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Technical FAQ: A review of carbon wheels

Lennard Zinn takes a close look at four sets of carbon wheels.

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I’ve been using four sets of carbon tubular wheels throughout the fall, and it’s time I reviewed them. Three of the wheels are 38mm deep: the Cole Shuriken T38 Lite, the Easton EC90 SL, and the Stella Azzurra Calibro. The other wheelset, a Ritchey WCS Apex, is 50mm deep.

The below table shows each wheelset’s rim depth and width, the weight for each wheel and for the pair, the number of spokes on the front and rear and the spoke lacing pattern, and whether the spoke nipples are internal or external to the rim.

Wheel Deep Wide Wt.F Wt.R Pair F # R# Nipple Approx. Retail Price
Cole T38 Lite 38mm 19mm 640g 840g 1480g 16 1X 20 R 2X L 1X Int. $1,600
Easton EC90SL 38mm 21mm 540g 710g 1250g 18 Rad 24 R 2X L rad Int. $1,800
Stella Azzurra Calibro 38mm 19mm 610g 730g 1340g 20 1X 20 R1X L 1X Ext. $1,500
Ritchey WCS Apex 50mm 21mm 590g 790g 1390g 20 1X 24 Rcrow L2X Ext. $1,520

I raced a full season of cyclocross on these wheels as well as trained with them, all at low tire pressure, and the first thing that I can say is that all of them held up great. I weigh 175 pounds, and I rode them hard, crashed occasionally, and hit some obstacles pretty hard. Every week in Boulder’s weekly Wednesday Worlds ’cross ride I hit some square-edge wooden impacts on bridge crossings on descents, making lifting the front wheel hard to do, generally with around 26psi in the tires. I’d expected to see damage and never did on any of them.

Getting ready to ride

Before installing wheels on my cyclocross bikes, I make sure that they are true and properly dished (the rim centered between the hub flanges). On a bike whose wheels you frequently switch around, particularly under the kind of poor conditions often encountered in cyclocross, it’s a drag, literally, to have brakes that rub and you can’t do anything about it without stopping. Untrue and off-center wheels are non-optimal on a road bike, but on a ’cross bike with cantilever brakes that are a lot more of a bear to center than a dual-pivot road brake (which can be twisted while on the fly to center them), it is not something you want.

Click for larger image
The Cole T38 Lite

I did some work on all of these wheels, as all of them had at least some side-to-side wobble, and every one of them except the front Cole wheel and both Stella Azzurra wheels were out of dish. I measured the amount they were off initially using a Park TS-3 super-rigid truing stand, which comes equipped with dial gauges accurate to 0.01mm of runout.

How much were they off?

• The Cole front wheel had plus/minus 0.27mm of side-side wobble, with perfect dish (within 0.25mm).

• The Cole rear wheel had plus/minus 0.18mm of side-side wobble, and its dish was off by 1.2mm (i.e., pulled over too far) to the drive side.

• The Easton front wheel had plus/minus 0.18mm of side-side wobble, and its dish was off by 0.6mm to one side.

• The Easton rear wheel had plus/minus 0.18mm of side-side wobble, and its dish was off by 1.1mm (i.e., pulled over too far) to the non-drive side.

• The Stella Azzurra front wheel had plus/minus 0.31mm of side-side wobble, with perfect dish (within 0.25mm).

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The Stella Azzurra Calibro

• The Stella Azzurra rear wheel had plus/minus 0.47mm of side-side wobble, with perfect dish (within 0.25mm).

• The Ritchey front wheel had plus/minus 0.12mm of side-side wobble, and its dish was off by 1.1mm to one side.

• The Ritchey rear wheel had plus/minus 0.13mm of side-side wobble, and its dish was off by 0.5mm (i.e., pulled over too far) to the non-drive side. More of a concern, however, was that the left-side spoke adjacent the valve hole on the rear wheel had zero tension on it. I increased the tension in all of the spokes somewhat to bring the wheel into true and dish with that spoke having some tension in it. But over the ’cross season, that spoke still loosened up as I was concerned it would.

I trued all of the wheels to under plus/minus 0.1mm of side-side wobble and to under plus/minus 0.25mm of perfect dish. I could then switch them around all season without problems. However, due to differing rim widths, I could not switch them around with complete impunity unless I wanted to constantly be adjusting my brake cable tension. The Ritchey and Easton rims are 21mm wide and the Cole and Stella Azzurra rims are 19mm wide, and I kept the Ritcheys and Eastons on one bike and the Cole and Stella Azzurras on the other bike. I kept tires with a Grifo tread on one set of each pair of like-width wheelsets and tires with a Fango (mud) tread on the other wheelset of each pair.

Cole T38 Lite

Central to Cole’s design are cylindrical brass spoke heads residing in transverse holes through the triple-wall hub flanges. Each stainless steel Swiss-made double-butted (round) spoke is double-threaded, with one end threaded into the internal nipple at the rim and the other end into the brass spoke head at the hub. Cole calls this Dynamic Spoke Alignment, or DSA, since the cylindrical nipples offer straight alignment of the spokes; the brass head is free to rotate in the hub flange until the spoke lines up straight from end to end. The spokes can be (and are) put under very high tension without running the risk of snapping them off at a J-bend elbow at the hub. To make room for these brass heads, the hub flanges are fairly tall, but where the spokes emanate from is about equivalent to an average low-flange hub.

