Turn Down For Watts

A fair few years ago I purchased a power meter off of Ivor, a cow-orker at Google. It was my first power meter, which I dutifully mounted to my CAAD 10 road bike, and it started me down the road of quantifying my on-bike fitness in real time.

When my CAAD 10 frame cracked, I ended up building an S-Works Tarmac to replace it, and the power meter was one of the parts I brought along. It's been serving me well ever since.

However, serving me well doesn't mean serving me perfectly. Since I bought the power meter second-hand, I wasn't able to pick the configuration to exactly match my preferences, and so I've been making do with these Shimano Ultegra chainrings.

What's wrong with them? Well, first off they're a 52-36 combo, which is commonly known as "mid-compact". It was created as a middle ground between what was previously the standard chainring setup of 53-39, and the newer compact chainrings that sported a 50-34 tooth count.

Those extra two teeth aren't the end of the world, but given that I spend a lot of my time in the hills and exactly zero time drafting in a group, I really wasn't getting any benefit from the taller gears.

Also, must more importantly, they're the wrong colour.

You see, the Quark Dfour power meter was designed to match up aesthetically with the Shimano Dura-Ace R9000 chainrings, which have a silver-on-black colour scheme and a different shaping where they meet the spider. They're also lighter, which is nice, and more expensive, which is why most people don't bother.

But I bothered.

So let's get these on the bike!

The first step is to take the pedals off. This might seem like a peculiar first step, but there's a method to the madness here, which I'll come back to in a bit. These are XTR SPD clipless pedals, so they come off using an 8mm hex in the back side.

Next we remove the drive-side crank arm so that we can pull the crankset from the bike. If you've ever removed a SRAM/Quarq crank arm, you'll know what the right tool for the job is.

No I am not kidding.

Now we reveal why I removed the pedals: I'm going to swap the power meter from this set of crank arms to the S900 crank arms that I used to build up my CAAD 12. The reason for this is that I've standardized on 170mm crank arms, and the ones that came on this power meter are 172.5. It's not a huge difference, but since I have the parts I might as well do the swap.

Except...

Yeah, I forgot about that part. The S900 uses the 3-bolt mount for the spider, whereas the Quarq uses the newer 8-bolt mount. RIP.

Oh well, 172.5 isn't all that bad. Plus having everything apart and the pedals out of the way makes it easier to clean things up nice and shiny, so it wasn't a complete waste.

Anyway, getting back on track, I mentioned that the Dura-Ace chainrings are lighter, and here's the proof.

Mind you it would be alarming if they weren't lighter, given that the DA chainrings are also physically smaller in this case, but it's nice to see that there's a meaningful difference between the two.

With that out of the way, it's just a matter of reassembling things, adjusting the front derailleur, and we're good to go.

Now that I've got this smaller chainring set, what effect will that have on my riding? Well, on the low end I'll be going from a 36:32 ratio to a 34:32 ratio, which means that if I'm grinding up a hill at about 60rpm I'll go from 5.3mph to 5.0mph. On the high end, I'm going from 52:11 to 50:11, so if I'm pedalling my legs off with a tail wind at 100rpm, that'll drop me from 37.2mph down to 35.8mph.

Is it a big difference? No, no it is not. But it's a difference in the right direction, and more importantly it looks way, way better now that the spider and chainrings aren't mismatched. My only regret is that the Quarq spider hides the silver ring on the 34t chainring in the back.