Mountain bike tyres: Carcass and rubber compound have this influence
Florentin Vesenbeckh
· 08.01.2023
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Content of this article
A mountain bike tyre is a compromise. High puncture protection or low weight? Plenty of grip and traction or good durability and low rolling resistance? All these properties can be optimised with the latest technology - but we bikers will probably have to dream forever of the one tyre that can do everything perfectly. So: set priorities. Which MTB tyre is the best for your personal area of use depends crucially on the structure of the tyre wall and the rubber compound. The tread pattern, i.e. the size, shape and positioning of the lugs, is by no means the decisive criterion. You could say: The true strength of a tyre remains invisible from the outside. A Maxxis combination of Assegai and Minion DHR II always looks the same at first glance. However, anyone standing at the counter theoretically has to choose one of 48 (!) possible combinations of these two profiles. With our two test candidates from Swallow there are as many as 54 variants. Incidentally, this does not include different wheel sizes and tyre widths.
EXO, EXO+ or Doubledown? Or would you prefer a DH or wire carcass? And which rubber should it be? MaxxTerra? MaxxGrip? Or rather dual compound? Anyone who shrugs their shoulders in puzzlement at these terms or can't decide should take a close look at this test. Because the construction of the MTB tyres behind these cryptic terms actually makes a bigger difference than the tread pattern. This was clearly demonstrated by our extensive test in the laboratory and in practice.
MTB tyres in comparison: the test setup
What influence do carcass and rubber compound have on the behaviour of a mountain bike tyre? To find out, we asked the three market-leading manufacturers Continental, Maxxis and Schwalbe to each test two tyre combinations. The tread and tyre dimensions are identical in each case, only the carcass and tyre construction as well as the rubber compound change. The result is three all-round and three extreme tyre combinations with completely different characteristics.
Why only Maxxis, Schwalbe and Conti? According to our current reader survey these three brands account for 90 per cent of buyer interest, with all other brands landing in the low single-digit percentage range. In addition, with a reduced variety of brands, there is more capacity to concentrate on the differences between the various model variants. From the three market leaders, we have selected the most popular and versatile treads for trail to enduro eMTBs. From Maxxis, the two classics Assegai and Minion DHR II; from Schwalbe, the Magic Mary and Big Betty; and from German rubber giant Continental, the all-round combination of Kryptotal Fr (front) and Re (rear) from the new Gravity series.
How we tested the tyres
Laboratory test
The EMTB test team measured all the tyres in the test laboratory of tyre manufacturer Continental to check the hard facts under comparable conditions. All tests were carried out at a tyre pressure of 1.6 bar on uniform rims. During the puncture test, a 10.1-kilo drop axe is dropped onto the tyre. The drop height is increased until the tyre runs out of air. The higher the drop height, the better the puncture protection. To simulate a puncture or slitting of the tyre, a metal spike penetrates the tyre. Once on the tread and once on the sidewall. The maximum force is measured until the tyre carcass is punctured. The rolling resistance is determined on a drum test rig at 30 km/h and a load of 50 kilos. This procedure maps the rolling resistance on tarmac and very hard surfaces.
Practical test MTB tyres on Scott Ransom eRide
For our practical test, we had three identical Scott Ransom eRide 910 tyres at our disposal. With an identical setup, we were able to quickly and easily switch between the tyre pairings and test the tyres in direct comparison with each other. Three additional 29er wheelsets allowed us to ride all 18 tyres back-to-back and in constant alternation in defined terrain situations and to filter out the differences in detail. From cornering grip on hard and loose ground, to traction on steep climbs or roots and braking performance on downhills, a total of four testers tested the relevant capabilities of a tyre combination. The autumn conditions provided the perfect conditions to get to the bottom of the wet grip of the rubber and the self-cleaning capabilities of the treads.
Briefly explained: The tyre structure
1. carcass
The carcass (also known as the casing) is the basic structure of a tyre and makes a decisive contribution to weight and stability. The more layers of rubber-coated nylon fabric there are on top of each other, the more robust the construction becomes. The puncture protection increases. But the damping properties also change. Thick carcasses are stiffer and cost comfort when travelling slowly. At high speeds, they absorb rough impacts more effectively. Stable constructions allow a low air pressure. Rolling resistance increases slightly with thicker carcasses, as more flexing work is required when rolling.
2nd/3rd protective shield
To provide additional protection against punctures, manufacturers add various protective layers. For example, in the form of a rubber buffer on the core, called the apex (3), or a puncture-resistant additional layer on the tread and/or sidewall (2).
