FSA SL-K Light Compact Megaexo chainset with bottom bracket

FSA's SL-K Light Compact MegaExo chainset might be a bit of a mouthful to say but it is light, stiff and strong while after six months of use the bottom bracket is still running as silky smooth as it was out of the box.

The cranks are monocoque carbon composite with "enriched glass fiber content" says the blurb (although we didn't have any luck finding out what enriched glass fibre brings to the party), they're also hollow to keep the weight down, with a unidirectional carbon finish. The 50/34 tooth chainrings are strong 7075 aluminium, CNC machined. They're held in place with Torx T-30 alloy bolts so swapping new chainrings in place when they eventually wear out is a simple job.

As usual with an external bottom bracket system, the 24mm axle is cromoly, while the chainset comes with a 145mm Q-factor (pedal stance width). The bottom bracket comprises oversized steel cartridge bearings in forged and machined FSA MegaExo cups.

According to the road.cc scales, the chainset (with 172.5mm cranks) weighs 646g (470g + 176g) which is exactly the weight FSA claim in their marketing literature. That's notable in itself. Manufacturers habitually seem to knock off about 5-10% when quoting product weights... well, lots of them do, although not all, which makes things complicated. The BB weighs another 100g.

That's about the same as Shimano Dura-Ace (£439.99), for example, while FSA quote 596g and 100g for their top-level K-Force compact chainset and bottom bracket.

Getting everything set up right is easy enough, although as well as the usual bottom bracket tool you need a MegaExo bolt pin tool (or a BB pin spanner that'll cost you just under £20). Or you could just get the guys in your local bike shop to do it for you.

Once up and running, the best you can say about a chainset is that you don't really notice it too much, and that's the case here. It gets on with its job without any fuss at all. I've used three different chains with this chainset - one from Shimano, one from YBN, and one from FSA - and they've all run smoothly with very little noise. They've all ramped up between the chainrings quickly and reliably too.

In terms of wear, the chainrings are looking pretty good still and, after a quick clean, the cranks are almost as shiny as they were on day one. I've managed to scuff a graphic slightly on the non-driveside somehow but apart from that you'd hardly know they've been through a winter and spring of regular riding.

The bottom bracket is going strong too without any creaks. You can't open it up so it's impossible to say for sure, but it still feels ultra-smooth without any contamination in there from wet and grimy rides.

The only question is why you'd buy this chainset/BB combo over anything else out there. You can't buy a complete SL-K groupset and there's no price saving over equivalents from Shimano and SRAM, for example. They're all similar on actual weights too - less than 20g between them. I imagine most people already on Shimano or SRAM are going to stick with those. Perhaps if your bike already has an FSA chainset and you want to go with what you know when upgrading, the SL-K Light will appeal. Whatever your reasons you do fancy making the switch the SL-K Light won't let you down.

The FSA SL-K Light Compact Megaexo is also available in standard (53/39T) and triple (52/39/30T) versions, in a BB30 option, and in 165, 170, 172.5, 175mm.

Verdict

Lightweight, strong and stiff chainset with a smooth and reliable bottom bracket