid this, the SL-K has less of an angle between the center and end of the crank (more on this later).

Weight
Weight for the crankset, including the BB is listed at 760g, which is pretty light.

On the Road
This is one sweet crankset. The bearings are exceptionally smooth (of course, they're brand new with only a few hundred miles on them so far), and it is one stiff setup. My other bike has an Ultegra 6500 crankset which is pretty stiff, but when I stand to climb or sprint, I can get a bit of derailleur rub. On this crank, the chainrings stay straight and true, no matter how hard I mash.

The only problem I have is that with my shoes set up with the cleats dead center on my shoes for my LOOK PP296 pedals, my heels rub the cranks if I turn them in more than a degree or two. This is due to the changed geometry of the crankarms. When I replace my cleats in a few weeks, I'll move them a 1/2 cm inboard, and this will take care of the problem by effectively increasing the "Q-factor."

Shifts are no problem with the IRD compact front derailleur I am using. Quick and sure.

I am very pleased with the change in gear ratios afforded by the new compact setup. I find myself rarely needing the 34 ring on flat terrain (except during some of the huge 30mph winds we've had lately) while I'm visiting Virginia, and am looking forward to trying it out on the mountains.

Overall
I am quite happy with the crankset. The changed crankarm geometry is a bit of an annoyance, and if you have very narrow hips, this may be noticable to you. I don't think it will be very noticeable to me.

The increased space between gears doesn't seem noticeable. Again, a higher-level rider might disagree.

Warranty
Currently, FSA offers a 10-year materials/workmanship warranty on the crankset, with a 1-year warranty on the bottom bracket and bearings.

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The LONG Story of Why Compact?
Compact cranks have made an impact on the market later. The difference between a compact and standard crank is the bolt spacing where the chainrings attach. Standard cranks on most modern road bikes have a 130mm BCD (Bolt Circle Diameter), with the common chainring combo of a 53 tooth big ring and 39 tooth small ring (53/39T).

A compact crank, on the other hand, has a 110mm BCD, allowing smaller chainrings. My SL-K came with 50/34T setup, but other common combos are 50/36, and 48/38 (popular in cyclocross).

Having smaller chainrings up front means that, given the same size cog in the rear, you get less revolutions of the wheel for every turn of the crank (pedals).

Now why would you want to do that? Well, a few reasons.

My other bike is set up with a standard 53/39T front, and a 12/25T cassette in the rear, a pretty common setup for a fast rec rider like myself. Using 700x23 tires, this gives you a range of 41.0 to 116.1 gear-inches (distance you move forward for each turn of the crank). 8 of those combinations are near-duplicates (within 2 gear-inches of each other), giving you 10 unique combos in an 18 speed drivetrain.

When I wanted to do hills, I would swap to a 12/27, which gave me a slightly better granny gear of 38.0 gear inches.

My new setup, with a 50/34T front, 11/23T rear, gives me a range of 38.8 to 119.5 gear-inches, meaning a lower low and a higher high gear, with only 4 duplicates, so 14 unique combos.

What's more, for hills, I can drop in my 12-27 cassette and have a real granny gear (33.1 gear inches). That's nearly as low as a standard road triple (a 30T little ring, 12-25 cassette gives you a 31.5).

Why doesn't everybody use one of these, then? A few reasons for this also.

First, the wider range means a bigger difference between gears - not huge, but it is bigger.

Second, since you can't go any smaller than 11T on the rear cog on current hubs, it means your tallest gear possible is 119.5 gear inches, while a 53x11 combo gives you 126.6 (and available 54 or 56 time trial rings can give you much taller gears).

Unless you are a CAT 1/2 or Pro-level racer who needs to spin out a 53x11 (at 120rpm, that means a difference of 45mph vs 42mph), this shouldn't be much of a factor.

One more thing - although I have talked to people who have used standard front derailleurs with compact cranks, technically the 16T difference between rings exceeds the capacity of Shimano front derailleurs. If you have a Campy setup, this is no problem - campy makes compact front derailleurs. I think they'll work OK with Shimano shifters also. Another option (the one I took) is the IRD compact front derailleur (about $50 list price).

Recommended: Yes