4th profile
The tread pattern makes the biggest visual difference between different tyres and shapes their character. Put simply, high lugs with large clearances are suitable for damp conditions and deep soils. Flat, more closely spaced lugs favour hard ground.
5. rubber compound
A tyre's grip and rolling characteristics are largely determined by the rubber compound. Hard tyres roll well and are durable, while soft compounds literally stick to the ground (high grip, high rolling resistance), but also wear out much faster. The damping of the tyre is also influenced by the rubber.
The tyre combos in the test
Two tyre combinations from each manufacturer are tested. One light with harder rubber, one heavy with a softer compound. The lighter combination is suitable for all-round use on MTB tours and trails. The thinner carcass offers less puncture protection but also a significantly lower weight. The harder rubber compound is less susceptible to wear and rolls better. The extreme combos are uncompromisingly geared towards grip and puncture protection and are therefore suitable for downhill-orientated enduro and park bikers. The heavier the biker and the wilder the riding style, the more a thick tyre combination makes sense. However, the high weight of MTB tyres makes bike handling more sluggish.
All-round combos:
- Continental Kryptotal Re Trail Endurance, 29 x 2.4 inches // 1033 grams
- Continental Kryptotal Fr Trail Endurance, 29 x 2.4 inches // 1011 grams
- Maxxis Minion DHR II EXO+ Maxxterra, 29 x 2.4 inches // 1052 grams
- Maxxis Assegai EXO+ Maxxterra, 29 x 2.5 inches // 1138 grams
- Schwalbe Big Betty Supertrail Soft, 29 x 2.4 inches // 1100 grams
- Schwalbe Magic Mary Superground Soft, 29 x 2.4 inches // 1012 grams
Extreme combos:
- Continental Kryptotal Re DH Soft, 29 x 2.4 inches // 1342 grams
- Continental Kryptotal Fr DH Supersoft, 29 x 2.4 inches // 1268 grams
- Maxxis Minion DHR II DH Maxxgrip, 29 x 2.4 inches // 1359 grams
- Maxxis Assegai DD Maxxgrip, 29 x 2.5 inches //1312 grams
- Schwalbe Big Betty Supergravity Soft, 29 x 2.4 inches // 1267 grams
- Schwalbe Magic Mary Supergravity Ultrasoft, 29 x 2.4 inches // 1321 grams
By the way: In most cases, bikers do not have a free choice of carcasses and rubber compounds. The very soft rubber is often only offered by manufacturers for heavy tyres with a thick carcass, while the light tyres are sometimes only available with hard rubber.
The results: What do carcass and rubber compound really matter?
Weight
The most obvious difference in the intra-brand duels: the weight. The tyres of the all-round combos, i.e. the light versions, weigh a good 1000 grams as 29ers, the heavy tyres land at around 1300 grams. The light Continental combination comes out on top, while the thick Maxxis tyres are the heaviest. The difference between the light and heavy combinations is significantly lower on the scales (24 per cent on average) than for puncture protection (50 per cent).
Puncture protection
On average, the heavy tyre combinations offer 50 percent more puncture protection than their lightweight counterparts. The tyres achieve this with more stable carcasses, i.e. several layers of fabric on top of each other and puncture-resistant protective layers or rubber inserts at the core (apex). More material = more puncture protection. This also increases the weight. On average, however, only by 24 per cent. In relation to the increase in puncture protection, the pounds are therefore well invested. This is especially true for Continental, where 80 per cent more puncture protection means only 28 per cent more weight. The Kryptotal combination offers the lowest puncture protection of all tyres tested in the Trail version and the highest in the DH version. You should pay particular attention to plenty of puncture protection on the rear tyre, as the rear usually hits rough obstacles with less caution and all the more momentum, while the front wheel can avoid obstacles more easily. A heavier front tyre has an even greater impact on handling than the rear. Steering movements and playfulness on the trail become more sluggish with a heavier front tyre.
Rolling resistance of MTB tyres
On average, the extreme tyre combinations roll 49 percent more slowly than the all-rounders. The main reason for this is the softer rubber compound. The soft lugs literally stick to the ground. If you value efficient rolling and cover longer distances on tarmac or hard surfaces, you should opt for harder rubber, at least on the rear wheel. This is where around 75 per cent of the pressure is applied, and the braking effect is correspondingly high. The rolling resistance of the front tyre costs significantly less energy. A stiffer carcass also increases rolling resistance, as additional flexing work is required. However, this influence is less than that of the rubber on the test tyres, as the example of Schwalbe's Big Betty rear tyre shows. The rubber compound is identical for both variants, the more solid carcass only slightly increases the value. Maxxis uses very soft rubber on both the front and rear wheels of the extreme combination. The rolling resistance is correspondingly high. The light combination from Continental rolls the fastest.
