The Shrinks

On longer rides on BlackBirb, my XC bike, I've been having issues with lower back fatigue and a peculiar amount of chafing on my upper buttocks. I'm no bike fitting wizard, but my instincts tell me that my cranks are too long (170mm feels nice to me, but this one came with 175mm) and the reach is too long (I could plausibly fit either a small or a medium frame from this brand, and I ended up getting the medium).

At some point I'm planning to get a shorter set of cranks, but I'm also planning to do a number of other upgrades at the same time (switching to a 12-speed 10-50 cassette instead of the 11-speed 11-42, getting new wheels, adding a power meter, getting a new derailleur and shifter...) so that's a project for future-me. But shortening up the reach is pretty easy to do on its own.

For reference, this is the current set-up, which is stock from the factory. A 90mm +6° stem, which is quite long by MTB standards though not uncommon for XC bikes at the time.

Having a longer stem is kind of nice when climbing because it puts your weight more over the front wheel, which helps keep it from lifting or washing out on really steep stuff. But if the total reach is too long, you just end up stretched out in an awkward position, which is no bueno.

So, I replaced it with a stem with more modern proportions: 40mm and 0°.

I took it for a quick spin around the block and honestly... it kinda feels the same? I'm not sure if I was expecting a really dramatic difference in handling or in how stretched out or compressed I felt in terms of reach, but people tend to make a big deal out of how much stem length affects these sorts of things. Apparently those people are all crazy.

This lack of difference is generally a good thing, though. I did like the way the bike handled before, so having that change dramatically would have been a disappointment. I'll need to go on a longer ride to see how the reduced reach impacts the lower back fatigue, but I'm hopeful for good things there.

Also, you might notice that I used a different top cap. The reason for this is that the steerer on this fork is cut to a really peculiarly awkward length, where it extends almost exactly 60mm above the top of the headset cap. The stem is 40mm, the garmin mount is 5mm, and all of my spacers are either 5 or 10mm. This means that either A: the top of the garmin mount lines up exactly with the top of the steerer, and I can't apply any preload to the headset, or B: the bottom of the garmin mount lines up exactly with the top of the steerer, and it therefore can't locate on the end of the steerer. The top cap I swapped in here (temporarily) has a little ridge on the underside to help locate against the topmost spacer, the stem itself, or in my case the garmin mount, whereas the original top cap does not. I've got a set of spacers ordered up that has some not-divisible-by-5mm heights, so I'll be able to get things a bit better sorted when that shows up.

But that's a project for another day.

Update: I decided that instead of waiting for more spacers, I'd just file down the top of the steerer a few mm. Now I can just run a 5mm spacer above the stem, with the garmin mount on top of that.

I also switched to the hinged garmin mount, as I needed just a tiny extra millimeter for it to not interfere with the front half of the stem.

Thankfully I happened to have on in my drawer of spare parts, so everything worked out nicely in the end.