Monday
Aug042014

Business in the front...

 

One of the tests we were most curious about was "the mullet."  Our lovingly pejorative label for the 34 front/52 rear combo aside, we get asked about this all the time - "is the tradeoff worth it?"  Despite having been accused of pulling the answer out of our rear by various internet eyeball aerodynamicists, we've actually put a bunch of study into it.  VeloNews has covered it, and Zipp used to publish offset depth tests, so becoming informed was easy with some Google-fu. In the end you don't know until you test, so test we did.  

First we have to start off with a disclaimer.  I move around too much on the bike to be used as a pedaling dummy.  My mom would say "of course not - I didn't raise no dummy," but my active riding style meant that it was impossible to do the "rider on" portion of this test.  More on this later, because it takes some special skill to be silent enough on a road bike to be a good dummy, and this has some ramifications.

Anyhow, to answer the mullet question, we ran three tests - 34s front and rear, 52s front and rear, and 34 front/52 rear.  What we found was approximately precisely what we'd guessed - that the rear wheel accounts for less of the aerodynamics than the front.  There's some "there" there, but the assumption that a wheel's benefit is the same front or rear is debunked.  If they were equally important, the 34/52 set should have been a 50% closure of the gap to the 52/52 set from the 34/34 set.  As it happened, it only crossed about a third of the gap.  

The major motivation for people to do the offset set is to get the crosswind handling benefit of the shallower front with the aerodynamic benefit of the deeper rear.  As it turns out, A2 is now able to quantify that as well, which will become part of the story soon.  As sticky as it is to editorialize on data, everyone's still going to ask us if it's worth it, so having tested, our answer will be thus.  If you want the shallower front in order to save weight, we've never seen a model where the sacrifice in aerodynamics would be worth the benefit in reduced weight.  If you want all the aerodynamics you can get but are incontrovertibly certain that a 52mm deep wheel is too much to handle, then there is a bit of benefit to be gotten from the setup.  As ever, my wording on the last sentence turns out to be quite meaningful.

Friday
Aug012014

November in the wind tunnel: "semi-aero"

Tunnel testing alloys was actually more exciting for us than it should have been.  While a lot of people choose to buy builds from us with the rims on test, this essentially amounts to a "public good" test, simply because these rims are so widely available.  The excitement mostly came from the fact that the internet was seemingly ready to have an aneurism there was so much demand for us to do this (which is a funny concept when you think about it - no one else spends the money to do this for people, not even the rim makers), and because so many "eyeball wind tunnel" experts had definitively pronounced the results long ago. 

We have to once again stress that directly comparing this test on this day with that test on that day is a fool's errand.  The way that we have designed our testing protocol, we will always be able to make significant back-references, but direct comparisons between different tests are worthless. Relative results of one wheel vesus another from test to test are valuable, which is why we have tied ourselves to the benchmark of the 404 wheel we used in our original test.  We will always keep that wheel as the reference standard. 

We tested these with a 23mm Continental 4000s II tire - one tire used in all tests, as it must be. That is perhaps the most popular tire used with the rims we tested, and is a standard for the wind tunnel.  Significantly, you must take note of the tire width as it is on each wheel when looking at these results.  The same tire will inflate differently on different rims: the wider the interior dimension between the brake tracks, the wider the tire will set up.  Among the rims in this part of the test, the differences are fairly small.  As we get into other rims, this difference will become more significant. 

 The biggest lesson out of this test is how much closer the Kinlin and Pacenti rims come to the performance of carbons than what the A23 did.  The overall delta between worst and first in this test was much smaller than it was the last time.  Tony Martin's not going to read this and think "you know, maybe I ought to use some nice mid-depth alloys in my next time trial," but the gap is much smaller.  Again, we are only able to make this statement because the A23 was tested against our reference wheel using the same tire (although we used a different type of tire last time), and the same reference wheel was used to measure the gap this time.  There is the noise of "maybe that's just a particularly bad tire for the A23" in there, but that's at most a very small part of the story.  Using our back-check method, the Rail 34 is faster than an RFSC38, while the alloys in this test are slightly slower.  

The Kinlin was the faster alloy.  As we will explore later, the tire's increased width on the Pacenti may account for all of the difference between the two.  It is impossible to normalize one tire to the same width on two different rims, and you wouldn't want to anyway.  What you could do is test a narrower tire on the wider rim and interpolate from there, but with these rims we were more interested in seeing if there were any gross differences between the two, and how they stacked up compared to the carbons on test.  We will explore the effect of inflated tire width in more detail in subsequent posts. 

 

Tuesday
Jul292014

November in the wind tunnel, part 1

 

Today was one of the most interesting days in my life, and I started it by oversleeping.  Late-shifted daylight hours, a comfortable bed, good blackout curtains, and no yammering birds saw me sleeping past 6am for the first time since sometime in the mid-aughts, and had me behind the curve driving from Blowing Rock to Mooresville.  Well, when in Rome, they say...  I made it in plenty of time.  

