Are they really that different?: Radial tyres put to the test by readers

BIKE: Conclusions from the reader test

Our reader test serves to compare theoretical advantages with practical relevance on the trail. What is surprising is the high level of riding confidence that the testers unanimously reported – even without perfectly controlled test conditions, rapid tyre changes or a blind test. For us, this leads to a clear conclusion: the effect of radial tyres is clearly noticeable in everyday trail riding and for ordinary mountain bikers. Theoretical drawbacks such as rolling resistance or spongy handling, by contrast, are of little significance. Comfort and grip are evidently much more important to the testers. - Adrian Kaether, Test & Technology Editor

No more slipping?!

The forest is steaming. The first day at the EMTB Trail Camp was sunny and lovely, but it rained during the night and now the forest is a washing-up room, our narrow uphill path softened into a slippery, brown track. First a tight right-hand hairpin, then steeply uphill through a chicane into a tight left-hander. Squeak! His rear wheel slips out; tester Klaus in front of me swears. Of all things, he hit that one smooth, polished stone, and that was the end of his forward momentum.

A setback right at the start of our readers’ test? No, because it’s only natural to miss the line now and then. That’s just how mountain biking is. And even if radial tyres are supposed to be the latest and greatest for off-road riding, they can’t work miracles, of course.

​30 per cent more grip: Why radial tyres are said to offer better grip

But that is precisely what we’re going to be looking at today: will radial tyres become the norm on mountain bikes? How significant are the advantages in practice, and how relevant are the drawbacks? We at the BIKE editorial team have already found out how radial tyres perform in a head-to-head test comparison. Our conclusion at the time was that the larger footprint provides more grip, which is a clear advantage on the trail. Comfort is also noticeably improved thanks to the more flexible tyre construction.

The fact is: the contact patch on a mountain bike – that is, the area of contact between the tyre and the ground – is quite small. Just a few square centimetres of rubber can make the difference between a fall and a fun ride. The idea behind radial tyres is to increase this contact patch slightly through a special tyre construction.

A question of alignment: what makes radial tyres different

In a standard (diagonal) tyre, the carcass cords – which form the tyre’s load-bearing framework – run at 90-degree angles to one another. This creates a diamond pattern on the tread. In a radial tyre, the carcass cords are arranged at a shallower angle to one another. They run almost parallel to one another. This is the case, for example, with car tyres, where the carcass cords can even run completely parallel to one another. Motorcycles have also been fitted with such radial tyres ever since Helmut Dähne perfected them on the Nordschleife. A game-changer back then, but that’s another story.

The effect is always the same. Because the threads in the carcass run more parallel to one another, the tyre’s tread is not as stiff and can mould itself better to the ground. At the same air pressure, the tyre’s contact patch increases, and with it the grip on the trail, by around 30 per cent. You can read all the basics about radial tyres for mountain bikes here.

Rolling resistance, puncture protection, range: the drawbacks of radial tyres

The example of cars and motorbikes shows that the concept of radial tyres is not new. Nevertheless, Schwalbe only recently began mass-producing the first radial MTB tyre. This was partly because, until then, scepticism had prevailed, particularly regarding rolling resistance. Naturally, this plays a much greater role in a bicycle powered solely by muscle power than in a car or motorbike. There were also concerns regarding puncture protection, as the softer tyre tends to be less able to withstand impacts.

Battery power through efficiency

At our EMTB Trail Camp, however, smooth riding is a secondary priority. With significant elevation gain over just a few kilometres, battery assistance and challenging trails, our reader testers are prioritising other factors. Riding safety and traction come first. And this is exactly where the Radial tyres really shine.

Reader tester Klaus tries again. On his second attempt, he manages to tackle the slippery, steep section. Perhaps it was luck, a better riding position on the bike or a better line. But the evidence that our reader testers are noticing the benefits of radial tyres is mounting.

