Wednesday
Oct292014

Interesting Times

There's an ancient Chinese curse (at least so the internet has told me) that says "may you live in interesting times." Whether a blessing or a curse, these are interesting times. A short while ago the question was whether 11 speed would have massive uptake (of course it would, of course it did - although Mike and I are both still on 10 speed for a few weeks more yet), now the rate of change has increased exponentially, mostly having to do with how you slow down more than how you go fast. Of course, the impact that how you slow down has on how fast you go is a prime consideration.

I'll admit that I've slowly been coming around to using discs for cross, the transition to which has been eased for me since, after all, it's my job to build and ride crazy nice wheels and learn how they work. The emergence of road disc looks all but inevitable at this point, and if Mike has become as big a fan of tubeless as he has in the amount of time he has (the old Life cereal commercial comes to mind: "let Mikey try it, he hates EVERYTHING!") we're fairly bullish on that as well.  

Parameters that weren't a consideration just a short time ago are THE parameters now. Interesting times, indeed.  

Sunday
Oct262014

Project Updates

We tested the Grail builds fairly thoroughly this week. Two sets got built for testing, a set of 24/28 with some old house mtb hubs, and a set of 24/24 on White Industries CLDs. The 24/28 got one wrap of tape and was used with Kenda Kwickers, while the 24/24 got two wraps and a Maxxis Padrone 23 on the front and a Hutchinson Intensive 25 on the rear. 

The rims are quite stiff. Weights on the ones we got were a bit higher than advertised - our average of 6 rims was 482g each, against an advertised 465.  Aluminum rims can vary quite a bit as the die wears. We don't freak out about differences of this magnitude, but we do note it. Finish quality was very good, with one superficial flaw in the whole lot.  

Thanks to the benefit of 135mm spacing, 24h rears are an option. I still prefer 28 since there's only 20g of downside and you get a stiffer and stronger wheel with 28, but for people who don't weigh a ton and aren't going to flog them around off road, 24 is an option.

Tubeless setup is outstanding. I put a few good rides in on the Kwickers including yesterday's race. We set these up exactly per the Stan's team setup, and I have utter confidence that you can use as low a pressure as you want. Interestingly, maybe Kwickers are just very supple, but I actually wanted to use more pressure than what I thought the bottom limit was. I used 27f/30r, and it just felt like less than that.  

Road tubeless setup was great until...

 

Apparently I ran over Freddie Kreuger about 1/4 mile away from home, after about 30 miles of riding.  Yoinks. For the record, sealant doesn't help with a slash that big.

We also got to test the 2:1 lacing, with 16 drive-side and 8 non-drive spokes. Immediately apparent is how much this balances tension.  You get about an 80% non-drive to drive side tension balance with this setup. That's awesome. Unfortunately, stiffness-wise, 24 spokes is still 24 spokes. The Kinlin rims are stiff enough that there was no appreciable difference between measurements at the spokes and measurements between spoke groups. We will have to try it again on an 18:9 setup. The tension balance is attractive and offers a lot of promise, but the stiffness measurements at 24 total spokes are less than what we like to see.  

Thursday
Oct232014

Why We Race

There are a million different ways and whys to ride a bike. One of the most important to us is racing. I'm not saying that we're mint at it, as even though Mike has his moments, generally this blog is a place of honesty and let's face it I aspire to a consistent mediocrity with occasional bouts of "not awful." So what's our why?

Schirm doesn't look like this except in races

We sell performance oriented stuff. Not that you have to use it in races, and I'd guess that slightly less than half the stuff we ship out ever sees a race (which is actually a gigantic percentage compared to the world at large), but racing reveals flaws. I'm not going deep and talking about character here (that would clearly imply self-incrimination), but rather flaws in stuff. When you race, you press hard, damn the consequences. My power files from races stand in STARK contrast to what I can do in training.  When you race, you know not logic nor pain nor concern. You just know you've got to hold that m-f'ing wheel, whatever the cost. Wind tunnels and bench tests are great and we rely on them for sure, but nothing makes the cut until we've raced on it.  

Dialed in and flying

 

Tuesday
Oct212014

What's on tap this week?

If the question is in regards to what's coming out of the beer faucet at Mike's house, not much for long is the answer. Proper cx race prep and recovery last weekend demanded that we try like mad to finish what was there. We got pulled before our last lap, but we're proud of the effort. As to why my legs just weren't all the way there on Sunday, I'm sure I have no idea...

In addition to the normal flurry of wheel builds we have to get out the door (thankfully there still is a flurry, as this period is usually about the nadir of our sales every year), we're looking at tubeless interfaces and lacing patterns this week.  Grails have been have been rarer than hen's teeth but Stan's seems to be catching up with demand so we'll be building a few sets to test two things in particular: how does a 20+mm bead seat width work with road tires, and what's the ideal setup for cx tubeless with these babies?

Got lots of building and test riding to do

On other fronts, we'll be testing some different lacing patterns in a steel cage match. Specifically, we want to see if there's anything to this 2:1 lacing. We'll build otherwise identical rear wheels, one with 24 spokes laced 2:1 (16 on the drive side, 8 on the nds), and one with standard 28h 2x/2x lacing. Not in response to any issue we're currently having, but it may hold some promise so we're looking at it to judge for ourselves. Look for some news on that later in the week.  

