You’ve overshot everything and now you’re coming into the rock garden far to the right, way too fast and nowhere near your line. A whole lot of brake is the obvious answer here. Some hard braking might let you get things under control, pick your way through slowly and figure this out, except--wait. What if you’re one of the best riders in the world? What if this is a World Cup downhill run and every tenth of a second matters? Suddenly that root on the edge of the course is looking big enough to boost over the whole first section of rocks, cutting across the worst of it at an angle to put the bike back down in that gap between those last two rocks. You can keep the front wheel high and out of harm’s way, but whatever’s down there between those two rocks, your rear wheel is about to blast into it at Mach ten.
There aren’t many riders in the world who can put a wheel into that situation. A lot of us might feel like we’ve been there (and no doubt there’s something to be said for the truly gifted amateur bike manglers out there), but when it comes to exerting completely ridiculous forces on bike parts, only a rare group of riders can do it consistently. With so much attention on Instagram and edits, it’s easy to forget that testing and development are some of the most important things a sponsored rider can do to help a company make better products.
At Stan’s, we’ve been working with racers from day one. Some of the first BST rims we ever made shipped straight to XC riders at the 2004 Olympics, and for several years, we’ve worked closely with the best downhill racers in the world.
While the tubeless performance of the original Flow EX and Flow MK3 made them popular choices for downhill and enduro racing, neither of these rims were built specifically to handle the extreme forces generated by a season of downhill races or repeated enduro stages. The new Flow EX3 rim is unapologetically focused on descending and an ability to withstand the most severe riding conditions.
Over the years, we’ve done some pretty nerdy testing on our rims (like using CAT scans to see inside inflated tires on rims), but the Flow EX3 development included a more primitive component, too. Nearly every rim damaged by a pro during the 2017 and 2018 seasons was analyzed. Some damage was the type of thing we’ve seen for years with all brands of rims, but there are always some more interesting ones, too.
We took the most extreme examples and studied those closer, forensics-style, until we could figure out how to create tests capable of doing those same things to a rim consistently.
Once we were able to simulate the most extreme and unique impacts, the real work started. This more brutal testing of Stan’s and competitors’ rims and wheels taught us some very important things.
Part of what it took to replicate what we were seeing in the field was to take our “drop test” (that weighted wedge that slams down on an aired up tire and rim) and rig it to wreak more havoc on a rim than we ever had. As it turns out, the forces that can be exerted on a wheel on the Mont-Sainte-Ann World Cup DH course go well beyond "extreme" and into the realm of "catastrophic." Rims we tested, including our own Flow MK3, struggled to handle the new drop. What was surprising was that our classic Flow EX (that skinny old rim with the triple cavity internal design) actually did quite well in this test. In fact, it did better than many modern downhill-specific rims. When it came to resisting damage and maintaining a tubeless seal, the EX outperformed nearly everything we tried.
A Flow EX3 hiding behind a set MK3 graphics at the 2018 Whistler EWS round
We knew the MK3’s 6069 aluminum was 10-15% stronger than the 6061 alloy used in the EX generation, and we knew any new rim had to be wider than the old EX models, but the shape of the original EX rim inspired our engineers to incorporate the best elements of both generations into what would become the all new Flow EX3. Once we had a few prototypes, it was back onto bikes for real testing.
We’ve worked with Martin Maes and GT Factory Racing for years, and as the team had been developing new testing protocols for themselves they were instrumental in the refinement of the Flow EX3. With GT’s systematic approach to their pre-season testing, equipment selection and evaluation, the analysis of multiple rim designs became a natural part of the overall process. Martin Maes in particular was very familiar with the Flow MK3, so he had a solid foundation to understand everything we were trying to do with ride quality and rim shape on the new Flow EX3. The results speak for themselves.
Only a handful of people knew it at the time, but the final version of the Flow EX3 rear wheel was on GT Factory pro Martin Maes’ bike when he took the win at the Whistler stop of the Enduro World Series in 2018 and again when he took the World Cup DH win in La Bresse.
Martin Maes, Noga Korem and Wyn Masters of GT Factory Racing
Kyle Warner, three-time North American Enduro Tour winner, also played a role in the development of the Flow EX3. Racing most of his career as a privateer, one of the key characteristics Kyle looks for in his equipment is durability. When he found out the new rim designed for maximum durability was finally ready, Kyle couldn't think of a better place than Bootleg Canyon to put the Flow EX3 through the paces.
For 2019, it’s also really special to be working with Rachel, Gee and Dan Atherton again. We’d worked closely with them on product development in the past, and much of what we learned through their partnership--especially about using rim shape to balance stiffness and compliance--went directly into the development of the Flow EX3. It means a lot to have the entire Atherton Bikes team running these new wheels.
Dan, Rachel and Gee Atheron - Photo: Moonhead Media
What did all this testing lead to? For starters, relative to the Flow MK3 we knew the Flow EX3 rim had to have a thicker spoke bed to withstand greater tension and forces on the spokes. Given the intent of the rim, it was also important to have the maximum available height inside the rim cavity so that when a monster impact does occur, the spokes have much further to compress before they could make contact with and damage the rim tape. Since making the profile of a rim taller also makes it stiffer radially (think of deep, ultra-stiff carbon aero road rims), the ride quality is often adversely affected and the rim more brittle, making it weaker in the long run than a lower-profile, more compliant rim shape. By thickening the spoke bed externally, we were able to balance both of these design goals without compromising the ride quality our rims are known for.
The Flow EX3 combines the best of both the MK3 and original EX
But the most important aspect of the Flow EX3 rim’s design is the Tiebeam: that inner bridge that runs across the inside of the rim. It’s this Tiebeam inner bridge that lets the Flow EX3 withstand impacts that would deform most rims to the point of air loss and structural failure. Even if a rider uses a tire insert, huge impacts can cause the side of most rims to fold, causing air loss and eventual rim failure. When you add the Tiebeam brace to support the patented low profile sidewalls on a Stan’s rim, you end up with a structure capable of resisting this folding force. The Flow EX3’s Tiebeam design means greater structural integrity, fewer dents and the best air retention in the industry. How much stronger were we able to make the new rim? Here's how competing rims and the new Flow EX3 performed in our catastrophic impact test.
The Tiebeam design allowed us to achieve these tremendous strength increases with only a minimal increase in weight. The 27.5 Flow EX3 rim weighs 580g, while the 29 version weighs only 618g.
The Flow EX3 is also available as a rim only in 27.5" and 29" options
Combined with the added durability of 6069 aluminum and WideRight 29mm inner width optimized for 2.35” to 2.8” tires, the Flow EX3 expands the Stan’s Flow family to handle the most aggressive riding. Every World Cup DH and Enduro World Series win, every hour of testing, riding, and improving: it’s all here in the Flow EX3.