KTM’S 2024 ENDURO MODELS: THE ‘STIFF FRAME CONCEPT’

KTM’s Off-Road Product Manager, Fabian Gusta, offers a fascinating and candid insight into the ‘stiff frame concept’ design philosophy behind KTM’s landmark new 2024 enduro models.

While a lot of attention has, understandably, been focused on the first-time appearance of a closed-cartridge WP fork on KTM’s 2024 enduro models, the most significant change to these landmark new models is arguably the all-new ‘stiff frame concept’, and the other design changes made to accommodate it.

At the recent international media launch for KTM’s 2024 EXC and EXC-F models in Lesotho, Transmoto’s Andy Wigan sat down with KTM’s Off-Road Product Manager, Fabian Gusta, for a fascinating and candid insight into the design philosophy behind these new-generation machines, and the new realm of performance potential Gusta says it has paved the way for.

TM: First up, just explain what your role as Off-Road Product Manager entails.

FG: Well, I am part of KTM’s product management team. My official title is Off-Road Product Manager, which means I’m responsible for KTM’s off-road strategy. That includes motocross, cross-country and enduro models, plus our line-up of mini models. I am the guy who does all the work before the bikes go into production, which is when the marketing guys take over. Basically, my key role is to align our design, development and business targets with our R&D teams, follow them throughout the development process, and then hand over the whole project once it’s completed and ready for production to the marketing and communication team. I also make sure that all the design elements of the motorcycles are communicated in the right way and that our sales colleagues are aware of what we are going to put out on the market and how we perform compared to our competitors. In my youth, I raced a lot of motocross, so that helped give me a connection to a lot of our test riders and development colleagues. And the relationship with those people is very important to the entire process.

So, let’s talk big picture for a moment, Fabian. After KTM released a new generation of motocross models a year ago, it was widely expected that your 2024 enduro models would adopt many of those sweeping changes – especially because of KTM’s focus on ‘standardisation’ of components across their off-road model ranges. Is it fair to say that the 2024 enduro models share more componentry with their MX counterparts than ever before?

This is not the first time KTM has built bikes using a shared platform strategy. But, yes, you could say we have taken that standardisation strategy a step further with these 2024 enduro models. For example, our motocross and enduro models have different fuel tanks, but they share the same seat and bodywork – aside from the headlight, of course. Take some other examples. In the past, we had different footpegs for our motocross and enduro models, but they are now the same. Similarly, the enduro and motocross models had a different frame geometry, but now they are the same. We have unified many parts, but we have only done that where it makes sense.

“With this new design concept, the stiff frame is there to create handling stability, while the shock can do what it’s supposed to do: independently absorb rear wheel impacts.”

Speaking about component standardisation, what really jumped out to me with the 2024 enduro models was how similar the frames appear to their motocross counterparts. In the past, KTM’s enduro-model frames had a different geometry, different wall thickness in several areas, and visibly less gusseting around the steering head when compared with the MX bikes – all aimed to give them a more forgiving and compliant ride. So, can you explain how you’ve adopted the more rigid MX frame to the enduro models without losing that off-road compliance.

We have created a more forgiving frame for the enduro models – or that “compliance” you refer to – in a different way for 2024, and we are confident it is a much better solution. Rather than building additional flex into the frame itself, we’ve now targeted a few other areas where that flex can be controlled better. For example, the enduro models’ frames are a little more flexible around the swingarm pivot and upper shock mount because that works much more effectively with the PDS shock absorber. Plus, components such as the triple clamp assembly and engine mounts on the enduro bikes are more flexible. Also, each capacity has its own individual characteristics. And that is why, for example, we have the cut-outs in the middle of the two-stroke models’ engine mounts, but not for the four-strokes. For riders who want to change the flex of their specific model, there’s the option to get the alternative engine hanger from our PowerParts program.

“We have taken the anti-squat chassis design a step further with the 2024 bikes. And we were only able to do that because the new closed-cartridge fork results in a less nervous front-end feel, which was necessary for the new anti-squat chassis to work.”

Visually, the most obvious difference between the MX and enduro models’ frames is that new lateral bridge that houses the PDS’s upper shock mount.

Yes, that bridge, as you call it, is critical to adapting the frame so it works in harmony with the PDS shock. It allows us to add, in a controlled way, the longitudinal flex into the frame. Also, as that flat cross-member is no longer connected directly with the frame’s main backbone, a lot less of any rear wheel and shock absorber impact is transferred to the steering head. And that is key in creating a more planted feel from the new chassis. With this new design, the stiff frame is there to create handling stability, while the shock can do what it’s supposed to do: independently absorb rear wheel impacts.

Just like KTM’s latest-generation MX range, there are three frames for the 2024 enduro range: one for the 150EXC two-stroke, one for the 250 and 300EXC two-strokes, and one for the 250, 250, 450 and 500EXC-F four-stroke models, right? But where can the major differences in those three frames be seen?

The only real difference between the three is the shape of the twin cradle tubes that sit under the engines. The rest of the main frame – and subframe, for that matter – is the same because we followed the same target of stiffness and rigidity across the whole capacity range, and retained the same positioning of the engines within the frames to take advantage of the anti-squat chassis concept that has proved so effective on our 2023 motocross bikes. Of course, on the two-stroke EXC frames, you will also find the cut-outs for the positioning of the separate oil tank, which is not in place on our SX model range.