This is how we carried out the test

At our EMTB Trail Camp in Kaltern, we selected three testers to try out the radial tyres for us and alongside us. They range from seasoned tech enthusiasts to occasional trail riders. Two of the three riders had even already gained some experience with radial tyres, but weren’t entirely impressed due to the somewhat spongy ride feel.

On the first day of riding, the three candidates were able to get back into the swing of things on the South Tyrolean trails using their usual tyres. We then fitted all three with new radial tyres from Schwalbe for comparison, each tailored to their specific use. Reader Michael was therefore fitted with heavy-duty Gravity Pro tyres to replace his Assegai DD and Magic Mary Supergravity tyres. For reader Marko, a moderate Romy Radial at the front was intended to provide a little more confidence than the Nobby Nic with a diagonal carcass he’d been using previously. Tester Klaus is assigned a medium-weight combination with a faster Romy at the rear and the new Tacky Chan at the front.

Less is more: low tyre pressure, even with radial tyres

It is striking that all three reader testers prefer low tyre pressure, even with radial tyres. In our test, they no longer mentioned the cliché about radial tyres having spongy and imprecise handling, although two of them had previously noticed this in their own experiences. This is likely also due to the fact that Schwalbe has made further improvements, particularly to the extra-heavy Gravity Pro version. Stiffer sidewalls are designed to ensure precise handling even with a radial construction and low tyre pressure.

A calculation that certainly paid off for our testers, at least at the Trailcamp. In the first round of feedback, all three recorded positive comments with an even higher tyre pressure. It was only when they switched to pressures of around 1.5 bar, however, that the real enthusiasm kicked in. “I wouldn’t have thought the tyre would make such a difference,” says reader tester Marko, who otherwise mainly goes on moderate rides.

It’s worth giving it a go

The ideal tyre pressure is likely to depend heavily on your weight and how you intend to use the bike. Heavier riders who go all out in the bike park will certainly need significantly higher pressure than more cautious riders on natural trails. It’s definitely worth experimenting a bit, though.

Back on the trail: the cart track winds its way steeply and rockily up to Leuchtenburg Castle, visible from afar, overlooking Lake Kaltern. Definitely e-bike territory. With those chunky boulders, you’d have to walk your normal mountain bike up here. It’s the last day of the EMTB Trail Camp, and here too the radial tyres get to show off their strengths once again. “You can really feel the difference. It’s the combination of low tyre pressure and the radial tyres in particular,” says tester Michael, summing up his impression. “For me, it’s the new ‘magic class’.”

“An incredible level of security”: the readers’ verdict

​I never would have thought that the tyre would make such a difference! My bike is also used as a family transport for rides with a child trailer. The Nobby Nic from Cube, fitted as standard, has always worked well for that. But the new Romy Radial on the front really gives me a lot of confidence. I can just let it roll over anything and nothing slips or loses traction. It definitely feels safer to ride. The old tyre was still on the back. You could really tell the difference when comparing the two. I’m now thinking about upgrading this one too, even though normal rides on gravel tracks will probably still be the main part of my everyday cycling. – Marko from the Black Forest

These tyres give me a tremendous sense of security, even on rocky trails. The traction is noticeably strong and makes it very easy for me on difficult terrain. I haven’t noticed any downsides in terms of rolling performance or range so far. Incidentally, my Rotwild came fitted with radial tyres straight from the factory. However, I had to ride the Albert Trail with slightly higher tyre pressure than usual. The newer Tacky Chan / Romy combo can handle significantly less air without feeling spongy and, for me, takes grip to the next level. - Klaus from North Baden

I’ve tried out loads of different tyres over the years. Lots of grip and low tyre pressure – that’s what works for me. The radial tyre really does offer superb comfort and excellent traction here. The highlight for me is that, with the new Gravity Pro casing, I can now go back down to my low pressure of 1.0/1.2 without the tyre feeling spongy or leaking fluid from the side. For me, it’s the new gold standard. – Michael from Graz