First Look | Brand New 1×13 SRAM RED XPLR Drivetrain & ZIPP 303 XPLR Wheels

SRAM has launched its new gravel-specific drivetrain, RED XPLR, which draws inspiration from the mountain bike T-Type Transmission that debuted last year. While it bears some clear resemblances, it features subtle differences to address the needs of gravel riding and racing. It also marks the brand’s first 13-speed system.

Alongside the launch of SRAM’s RED XPLR gravel drivetrain is a brand new wheelset from sister company ZIPP. The all-new ZIPP 303 XPLR SW and S wheelsets see a sizeable increase in rim width and a revised rim hook profile, increasing the tyre volume and improving the sidewall fit.

Jono and Nick from FlowHQ recently spent a day with the team from SRAM Australia learning and riding the new component range. The RED XPLR drivetrain impressed and is without doubt SRAM’s most refined gravel-specific groupset to date, but the 303 XPLR wheels stood out as the biggest improvement over its predecessor. Here we dive into the details, and provide you with our initial impressions on the latest and greatest from SRAM and ZIPP.

The Cervelo Aspero sits firmly on the racey side of gravel bikes, as we recently found out during our test.

SRAM RED XPLR Overview

The most notable leap for RED XPLR is the adoption of the hanger-less mounting design. Called Full Mount, this has been made possible by SRAM’s own Universal Derailleur Hanger interface, commonly known as UDH. Full Mount was first introduced with the launch of AXS T-Type mountain bike transmission, and the pesky derailleur hanger was arguably made redundant from that day forward, depending on who you ask of course. The result? An incredibly robust connection that is designed to better handle unexpected impacts out on the trail.

RED XPLR also marks the brand’s first toe-dip into the world of 13-speed, with the cassette ranging from 10-46T with some well-thought-out steps in between. Fear not, they have managed to do so without the need of yet another freehub body or chain width, and is compatible with existing XDR freehub bodies.

At launch, RED XPLR will be offered as components only and not as a complete groupset, and the individual components can be paired to the matching SRAM RED levers, brakes, and cranks to form a complete groupset.

SRAM RED XPLR Technical Details

As with earlier SRAM AXS and T-Type Transmission systems, the central control unit of the drivetrain is integrated into the RED XPLR rear derailleur. This centralised system handles the intricate tasks of shifting, gear indexing, and ensuring precise adjustments throughout the drivetrain. The gravel-specific derailleur features the same Magic lower pulley wheel from the XX Transmission along with a lighter clutch spring that’s claimed to be better suited to the demands of gravel bikes.

SRAM’s top tier cassettes can often be mistaken for pieces of metallic jewellery, and the new RED XPLR 13-speed cassette is no exception. With a claimed weight of just 288 grams, the 13-speed cassette uses machined steel for the first 10 cogs, with the final 3 being hardened aluminium to save weight. It will be available in a single range option of 10-46T, delivering a whopping 460% range. Despite having an extra cog the 13-speed cassette mounts to the same SRAM XDR freehub body seen paired with previous SRAM 12-speed road drivetrains.

T-Type Transmission set the benchmark for shifting precision under load, with the byproduct being marginally slower shifting. However, RED XPLR has different goals when it comes to shifting speed and precision. RED XPLR forgoes shifting under load as the top priority, with precision and resilience taking the top design goals to deliver fast and accurate shifts. This design reverts to a traditional tooth profile, aiming to boost shifting speeds and fine-tune gear ratios by incorporating odd tooth counts, in contrast to the even tooth counts and full X-SYNC profiles used in the T-Type Transmission series.

Key Details

SRAM RED XPLR Component Compatibility

Due to the adoption of SRAM’s ‘Full Mount’ hanger-less interface, only frames that have adopted UDH hangers will be able to accept the RED XPLR rear derailleur. While there are limited gravel frames on offer from manufacturers at the moment, we expect this will change with the launch of new models. This design has proven extremely robust on the brand’s T-Type Transmission, and we expect RED XPLR to be no different. SRAM noted a minimum chainstay length of 415mm to avoid shifting issues caused by excessive chain line offsets. This won’t affect many bikes, but one that has already been flagged at launch is the newest iteration of Trek’s Madone, which features a chainstay length between 410-412mm.

To avoid designing yet another chain width, SRAM has engineered RED XPLR to operate using the existing RED 12-speed Flattop chain. This may not be significant to many, but your local bike shop will definitely appreciate not having to add another chain variant to its inventory.

The RED XPLR cassette adopts the same XDR freehub driver seen on previous generations of SRAM road and gravel drivetrains. The XDR interface extends 1.85mm longer than the XD interface and is specifically designed for road hubs. It preserves the same hub spacing and flange positions as the 11-speed road-compatible HyperGlide freehub bodies.

As the RED XPLR cassette adopts a more conventional tooth profile, along with an extra cog, there is no cross-compatibility with the brand’s T-Type Transmission mountain bike drivetrains. This excluded of course the shifters, with the RED XPLR derailleur being compatible with any of SRAM electronic shifters regardless of the generation.

Will RED XPLR fit on your lightweight XC build? In theory, yes, everything will bolt up just fine. The main drawback you’ll find is the reduced gear range on the cassette, and the lighter clutch spring found in the gravel-specific derailleur being slightly lighter than that found in a T-Type Transmission derailleur.

The battery locking tab is removable and replaceable on Red XPLR, a great feature and one we hope rolls onto Transmission derailleurs.

ZIPP 303 XPLR SW & S Wheels

The launch of the ZIPP 303 XPLR SW and S wheels sees the carbon wheelset grow to a whopping 32mm internal rim width. This is a sizeable 5mm increase from the brand’s current 101 XPLR wheelset, and 2mm increase from its 3ZERO MOTO mountain bike wheels.