We've got a few things to finish up, so while we can't yet start publishing what we learned, I thought it would be fun to go through the logistics of a day in the tunnel.  

We got 17 runs in today.  That might be some kind of a record.  Wheels we tested were: Rail 52*, Rail 34*, Zipp 404*, Enve 3.4*, Pacenti SL23^, Kinlin XC279^, Rail 52 Disc^, Rail 34 Disc^.  Wheels with a * were tested with both 23 and 25mm Conti 4k tires, wheels with a ^ were tested with a 23mm Conti 4k only.  Rail 34 Disc was tested with a full positive and negative (-20* to 20* in 2.5* increments) sweep, everything else was done from 0* to 20* in 2.5* increments (update - Wednesday morning we tested a Rail 52 Disc through a full sweep from -20* to 20* with both a 140mm and a 160mm disc since I wrote this).  We then tested the 34s, 52s, and a 34 front/52 rear combo on my Wheelhouse.  Those were done with a 23mm tire front and 25mm tire rear.  Finally, we started to run all those bike/wheel tests with me on the bike, whereupon we found out that I move around too much to be a usable pedaling dummy.  I got ants in my pants and I need to dance, I guess.  

Accomplishing all of this in one day made for a crazy busy day.  You only use one of each tire that you're testing with, so a lot of the day is simply swapping tires from one wheel to another.  We had a good system where we'd run one with on its 25mm tire test while swapping the 23 from one wheel to another, which erased a ton of potential downtime.  At one point, I was inflating a tube (they have a compressor-driven Prestaflator, I'm getting one) and the tube failed.  I thought I must have pinched it somehow, but found out that the valve stem had ripped the tube, and realized that this tube had been installed and removed about 10x more than any other tube I'd ever used - all in the course of around 4 hours.  

As the test in going on, you watch the data set develop on the screen in front of you.  It's a very lively experience, fraught with anxiety and joy and relief and it's really just exciting.  Of course you don't have much time to watch because you have to prep the next wheel to go out for a test.  The thing in the world it's most close to is probably being backstage at a fashion show, except there's no hot models walking around half butt naked.  It would be cooler if there were a lot of hot models walking around half butt naked.  

The tunnel itself was designed and built in-house.  The bigger Aerodyn tunnel next door (same corporate parent) is where NASCAR teams do their testing (a Nationwide Cup car team was there today), but the A2 tunnel can test anything from bikes to cars, too.  The fans have a staggering 640 horsepower between the 4 of them, but in testing bikes at 30mph, you only use around a quarter of that.  A Computrainer is the guts of the wheel contact part.  The tunnel is cool, but the sensors and software are the business.  Their IT guy is smart.  They've incorporated a new measurement for steering axis torque since our last visit, which we'll be talking about in more detail, but boy did the results not make me a liar for all the times I've said 34s are invisible to cross winds. 

This endeavor is FAR from cheap, but it's necessary.  For example, we get asked about the 34 front 52 rear "mullet" combo all the time, and though we were quite laughably accused of pulling answers out of our butts on what we say about that (we've actually researched it quite a lot), we suffered the expense of testing it because until you really know, you really don't know.  The quote at the top says it all.  Today was a really interesting day.  

 

Monday
Jul282014

The Carolina Swing, Part 1

If we'd followed the original plan for this testing jag, we'd be done by now.  A recent comment on the previous blog reminded me that there are a lot of people who are sitting there thinking "so... ?"  The simple explanation is that Mike and I were talking about the wind tunnel menu, and decided to pitch it as a story.  Homer on the first pitch on that part, but there were suddenly a whole lot more logistics, and they all required input from people who were really busy with what was going on in France.  We got delayed a bit, but it's a way better outcome for us, and it inspired us to double down on the tunnel piece.  

Anyhow, the wind tunnel starts tomorrow and we're testing a pantload of stuff.  More on that later.  Today was a side trip to Beech Mountain, near Boone, NC, to do some more brake heat testing.  The test was simple: do three runs down the 3 mile stretch that's the crux of the climb from the south, a section known for killing carbon clinchers.  I'd have liked to do 20 runs, but it was just me and no way was I climbing that thing 20 times, especially since I was back on the "kettle bells in a backpack" program.  

I always seem to take pictures like this.  The hills in Western NC are big, for real hills.  Beech isn't necessarily very long, but it's steep, with some crazy pitches, and it's all switchbacks so it's a fairly technical descent. This particular climb also has an interesting bit of history.  It was used as the finishing climb of the Tour duPont a few times, and is supposedly the place where, in 1998, Lance decided that he did indeed want to come back from testicular cancer and be a pro cyclist again.  Which explains the still-very-likely-to-be-ironic "Viva Lance" slogan freshly painted on the road near the top.

