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We also hand build custom alloys. Rims by Pacenti, Stans and Kinlin. Hubs by WI, Chris King, Tune and PowerTap.

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Wheel Design Charts and Graphs

If anyone's left standing, I've got a couple of quick graphs that help explain two of the more important considerations that go into our wheel specs.

The first is simply the % of spokes you are gaining or losing when you add or subtract spokes. This helps illustrate the point of diminishing returns in spoke counts. The series of points starts at 16 spokes and ends at 40. % change in # of spokes going from 16 through 40 spokesAs you can see, when you go from 20 to 16 spokes, you take away an impressive percent of the spokes in the wheel. Going from 36 to 40? Not so much. The points start to become more clustered at 24 and really get tight at 28. Early on, each spoke you add is a big increment of the number of spokes you had. Later on, each additional spoke becomes less significant.

The next chart is of a concept I call "unsupported span." This is simply the distance between spokes.  Again, as you add spokes early on, you chop that unsupported span down quite quickly. Later on, the gains are smaller. This will have an impact on both radial and lateral stiffness of the wheel. Rim stiffness comes into play a lot here, in a way which I think of as "bridging."  Think of an 8 foot long 2x4 resting on a set of saw horses that are 5 feet apart - there's going to be almost no "sag" deflection in that 2x4. Now think of an 8' long sheet of plywood resting on the same saw horses. Huge sag. Put another saw horse halfway between the two original ones, though, and the sag goes away.  

16 thru 40 spokes once again, based on a rim ERD of 588

The law of diminishing returns is evident here again, coincidentally with the inflection coming in that 24 to 28 spoke zone. Must be something to that sucker...

Last is a chart of weight gain, as a percentage of the total wheel weight, from adding the last 4 spokes (so 16 spoke weight gain % is from a 12 spoke wheel). This is based on a 450g rim, a 240g hub, and 5g spoke + nipples.  

Again we see a line that is not straight, but there is no pronounced inflection. 

The old convention of 36 spoke wheels (the time when 32 spoke wheels were those new-fangled get offa my lawn weight weenie wonders was not that long ago at all) was based on very shallow and very soft rims. Those days are long gone, and today's deeper rims made from harder metals change the dynamic of how wheels work. However, increasing structural imbalances in the move to ever more dished rear wheels work against that. You want to build a strong, durable, stable, stiff wheel, but you balance those features against aerodynamics and weight.  

If the tryptophan doesn't get you tomorrow, this might do the trick. Have a nice Thanksgiving.  


The comment that became a post

Yesterday's blog inspired a comment question so involved that the answer requires its own post. We've never done this before, but it gives us a chance to articulate how we tie all of the testing that we do into better recommendations and, hopefully, better wheels for you. I've (severely) edited/paraphrased the questions for brevity, but you can read the whole comment at yesterday's post. Incidentally, we probably have to spend some time figuring out how to catalog all of this info.

Q: How would 2:1 lacing affect the parameters that you describe here?

A. We’ve actually previously laced a wheel 16:8 on a 32 hole rim and tested it for tension balance and lateral stiffness. The tension balance was exceptional, the lateral stiffness was exactly the same as if it had been a 24 spoke wheel laced 2x/2x (it was compared directly to one of those). For radial stiffness, we haven't measured it. Presumably it's got a bit of an advantage because there are more drive side spokes, and so they're in closer proximity to one another.  The quantity and bracing angle of non-drive spokes seems to affect wheel lateral stiffness as much/more than anything else. I think that wheel is still built, if it is I will give it a check when I have a chance. Not sure that my measuring system is sensitive enough to parse out that difference. It's also built on a Kinlin rim, so that would be noise in the answer. Here is where we talked about that setup 


Q: Does spoke count affect lateral stiffness?

