For those following the Firecrest evolution at Zipp, the introduction of the new rim design to the 202 may seem like it was just a matter of the engineers getting around to updating the design of the tubular rim, but the process was much more involved. Last year at Ausbike, I was able to speak to Josh Poertner, the technical director at Zipp, about some of the hurdles they had to contend with while developing the Firecrest 202 clinchers.
Before launching into some of the specifics, it is worth mentioning Josh’s background. He joined Zipp in 2000 and has been involved in wheel design and aerodynamics since then, playing a major role in convincing professional teams (like Riis’ CSC team) to use Zipp’s aerodynamic wheels for road races. Poertner is a scientist — he likes data and relies on it to guide the design of new wheels. Wind tunnel testing obviously played a key role in the development of the Firecrest design, as did a lot of CFD (computational fluid dynamics) modelling, and thermal imaging was crucial too.
We all know that braking causes a lot of heat in a rim: tubulars will roll off as the glue melts, clinchers will blow out, and the rims may even warp under the heavy and sustained braking associated with long, steep descents. The problem is exacerbated by carbon composites, and then made more difficult again when the rim has a low profile, such as the 202.
A low-profile rim has a lot less material to absorb heat from the brake track, and therefore it is more prone to overheating. Poertner and his team of engineers started with the carbon composite and tested new resins with greater heat-resistance. They also designed a new brake pad that has extra channels for cooling, plus a greater surface area to disperse heat at the rim. Finally, they refined the rim tape to achieve a compromise between weight and insulation so as to protect the inner tube from the heat generated in the rim.
A lot of work went into applying the Firecrest shape to the low profile 202 rim. I recently described the role of CFD in the development of Bontrager’s Aeolus D3 rims, where computer modelling allowed engineers to test different rim shapes in a virtual wind tunnel rather than constructing an actual prototype. Over 200 permutations for the 202 Firecrest rim were tested by CFD to determine the final shape. Compared to the 202 tubular, the Firecrest rim is wider (22.6mm versus 25.4mm, respectively) and provides a significant reduction in aerodynamic drag when compared to other low-profile wheelsets in the same price bracket, such as Campagnolo’s Hyperon Ultra wheels.
A carbon clincher rim was always going to weigh down the new wheelset, and it does a little, coming to 1375g sans skewers and rim strips (202 tubulars weigh in at 1115g). The extra weight pushes these wheels out of the lightweight category so Zipp has chosen to market it on the strength of its versatility, calling it a “classic wheel, revolutionized.”
Before the ride
Aside from the new rims, the Firecrest 202s clinchers essentially resemble the tubulars that we tested last year. The hubs have been updated in two regards: first, they are now black, and second, the rear hub has been redesigned to suit Shimano’s 11-speed specifications. The semi-aero bearing caps still feature in the design of the hubs, the internals are identical to those found on the 202 tubulars, and they roll on aftermarket ceramic bearings. The test wheels weighed in at 1460g with rim strips and skewers.
The wheel build remains unchanged for the new 202 clinchers. Sapim straight-pull spokes are used throughout, 18 spokes up front (laced radially) and 24 spokes out back (drive side, radial; non-drive side, 1-cross). External alloy nipples take care of tensioning the spokes. Interestingly, Zipp spent some R&D dollars to engineer a titanium washer for the nipples to reduce the risk of galvanic corrosion that can occur when alloy comes into contact with carbon. A simpler solution would have been brass nipples, however the extra weight of the brass would have been considered a massive faux pas for a performance wheelmaker, so Josh and his team engineered the washers.
Zipp recommends the use of their Tangente brake pads with the Firecrest 202 clinchers. They are made by SwissStop, and as mentioned above, a combination of materials, a larger surface area, and cooling channels act to reduce the amount of heat generated during braking.
The Tangente pad is also a little narrower to compensate for the wider Firecrest shape. For this review though, I was provided with SwissStop’s new Black Prince pads that improve upon the company’s formula for carbon rim-specific braking.
The recommended retail for 202 Firecrest wheels is $3299 and includes rim tape, brake pads, skewers, and inner tubes for both wheels.
After the ride
My first impressions of the Firecrest 202s was that they were fairly unremarkable. The wheels felt light, as expected, and they provided a smooth and comfortable ride, but so do my regular aluminium clinchers and they only cost $1,000.
A week later they were proving to be a very fine set of wheels. Out of the saddle, the wheels felt firm and responsive and they were easy to accelerate, thanks, no doubt, to their low weight. The 202s cornered well, they felt fast while descending, and they were never troubled by crosswinds, just like any good set of low-profile wheels.
I was impressed with the quality of the braking. The Black Prince pads worked well with the Firecrest rims to provide both the feel and modulation of aluminium rims, at least while everything was dry. The onset of rain brought with it a second or two of sheer terror as grabbing a handful of brake did absolutely nothing. But then the pads started to bite as the water was cleared and they worked almost as well as they do in the dry. Aluminium still outperforms the latest in carbon resin and brake pad technology, but the gap has narrowed significantly (and in practical terms, disappeared altogether).
I didn’t have the wheels long enough to judge their durability, however they were a demo set and had been through a few bike shops and test rides by the time they reached me. The braking track looked pristine and a few turns of a spoke key were all that were required to get the back wheel perfectly true, while the front wheel didn’t need any work.
Zipp has data demonstrating the Firecrest shape reduces the aerodynamic drag of the 202 clinchers when compared to a standard box section rim but I didn’t notice any savings in effort compared to my regular aluminium clinchers (24 spoke HED Belgium rims). Two weeks later, I swapped the 202s for a set of Mavic R-Sys SLR wheels which, at a claimed 1295g, actually weigh less than the Firecrest 202 clinchers. They also lack any consideration for aerodynamic performance, and indeed, the guys at Roues Artisanales found that an early iteration of Mavic’s R-Sys platform was one of the least aerodynamic wheelsets on the market. The contrast was startling.
I spent two hours on the Mavic wheels and I felt like I was riding through mud the whole time, but I wasn’t convinced it had anything to do with the wheels until I swapped back to the 202s and headed out for a few more kilometers. The difference in effort was remarkable, it was as if I had shifted from the big ring to the small, and I had found a new appreciation for the Firecrest 202s. Indeed, in those first few moments, I was prepared to pay $3000 to keep them on my bike.
The Firecrest 202 clinchers didn’t immediately impress me in the same way as the tubulars but there is a lot to appreciate about these wheels. Buyers can trust that the R&D effort by Josh and his team of engineers has yielded a wheel design that is very efficient, and indeed some riders will enjoy a significant improvement when fitting these wheels for the first time.
However, keep in mind that aluminium clinchers such as HED Belgium rims and even Zipp’s 101 wheelset offer similar improvements in aerodynamics and quality of ride when compared to standard low-profile box section rims. For those riders looking for a high-performance wheel that will be untroubled by the wind, then the Firecrest 202 clincher is a sound option — perhaps even a great option — and I have no quarrel with Zipp’s hyperbole: they have improved upon the design of a low-profile wheelset.
FURTHER READING: Interview with Zipp’s Dechnical Director, Josh Poertner.
- Smooth, blissful ride
- Low weight for a versatile clincher
- Similar performance can be found with high-end aluminium clinchers