Rail 34s once again, although different ones than the ones from VT, and SwissStop Black Prince pads.  New Michelin Pro4 SCs, tubes, set to 95 front/100 rear.  It was a WINDY day, and cool for the time of year - mid 60s. The first run down, I had the full 40 pounds in the bag, and tried to mimic what I thought a very timid descender would do.  I let myself gain speed, but then scrubbed speed whenever I got going faster than what a lot of people would be comfortable with.  Before turns, I braked really hard and went through the turns slowly.  I stopped 4 times to check rim temperature.  Max heat recorded was just over 200f.  

Second run, I was down to 175 on the scale, thanks to a miracle diet known as leaving a 25 pound kettle bell at the bottom of the hill.  Still had to climb up with the 15, though.  Second run was more of a constant low-20s run.  Never got going too fast, never had that much speed that I had to get rid of.  Turns were similar speed to the first run.  As expected, this heated things up quite a bit.  After 90 seconds or so of constant braking through the steepest pitches, the front rim got up to 213f, which was the highest recorded temp, even though rider weight was lower.  After about 5 seconds, heat was down to 186.  Each check was similar, just not quite as high.

Third run, I was down to body weight (still 158) and just ripped the downhill.  Absolutely sent it. Wow.  My job's fun.  Unfortunately, I got stuck behind cars about halfway down so I couldn't go as fast as I wanted, but the fun part's at the top anyhow.  Rim temp after the stop at the bottom was a blistering 126.  

This part of things isn't pure science, we know, and it's not designed to be.  It's designed to expose things that happen in the real world, quantify them, and interpret what it means.  In this case, what it means is that a Rail has no problem being ridden down one of the most iconic descents in the east, either by a timid 200 pounder, or a 175 pounder who's a bit more enthusiastic but doing it all wrong.  And that they're fun as hell when a 160 pounder gives them full stick down it.  

Tuesday
Jul222014

Testing 1-2-3

Since the beginning, we've focused on doing what others either wouldn't or couldn't.  Early on, this meant delivering reliably sourced and expertly handbuilt wheels (the FSW clincher and RFSW tubular), and the Wheelhouse.  The Wheelhouse, available as both a component frame and complete build, wound up being far far more than we ever imagined it could - those who've owned or even ridden them are absolutely smitten with them, even after all this time.  Unfortunately, the supplier went nutso on terms and we can't offer the original any more, but the lingering enthusiasm for what it is and what it does has moved us to have one of the world's top builders resurrect it for us.  More on that later.  

the joke comes at the end

The Rail rim series was a big step for us, a heat resistant carbon clincher with verified world class aerodynamics, built by hand with the best components you can find.  Developing the Rail opened our eyes to the value testing offered to us and our customers.  As ever, the "how" of testing was just as important to us as the "what" of it - just proclaiming empty and untethered statements like "10% faster" or "18% stiffer" without explicating what the comparisons mean, and being transparent about how we arrived at them, didn't do it for us.  It had to be the November way, completely open book, as objective as we could possibly be.  

When we test in the tunnel, it's directly against a proven class leader, as when we benchmarked the Rail 52 against the Zipp 404.  This week, we're excited to be going back to test an actual production 52 (with 20 spokes rather than the 24 that our prototype had), as well as to test a 34 against an Enve 3.4.  Beating up on some nebulous "standard 32 spoke box section wheel" that no one has any interest in riding anyway is one way, but openly testing against known leaders is a much more informative (and, for us, exciting) way to do it.

Now we've gotten into testing wheel and rim stiffness, in ways that allow us to get much smarter about what wheels we recommend.  Since so many of the wheels we sell are available from other sources, why do we do it?  Who in their right mind would test their proprietary carbon rim against an alloy rim that you can get in a build from many dozens of builders?  We're excited to learn, and we know it improves what we do and how we do it.  If knowing what we feel like we need to know costs us the time, expense, and potential risk that these tests expose us to, so be it.  The final result, whatever the result, is that we're better able to help you find the build that's best for you.

And what of the shared benefit of this knowledge?  We know that once we publish what we find, the info is going everywhere, and people who've gained knowledge on our dime can use what we've shown to their own benefit completely outside of us.  For one thing, results are one thing and process is quite another.  Going through all of the steps to learn what we are simply makes us smarter.  Borrowing our facts is well and good, but the fundamental knowledge we gain is ours to keep.  For another, being a leader in the testing game has already opened doors for us and continues to do so in exciting ways.  

In the long run, we know it comes back, and that people want to work with the people who move the game forward.  To date, we feel that we've helped drive the conversation to more rational places.  For example, the way we benchmark aerodynamic tests is something that's gotten a lot of notice, and people now expect more from the information they're given.  The joke that is "claimed weight" is being exposed for the farce that it is.  We'll be more than happy if we can help drive a substantive change away from the way a lot of this stuff has been done, but if we have to be out standing in our field, we're good with that, too.  

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