The Elephant in the Rim: Sealant, Slots and the New AXS Tire Pressure Sensor
We chat to Ben Waite, a Senior Design Engineer at Zipp, to get the lowdown on the little innovation set to make a big difference to how you ride.
May 22, 2025
visibility
INTERVIEW
The Team Behind the New Zipp 353 NSW and 303 SW Wheels Talk Design, Speed, Pressure and Testing to Extremes
Two weeks before Zipp released its new road and all-road wheels, we flew to the hub of the brand's operations in the US and sat down with the designers, engineers and brand teams responsible for the next phase in the Zipp revolution.
PUBLISHED
May 22, 2025
WORDS
Regroup staff
PHOTOS
Regroup
Today, Zipp launched a host of updates to its NSW and SW line. Some of the changes are small; some are seismic. Of the former, the brand's 454 and 848 NSW wheels receive a slight refresh. While the shallowest profile in Zipp's flagship wheel line, the 353 NSW, receives so many improvements, Zipp would rather you see it as a ground-up redesign. Alongside the micro and macro updates to the NSW wheels, the newly-named 303 SW, formerly the 303 Firecrest, also sees a slew of updates.
Between the NSW and SW changes, there’s a lot to unpack. But rather than interpret the changes from a product sheet, a couple of weeks ago, we had the good fortune to receive an invite to Zipp’s US head office and manufacturing plant in Indiana, where we got the chance to talk with Zipp’s product team, its engineers, managers and marketing people, to dive into all the changes and get under the hub of the new wheels. The access into the world of Zipp and the time we were afforded went beyond generosity, and we’d like to thank everybody at Zipp for their warm and wonderful hospitality.
Here’s our conversation, which we edited for readability, brevity and the need to protect a few of Zipps’ trade secrets.
Hey, all, great to meet you. Ok, to kick things off, you've got a lot of new product landing soon. Can you talk through what's coming down the pipe?
Nathan Schickel (Product Manager): Thanks, Pete. Great to meet you too. Well, we actually have four wheels launching—the three NSW models comprising the 353, 454, 858, of which the 353 is entirely new, plus the completely new 303 SW.
What headline updates should riders know about the new 353 NSW and 303 SW models?
Nathan: From the perspective of the 353 NSW, it is a ground-up redesign. It has a new, shallower rim shape, which includes a cavity that houses the new SRAM AXS wheel pressure sensor. Previously, you would have seen pressure sensors externally mounted around the valve, but with the new 353, it’s hidden and integrated into the rim —you wouldn’t even know it’s there unless you see the LED flashing.
We’ve introduced a new way to decorate the 353 rim with what we call “In-mold Graphics”. That’s where the gloss sections that form the Zipp logos are created directly in the mold. Unlike decals or our Impress method, these graphic elements are part of the rim structure itself, making them more durable and visually more appealing.
It's worth noting that at Zipp, you don't paint your rims.
Nathan: Right. So, everything we do has to maintain a pristine finish, including the new In-mould method. When you don’t paint your rims, you better make them well, otherwise you’ll see plenty of flaws!
Moving to the hubs, all NSW wheels now feature a new hub called the ZR1 SL. It’s a development from the hub on our Firecrest/SW line called the ZR1. We lightened that model, added ceramic bearings, and created a hub set worthy of an NSW wheel, our flagship range.
Why not take the existing NSW hub and open that up to the SW line?
Nathan: One of the things that we were looking for was commonality in spare parts between different lines. The older Cognition hub set from the NSW line had very individual spare parts. But by bringing the ZR1 level up, we created commonality in axles, bearing sizes, driver bodies and end caps – a lot of the spares we sell. Ultimately, it’s much better for the consumer and our dealers.
For now, you're not carrying forward Cognition's Axial-clutch system?
Nathan: Correct. That wasn’t something we could reduce in cost. Plus, the system had some inherent limitations – fewer points of contact, all of which are mitigated by using the pawl and ratchet ring system inherited from the ZR1.
One of the more notable changes seems to be the spoke reduction across the new releases.
Nathan: That’s right. One of the things the team did, for weight and aerodynamic purposes, was to reduce the spoke count from 24 to 20 per wheel, and play around with the spoke pattern and the carbon laminate in the rim. We ended up with the same strength and durability but with fewer spokes. And if anyone has any concerns about that, rest assured that at Zipp, all of our products are tested to ISO standards. Further, over the past 30 years, we’ve developed our own testing standards. Between ISO and our own, we take testing to extremes to ensure strength and durability, particularly as it relates to impact strength. To speak to that, the new 353 NSW is 16% stronger than the previous iteration. Plus, it’s backed by Zipp’s lifetime warranty.