The rim’s outer surface is unidirectional carbon with woven carbon on the brake track. The gluing surface is of uniform curvature, and it came with lots of stickers on it, some quite large, which took some work to scrape off to expose the carbon gluing surface.

Comes with a padded double-wheel bag.

This is a tough, stiff, great-tracking wheel and a low enough weight to be competitive. Truing is not possible with the tire mounted.

Easton EC90SL

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The Easton EC90SL

Easton’s round, black Sapim double-butted straight pull spokes are double-threaded into the spoke flanges and into internal rim nipples and are laced at very high tension without fear of breakage thanks to eliminating the weak point at the elbow. They are laced radially on the front wheel and the rear wheel’s non-drive side, while the drive-side rear spokes cross once inside of the high drive-side flange and once again between the hub and rim. Other than the drive-side flange, the hubs are low-flange units.

The rim’s outer layer is all unidirectional carbon, and the wheels come with yellow SwissStop brake pads for carbon rims, as well as a nice truing wrench for its internal nipples. The EC90SL rim bed has a central deeper groove for clearance for the stitching bulge in some tubular tires, and with the extra 2mm of rim width, there is still ample gluing surface for the base tape of the tire on either side of the stitching bulge. Easton is so confident of this wheel that it specifically stipulates that the wheel has no maximum rider weight.

The R4SL hubs have Grade 3 ceramic bearings inside, and they are super easy to adjust, which I needed to do on the front since there was some bearing play. That completed, they spin extremely smoothly.

This is a very light yet durable wheelset that accelerates quickly and rolls smoothly on ceramic bearings. Truing is not possible with the tire mounted.

Stella Azzurra Calibro 38

The Calibro 38 has high flanges and black DT Swiss Aerolite stainless steel double butted and bladed spokes with J-bend elbows. The silver alloy nipples are external (they stick out of the rim in the traditional way). It’s the only wheelset here with the same number of spokes front and rear (20), as well as the same spoking pattern front and rear (one-cross).

The rim’s top layer is woven carbon, including on the brake track. The gluing surface is a uniformly-curved rim bed.

The hubs are high-flange with large cutouts, with the exception of the drive side of the rear. The drive-side hub flange holes are dogbone-shaped (see the explanation under Ritchey, below) and thus reduce the strain on the elbows of the most highly stressed spokes of the set, while the high flanges front and rear all have keyhole-shaped holes for the bladed spokes.

Even though Stella Azzurra’s Web site says that these wheels are specifically not recommended for cyclocross (or for riders over 85kg), I used them for ’cross anyway (after considerable riding on the road with no problems), and I would love to use them again for that. The external nipples are a bonus for ’cross, since you can true the wheels without removing the tires, much less having to contend with glue in the spoke holes in the rim bed complicating access to internal nipples. Aerodynamics plays a very minor role in ’cross, so there is no down side to the rider that I can see to external nipples.

Comes with a padded double-wheel bag.

This is a fast, light wheelset that can take a beating and can be easily trued if badly abused.

Ritchey WCS Apex

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The Ritchey WCS Apex

This 50mm-deep Ritchey wheel has a thin, low-flange front hub and medium-height rear hub flanges. The wider bearing stance increases the spoke angle to the rim for greater lateral stiffness. The stainless steel Sapim CX and CX-Ray spokes have external brass nipples at the rim. The drive-side rear spokes are laced in a “crow’s foot” pattern with each group of three spokes crossing at a point: two crossing-angle spokes and a single radial spoke.

The 50mm-deep, 21mm-wide rims have a unidirectional carbon outer layer, and the rim bed has a central deeper groove for clearance for the stitching bulge in some tubular tires.

Except for those at the four radial spokes on the drive-side rear hub flange, all of the spoke holes in the hub flanges are “dogbone” shaped (like an oval with large lobes on the ends). Lacing wheels with bladed spokes requires slotted holes in the hub flange to allow the bladed sections to pass through. Normally, the slot is cut radially inward from the hole, forming a keyhole shape, but Ritchey instead joins two closely-spaced adjacent holes with a slot connecting them to form the dogbone. This does reduce the strain on the spoke elbow when the spokes are pulled tight.

The skewers have titanium shafts, and the aluminum heads are cold-forged with a blind hole on one side.

While this wheelset did start out with a loose spoke (see above), I love that it has external nipples, as they make it very easy to true the wheel (no need to pull off the tire).

This wheel doesn’t exact much of a weight penalty for its 50mm of depth. It offers great tracking, stiffness and durability as well as ease of truing.

While these wheels have subtle differences in riding characteristics, I liked the ride of every one of them. You simply can’t go wrong with any of these wheels. All of them are tough as well as plenty laterally and vertically rigid, and they all steer and track well. With proper brake pads and a bike without brake shudder, all of these wheels offer acceptable braking under cyclocross conditions (I did not test them under hard descending on the road on a hot day, a totally different test of braking effectiveness). Their gluing surfaces are sufficient to allow properly-glued tires to stay on well. Their deep, V-section rims steer accurately through mud and sand and shed mud rapidly. They all are quite light and have smoothly-spinning bearings, and I would eagerly race and train with any of these wheels again.

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Technical writer Lennard Zinn is a frame builder (, a former U.S. national team rider and author of numerous books on bikes and bike maintenance including the pair of successful maintenance guides “Zinn and the Art of Mountain Bike Maintenance” – now available also on DVD, and “Zinn and the Art of Road Bike Maintenance,” as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn. Zinn’s column appears here each Tuesday.