Why so wide do you ask? Through development between SRAM and ZIPP, they found that lower tyre pressures and higher volumes resulted in reduced vibration through the bike, and allowed riders to maintain higher speeds with less power input compared to narrower tyres at higher pressure.

The wheels are approved to use with rim inserts which some gravel racers opt to run, however the general consensus from ZIPP is that these are no longer necessary due to the increase in volume and sidewall support provided by the wider profile. Aerodynamics play a big role at the speeds these wheels are intended for, and the additional width also allows for an improved tyre sidewall to rim interface which reduces overall drag.

ZIPP 303 XPLR Details

The 303 XPLR wheelset is offered in two versions: the premium SW series and the more affordable S option. To the untrained eye, the wheelsets appear identical, but as always the devil is in the details.

The rim profile of the SW and S wheelsets is identical, however the rims vary in the carbon laminate used, along with the SW rims featuring the iconic dimpled profile, compared to the smooth finish of the S series rims. Spokes are taken care by Sapim, with the SW wheelset using CX-Ray spokes and S wheelset adopting CX-Spring spokes to reduce costs.

Hubs are taken care of by ZIPP’s in-house hubs, with the brand’s premium ZS1 found on the higher-end 303 XPLR SW wheelset. The bring down costs, the 303 XPLR S wheelset features the brand’s 76/176 hubset, contributing to the small weight penalty between the two wheelsets.

Due to the increase in width, only tested and approved tyres can be used on the 303 XPLR wheels. At launch, only 25 tyres are approved for use including the Goodyear XPLR tyre range launched alongside the wheels. Additionally, ZIPP’s own Tangente G40 and Schwalbe G1 are approved for use, with multiple manufacturers and over 100 additional tyres currently being tested for approval.

Only 25 tyres are approved for use with the ZIPP 303 XPLR’s at launch, with another 100 tyres currently in testing.

ZIPP 303 XPLR SW Key Details

ZIPP 303 XPLR S Key Details

Canyon’s latest Grail fitted with all the candy from SRAM and ZIPP

Flows First Impressions

We’ve had a few hours to ride the new SRAM RED XPLR drivetrain and ZIPP 303 XPLR wheels during the media launch event, and while this isn’t enough for a comprehensive review, it provided us with a very good first impression.

SRAM’s T-Type Transmission sent shockwaves through the mountain bike industry, delivering an effortless shift and a level of robustness we had never seen before. RED XPLR has taken what the brand has learnt from Transmission, and tailored it for the needs of gravel riders and racers, and the robustness has certainly been carried over.

Previous hanger-mounted systems, regardless of discipline, feel flimsy in comparison to SRAM’s Full Mount derailleurs. On the trail, or gravel, the shifting is quick and precise, and if T-Type Transmission is anything to go by, the robustness will likely keep it that way.

The launch of ZIPP’s 303 XPLR wheelset range sees the brand redefine rim widths and tyre profiles for gravel bikes, and we were certainly surprised at how wide the rims truly were. The increase in contact patch, and ability to run lower pressures as low as 21psi allowed us to take our test bikes into some terrain that would previously be reserved for our mountain bikes. We had more grip, and were more comfortable on the bike compared to previous setups, which allowed us to push the wheels further into some questionable terrain. It is worth mentioning that during our brief time on the wheels at the recommended pressures, both Jono and Nick found themselves bottoming out the tyre on the rim from square-edged hits. While this never resulted in any flats, it felt a little unnerving, and we aren’t fully sold on the super-low pressures just yet.

SRAM RED XPLR vs Shimano Di2 GRX

How does one choose between Shimano’s recently released Di2 GRX and SRAM RED XPLR? Pricing alone separates them pretty quickly, with Di2 GRX being close to $1,500 AUD cheaper for the full groupset. Those seeking an electric 1x gravel drive will likely lean towards RED XPLR, as Shimano’s Di2 GRX is only available as a 2x system. Or if you are a Shimano fan and have your heart set on 1x, GRX is offered in this configuration as a mechanical groupset which we reviewed recently. As for on-trail performance, it’s a little early to say. Once we have spent a little more time on RED XPLR we’ll be able to draw some more definitive conclusions between the two.

The SRAM RED hoods are carried over from the road groupset to RED XPLR, and the ergonomics of these were brilliant. The ability to one-finger brake was excellent, and allowed us to maintain a good grip on the bars on rougher terrain whilst braking.

The cost of both SRAM’s RED XPLR drivetrain, and ZIPP’s 303 XPLR wheelsets is unquestionably high and there is no hiding that. Will we see the technology trickle down to a more wallet-friendly Force level? Based on SRAM’s history, surely this is just a matter of time, but we are yet to see any details. We’ll be receiving a RED XPLR groupset to run on one of our long-term test bikes soon, so stay tuned for a full in-depth review.

SRAM RED XPLR and ZIPP 303 XPLR’s certainly look the part, and from our brief time testing, they ride as good as they look.

Editorial Guidelines
At Flow Mountain Bike, we’re committed to delivering engaging and trustworthy content, from product reviews to destination showcases, news, interviews, and features. While many of the brands and destinations we cover may advertise with us, our editorial team operates independently, ensuring our content is guided by expertise and passion—not commercial influence. Sponsored content is always clearly disclosed, and we remain dedicated to providing honest and unbiased coverage across everything we publish. For more details, see our Transparency Report.

It appears you're using an old version of Internet Explorer which is no longer supported, for safer and optimum browsing experience please upgrade your browser.