Following the recent announcement of Zipp’s ‘budget’ 303 S wheelset, Zipp has released details of its updated top-flight 303 Firecrest tubeless disc-brake carbon wheelset.
Headline changes include an overhauled rim design, which is both hookless and 25mm wide internally (which is so wide it’s almost in MTB wheel territory), a new hub set and a claimed 300g reduction in overall weight.
Zipp says this makes for a wheelset more suited to varied terrain – which we take to mean endurance road and gravel.
Following the 303 S’s more subtle branding, the updated 303 Firecrest wheelset also receives grey, more toned down decals.
How wide did you say that rim was?
Twenty-five millimetres, internally. This is so wide it would have been in mountain bike territory only a few years ago, and even now is wider than some wheelsets specifically designed for gravel and off-road use.
Being hookless, the rim is only compatible with tubeless or tubeless-ready tyres. Standard clincher tyres are not compatible with these new rims.
Inner tubes can be used, but only with tyres that have a tubeless-specific bead. This setup wouldn't be optimal in terms of weight, tyre pressure or rolling resistance though, according to Zipp.
Zipp claims the new rim profile means that tubeless tyres can be fitted and removed tool-free, and that there’s no need for an air compressor to seat tyres.
As with the hookless 303 S rim, the maximum inflation pressure on the new 303 Firecrest rim is notably low at 72.5psi. The maximum rider weight limit is 115kg.
Externally, the rim grows a more modest 0.1mm to 30mm. At 40mm deep, it’s also 5mm shallower than the previous generation 303 Firecrest and the new 303 S wheelsets (which have 45mm deep rims).
Interestingly, Zipp didn't test these new wheels in a wind tunnel. Instead, Zipp says an independent third-party company used an on-bike aero sensor (like the Notio Konect) to test the wheels' ‘real world efficiency’ on a dirt road.
Despite the reduction in rim depth, Zipp claims the new 303 Firecrest wheelset will save you 15 watts at 40kph over the outgoing model and 5 watts over the 303 S, when taking into account both aerodynamics and rolling resistance.
In terms of performance on smooth roads, Zipp conceded the overall efficiency savings would be smaller, but it also claims the difference would be larger on rougher surfaces than that used for testing.
Zipp notes the testing was performed with 28mm Zipp Tagente RT28 tyres across all wheelsets, which is also the minimum tyre width compatible with the new rims. You can run tyres up to 55mm wide on them according to Zipp though, assuming your frame has enough clearance.
Lighter on your bike and your wallet
The claimed weight for the new 303 Firecrest wheelset is 1,355g – 300g lighter than the previous generation.
Some of this claimed weight reduction is likely to be accounted for by the shallower, hookless rim design and improved carbon layup. A switch to aluminium spoke nipples may also account for a few grams too.
At £1,600 / €1,800 / $1,900 they’re also £700 / €800 / $600 cheaper than the previous 303 Firecrest wheels, which represents a pretty substantial cut in cost.
Of course, £1,600 is still a lot of money for a set of bicycle wheels in absolute terms. However, this reduction in RRP certainly makes the new 303 Firecrest wheels more competitive in an increasingly crowded market.
Zipp is also now offering a lifetime warranty against manufacturing defects and impact damage (during intended use), for the original owner. While you hopefully wouldn’t ever need to use it, it’s definitely nice to have.
New hubs, disc-brake only
As with the rim, the 303 Firecrest hubs have also received a complete redesign.
Called the ZR 1 DB hub, it rolls on stainless steel cartridge bearings and has an updated seal design for a claimed improvement to durability, further signalling Zipp’s intention for this wheelset to be used both on- and off-road.
The rear hub features 66 points of engagement for snappier pedalling response.
The wheelset is laced using 24 j-bend Sapim CX-Sprint spokes, in a two-cross pattern, front and rear. It's also disc-brake only (which is increasingly the standard for road bikes nowadays) and is compatible with Centerlock rotors. Lockrings are included with the wheels.
The rear wheel is available with an XDR driver or SRAM/Shimano 10-/11-speed freehub as stock, but a Campagnolo-compatible freehub can also be purchased separately.
Time for new standards
The European Tire and Rim Technical Organization (ETRTO) standards (which aim to reduce compatibility issues across manufacturers and help ensure rider safety), currently state that a 25mm internal rim width is suitable only for tyres 42mm or wider.
When we put this to Zipp, it pointed out that this standard specifically refers to standard clincher tyres and doesn’t cover road tubeless tyres or hookless rims.
It also insisted the current ETRTO standard is outdated and that Zipp is currently involved in talks with the International Organization for Standardization (ISO), as well as other rim and tyre manufacturers, about the creation of a new standard for road tubeless systems (which we’ve been hoping would happen for a while now).
In fairness to Zipp, tyre giant Schwalbe also notes on its website that the ETRTO standards often lag behind industry progress. Worryingly, though, it nevertheless says using its tyres in combinations outside of ETRTO recommendations is done "at your own risk".
In terms of tyre compatibility with its own hookless rims, Zipp does not have a list of approved tyres. Instead, it says all current tubeless and tubeless-ready tyres are compatible with the new 303 Firecrest (and 303 S) wheels, unless the tyre manufacturer specifically states the tyre is incompatible with hookless rims.
This is in contrast to Enve which has an ‘approved/recommended’ list of compatible tyres for its hookless SES 3.4 AR road rims (which also have a 25mm internal width), as well as a list of ‘not approved/incompatible tyres’ that includes popular tyres such as the Continental GP5000 TL.
When asked, Continental told us that while tyres in its Terra Gravel range are compatible with hookless rims, with a maximum pressure of 73psi, tyres in its road range (of both clincher and tubeless variety) are not. As things stand, it recommends none of its road tyres are used with any hookless rims.
As we noted with Corima’s recently launched G30.5 hookless wheelset, we would always recommend double checking with manufacturers that your chosen rim-tyre combination is fully compatible.
