Wednesday, November 06, 2013

Equipment - Custom Stem Thoughts

I've written about my whole bar dilemma. Basically it comes down to this - I spec'ed out my Tsunami Bikes frame set based on a slew of bars I've accumulated over the years, old style crit-bend bars. They're not readily available now so I started looking for another bar, something more current than, say, 20 years old. This is sort of like my saddle search, looking for a saddle that was made beyond the year 2000.

At any rate a sprinter-type friend recommended I try the FSA Compact bars. Another racer, who happens to own a shop, also recommended them for a rider like myself. I decided to get a set to check them out. This involved more than just buying the bars - since they were the 31.8 oversize bar diameter I had to get a stem as well.

Everything about them felt great except for one thing - the actual position of the drops. Not "the way the drops felt", which were fantastic, it was the location of the drops that caused problems.

See, the compact bars were 3 cm shorter in reach and 3 cm shorter in drop.

I had bought a longer stem, 2 cm longer, and that was okay, but the drop… I couldn't get the drop. I actually considered commissioning  Joseph at Tsunami to build a new frame for me, but then I realize that it would effectively move the front wheel forward relative to me.

See, if the front wheel is in a good spot relative to me using the old style bars, then I need to keep the front wheel in the same spot. It's good for center of gravity, for cornering, etc. If I had a frame where the front wheel went forward 3 cm then I'd be a bit less over the front wheel.

Also, and this was a deal breaker, Joseph can't do a shorter head tube. I actually asked for "the shortest head tube possible" with the idea of buying 80 and 90 degree stems, stems much more available in various lengths than the 73 degree stem that I was using at that time.

With no reason to commission a frame I had to look closer at the bar/stem problem. I decided to tackle it by getting deeper drop bars. I bought some FSA Energy bars, which advertise a much deeper drop, 3 cm more in fact. Technically that might be true but the shape and position of the drops meant that they effectively dropped less.

The FSA Compact bar in front is where I want the bars.
The FSA Energy bar in back.
Effective drop is maybe 2 cm less than I want.

You can see how the curve of the drops differs significantly. The Compact has a flatter drop that comes up much later. The Energy bar curves up almost immediately, effectively raising the drops by a couple centimeters.

You can also see how tilting the Energys down (twisting them so the brake lever drops a bit) won't help - if anything they'll bring the drops further up. I could tilt the Energys up, so the brake levers go up, making the drops a bit more vertical, but then that would screw up the tops. Therefore the bars won't work for me.

Tops of the bars.
Gives you an idea of how much lower I want to be.

I'm holding the tape measure a bit skewed due to trying to hold the camera but it's 3 cm.

Based on what I found with the different drops I decided that a 3 cm drop would work out pretty well. If it ends up a bit aggressive I could always put a 5 mm spacer under the stem. Realistically it should be very close though.

I understand that the tops would be 3 cm lower as well. That made me think a bit but I decided that would be okay. I'd be in a much lower position on the tops, basically a bit closer to a drops position. The hoods, too, would be 3 cm lower. That I was okay with, I didn't think about that too much. My main concern was the position of the drops.

Once I have a stem that allows me to use a compact type bar it means that I can by any bar I want! This is huge - it really opens up the world to me. Anything with about an 8 cm reach and 12 cm drop becomes possible. Trying to use a stock stem limited me to an 8 cm reach and 15 cm drop, a rarity in the handlebar world.

Since I don't remember my plane geometry I did my calculations the old fashioned way - using a real scale drawing with rulers and a protractor.

My current stem is a 70 degree stem, or a -20 if you will, so the top of the stem wasn't exactly flat, it was already tilted down 3 degrees (both bikes have 73 degree head tube angles).

I didn't want to lose reach so I drew a line straight down from the current clamp point, making that the center of the bars in the new position. I'd lose reach if I just "pivoted" around the stem's clamp point, meaning where it clamps to the fork.

I then measured the distance from the clamp point (center line of the steerer tube) to the bar's new position.

14.5 cm.

So a right triangle with a 14 cm whatever side (second longest side) won't get much longer than 14.5 cm, at least not when it's dealing with stem angles.

I measured the angle with a protractor. 12 degrees down from the current stem (aka "-12 degrees" in stem talk), 15 degrees down from horizontal (aka "-15 degrees" in stem talk). Add the -17 degrees (in stem talk) that gets you to horizontal and you get, ahem, -32 degrees.

I'd need a 14.5 cm stem, -32 degrees.

My scale drawing study.
My head tube started at 67 degrees, not 73, hence the three off angle lines near the "stem clamp" area.

I went looking for some custom stem folks. I could justify spending $200-300 on a stem but not $500. Therefore no titanium. For some reason no one makes custom aluminum stems. I'd be getting a steel stem. That's okay - my best sprinting I ever did was on a steel stem. I went to aluminum begrudgingly and only because it was lighter, but the steel stems I had, those were the schnizzle.

I'd been eyeing the Steelman site back when I was considering making my own carbon frame. They had some great examples on their site, like this one, and I decided back then that it was a good company. I never did build the carbon frame - my super long set up would have required a weird angle at the BB shell and it fell outside of the range of angles offered by Dedaccai (at the time Bringheli was selling the tube sets). My custom frame thoughts went into hibernation at that point.

When I started asking about custom stems someone recommended Steelman. I checked out their short and sweet stem section.

$250 for an unfinished stem, $300 for a finished one.

I'd already spent at least $500 on various bars and stems so two more stems (one for each bike) wouldn't be out of the question. $250 for each, in an unfinished state, and I'd use some paint I have in the garage to paint them black. I even have a satin black so it won't be too shiny.

(This means that yes, I have two FSA Energy bars for sale including one that has never been opened, as well as a slew of 12, 13, and 14 cm stems that have various aggressive angles from -25 to -20 to -17 degrees. I'm saving one for the tandem, the rest need to go.)

I emailed Steelman and got a response from the man himself, Brent. He didn't question my sanity or my math when I sent him the picture of my full scale drawing. He did ask for the dimensions of the headset stuff under the stem, noting that the radical angle may require a thin spacer so that the stem would clear the headset. His lead time?

Two weeks.


With that I gave the go ahead to start the stem. I'd put it on the red bike first, the one that's my main bike now, and if it works out then I'll order a second for the black bike.


Axel said...

Hi Aki, love reading your blog! There's a lot of wisdom in these posts.

Just wanted to let you in on a little secret when it comes to thinking about stems:

Web applications where you can see the result of different spacer stacks / stem lengths / stem angles / headtube angles.

It could save you some time drawing it out!

Aki said...

That's great! I double checked my stem math and it was spot on. Apparently I'll have 1 mm more reach and 30 mm drop, which is exactly what my "scale drawing" showed. Of course it took about 10 seconds to plug in the numbers vs an hour or so for my diagram.