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

Monday
Oct132014

Stiffness testing in practice

So we do all this fancy testing and figure out which wheels are stiff and which wheels aren't and all of that fancy stuff, but what good does any of it do? How does it help us make better wheels for you? Numbers ALWAYS tell a story, and sometimes they tell several all at once. The stories we try to look for in these numbers are ones about points of diminishing returns, points of transferability, and stories about use optimization.  

First, let's take a quick look at why a stiff front wheel is a good thing, and some of the other factors going on there. To me the primary benefit of a stiff front wheel is in steering. A soft front wheel can lead to noticeable understeer. You don't want this. A soft front wheel will also potentially clang back and forth on the brake pads as you climb out of the saddle, or especially when you sprint. When you sprint, you typically weight the front of the bike much more than just in general riding. Without crashing because of it, take note of what your tire does the next time your sprint - yup, that bounciness is because you are weighting and stressing the wheel much more than you just just riding along.  Other factors are strength, which can be described as the wheel's ability to handle unusual stresses (airborne instances, crappy roads), and durability. The more spokes you have, the less work each one has to do - many hands make light work. Last, you have to think about the hub flange. Radial lacing is great for 20 and 24 hole fronts, but start putting 28 holes in that same circle and all of a sudden there's not much meat to handle the higher radial spoke load. Crossing works much better with higher spoke counts.  

We've advocated 24/28 laced alloy wheels for a long time. Where other people said a 20/24 build was appropriate for 190 pound riders, we were saying you should be thinking about going to 28/32 for the same weight. Among the things we've learned is that we were both right and wrong. With rear wheels, we were right. There's a lot going on with rear wheels, especially with the move to 11 speed hubs, and this piece is mostly about fronts, but a 28 spoke alloy rear does a lot of stuff a lot better than a 24 hole alloy rear. Up front, not so much. Because front wheels are inherently such better wheels than rears, front wheels with stiff rims really start to get quite good at 20 spokes.  A Pacenti SL23 (quite stiff for an alloy rim) laced to a White Industries T11 front hub with 20 spokes isn't appreciably less stiff than the same setup with 4 more spokes.  Some people understandably like a bit of redundancy in their setups, so there's still plenty of room in the world for the 24 spoke alternate, but you're not getting what you might call primary benefit from it. Note that one of the next things we're taking a look at is the implications of 1x lacing on 24h fronts, just in deference to the flange issue discuess above.  

Conversely, yesterday I talked about a 28h Stan's Alpha 340 being a nice stiff wheel. The rim is soft enough that it needs a lot of spokes, but when you add enough spokes such that the distance between them gets small enough that adjacent spokes are working together to keep the rim in line, that rim comes into its own. With any of the front hubs we use, that's going to be a nice wheel. It's not the most aerodynamic wheel under the sun, but it's quite light (a 20h Rail front with equal hub is the only lighter front wheel we do) and also quite stiff.  The 2x lacing relieves stress on the hub flange, and the spoke count means that if you somehow manage to break a spoke, you're still riding home.  Add the benefit of tubeless and this is an ideal high mileage winter wheel.  

When spec'd properly, an amazing wheel Disc front builds will never be as good as rim-brake front builds for the simple reasons that disc hubs have narrower flanges, and the wheels are dished, so it works out fine that disc hubs start at 24h. Even then, a 20h build on a rim-brake hub is going to be stiffer than a 24h disc build using the same rim and spokes. Disc rims also highlight suitability for application. As an example, a Rail 52 on a CLD hub, with 24 spokes, is a bit stiffer than a 28h HED C2 disc specific tubular with a CLD hub. But it's also about 80g heavier. On a road disc build, where aerodynamics still matter a bunch, the 52 makes a lot of sense.  On a cx disc build, where you might still really want to use tubulars, and weight seems to be at a higher premium (**the debate on the actual value of which may never end), and where aero is quite distantly far from everything, all of a sudden the higher spoke count C2 looks really good.

It's always going to be a challenge to correlate bench test results with real world application, but that's no excuse not to learn everything you can about how wheels react to stresses designed to mimic what they will see in use. 

Wednesday
Oct082014

Anatomy of a test

Earlier on, when we initially announced the Rail, some chucklehead on a forum somewhere threw the BS flag at us, saying essentially "let me get this straight - the company that makes no bones about selling other people's products that they haven't developed, and does no testing, is going to develop and launch their 'own' product. No f-ing way." It was easy to shoot the guy down, simply because we had always been completely up front about how we did what we did. When we did open mold stuff, we were unique in that we didn't BS about "we had design input here" or "this is a product we developed in house" like other people were doing. Mostly that's called lying, and we're not fans.  

Anyway, that one encounter/accusation, though misplaced since we actually had done a bunch of testing, had a big impact on us. We've always wanted to know as much as possible about how everything we work with works, and to share that knowledge wherever possible. A lot of our testing is iterative, as it should be - the real world is always going to tell you things that the bench doesn't, and what you see in the real world makes your bench tests better. Sometimes the best test is a hybrid - after paying a lot of attention to tubeless cross tire setups for the last couple of months, I've got a test track set up that is designed to produce the dreaded burp if the dreaded burp is there to be produced. 

This was a pain in the butt but worth itThis rig is one of our most important test fixtures. With it, we can measure the stiffness of any wheel we build. We use it to isolate variables like spoke count, spoke lacing, spoke choice, hub choice, and rim stiffness within a build. Benchmark a known entity, then test a controlled variant of it. Our accuracy is to within a couple thousandths of an inch. By changing the configuration, we're able to measure rim stiffness in isolation, and we've measured several samples of every rim we've build with, along with several that we don't. Testing components both as parts and then within assemblies gives good insight. For example, some rims might not be very stiff on their own, but can shine as a component of a properly spec'd assembly. We wouldn't sell you a 20h Stan's 340 front build, but put that rim in a 28 build and it becomes the backbone of a great wheel - light, stiff, strong, durable, and ready for tubeless. If you want an awesome wheel to do your heavy mileage on all winter without worry, it's a great choice.  

What gets measured gets managedEveryone's got a scale, so everyone pays attention to what things weigh. Weight is also an important part of inbound QC - we don't like to see a lot of variance at all. Alloy rims will move around a bit more than carbons, simply because as the tooling wears, the parts get heavier.  You have to account for that in stiffness testing, too - weight and stiffness impact each other, so you have to normalize for component weight when checking stiffness. "Claimed weight" is a large stack of BS - things weigh what they weigh. We fully expect that everyone who's concerned about weight will weigh what we deliver to them. Anyone who makes a purchase decision based on what something's supposed to weigh, and then doesn't weigh it? Yeah...

This is our newest test calamity, lovingly named Frank the Tank. With Frank, we can test brake heat, rolling resistance, brake track durability, bearing effectiveness, lube effectiveness, and probably a bunch of other stuff we haven't even figured out that we can test yet. This one was a pain in the butt to sort out, but will give us a huge depth of insight into a world of different stuff.  

As we develop products, we'll always try and quantify any aspect of their performance that we can. We're right now on the hunt for some great hubs that offer a good compromise between the top end hub selection that we've got now and the OEM stuff that's around. We've got some candidates identified, so we're testing the crap out of them in every dimension to see if any are going to make the team.

Mike has jokingly asked a few times whether it's possible to build a wind tunnel from the McMaster catalog. He should not joke about such things. For the time being, that remains something we're happy to outsource, but don't think I don't have a few pages bookmarked for when the time comes.