A: We've done much more measuring of lateral stiffness than radial. Here is the most recent post about how spoke count affects lateral stiffness. Lateral stiffness is more affected than radial stiffness by hub selection, and is also affected by rim stiffness.  In the post prior to this one we quantified the lateral stiffness of all the rims we currently use - those aren't guesses they are quite precise measurements.  The short answer is that every rim/hub combo has a point of diminishing returns for lateral and radial stiffness.  For lateral stiffness, that depends on the “recruitment point” as I think of it – given the rim’s stiffness, how far can the support imparted by one spoke span. This is easy to see in building wheels – on carbon rims, tightening one spoke will loosen the adjacent spokes. That’s recruitment in action, as that spoke’s tension is spanning past its neighbors. 


Q: How about quantifying the tradeoff between aerodynamic penalties and structural gains from more spokes?

A: This would be an incredibly involved piece of measurement, and I don’t think you could ever make it totally accurate.  I’m going to do what I rarely do here, and break my arm patting us on the back here. We’ve done tunnel tests of a front wheel at 20 spokes versus an otherwise identical wheel with 24 spokes (a small but measurable difference. We’ve published tunnel tests of bikes with 34/34, 34/52, and 52/52 wheel combos,which is instructive on the relative importance of front wheel aerodynamics versus rear (front wheel is way more important). We’ve done lateral testing up the wazoo, and now radial testing. So we’ve tested every discrete component to that answer. I don’t see where anyone else has published even one of those component tests, and quite frankly I doubt they do them.  The rub is that you have to credibly quantify performance impact of radial and lateral stiffness in order to gauge that versus aerodynamic gains and losses. Given the tests we’ve done, I have no problem claiming that we are better prepared to say that adding four spokes to a rear wheel does precisely jack squat to your system’s aerodynamic performance, so that there is no value in trading for fewer spokes until you reach the point of diminishing stiffness returns. In effect, every wheel recommendation we make to a customer or inquiry already encompasses this info. That’s why we do as much testing as we do.  Admittedly though, we are making that tradeoff in light of durability vs performance. I don’t know how to do it as performance vs performance, at least in a way that will reach consensus. 

On alloy wheels, the 20/24 convention is fashion, pure and simple. There is no objective support for this convention at all, but it does engender a lot of positive eyeball aerodynamics estimates, and I suppose helps bikes look cool on web sites. 20 spoke fronts are often desirable and defensible because they are adequately stiff and strong as is (front wheel structure is better), so we often recommend them. For carbon rims, 20/24 is very often at the sweet spot anyway.  For very very deep rims we’d go fewer spokes, but we have no plans for a rim that deep.


Rim Strength And Lacing

More charts and graphs today! I finally figured out how to illustrate a point that's been banging around in my head for a long time, which is how rim strength affects lacing. We've talked about lateral stiffness in rims a bunch of times (enough to earn ourselves the clearly affectionate sobriquet of "fun sponges"), but radial strength is as big a deal. 

I took 2 rims, 2 built wheels, and a large clamp, and simply applied pressure at 12 and 6 o'clock to show what happens to rims and wheels when they are loaded this way.  The two rims were a Rail 34 and a Pacenti SL23. The two wheels were a Pacenti/Miche 28h rear, and a Pacenti/WI 24h rear, both laced 2x/2x with CX Rays. I chose these rims because they are both stiff relative to their category, plus I already had the Pacenti wheels built up for something else.

Wheel testRim test

To do this test to lab standards would require time and fixtures/equipment not currently at our disposal, but as an illustration of the concept this worked beautifully.

Part 1 - Compress the rims: With a rim loaded into the clamp as shown above, I applied clamp pressure by the trigger until I couldn't squeeze anymore. With the Rail rim, that point was reached once the clamp's pads compressed. The Pacenti rim was much easier to squeeze. I didn't want to ruin the rim but compressing it 1/4" was easy. Once unloaded, it snapped back into roundness. These results were completely as expected. A heavier and/or deeper alloy rim would have resisted compression better, but is that worth it?  Read on..

