Test Zipp 303 XPLR S: The super-wide gravel wheelset ensures secure tire seating even at low air pressure, combining grip and comfort with neutral handling. In practice, this aspect almost outweighs the aerodynamic advantages that the new Zipp wheels are supposed to bring.
Aerodynamic optimization has long since become mainstream in racing bikes. The typical road bike now has corresponding frame shapes, and falling prices have ensured that wheel sets with deep carbon rims are no longer a professional privilege. And gravel bikes have also been infected with the aero virus. Gravel racing has become more professional, and riders are demanding that their suppliers provide material that makes them faster over long distances. Race gravel bikes now look very similar to their road siblings, and of course they also roll on aerodynamic wheels. But these have not yet quite come close to the performance that aero wheel sets offer for racing bikes.
Why is that? In addition to the profile of the rims, their width is also crucial for good aerodynamics: the wheels cut optimally into the airflow when the rim is as wide as the tire or even slightly wider. However, gravel wheel sets have so far been rather narrow in relation to the tire: the rim width is usually 25 mm, the outer width 30 or 32 mm. But now the SRAM-owned supplier Zipp has gone one step further: With the Zipp 303 XPLR S, the US manufacturer has presented the currently widest gravel wheel set on the market - with a 32 mm rim width and 40 mm outer width.
Zipp 303 XPLR S: rim width tailored to gravel tires
Fresh out of the box, these wheels look unusual, almost a little exaggerated. On the scales, the massive Zipp wheels cut a good figure - 758 grams for the front wheel and 866 grams for the rear wheel including rim tape (i.e. 1.624 grams) are quite low, especially considering the material-intensive construction. For comparison: the closely related Zipp 303s weigh a good 1.550 grams, and their rims are 45 mm deep. The 303 XPLR S has a 54 mm deep profile.
The unusual appearance changes as soon as the tires are mounted. The Goodyear XPLR supplied by SRAM are nominally 45 mm wide, but only a good 43 mm on the rim. This means that the size ratio of the tire and rim corresponds almost exactly to a racing bike wheelset with the 28 mm tires that are common today. And this also improves the aerodynamics of the overall system.
performance savings in the single-digit range
But you shouldn't expect miracles: at a speed of around 32 km/h, Zipp says it uses 2 watts less power than an unknown competitor; at 40 km/h, it's already 4 watts. This shows that the new wheelset is aimed more at racing drivers who are really looking for "marginal gains" in order to save power. Zipp promises somewhat greater advantages in terms of performance in another area - that of vibrations and rolling resistance. It is well known that vibrations cost power; likewise, that low tire pressure can reduce vibrations and rolling resistance. And this is where the super-wide rims are supposed to bring advantages, because since the tire hardly bulges out over them at the sides, it is very stable even at low pressure and therefore does not need to be pumped up as hard.
For a rider weighing 77 kg and a 9 kg wheel, the Zipp air pressure calculator gives values of around 1,9 bar for the front wheel and 2 bar for the rear wheel; but it can also be significantly lower. Even at 1,6 bar, the 45 tire sits very firmly in the rim and does not deviate to the side when leaning. The rather fine profile of the Zipp/Goodyear Inter feels easy to roll and is similar to a road tire on asphalt; off-road, the tire has a lot of grip at low pressure and is very reliable even on muddy surfaces thanks to the pronounced shoulder lugs. At around 515 grams, the tire is rather light for a 45; how durable it is remains to be seen.
Wide rim flank to prevent punctures
Punctures are also an issue with tubeless tires; this can lead to sidewall damage if the tire is caught between the road and the rim. Zipp minimizes the risk by using a 4 mm wide (hookless) rim flank that is flat rather than tapered at the top. This means that the pressure on the tire in an emergency is more even and less localized. This measure will also have to prove its effectiveness in long-term use.
Mounting the tires on the new Zipp 303 XPLR S is pretty easy: you do have to use a tire lever for a moment, but then you can fill the tire without a compressor. Dismounting it is also no problem. The driving experience is very pleasant: the relatively low total weight of the wheelset and tires makes handling playful; at higher speeds, even on asphalt, you can feel the aerodynamic advantage of the deep rims. On windy days, they also seem very stable; sideways wind does not create any noticeable pressure on the front wheel. And once mounted on the gravel bike, the Zipps no longer look so extremely wide - they should fit well with an aerodynamically designed bike.
But above all, I like the secure fit of the tires, which don't feel at all spongy and don't require any compromises between traction and damping on the one hand and neutral handling on the other. In this respect, the large rim width definitely has a positive effect.
Solid hub set with pawls
Like its street sister model, the 303s, Zipp builds the wheelset on the 76/176 hub set, which is equipped with a three-pawl freewheel, plus 24 double-crossed flat spokes. At an official price of 1.200 euros, this wheelset is also on a par with the Zipp 303s; the 150 XPLR SW, which is around 303 grams lighter and has Zipp's typical "dimples," costs a full 600 euros more. With a "street price" of around a thousand euros, the new Zipp 303 XPLR S is not all that expensive considering its innovative design.
So far almost only Schwalbe tires approved
The fact that the wheelset is optimized for wide gravel tires has only one small disadvantage: Narrower tires than 40 mm cannot be used; in any case, the List of approved tires still quite short. Apart from the special Goodyear and the Zipp Tangente, only the various gravel tires from Schwalbe in 40 and 45 mm width are approved so far. The main focus here is on a secure hold of the tire on the hookless rim. The company from the Bergisches Land has been working with Zipp for a long time; we don't know if and when the competition will follow suit. It would certainly be smart.
A 40 mm wide Schwalbe G-One RS that has been in use for some time can be mounted on the Zipp rim just as easily as the Goodyear – and surprisingly, at 42 mm, it is almost as wide. On a Zipp 303s, the G-One RS is only 39 mm wide; however, the wider rim changes practically nothing in terms of the tire contour.
Apart from the limited tire selection, the Zipp 303 XPLR S can definitely be recommended. Gravel bikers in particular who prefer low pressure and 45 or 50 tires get a perfectly matched wheelset here; those who ride fast should also benefit from the aerodynamics, which do not come with any disadvantages such as susceptibility to crosswinds. Added to this is the unique look, emphasized by the eye-catching, painted-in decor - a wheelset that people will definitely ask about and that you can tell a lot about.
