Aerozine X13 compact chainset

Taiwanese company Aerozine Titanium has a small but growing range of components, including several mountain bike chainsets and this, the X13 road chainset. It's available in both standard and compact configurations, is compatible with 10 and 11 speed setups and has a Shimano-compatible 24mm axle.

Perhaps disappointingly for something which has the word "Titanium" written on it fairly prominently, there's no actual titanium involved at all here. The arms, chainring and chainring bolts are all aluminium (forged 7050T6 for the cranks, machined 7075T6 for the chainrings). The standard axle is chromoly steel, with an optional upgrade to titanium available (we couldn't find a price for this upgrade), but on our test unit the axle was steel.

The X13 is available in standard 53/39 and compact 50/34 combinations with 130mm and 110mm bolt cirles respectively. Aerozine use a traditional five-bolt design unlike Shimano's recent offerings and there's nothing wrong with that in my view. This also means that they're compatible with Rotor Q rings and Aerozine offer the X13 with Q rings if that's your thing.

Arguably the most interesting feature of these cranks from a technical perspective is the "ALS" concept, first developed by Stronglight. ALS stands for "adjust length system", and allows for the crank length to be changed from 170 to 172.5 or 175mm. This is achieved via tapered inserts which push from the back of the cranks into the extended holes, held in place when you screw the pedals in. Our set came with two sets of inserts, one of which is reversed to give the 170 and 175mm options, and a second set with the holes in the centre, for the 172.5mm length.

I'm fairly tall with longish legs, so I generally use 175mm cranks, and my bike fit confirmed that this was best for me. If you've not had a bike fit and you don't know what's best for you, then a set of these cranks would allow you to try different options, quickly and easily. If you have legs of different lengths, this would doubtless be a major selling-point. The ALS system is simple and neat, and adds almost no weight. With a smear of grease on the inserts when fitting them, I had no squeaks or other misbehaviour from it.

You can fit this chainset as a direct replacement for a Shimano set (or those of a number of other brands who use the 24mm axle). I fitted it to a bike with a BB30 bottom bracket, and used BB30 adaptors from Wheels Manufacturing initially (which are basically turned Delrin shims), later swapping to a set of Aerozine's own ceramic BB30 adaptors - nicely-machined aluminium units which replace the BB30-standard 6806 bearings and fit straight into the BB shell, fitted with smaller ceramic ball bearings.

Claimed weight is 690g for the compact and 700g for the standard, a mite optimistic given that we weighed the compact with no BB or adaptors at 749g. By comparison, Shimano's Ultegra 6800 chainset (list price £200) is just under 700g, so we're in the same ball-park. Shimano's chainsets have a great reputation with our Dave giving the 6800 a whacking 9/10 earlier this year, so there's tough competition, but according to Craig from distributors NRG4, Aerozine's customers tend to be those who want something a bit different from the mainstream.

Lookswise they've done a good job - the shiny CNC'd aluminium contrasts nicely with the black sections and the black arms. On a bike I'd say they stand out more than just another set of Ultegra or 105 cranks, certainly. Fitting cranks nowadays is extremely straightforward - the worst you're likely to have to do is tweak the front mech settings a bit to account for any slight change in chainline, although the X13 has the standard 43.5mm. The non drive-side arm is held onto the axle splines via a captive aluminium screw, similar to the FSA Gossamer chainset which these replaced. Earlier versions had a pair of pinch-bolts in addition to this screw but these are no longer present. In any case, I never had any issues with it coming loose.

Stiffness is king in the bottom bracket and cranks area; unlike in other areas of a bike, there's no need to balance comfort or compliance. You want all of your pedaling inputs to arrive in their undiluted fury at the drivetrain, whether you're smashing it up a hill or surging across the line. Here, the spider (the part which joins the drive-side crank arm to the chainrings) appears quite slender when viewed from above, but I didn't feel any lack of stiffness when putting in the power. Lack of stiffness around the bottom bracket tends to manifest as chain rub on the front mech, and again here there were no issues. I don't have the means to provide an objective comparison of stiffness and to be honest couldn't really discern a difference positive or negative between this chainset and other quality alternatives.

I had wondered whether the raw finish on the chainring teeth would make them more susceptible to wear than those with a hard-anodised finish, although having done some reading on this, a hard-anodised component is only marginally more wear-resistant, despite the fact that the oxide itself is much harder than the raw metal. Suffice to say that there was no evidence of excessive wear on the teeth after the test period.

Chainrings have shift pins and ramps located around the circumference plus a sequence of varying tooth shapes to guide the chain from one ring to the other. Those included here worked just fine. Initially I found the chain would sometimes drop off the top chainring but I was fairly sure this was due to a pretty tired Microshift front mech, and switching this for a Shimano 105 unit prevented further occurrences. Shifting was reliable, although my combination of well-used SRAM Apex shifters, 105 front mech and the Aerozine chainset was not a match in terms of slickness for the full SRAM Force setup that I have on my race bike.

As I mentioned earlier, unlike some others, Aerozine use a different bolt circle diameter on the standard chainset to the compact version. Keeping the chainring bolts as far out as possible undoubtedly helps with stiffness but it does mean that you can't change from standard to compact rings and vice versa. For my needs (hilly commuting and some touring) this wasn't an issue.

All in all then the X13 is a smart-looking chainset at a reasonable price. The ALS system is a unusual feature with no real downsides, allowing riders to experiment with different crank lengths. It's a well-made unit that seems on a par with the established competition in terms of shifting and stiffness. You can pick up a SRAM Force or Shimano Ultegra chainset for a similar price, mind, so this will probably appeal most to those who like something a bit outside the mainstream.

Verdict

Smart and well-made cranks with an unusual feature - adjustable length