To take a broader focus on the NSW line for one moment: while the 353 benefits from a complete redesign, the 454 and 858 are essentially unchanged, right?
Nathan: That’s correct. The only change to the 454 and 858 NSW wheels is the new hub set, which moves from the Cognition to the ZR1 SL. It’s not a complete redesign, of course. But the fact that we have the same new hub set across all three rim profiles within the NSW family ensures uniformity, ease of service and a slight performance improvement for the 454 and 858, even though they are otherwise unchanged, because the ZR1 SL is a slightly lighter hub set than the Cognition model it replaces.
Nico Deportago-Cabrera (Zipp/TIME Brand Manager): To expand on what Nathan said, even though we have the NSW family, each wheel has its own requirements, which might call for different technologies and features from its stablemates. Addressing those needs, and the rider’s needs, is often best served by bringing out updates individually.
For those new to Zipp, could you clarify the specific ride characteristics and intended uses of the 353 NSW compared to the 303 SW?
David Morse (Category Manager): The 353 NSW is tailored for road riding or light all-road riding, whereas the 303 SW in its former life as the 303 Firecrest, is the wheelset people put on their all-road bikes, their gravel bikes, and it’s the wheel our professionals use for cyclocross and the cobbled Classics. With the new update, the 303 SW is optimized for 30-35mm tires, but it can take anything from a 29mm to 44mm, balancing toughness and aerodynamic performance with a similar 20-spoke setup to the 353 NSW. Notably, it also features the same integrated AXS tire pressure sensor. However, unlike the 353 NSW, the 303 SW uses our ZR1 hub, not the ZR1 SL. Other notable differences include the finishing details, which for the 303 SW combine our Imprint and decal methods.
Nathan, earlier you mentioned Zipp's testing procedures. Can you discuss how you combine lab and real-world testing, and how the new wheels benefit from those programs?
Nathan: Absolutely. Over the past 18 months, test riders have been logging over 100,000 kilometers on the 303 SW and the 353 NSW. That’s a level of validation that we take beyond the laboratory, where people ride them every day, trying to abuse and break them. If the lab gives us feedback over the short term, test riders give us feedback over a longer term.
Can you give an overview of how your test program works?
Nathan: Sure. We have testers who ride a certain number of hours a day. We might give them conditions such as a 6000km ride over the next month, with an additional year of testing for a total of 15,000km. Our internal system syncs with Strava, so all the rider has to do is upload it there, and it automatically syncs with our internal system. If they have a problem or specific commentary, they can also log into our internal system to file that with us as well. As a Product Manager, I see a weekly digest, and our engineers receive every file as it’s updated. It’s also worth noting that from early samples to later fully developed wheels, everything stays out on the road, with our testing pool, which may have started as a small group to later, a much wider cohort that parallels the product’s maturity as it nears launch, continuing to put in the miles on the wheels we originally supplied them until they are eventually replaced.
When did the new 303 and 353 wheels start their testing journey?
Nathan: We were riding early prototype samples as far back as December 2022, if you can believe it.
Nico: I actually raced the new 303 SW, albeit without the AXS wheel sensor, at Unbound in 2023.
Nathan: From a total field test perspective, we’re probably up to 250,000 kilometers per wheel over all iterations of the 303 SW and the 353 NSW products.
There's a lot going on with the new updates. I'd be interested to know how you decide when to release a new iteration. In other words, why now?
Ben Waite (Senior Design Engineer): That’s a good question. We’re always working on a bunch of tech all the time. So very often it’s not a case of ‘what can we put into this product’, but ‘alright, what things are mature enough we feel we can integrate into it?’.
These are ideas you have bubbling away in some stage of evolution?
Ben: That’s correct. For example, 858 came out in 2022 with 20 spoke holes. Right then, we wondered if a more all-road wheel like the 303 SW could work with only 20 spokes. So we adapted a few sets of existing wheels and sent them out into the field to get beaten up to see what would happen. We knew they’d be safe, just from what our internal testing said, so the next step was field testing to gather more intel.
As I understand it, the 303 SW has been in use throughout the Classics season, so it's clearly one tough wheelset.
Nathan: Our professional teams received their first batch of 303 SW a few weeks before Omloop, and then prepared them and raced them at that race and the rest of the season.
A professional rides at a different level than an amateur. That must make for interesting feedback.
Ben: Absolutely. They’re just all out. The speed at which they go, hitting everything, helps us round out the testing. It’s a great complement to our in-house and wider field testing programs. From what we’ve seen and heard, everything has gone well.
