Are thinner narrower tires faster than the wider ones?

Question

My bike is this one: https://www.cube.eu/de-en/cube-aim-race-black-n-azure/601400

Overall, I'm very happy with the bike to be honest. The tires are Schwalbe tires on the Cube Aim Race bike, which is a cyclocross (at least I think it is, could be a regular MTB) bike.

I'm asking specifically if the thickness (width) of this particular tire brand (Schwalbe) makes difference speed-wise, but I guess the brand of the tire itself doesn't make much difference in this sense.

I am talking of course about the speed of the bike on flat road.

_{from https://www.cube.eu/de-en/cube-aim-race-black-n-azure/601400}

Answer 1

At same pressure, riding on hard surface like pavement, thinner narrower tires are:

• Faster due to less air resistance than wider tires
• Faster due to less weight, mainly on climbs, but do note that weight itself also increases rolling resistance
• Slower due to more rolling resistance than wide tires, IF they are run at the same pressure

So it's complicated. Also, nobody runs narrow and wide tires at the same pressure. Firstly, the casing tension is proportional to tire width and tire pressure. So the wider tire you have, if you run the same pressure, the more casing tension you have. Eventually the casing tension is so high that the tire can't withstand it and explodes.

Also, at the same pressure, narrower tires have a long and narrow contact patch. Because the contact patch is long, it's deep. Wide tires have a short and wide contact patch. Because the contact patch is short, it's shallow. These two contact patches have the same surface are but different shapes. So at the same pressure, the wide tire deforms less vertically. Thus, it's less comfortable. This too explains why narrow and wide tires aren't run at the same pressure.

Also narrow tires are often run at very high pressures due to possible pinch flats. Wider tires are less susceptible to this, so they can be run at very low pressures.

So there are three factors to consider when deciding tire pressure: casing tension, how much the tire deforms vertically, and whether the tire at this pressure has enough resistance against pinch flats.

The question of whether wider tires have more rolling resistance than narrow tires is therefore very hard to answer, since you have to have some law of how to vary the tire pressure as a function of tire width.

---

However, all of this changes on loose surfaces. You can test this as follows: put 28mm slick tires on a road bike, pump them up to 7 bar, go riding on soft sand road that is wet (this is best done in regions that have snow because the melting water from snow will make the road deeply saturated in water). You will immediately notice that you will slow down quite a lot compared to hard pavement or even the same sand road when it is fully dry.

On loose surfaces, it is heavily beneficial to have a wide tire at low pressure instead of a narrow tire at high pressure. This is so beneficial that on loose surfaces, it almost always overcomes any air resistance drawback from the wide tires. If you can't ride more than 20 km/h due to rolling resistance slowing you down, air resistance is anyway so small that it doesn't matter. Reducing that rolling resistance matters a lot.

---

Because rolling resistance is a constant force and linear power, and wind resistance is a square force and cubic power, whether or not air resistance or rolling resistance matters more depends on the speed. On hard surfaces, it's hard to answer. On loose surfaces, the drawback from high rolling resistance of narrow high-pressure tires is so great that less rolling resistance almost always wins.

Answer 2

As this is a mountain bike, the fastest tyres are probably those most appropriate for the surface you're riding on.

On dirt trails, you need grip to accelerate, turn, and brake. This is often best served by wider tyres with tread, which are slow on paved surfaces.

Riding even well-finished trails on slick touring tyres, which are far quicker on roads than MTB tyres, is slow going. I've done it. The lack of grip means slowing down more and earlier, and sometimes some wheelspin when you pedal hard.

Fairly smooth gravel is somewhere in between, as are gravel tyres.

If you've got a mountain bike and you're using it on the road - perhaps for commuting - your biggest benefit will come from using smoother tyres, though most of them are also thinner. Go too thin and the tyres won't fit the rim well. For typical hardtail stock wheels, slick tyres in the 35-45mm range will make a big difference, 50mm if you also want to handle rough but grippy surfaces.

Rather than concentrating on the brand, the specific model of tyre is more important. All the major manufacturers make knobbly tyres, road racing slicks, and endurance slicks. I have Schwalbe Nobby Nic on my MTB, and Schwalbe Marathon Supreme on my endurance road bike, sticking to examples from the brand you have.

Pressure is also crucial. Silca have a pressure calculator which is worth a look. Note their disclaimer - if the calculator produces a result outside the manufacturer's specified pressures, limit yourself to what that manufacturer says. This will still tell you which end of the range to inflate to.

Answer 3

First, what do you mean by thickness? (Note, I wrote this before the OP clarified that they're on an MTB) Time trial tires have very thin casings. Performance road tires usually have two or three plies of casing material; the higher performance ones probably forego a puncture strip, but many others have that. The strip adds rolling resistance. For example, on bicyclerollingresistance.com, compare the Continental Grand Prix 5000 S TR to the 5000 AS TR - the latter is the endurance version of the tire, and I believe it has a puncture strip. Within a manufacturer, their TT tire, if they make one, will be the thinnest and the fastest. If they make an endurance road tire and a performance road tire, the latter will probably have a thinner casing, may forego the puncture strip, and will be faster.

To some extent, a thinner casing probably means less hysteresis loss when riding. When you go over a bump, the casing compresses, and then it rebounds. Some energy is lost as heat. The same is true for things like the kevlar (or whatever material) puncture strip.

However, note that tires also have friction between the tread and the road. I forget the technical term for this. In any case, tire makers will work with the chemical formulation of the tread to optimize between rolling resistance and grip (and whatever other characteristics). And some manufacturers, like Continental, Vittoria, and Schwalbe, are known to have good compounds, while others, like Maxxis and formerly Tufo, are behind the best in class. Again, you can verify this on the site mentioned above. So, the differences between manufactures for the same class of tire (e.g. comparing among endurance road tires) can be substantial.

Alternatively, by thinner, did you mean narrower? Here, wider tires can definitely have similar rolling resistance than narrower ones, and potentially less rolling resistance given that you selected an optimal pressure. Aerodynamically, all else equal, thinner should be faster, but you can design the wheel such that the wheel + tire system is fast with wider tires, e.g. many modern road wheels are converging on 28mm tires.

Answer 4

As a very, very general rule skinnier tyres are faster rolling, but there is really a whole heap more variables to consider than just the width of the tyre. Things like weight, tread patterns, tyre pressure all play a significant part in the equation, not a comprehensive list of factors of course. It's more than possible some wider tyre combos will roll faster than skinner tyres because of other factors such as construction.

Also, worth considering when evaluating tyre width choices is the rim internal width. Some rims will just plain work better on different rim.

Answer 5

It depends on the use of the mountain bike. Do you use it as a mountain bike? Or do you just use it on paved roads and cycling paths?

The MTB world is shifting towards wider and wider tyres to be faster. Even in cross-country where the world cup riders now regularly use 2.3" wide tyres. Such wide tyres are faster in a real MTB terrain, even if just cross-country and not enduro or downhill.

For cyclocross racing, the tyre size is kept at 33 mm by the rules, but most often the riders would happily go for wider ones, if they were allowed to do so. It would make them faster on the cyclocross course.

After the question edit:

If you just wast to be fast "of course" on a flat road than you mainly chose the wrong type of bike. It will never be as fast as a road bike but it can be made faster by dedicated for road use. These will be more narrow and have little tread (perhaps even slicks). The width will depend what your rims allow but remember that even in road racing the tyres get wider, 28 mm is now the norm. Do not become obsessed with as narrow as possible. The design of the tyre specifically for roads is more important.