Grip and traction
In addition to the tread pattern, the rubber compound plays a major role in the cornering grip and traction of mountain bike tyres. Especially on hard surfaces or in wet conditions, a soft rubber tyre has a much better grip than the harder version. A soft compound adapts better to the ground and literally interlocks with obstacles. This noticeably increases riding safety, especially on the front wheel. What's more, with a thicker carcass, lower air pressures are possible without an increased risk of punctures or unstable tyres. This increases grip even further. In winter, there is another point: soft tyre rubber is more resistant to the cold. This means that they remain more supple at lower temperatures and then offer significantly more grip.
Wear on E-MTB tyres
Everyone knows this from school: a soft eraser rubs off quickly. It's the same with tyres. The magic words Ultrasoft, Supersoft or MaxxGrip may promise plenty of traction, but the soft rubber compounds also wear out much faster. This is not ideal, especially for frequent e-bike riders. Here too, the rear wheel is particularly affected, as it wears out much more quickly! A super-soft e-MTB tyre should only be used here with careful consideration.
On the trail
In a back-to-back comparison of the individual MTB tyre combinations between light and heavy, the difference in weight is most noticeable during normal riding. Almost 300 grams more rotating mass per wheel make the ride noticeably slower. Steering movements at slow speeds or playful riding manoeuvres, such as jumps, become noticeably tougher. But there are also positive changes. When riding fast on rough terrain, the bikes with the thick tyres are firmer and literally grip the ground. The rougher the terrain, the more noticeable the positive effect. On shallow trails with little gradient and smooth surfaces, however, you want the liveliness and lively ride feel that the light bike tyres provide.
And what does it look like when cornering? The increased grip from the soft tyres is very noticeable in direct comparison. And that's even with identical tyre pressure! If you let some air out of the tyres on the extreme combos, which the thicker carcasses easily allow and in some cases even require, grip and traction increase even further. As a result, the subjective riding safety and cornering grip of all three extreme compounds is noticeably better than that of the grippiest all-round compound (Maxxis). However, the thick carcasses also have a disadvantage when travelling slowly. The stiff construction of the sidewalls reduces riding comfort, as the tyre is less able to hug bumps. This can be a disadvantage, especially on technical uphills. This effect was most noticeable on the super-stiff Contis with DH carcass. Maxxis, on the other hand, does an excellent job of breathing a surprising amount of comfort into the heavy combination with DH casing.
What the testers say
Max Fuchs, test editor BIKE
Minimum tyre pressure means maximum riding pleasure, because the grip increases massively! However, this only works with a stable tyre, which is why puncture protection is my top priority. On an E-MTB, I don't mind the higher weight and greater rolling resistance of thicker tyres anyway. If everything has to fit, I even reach for soft rubber at the rear.
Laurin Lehner, FREERIDE Magazine
Admittedly: In direct comparison, you can feel the advantage of the soft rubber compounds. But these are only nuances. The increased wear is out of all proportion. Your wallet and the environment will thank you if you go for the harder rubber - this applies even more to E-MTBs, where the tyres are planed down in fast motion.
Florentin Vesenbeckh, Test Manager EMTB
A lot helps a lot? It doesn't make sense to just blindly reach for thick and heavy tyres. The increased weight on the wheels makes handling noticeably slower. On shallow trails, this can be a real fun-killer. Depending on the area of use and riding style, the massive tyres can be a real disadvantage. This also applies to e-MTBs, especially in the light category. The wilder the terrain and riding style, the more worthwhile a thick tyre is.
Conclusion on the MTB tyre test
Yes, it's a fact: the rubber compound and carcass construction are largely responsible for the properties of a mountain bike tyre and the differences are significant, despite the identical tread pattern. So don't just click "buy" when you see the next special offer on a Magic Mary or Assegai, but take a closer look first. The bad news is that we can't say which MTB tyre or which model is the best. Everyone has to find the best compromise for their personal requirements profile. We have created the right data basis with this test.
The complete test with detailed evaluations of all six tyre combinations can be found in EMTB 6/22 - available now at newsagents or digitally!
Florentin Vesenbeckh
Editor CvD
