Test: The tire from the US supplier Donnelly is a real Gravel tire in terms of profile and dimensioning - but this rather stands for great versatility, because the tire convinces on the road as well as on natural paths with a wide variety of surfaces. There are also a few special features that should convince friends of the young racing bike category.
Tires under the Donnelly name have only been around for almost three years. For seven years, the company manufactured mainly cross-country and racing bike tires under the licensed name Clément, then the traditional brand name went back to its owner Pirelli. The products, now with the new Donnelly brand logo, have hardly changed, apart from the fact that new models have been added with the gravel boom, as well as carbon frames for cross bikes and gravel bikes. The Americans call their tires for natural roads and moderate terrain “adventure tires”. Most of these feature small, dense tread blocks and low negative tread; so they look more like trekking bike tires than those you know from cross bikes. Sure, because they don't have to deal with muddy off-road tracks, but should roll over asphalt and roads with loose surfaces - the famous "gravel roads".
Donnelly provided us with the best-selling X'plor model with a sand-colored skinwall sidewall, which comes in a variety of sizes, from the 30mm narrow CDG with herringbone tread to the 50mm wide 650B tire, which has the same profile as our tubeless version. The latter is designed for "ambitious adventures" over changing terrain; According to the Donnelly website, this means gravel roads, trails, asphalt and cobblestones. In theory, therefore, a veritable all-rounder, with a width of 40 mm still just compatible with conventional material: A wider tire would no longer fit into the rear triangle of the crosser, which serves as a test bike, and the rims with an inner dimension of 18 mm would no longer fit either ideal. On the other hand, the fact that the tire has advantages over narrower models can be seen from its sidewall: the official minimum pressure is 2,4 bar, which speaks for a high level of comfort. And thanks to its large volume, the tire should not tend to bottom out even at low pressure.
The X'plor weighs 500 grams, so it's not super light; In return, its manufacturer promises high puncture protection. This is also indicated by the assembly, because the rather stiff tire cannot simply be pressed into the rim base with your thumbs - it only works when the tire lever is applied. Once inside, there is a surprise: the Donnelly fits so tightly that it can be filled with the mini pump; high pressure from the compressor is not required for sealing. At 3 bar it is 39 mm wide, so slightly narrower than stated - on a real Gravel rim with a larger internal width it should be slightly wider than the nominal size.
If the air is released again to fill in the sealant, the tire retains its shape and its firm seat in the rim base. This is good news for cyclists who ride long tours with the X'plor - if they have a defect that is accompanied by a complete loss of air, the ADFC does not have to be called immediately.
We take the X'plor at its word and set off with 2,5 bar, i.e. close to the minimum pressure. Nevertheless, the tire is far from being overwhelmed by the total weight of 87 kilos. At high pedaling frequency, it rocks minimally, and it doesn't bottom out even with transverse, high roots. Compared to a 35, the Donnelly (which is around 5 mm higher than that) allows a passive driving style – just sit and pedal, come what may. Which in our case means: asphalt, forest paths with firm, gravelly surfaces, paths with loose, sharp-edged gravel, potholes of varying depth and a pinch of deep, sandy riding paths. In addition, a muddy puddle at a junction, which is driven with a slight incline and makes it clear that the cornering grip is pretty good thanks to the large shoulder knobs, even if the next few dozen meters the mud clumps just fly.
The 40 tire accepts the listed pads stoically and unimpressed. With the low pressure, it is of course not a particularly smooth runner, but thanks to the 120 tpi carcass it is quite supple, pleasantly comfortable and very easy to absorb. Larger boulders on the road can also be run over; everything with an edge length of up to 1 cm is hardly noticeable. Uncertainty does not arise even with loose ground; However, when accelerating (and) pedaling out of the saddle, the disadvantage of the low pressure becomes apparent: the tire appears spongy and sluggish and deforms visibly when the wheel is moved under the rider. This set-up doesn't allow for brisk acceleration, but that can be changed: for an asphalt tour with a minimal proportion of forest paths, we aerate the Donnelly to 3,2 bar. So not that much more, but the effect is great: the tire rolls noticeably easier and is much more agile on steep sections when pedaling out of the saddle. Strong inclination is no problem; the Donnelly adheres well and sits firmly on the road. However, the large volume means that the wheel has to be "bent" more at the same cornering speed. As expected, the higher pressure means that the tire rides a little harder; it is by no means uncomfortable. And even if there are smoother gravel tires - whether they are as solid and puncture-resistant as the X'plor MSO is another question.