Part 2 - Compress the built wheels: The exact same protocol was used for wheels as rims - squeeze the trigger until I couldn't, this time measuring the change in spoke tension that resulted. This admittedly inexact loading was used simply for lack of the equipment to precisely repeat the loads, but since a large part of my life is spent squeezing and plucking spokes I'm exceptionally well calibrated for this kind of thing, and, well, this loading was pretty close.  

As expected, the 24h wheel's spokes both gained more tension in the 9 o'clock - 3 o'clock axis and lost more in the 12 to 6 axis, along which the load was imparted.  This is simply the axiom of "many hands make light work" in action - with the adjacent spokes closer to the spokes most directly affected to the load, they were able to help the most affected spokes carry the burden.  If I was a graphics ninja I would graph this but instead you can interpolate the graphs below.

28h DS spoke tension loaded v unloaded24 DS spoke tension loaded v unloaded

As you can see, the spokes in the 24h wheel saw a bigger change than the spokes in the 28h wheel. The NDS spokes acted exactly the same way, to no surprise. In both cases, the NDS spokes at 12 and 6 o'clock went completely slack, but the 3 and 9 o'clock spokes gained less tension in the 28h wheel than they did in the 24h wheel.  

The more spoke tensions are cycled in this manner, the more quickly the wheel will wear out. This will manifest as either non-drive spokes breaking (usually at the hub), or drive side spoke holes in the rim cracking from stress (or, less likely, spokes breaking at the hub). This whole dynamic is why we are generally in favor of more spokes than others when it comes to alloy rear wheels. A heavier rim, as mentioned, would counteract this behavior - hence the number of 20h rear wheels (OEM and otherwise) that don't explode under riders. In our opinion, adding weight at the rim is a bad trade there. Adding 4 spokes makes an easily seen difference at a cost of 20 grams - to us, that's the best trade.

This isn't a perfectly precise mapping of everything that goes on in the wheel (wheels get loaded between the wheel perimeter and the hub, for instance), but it's a great illustration. 


November Rim Survey - Road and CX

There are more ways to get in trouble with the naming of this post than you could shake a stick at. Since I'm about to be a fun sponge anyhow, prattling on about stiffness and the like, I'll just play it safe.

We are often asked for recommendations on rims to go with a certain build, and have long had it in mind to do a survey of the rims we use in order to help people make the decision.  Herewith, we present our first rim survey. This is also doubtless going to engender two responses which disagree with us: our subjective ratings are wrong, and we should sell rims that we don't.  I'll give the only responses I can to both straight away. To the former, these judgments are our best assessments after a lot of experience with each one. We are happy to build with any of them (that's why we sell them), and all of the alloys are available from a lot of places besides November. We aren't trying to sell one thing over another here. To the latter, you just can't sell everything. We sell as broad a range of stuff as we can maintain expertise with, within our limits.  


The Rail rims are included as much as a foil as anything else. They score well in a lot of regards, but you will notice that their finish and structure scores aren't quite as high as the HED rims. I've scored these on a curve: even though Rails build as round or rounder than HED alloys, carbon rims have the advantage of not having a joint. What I'm saying there is that a HED alloy is darn near at the limit of what an alloy rim can be, fit and finish-wise. And they charge for it. This isn't to say that there are carbon rims out there that are the carbon equivalent of what I find HED alloys to be - I've built several carbon rims and they have their strengths and weaknesses. All of the rims in this test score more than acceptably well in the subjective categories, otherwise we wouldn't sell them.  

"Stiffness" is a relative score, as measured on our lateral deflection rig. No surprise that Rails are stiffest. To me, the Pacenti is the standout in this column. For its weight, it is very stiff - it approaches Rail stiffness, and Rails are the stiffest carbons we've tested (if you paid attention to our wind tunnel tests it should be obvious which ones that includes). The point of stiffness testing is primarily to indicate spoke count, but other factors come into play there.  We still think 28 is the minimum for an acceptably stiff, strong, and durable alloy rear.

