Test: Stöckli Morion RSC 975 - one bike, two wheel sizes

Stöckli is one of the manufacturers that combines two wheel sizes in one bike. While this has long been the norm in motocross, many people are wondering what it means for mountain bikes. The advantages sound plausible, but what about the disadvantages? The ride test provides the answers.

While manufacturers such as Liteville or Transalpes use mixed wheel sizes in the all-mountain segment, Stöckli is transplanting the size mix of 27.5 and 29-inch wheels to the "Morion RSC" cross-country fully. This is still designed as a racing-oriented bike. The mix is intended to make the bike easier to accelerate, smoother at the front and roll better over obstacles. The Stöckli team riders Mathias Flückiger and Matthias Stirnemann will not be able to use this bike in racing for the time being. UCI regulations stipulate that a bike must have two wheels of the same size. Nevertheless, Stöckli is launching the Morion RSC 975 on the market, as Tom Steger, Product Manager Bike at Stöckli, explains: "We are so convinced of the advantages of this concept that we don't want to withhold this bike from our customers under any circumstances."

After the brief technical discussion, it's time to test. The first thing we notice is that the "Morion RSC 975" feels noticeably different when steering than when both wheels are the same size. During extreme cornering in the parking lot, the front behaves noticeably more sluggish than the rear. On the trail, however, any concerns about potentially irritating handling vanish. The Morion can be steered precisely around corners and you hardly feel any difference to a bike with the same wheels. It is also astonishing that the rollover behavior of the rear wheel differs only slightly from that of the larger front wheel. The setting of the Fox suspension also remains the same, which is adjusted as usual according to the optimum use of the suspension travel.

The biggest advantages on the downhill
Due to the difference in size between the front and rear wheels, the "Morion" leans slightly backwards. Downhill, this turns out to be an advantage, as you tend to shift your weight to the rear on cross-country bikes to avoid going over the handlebars. The larger front wheel allows a more central downhill position on the bike and therefore more control over the bike. Furthermore, the 29er front wheel provides extra grip and more reserves due to better rollover behavior. Especially on steep or rough sections, this combination gives you a much more secure feeling. The bike also feels secure on fast descents, as the 29-inch front wheel also generates a smoother ride than the smaller rear wheel. Despite the smooth ride, it can be accelerated nimbly out of corners and the "Morion RSC 975" also plays along well when playing around.

What has advantages downhill is only of limited use uphill. On technically demanding climbs, the responsive rear end still has some advantages. However, the mix of sizes no longer provides an advantage. On asphalt or gravel roads uphill, it rides practically like any other bike. If you climb steep ramps on the Morion, you need to shift your weight forward more to keep the front wheel on the ground - but only at the limit, of course.

The stiffness of the "Morion RSC 975" in the bottom bracket area is striking. When pedaling, the new Morion feels stiffer than the first model from last year. Stöckli developer Marco Quinter confirms the assumption that something has been improved in this respect: "In a collaboration with ETH Zurich, we identified the weaknesses as part of a thesis and incorporated the findings directly into the development of the new frame."
The new Morion now uses a high-strength fiber that is even more tensile. In addition, the layup, i.e. the design of the fibre, has been optimized in order to achieve greater stiffness with almost the same weight and wall thickness.

Conclusion: Stöckli has increased the range of use of the Morion RSC with the concept of different wheel sizes. The improved propulsion due to the higher lateral stiffness, precise handling and more reserves downhill make it easy to get over the slightly poorer climbing characteristics. This makes the RSC-975 version the ideal mid-country rocket for mountain bikers with a sporty riding style, but who want to ride something more than "just" a full-suspension cross-country bike.