What started off 25mm is now 26.2mmMike's several hundred miles into his road tubeless evaluation and enjoys it quite a bit. Smooth riding (at least in context of the treachery of Beach Drive and environs), no flats, and good road feel.  The tires, 25mm Hutchinson Fusion 3s, which started life exactly at their stated 25mm width, have now grown to 26.2mm width. This is an entirely normal phenomenon for tubed or tubeless tires, and is something you should have in mind when evaluating tire/frame clearances. 

The Kenda Kwickers should be a fortuitous choice for this week as the forecast is for rain through the week. Saturday's race should be a real laundry-fest, and I am decidedly NOT a mudder.  Wheel/tire setups for DCCX last weekend were Clement PDX front and rear on Blunt front rim and Arch rear for Saturday, with a Kenda Small Block Eight on an Iron Cross rim subbing in for the rear on Sunday. 25 front/29psi rear both days. The PDX were phenomenal in Saturday's "every surface variety under the sun" conditions, while the SB8 was maybe a little quicker on Saturday's drier track. The SB8 suffers on loose climbs but is otherwise crazy fast so long as it's dry.

The other big news from the weekend is that I might, maybe, sort of had a bit of a disc-brake epiphany on Sunday. There was an off-camber right the you approached going about a billion and six mph, shooting downhill into a sharp-ish left flat turn, after which was a very short uphill, into another off-camber downhill right. Done correctly, you could carry your original momentum all the way through this series and just float up the little uphill. Done poorly, you had to pedal hard to go anywhere at all on the short up part. In a great "well, let's just see how this works" deal, I followed two guys into the thing and braked way later than they did, skidded the rear into the off-camber right and took the inside on them, then held the outside through the left and gapped them decisively on the up. It was actually pretty sweet. 

Thursday
Oct162014

Thursday Test - 24 v 28 spokes

A lovely rainy day to show some wheel testing.  First up, a comparison between a 24 hole Pacenti rear, and a 28 hole Pacenti rear. We've also included a 28h Stan's Alpha 400 as a foil.  

In order to test deflections, we hold each wheel in the frame fixture as shown, and apply a calibrated downforce by hanging a weight (or mass, if you prefer) from the blue rope with the red stop ball in the foreground. Deflections are measured at the places where each red arrow points.  

Different wheels are known to respond differently.  For example, a very stiff rim without enough spokes would deflect significantly downward at the front arrow (the 0* point on our table below), and significantly upward at the rearmost arrow (the 180* point). It would typically not deflect much at the 90* point (arrow to the left).  A soft rim would deflect downward quite a lot at 0*, upward quite a bit at 90*, and downward a bit at 180*. This is why rims hitting brakepads is often not a sign that your rims are not stiff enough, but rather that they are underspoked.  

The magic of system design is to build the wheel to minimize deflection all around. In a race wheel, you want to be just at the point of diminishing returns in order to minimize weight, where in a training wheel you might want a bit more margin for error in the system. The softer (edit) the rim, the more spokes you need, simple as that. A softer rim will "sag" more between spokes. I think of the distance between spokes as the "unsupported span." On the 24h Pacenti rim, the unsupported span is 75mm, on the 28h Pacenti it is 64mm, and on the 28h Stan's rim, it is 65mm. The unsupported span per given spoke count decreases with increased rim depth - a 24h Rail 52 has an unsupported span of 68mm, which is closer to the span of the 28h Pacenti than it is to the 24h Pacenti. The stiffer the rim and the shorter the unsupported span, the fewer spokes you typically need - up to a point.  That point is where the rim "overpowers" the spokes, and you get the "tilted" deflection where the rim goes down hard at 0* and up hard at 180*.

It's not super easy to see in this photo comparison, but the distance between spokes is just about 11mm more on the bottom photo. In case anyone wonders, we are big fans of the Pacenti SL23. It's a nice, stiff rim that's well construction and relatively light. I often ride them, and am currently using them to test a new hub we're evaluating.   

As you can see from the data in the table below, the 24h build comes closest to overpowering the spokes. It deflects downward the most in the front, and upward the most in the back. The actual amounts are worthless in comparison to tests not done on this rig, but from what we've learned these characteristics get you close to where we don't want to be.  You start to put a lot of stress on the rim at the nipples as the rim "works" against the spokes, and this is often borne out by the failure of "underspoked" wheels coming through cracking at the spoke holes. It's not necessarily the static load that gets them, it's the dynamic load transmitted through the deflection.  

A last point to make is how rim depth affects this whole calculus. A deeper rim makes for a better spoke bracing angle. As you move the hub and the rim closer together, the angle that the drive side spokes makes from hub to rim becomes more acute.  This is always a good thing.  

The stated deflection increments are thousandths of an inch.  .177" is very roughly equivalent to 3/16." A 25 pound kettlebell is used to create the deflection load.  

There are a few other things going on here, like how critical each spoke becomes as you have fewer and fewer (a not great builder plus few spokes often equals disaster) but we are running out of time here as it is.  

 

Rim

Pacenti SL23 Pacenti SL23 Stan's 400
Hub WI T11 WI T11 WI T11
Spoke Type CX Ray CX Ray CX Ray
Lacing Pattern 2x/2x 2x/2x 2x/2x
Spoke Count 28 24 28
0* Deflection -0.176 -0.185 -0.177
90* Deflection 0.007 0.006 0.006
180* Deflection 0.051 0.062 0.048
Wheel Weight 803 783 824
Distance Between Spokes 64mm 75mm 65mm