SQUIRREL_13642010
Zipp’s latest 303 SW wheelset adds data-driven tech to what were already the brand's most versatile wheels.
The all-new 303 SW builds on an impressive all-rounder design. It has been given a high-tech makeover, with built-in tyre pressure sensors that transmit live data to your GPS head unit. This opens up a world of pressure experimentation and safety monitoring as you ride.
The new 303 SW retains the broad 25mm internal width and the 40mm-deep profile. The rim sidewalls have got a little thicker and Zipp claims the shape is optimised for 30-35mm road tyres, where the previous 303 Firecrest was optimised for 28mm tyres.
Zipp claims the new rim design has improved impact strength by 10% and the new thicker sidewall shape helps to shield the tyre from impacts that can cause pinch flats.
The 303 SW continues to use the ZR1 hubset of the previous generation, with a small but important upgrade. That’s a switch to full stainless-steel bearings, which Zipp claims improve durability and make for smoother running.
Zipp gives a claimed weight of 1,440g for the complete wheelset, including tubeless tape, sensors and valves. The wheelset is priced at £1,700 / $2,200 / €1,900 / AU$3,350.
On my scales, I measured a combined weight of 1,442g (660.5g front, 781.5g rear). That’s 33g heavier than the previous-generation wheels, which is an impressive feat when you consider both the front and rear wheel now have built-in tyre pressure sensors, each with its own CR2032 coin cell battery.
The wheels come backed with Zipp’s lifetime warranty against impact damage under normal use. The 303 SW is classified as a road/all-road/gravel wheelset, so in theory it's covered for more rugged riding than purely road use.
Zipp 303 SW setup
Setting up the wheels with the Zipp-supplied Goodyear Vector R Z35 SW tyres was simple, with the tyres seating and sealing quickly, and no sealant seepage or pressure loss.
Getting the right pressures involves using SRAM’s tyre pressure app, then inputting the wheel, tyre size, rider weight and intended use. The app gave me figures of 51psi for the rear and 49psi for the front.
You can make sure the tyres are sealed properly before riding, thanks to the in-built pressure sensor, since you’ve synced the wheels to your head unit or AXS app.
To sync the wheels, it’s a case of opening the SRAM AXS app, searching for new sensors and spinning the wheels to wake them. You then simply connect and add your desired pressures, and the app will track them.
Adding the wheel sensors to a Hammerhead Karoo bike computer brings the same information and a dedicated data screen that shows current pressures front and rear. This will change to red if it detects pressures outside of the safe zone, around 10% +/- from your ideal pressure.
Zipp 303 SW ride impressions
The 303 SWs feel just as impressive as the previous 303 Firecrest. The wheels are stiff without being harsh, and the fast-engaging freehub with its 66-point engagement for a rapid 5.5-degree pickup gives the feeling of instant acceleration.
The ride quality is obviously influenced greatly by the large-volume 35c Goodyear Vector tyres. They provide heaps of grip and lots of compliance, especially being able to run at significantly lower pressures than the 28c tyres I’d been using on the older 303 Firecrests.
They didn’t feel in any way slower, even though the tyres added a bit of weight. I think the trade-off in grip and comfort is worth it.
The rim shape handles crosswinds without drama, tracking straight with no front-wheel buffeting.
Monitoring on the fly
I’m now convinced tyre pressure sensors are a good thing. I have used the add-on Quarq TyreWiz before and it's a great idea, if a little pricey, especially once you’ve already paid out for a wheelset.
Here, however, the sensors are integrated cleverly, adding minimal weight. Most importantly, they are cheaper than adding a set of TyreWiz 2.0s at £130 / $130 / €145. The new 303 SW is £100 / $100 more expensive than the outgoing 303 Firecrest.
On a long ride (110 miles in a heatwave, where the temperature was hovering around 30ºC / 86°F), my on-bike pressures fluctuated more than I would have imagined. At my mid-day lunch stop, where my bike was left in the sun, the rear tyre crept up to 62psi, with the front touching 54psi.
Before I restarted my ride, I released a bit of air to get back to the optimal pressure. When I finally arrived home, the rear had crept back up to 53psi and the front touched 51psi (up from 51 and 49psi respectively).
While these pressure changes are well within safe limits, they made me realise that tyre pressures can change greatly through a ride. If I’d been travelling prior to my ride, or my bike had been left in a hot car, pressures could rise to dangerous levels. Being able to check instantly and monitor on the fly is a very good thing.
Being able to repair a puncture and reinflate to my optimal pressure (without the need for a gauge pump) takes the guesswork out of roadside fixes.
It's also helpful to be alerted to a pressure drop should you hit a pothole or puncture. It takes away those moments on a ride where something doesn’t feel quite right, but you’re not sure if it’s full-on air loss.
Zipp 303 SW bottom line
The 303 SWs are truly excellent do-it-all wheels; they are light, fast and stiff, yet comfortable.
The added element of pressure monitoring is something I didn’t know I needed, but now feel safer for having it.
Aside from warning you when something isn’t quite right, the fact that it records pressure data through the AXS app on a ride opens up the ability to experiment, comparing like-for-like rides afterwards.
That's not necessarily of huge importance to sporty recreational riders like me. However, if you're racing, being able to find issues and set the optimal pressures for your tyres could be the difference between winning and losing.
The only thing I don’t like about the 303 SWs is the same problem I had with the 303 Firecrest. The large Zipp logo graphics are stickers, rather than the Impress print found on Zipp's premium 353 NSW wheels, or the old water decals found on the original 303 Firecrests.
My test 303 SWs already have a couple of nicks in their graphics after being leaned against another bike. It’s irritating that they now don’t look as slick as their performance.
SQUIRREL_13642010