To change the tack for one moment, I'd like to hear about Zipp's experience with what seems to be the ever-evolving topic of tire pressures and widths and how the professional scene is changing in response.
Nico: Convincing a roadie that they can go faster on a 30mm tire at 55psi than a 23mm at 130psi is a lot easier if you can show that the pros are changing what they ride. Luckily, we do have the opportunity to work closely with our pro teams, and one of the things we would often ask our road sports marketing teams, who work one-on-one with our pro riders, is the pressure a specific rider was running when they crossed the line. For example, Alejandro Valverde got 2nd place at Strada Bianchi a few years back, and we wanted to know what his tire pressure was, and it was in the low 50s. For someone of his era, who would have been using thin tubulars at super high pressures back in the day, to be convinced of the value of lower pressures and wider rubber gives us the confidence to drive the conversation with the wider cycling community.
And communicate that comfort is the key to speed?
Nico: That’s it. The idea of discomfort being a barometer of speed and efficiency is gone. And we’re even seeing the geometry of pro bikes changing, with higher stacks as just one change. The market is moving to a point where comfort as the driver of speed is much better understood.
Has the way you design wheels changed in response to those developments?
Ben: It’s changed a lot. One of the things we’ve worked on with the move to hookless rims is the use of hard steel tooling, which has led to us being able to get super tight on our measurement tolerances in the rim bed. So we now know the perfect amount of what we call compaction, which is when we compress the pre-preg carbon, ply by ply, strip by strip, to get a consistent measurement. Ultimately, improved tooling and the move to hookless rims allow us to be more precise than ever before.
Are you also exploring other types of carbon fiber?
Ben: We’re introducing advanced, sometimes more exotic carbon fibers and customizing stiffness and compliance more precisely where needed in the rim. Previously, our rims were uniformly thick throughout; now, we strategically vary thicknesses between spoke holes and other areas, which is analogous to frame tubing butting. It’s an approach that improves strength, reduces weight, and allows us to better tune ride feel.
Let's dive deeper into that rim-integrated sensor, particularly how you solved the challenge of tire sealant interfering with the sensor.
Ben: That was a huge hurdle. The valve that goes into that wheel and into the rim has a little hole that transmits air into the sensor to gauge the pressure. But sealant is designed to go into and close little holes, so it was a big battle! Ultimately, solving that problem involved a study of complex fluid dynamics to make the path for the fluid to get to where the sensor is as difficult as possible. Additionally, we also had to run the valve through the pressure unit, so as you inflate or deflate your tire, any sealant that would start to get close to the sensor gets sucked out. So the air flowing through the valve sucks the sealant out to prevent it from plugging the sensor.
That is simply an incredible feat of engineering. What did the testing program look like?
Ben: We did a lot of testing in general, but specifically, a lot of work around the sensor’s air ports, testing many different shapes and sizes, to really dial that in. And many different types of sealant, too. When our solution had matured, we had well over 100,000 kilometers of people riding the system without a single failure, which we would define as sealant getting into the sensor.
As we come to the end of our chat, I'm conscious that you're all sitting in your HQ in Indianapolis, which is also a manufacturing base for Zipp. Can you talk about what products you make in-house there?
Nathan: Sure. At the top, most NSW and Firecrest/SW rims are molded here in Indianapolis. Aside from the molding, we also build all wheel models here, so we’re really integrating product development, management, and manufacturing in one place, with all of the many benefits that brings. Specific models like the 808 Firecrest and 303S rims are molded in Taiwan but assembled in Indianapolis.
Our hubs—the ZR1 SL and ZR1—are designed in Schweinfurt, Germany, a renowned hub-engineering location with over a century of history. Hub manufacturing takes place in SRAM’s facility in Portugal.
Finally, as the market for wheelsets grows and develops with more brands joining the fray, how do you see Zipp's position in the industry?
David: We’re bike riders, so we love to see growth and excitement in the industry and new players. If we look at our history, we can see that we were there when it all began. Carbon wheels began with Zipp. Along the way, many of our innovations have become industry standards. Ultimately, we thrive on competition, but the spirit of innovation, relentless curiosity about the bike and where it can go, and our ever-long journey to make the rider faster keep us pushing on and at the front of the sport.
Nicely said! Thanks for your time today, team.
Zipp: Thanks, Regroup!
FEATURED PRODUCT
ZIPP 353 NSW WHEELSET
A sensational new hub, less spokes yet more strength, integral tire pressure monitoring and an all-new cleaner graphics. Meet the new Zipp 353 NSW wheel.
