Cyclist
New Zipp 303 XPLR gravel wheels combine mountain bike width with road depth
In conjunction with SRAM’s new Red XPLR AXS groupset, Zipp has launched 303 XPLR gravel wheels. They are hookless, and combine a 32mm internal rim width with a 54mm rim depth.
Zipp says their design creates a smooth rim-tyre transition with tyres in the 40-60mm range, for better aerodynamics, while providing the casing support for lower pressures, for better grip and comfort and lower rolling resistance.
There are two versions of the wheelset: the 303 XPLR SW, with a claimed weight of 1,496g and price of £1,600 / €1,800 / $2,200; and the 303 XPLR S, with a claimed weight of 1,610g and a price of £1,100 / €1,200 / $1,400.
Zipp has also released two tyres in partnership with Goodyear, specifically designed for the 303 XPLR wheels. The XPLR Inter and XPLR Slick are available in a 700C x 45mm guise only, and retail for £80 / €90 / $80 each.
Need for speed
As gravel moves from niche to mainstream it’s getting more competitive and average speeds are increasing.
‘Take Unbound for example,’ says David Morse, Zipp’s wheel category manager. ‘The winning speeds have been around 32kmh in recent years. We started work on these wheels in 2021 and our rationale has only been more confidently supported since.’
Morse explains that speed is increasing to such an extent that aerodynamics now have a crucial role in performance, but most gravel wheels, being generally no wider than 25mm internally, don’t have the width to create a smooth transition when paired with gravel tyres.
‘The rim-tyre pairing looks more like a lightbulb than an aerofoil, which undermines any aerodynamic advantage the rim may otherwise provide,’ he says.
So Zipp saw the opportunity to widen the rim drastically, pushing it out to 32mm internally and 40mm externally. This means the rim is a similar width to the tyre, creating a smooth transition and maximising the laminar airflow across the rim-tyre system responsible for lowering drag.
3T was the pioneer of this rationale for gravel, releasing its Discus LTD 45 | 40 wheels (29mm internal, 40mm external) several years ago, and Reserve has recently jumped into the category too with its 40/44 GR wheels (27.4/27mm internal, 36/34.4mm external), but Zipp has been the brand to take it further than anyone else so far. The new 303 XPLR wheels dwarf even the brand’s own 1Zero Hitop mountain bike wheels.
‘We took the wheel to the wind-tunnel five times and are confident that the rim shape saves two watts at 32kmh in pure aero terms alone, versus the nearest competitor, but that’s before we even get onto the other ways in which the 303 XPLR makes the rider faster,’ says Morse.
Many facets of going fast
Just as the brand did when it overhauled its road wheelsets, Zipp says it focused on what it dubs ‘Total System Efficiency’, where it optimises across a range of barriers to speed, rather than just a single attribute such as aerodynamics or weight.
‘Gravel surfaces can generate up to 100 watts in vibrational losses as the tyre, being overinflated, bumps up and over ridges rather than deforming around them,’ says Morse. ‘The width of the 303 XPLR rim lets the rider lower tyre pressures dramatically because the tyre sidewalls, being spaced so far apart, have adequate support. This can save the rider up to 14 watts at 32kmh while preserving bike handling characteristics.’
Zipp has expanded its tyre pressure calculator to include the 303 XPLR wheels so riders can easily work out their new optimal pressures.
The 303 XPLR wheels also look to guard against pinch flats with 3.9mm wide sidewalls.
‘Aero wheels aren’t that fast if they are liable to puncture tyres,’ says Morse. ‘The wide sidewalls distribute acute pressure caused by rock strikes better, protecting the tyre.’
The new wheels sound like a ‘have cake and eat it too’ proposition, but there’s a small catch to do with tyre compatibility. Zipp’s recommended width (40-60) falls outside the ISO recommendations for 32mm internal width rims, which is 54-80mm. As such, only tyres that have been validated by both Zipp and the tyre manufacturer are clear to use on the Zipp 303 XPLR wheels.
The current list of approved tyres stands at: Zipp’s Tangente G40, all Schwalbe’s G-One models in 40mm+ widths, as well as the new 45mm XPLR Slick and XPLR Inter, which have been made for Zipp by Goodyear.
‘These have been made specifically for the 303 XPLR wheels and ensure best performance,’ says Morse. ‘The width of the tread cap, position of the nobs and width of the tyre on the 303 XPLR wheels has all been considered.’
Zipp XPLR range
There a several new components from Zipp to complement the new SRAM Red XPLR AXS groupset. The 1,496g Zipp 303 XPLR SW is the lighter of the two wheels in the range, with the 1,610g 303 XPLR S trading in a smidge over 100g to save around £500 / €600 / $800.
The XPLR Inter (for mixed conditions) and XPLR Slick (for dry conditions) tyres are available in a 700c x 45mm guise only, and retail for £80 / €90 / $80 each.
Zipp has also released some SL 70 XPLR bars designed to pair with the new SRAM Red XPLR AXS groupset, which costs £320 / €320 / $360.
- For more information on the new Zipp 303 XPLR wheels, visit sram.com
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