“We had extracted all the performance the previous design concept allowed, so it was time to develop a completely new generation of machine; one that had more potential to evolve into an even faster package.”

Adding frame rigidity to your enduro models is a completely different philosophy from, say, the 2012 EXC and EXC-F models, which had something like 30% more longitudinal flex than their predecessors.

Yes, our 2024 enduro models use a very different design philosophy. Compared with the 2023 enduro models, the new frame is between 20 and 30% more rigid, depending on which axis you’re talking about. This rigid frame is designed to create the platform for straight-line stability, while we have improved handing and chassis compliance in other, more controllable, ways. We are now at the beginning of this new generation of enduro models, but we knew we needed to take a different design direction to allow further progression in the bikes’ performance.

Explain what you mean by that.

Well, our previous generation of enduro models were refined over many years, but it became apparent that they had got to a point where they were as good as they could be. Put simply, our test riders and racers were telling us that they were unable to continue getting any faster on the previous-generation bikes. We had extracted all the performance that that design concept allowed. Which confirmed for us that it was time to develop a completely new generation of machine; one that had more potential to evolve into an even faster package.

“You could say we have taken that ‘standardisation’ strategy a step further with these 2024 enduro models. We have unified many parts, but we have only done that where it makes sense.”

Is there a risk that means you have to take a step backward before taking several steps forward?

There is always that risk. The important thing is the ‘several steps forward’ part [laughs]. We are at the beginning of this new generation of enduro models. If you compare lap times now, old against new, the new may be the same or even slightly slower in some circumstances. But the overall potential of the 2024-model generation is significantly higher. And with ongoing development, we know we will be able to get much more out of the new package.

‘Ready to Race’ has been the hallmark of KTM as a brand for many years. So, why has it taken so long to introduce the race-ready closed-cartridge fork to your enduro models – particularly as KTM owns WP? It’s been apparent for some years now that the design limitations of the open-cartridge XPLOR fork was holding fast riders back.

To be honest, it’s a balancing act for us because WP Pro Components is also an important part of our business. With the previous generation of enduro bikes, the XPLOR fork worked very well for a greater majority of riders (and you could argue that the open-cartridge fork is actually better for extreme enduro riding), while fast riders and racers fitted one of the aftermarket options available from WP. With the 2024 bikes, however, we knew we needed a higher-performance closed-cartridge fork to better complement the stiff frame concept and create a more comfortable ride across a wider range of terrain and obstacles. The WP XACT Closed-Cartridge fork now fitted to the 2024 bikes is very similar in its design and performance to WP’s existing aftermarket option, the XPLOR Pro 6500 Cartridge Kit. It allows the bike to maintain or even improve that initial plushness over small bumps, but it also has much better control through the stroke and more resistance to fading and bottoming out. And it works hand-in-hand with the new frame concept.

The ‘anti-squat chassis concept’ was central to KTM’s all-new 2023 MX models (which use a rising-rate linkage), so what was required to adapt that design concept to these 2024 enduro models (which use a no-linkage PDS rear shock)?

With a chassis, you have two approaches: either you follow a squat or anti-squat concept. The former is when the bike squats (that is, the shock compresses and the rear wheel is pulled up) under hard acceleration and the chassis geometry becomes more raked out. With the anti-squat concept, the opposite happens under acceleration; the rear wheel pushes down onto the ground for better traction and less tendency to wheelie. Our previous generation already had an anti-squat design, but we have taken that a step further with the 2024 bikes. And we were only able to do that because the new closed-cartridge fork has a plusher initial action and more planted feel. That results in a less nervous front-end feel, which was necessary for the new anti-squat chassis to work. And it is also why the enduro models are able to use the same frame geometry as the motocross models. To answer your question, it was definitely a challenge to adapt this design to the PDS set-up on the enduro models, mainly because we needed to cover many capacities and because there are implications for the size of the both the countershaft sprocket and rear sprocket. So, it’s a compromise for some models. But whenever we talk internally about a compromise, it means that the effect is not negative to any specific model; more that it potentially could be even more beneficial to some other models.

“Rather than building additional flex into the enduro models’ frames, we’ve now targeted a few other areas where that flex can be controlled better.”

With the primary focus on these 2024 bikes’ all-new closed-cartridge fork, PDS shock and chassis, are there any other new features that you think were overlooked as a result, and deserve more attention?

Yes, many of them [laughs]. Seriously, there are so many things. The LED headlight alone is worth mentioning because it’s now three times as strong as last year’s. In fact, the whole electronics package on the bikes has come forward a long way. Then there’s the completely new sidestand, which not only works very well, but also looks great. I mean, what else? The chain guide and chain sliders are both tougher. There’s now a lip on the swingarm and rear brake calliper so the rear wheel sits in place without the axle inserted. The new plastics are even more robust, and they give your legs a better grip on the bike. There are many more examples. It’s all these details – which we took from colleagues in many different departments at KTM – that add up to make a huge difference. And I think this is one of the main things that makes KTM so successful as a company.

Thanks for your time, Fabian. It’s been fascinating to get an insight into the philosophy behind the 2024 models’ design.

You’re welcome, Andy. We can’t cover everything on our website or brochures, so it’s important for us that riders understand what our objectives were with these bikes, and the key design elements we’ve used to achieve them.