"Weight" is averaged across a large lot of each rim, expressed in grams/10 (a rim scoring 50 weighs 500 grams). This helps the chart make sense. Claimed weights are ignored in this chart.

"Tubeless" is subjective, 5 being "it's as easy or easier to install a tubeless on this as it is to install a tubed tire." All of the rims here have been used tubeless by us. Pacentis can offer an unholy challenge in mounting, the rest won't reliably inflate with a floor pump. That's the whole story there. The HEDS are tubular.

Width and depth measures should be self-explanatory. Again, the tubular HEDs don't show an inside width.

"Aero" is a relative score, as measured by us at A2 this summer.  No external references are made - the 52 is the fastest of this bunch, so it gets maximum points. If we didn't test a rim at A2, it's not in here. Eyeball aerodynamics tests are worth no credit.  

"Structure" is necessarily subjective. This is basically "how easily and reliably can this rim be built into a shining example of everything we think a wheel should be." As mentioned above, HED alloys do well here. Stan's and Pacenti are quite similar, and if you look at the serial #s in the rims I think an explanation is right there. The Grails seem to be a small bump up in structure - they are quite nice. 

"Finish" is again obviously subjective. If I were Michael Kors (Katie used to make me watch "Runway"), I would express this as "how expensive would you guess each rim is, based on how it looks." Again, HEDs do well, but you don't find them at Payless either. The Kinlin's finish is a bit shiny, and it's graphically bereft. That's preferable to bad graphics, by far.  We're working on a thing there.  

This will be memorialized in a link from our custom builds page for reference, and if we feel the need to update it, we will baseline any updates to this post.  We'll also follow with a brief write-up of each rim.


Hub Anatomy

Hubs are black magic to a lot of people. I know that when I started screwing around with bikes back in the pennyfarthing days, when your hubs were also your cranks, I was intimidated by the whole setup. In truth, they're actually pretty simple beasts.  

Witchcraft, I know, right? Let's pull it apart and see what we've got. 


The hub shell is just a piece of aluminum (forged, then anodized and machined) that houses a few bearings and holds everything together. Apart from needing to be strong (the spokes anchor to it) and precise (the bearings get pressed into it, and the drive ring is in it), it's just a hunk of aluminum.

The cassette body holds the cassette, and the interplay between the cassette body and hub shell constitutes the transmission (next photo). When you coast, the pawls retract in against a spring, and the cassette body rolls against the drive ring of the hub shell. When you pedal, the springs pop the pawls out and engage them in the drive ring. That makes the bike go forward - the pawls are IMPORTANT little m-f'ers, as are their springs.  No them, no go.


The pawls engage in the detents in the drive ring. This interaction is fairly important.  

The axle and its end caps (sometimes both are removable, sometimes - as in this case - just one is) are how you attach the hub to the bike. The axle's other massively important job is to be the axis around which the bearings turn. A flexible axle is bad for wheel stiffness, and will cause premature bearing wear - it's generally bad for business.

Deconstructing this hub took some elaborate tools - two 5mm hexes. Most are similarly easy to pull apart, some even easier - you can pull a Powertap hub apart with your hands.  A front hub is even simpler - it's just a hub shell, axle, bearings, and end caps. 

Hub maintenance is simple, infrequent, and important. Once a year or so, depending on how much you ride and what conditions you ride in, pull things apart (take some phone pictures as you do it so you have an exact record of how everything goes back together), flush things out with WD-40 or some other super weak solvent (WD-40 works great - just use that), clean things off/out with a cotton rag and some Q-Tips and toothpicks, put some new lubricant in (check your hub maker's web site to see what to use - most are tolerant of a range of different stuff but some aren't), and close everything back up. If you're slow and deliberate, it might take a half hour to do both wheels. 

Your service intervals will vary A LOT depending on your riding conditions. After the exceptionally muddy, nasty, and long Hampshire 100 this summer, I stripped and serviced a brand new set of hubs. Other times, I've gone a year between services and been totally fine.