How to choose the right wheelset for the task at hand (Part 2)

There’s a mania for low spoke count wheels right now, and oddly enough it’s often the big guys asking us “what’s the lowest spoke count I can possibly get away with?”  To my mind, this is purely a (very unhealthy) case of fashion over function.   

Deeper section (often erroneously called “deep dish” - deep dish is pizza you get in Chicago, while wheel dish refers to left/right displacement due to the cassette) rims offer two benefits.  One is radial stability, one is aerodynamic benefit.  In reality, aero benefits only really come in at around 38mm and really get good at around the 50mm depth.  The Roues Artisanales test is the most compelling test I’ve yet seen and bears this out perfectly.  It’s pretty easy for the deeper carbon wheels to get down to the low 20s of drag, yet the American Classic 420, which is a 34mm deep aluminum rim, is the only aluminum rimmed wheel that breaks 25 (and barely - barely - at that).  Most of the aluminum wheels are backmarkers in the aero category, whether they are 20 or 30mm deep, high spoke count or low.  We can more or less disregard notable aerodynamic benefit when we’re talking about aluminum wheels.   

One thing that deeper aluminum rims can and do offer is radial stability.  That is, if you stand a rim on the ground as though it were on a bike, and put weight on the top, it takes more weight to make the rim lose its circular shape.  This can be important - critically so if you want to get rid of spokes.  It comes, of course, at the expense of weight - you need more material to create the deeper section.  

So if you want to make a “big guy strong” wheel with few spokes, you start with a 30mm deep rim (which for a few reasons is the popular maximum depth for aluminum rims), which weighs about 510 to 550 grams (somebody will mention the Kinlin XR-300 at 455 claimed grams, to which I will reply that it’s not a particularly stout rim, nor has there ever actually been one that weighed 455 grams - not even close).  Then, you put 18 or so spokes in the front and 20 or so in the rear.  Most of the time, these spokes are a proprietary bladed “aero” spoke.  Aero?  Maybe.  Lightweight?  HAH!  They’re often 5 or so mm deep, by 1mm wide, so each one has the equivalent material to between 2 and 3 2.0/1.8/2.0 double butted (Sapim Race, DT Competition) round spokes.  So in a wheelset with 38 spokes, you are carrying the weight of well more than 60 regular spokes.  

The are a few prime liabilities of this type of system.  First is that each spoke is more heavily loaded, which increases the load on the inner rim at the spoke hole and in the hub flange at the spoke hole.  There are plenty of big dudes out there who’ve nuked wheels by cracking spoke holes at the rim or destroyed a hub flange.  The other biggie is that there is a big unsupported span at the rim between each spoke, and each piece of unsupported rim becomes a weak spot.  Deeper section rims alleviate this to some degree, but they don’t eliminate it.  Probably the biggest issue to me is the likelihood of broken spokes.  

Spokes don’t break because they’re too tight, they break because they’re too loose.  In each revolution of the wheel, the spokes on a 20 hole rear rim will each, momentarily, support the entire load of the rear wheel.  That’s generally about 60% of the total rider/bike/gear weight.  So a 220 pound guy, on a 20 pound bike, with 5 pounds of shoes/helmet/seatbag/clothing/water bottles, is putting roughly 145 (60% of 245) pounds of load on each spoke every time the wheel goes ‘round.  Spokes can generally be loaded up to 110 kg (242 pounds) in an aluminum wheel, which is great.  But that’s just the drive side.  In a well built wheel, the non-drive spokes have about 65% of the tension of the drive spokes, so about 157 pounds of force.  Which means that the non-drive spokes are potentially being unloaded every time the wheel goes ‘round (there’s a bit more going on that that, but not much) under our 220 pound guy, which means the spoke is cycling - it’s not in constant tension.  Flex a spoke back and forth in your hands for an hour - it breaks.  Big guys break spokes at the hub or rim, on the non-drive side.  On front wheels, they crack hub flanges.  That’s how big guys break wheels.  And let me tell you, when you break 1 of 20 spokes, you’re not riding that wheel home, no way.

Our take is to ignore fashion (actually we very much want to set a new fashion) and take an approach that makes more sense.  We start with the Velocity A23 rim, which is 23mm wide and 19.5mm deep.  It’s not an “aero” rim, but neither is a Ksyrium or really any other rim under about 35mm deep.  The extra width makes it especially suitable for 25mm or wider tires, and gives it some extra lateral stiffness.  Our standard wheel has 24 spokes in the front and 28 in the rear, all laced 2 cross.  2 cross lacing reduces hub flange loading and puts the spoke at a more tangential angle to the hub.  This helps the wheel respond more quickly to power input (eliminating the dreaded “windup”).  We lace them tight - about 100 kg on the drive side and slightly less in the front - and we are nuts about getting the spoke tensions even.    For our SOB build, we up the spoke count to 28 in the front and 32 in the back, and we 3 cross the rear wheel.  Each spoke is doing less work, each hole in the rim and hub is doing less work, the load pattern that the hub flange is seeing more closely matches its strength - things become a lot more appropriate for buttressing the wheel’s strength.  For our new “THE KING” build, we go full hog with 32 spokes, 3 crossed in the front and rear.  We use brass nipples throughout for their greater strength, and take that small weight penalty.  We also spec them with Chris King hubs, which have high diameter bearings which are very adept at dealing with the high loads that big riders put on their wheels.  

All of this comes at a surprisingly small weight penalty.  Each spoke with an alloy nipple adds about 4.5 grams, while each one with a brass nipple adds about 7 grams.  So THE KING, with 18 extra spokes versus a wheel that’s laced 18/20, will have a 126 gram weight penalty assuming that the spokes weigh the same, which they don’t.  Realistically, the penalty is closer to nothing.  The rims weigh 450 grams each (I just weighed a whole big stack of them, they weigh 450).  You wind up trading a bunch of weight out of the rim and replacing it with a little bit of weight in extra spokes, for an overall benefit of lighter weight and significantly increased strength.  Chris King hubs go about 340 for the set.  Total wheel set weight is about 1600, which is pretty remarkable for a wheel set that comes in way under a grand, and will be a stiff, lively, and wonderful lifetime wheel set for guys who weigh in the 250 pound range.  

The FSW23 SOB set comes in at around 1540 grams, which is competitive with aluminum wheelsets that cost twice as much and aren’t anywhere near as appropriate for guys up to about the 235 pound range (as a comparison, Mavic puts a 225 pound rider AND bike and gear limit on their Ksyrium line).  Pretty snazzy for a wheelset that a 210 pounder could easily ride all for 9 months on the road and then use it for cross in the fall.  

We think having a lighter, stronger, cheaper and more durable wheel set makes a pretty powerful fashion statement indeed.