{"id":70165,"date":"2024-10-14T15:00:00","date_gmt":"2024-10-14T13:00:00","guid":{"rendered":"http:\/\/ff7ade4f-eb11-4abd-9839-139cb5c8803d"},"modified":"2024-10-14T15:25:32","modified_gmt":"2024-10-14T13:25:32","slug":"what-is-rolling-resistance-and-why-does-it-matter","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/cyclingplus\/rss_feed\/what-is-rolling-resistance-and-why-does-it-matter\/","title":{"rendered":"What is rolling resistance and why does it matter?"},"content":{"rendered":"

Why roadies, gravel riders and mountain bikers need to consider their tyres\u2019 rolling resistance <\/p>

By <\/p>

Published: Monday, 14 October 2024 at 13:00 PM<\/p>

\n\n

Rolling resistance is one of the most important of a range of forces you need to work against to move forward when riding a bike.\u00a0<\/p>

When cycling uphill, you\u2019re also working against gravity, of course, gaining potential energy that you can put to good effect on the descents.<\/p>

In a review of bicycle aerodynamics<\/a> in the Journal of Wind Engineering and Industrial Aerodynamics<\/em>, published in 2020, Malizia and Blocken point out that on the flat around 90 per cent of the resistance you\u2019re working against when riding a bike at speeds over 40km\/h is air resistance. Hence roadies’ fascination with all things aero<\/a>.\u00a0<\/p>

Beyond that, though, the friction \u2013 or rolling resistance \u2013 between your tyres and the road or trail is a major contributor to the forces you need to overcome to get going \u2013 and to ride faster<\/a>.<\/p>

Here, we\u2019ll tell you what rolling resistance is, how it\u2019s measured and the factors that influence it. Although it\u2019s often considered a roadie thing, we\u2019ll explain why it matters a great deal to mountain bike and gravel riders too.\u00a0<\/p>

We\u2019ve also got details of three of the best road bike tyres<\/a> that we\u2019ve found in our own tests to offer low rolling resistance.<\/p>

What is rolling resistance?<\/h2>
Deformation as your tyre rolls is the major source of rolling resistance. Schwalbe<\/span><\/figcaption><\/figure>

According to tyre maker Schwalbe, rolling resistance is simply the energy that’s lost when the tyre is rolling. This energy loss comes from a number of sources, with the main one being energy sacrificed to the deformation of your bike\u2019s tyres as you ride.<\/p>

There\u2019s also a frictional component between the tyre and the surface, which is why riding on a smoother tarmacked road is so much easier than riding on a chip and tar road surface, or riding off-road. There\u2019s still more opportunity for energy loss from the compression of a soft surface when it\u2019s rolled over.\u00a0<\/p>

The deformation, or hysteresis, a tyre experiences results in heat and sound generation, and loss of energy from the system. In a bicycle tyre, it\u2019s affected by the tyre\u2019s width, diameter and pressure. Other factors, such as the flexibility of the tyre’s casing and the composition of the rubber compound used in the tread, also play a part.\u00a0<\/p>

Replacing some of the carbon black in a tyre compound with silica can reduce energy loss to hysteresis and thus rolling resistance, which is why performance bicycle tyres often include silica. Graphene is claimed to have similar effects and is used by Vittoria in its high-performance bicycle tyres.<\/p>

If you\u2019re riding a time trial or race, you may be prepared to sacrifice tyre longevity and puncture protection for increased speed. Racing tyres typically have thinner treads and casings, and may not even include a puncture protection layer.<\/p>

On the other hand, if you ride on rough roads or trails, or simply hate fixing punctures (don\u2019t we all?), you may be prepared to accept some additional rolling resistance for better flat protection, grip and increased tyre mileage.<\/p>

Why does rolling resistance matter?<\/h2>
\"BMC
Tyres with reduced rolling resistance can save seconds in a time trial. BMC<\/span><\/figcaption><\/figure>

Rolling resistance is one of the most tangible forces slowing you down, but also one of the easiest to do something about. After aerodynamic resistance, it\u2019s a large chunk of the resistance you encounter when riding, and at lower speeds may equal or exceed it.<\/p>

Pretty much every cyclist wants to either ride faster, further or with less effort, and reducing rolling resistance is one of the easiest, lowest-priced ways to achieve this. As Schwalbe points out: “a cyclist has only (very limited) physical power which they want to apply as efficiently as possible.”<\/p>

It\u2019s relatively cheap to choose tyres that lower your rolling resistance, but are well-adapted for the conditions and places in which you\u2019re riding. Optimising your tyre pressures for where you\u2019re riding is free.<\/p>

How is rolling resistance tested? <\/h2>

The tyre to be tested is mounted on a test wheel and inflated to a predetermined pressure. It\u2019s placed in contact with the drum, with pressure applied to the wheel to simulate a rider\u2019s weight deforming the tyre.<\/p>

The system measures the excess power or torque required to keep the drum rotating at the specified speed and this is used to determine the tyre\u2019s rolling resistance. The run is typically performed multiple times to ensure accuracy and repeatability, and there\u2019s usually a warm-up period before measurement to ensure the system and the tyre have equilibrated.<\/p>

Bicycle tyre rolling resistance is typically expressed in terms of watts, because this is a currency many cyclists are familiar with, although there are other ways to express the measurement.\u00a0<\/p>

The main alternative is the coefficient of rolling resistance, or Crr, which is the force required to overcome rolling resistance, divided by the wheel load. In scientific units, this would be measured in Newtons per kilogram.\u00a0<\/p>

Rolling resistance of clinchers, tubeless tyres and tubulars compared<\/h2>
\"Michelin
Tubular tyres are expensive and often incorporate a latex inner tube. Matt Grayson \/ Our Media<\/span><\/figcaption><\/figure>

One factor in the rolling resistance of a bicycle tyre is the friction between the inner tube and the tyre casing, which occurs when the tyre deforms under load.<\/p>

Bicyclerollingresistance.com<\/a>, as its name says, specialises in testing tyre rolling resistance and the factors that affect it. <\/p>

It tested the effect on rolling resistance of different inner tubes<\/a>, when used with the Continental GP 5000 S TR tyre in 25mm width at a range of pressures. The tyre was set up tubeless<\/a> with sealant as a reference point and its rolling resistance assessed against the same tyre mounted with a range of 10 inner tubes, with TPU, latex and butyl tubes tested.<\/p>

It found an increase in rolling resistance of between 0.2 watts and 3.8 watts when using a tube over the tubeless setup.<\/p>

Latex inner tubes have the least effect on rolling resistance, with most TPU inner tubes performing better than butyl tubes.<\/p>

The site concluded that, in a tubeless tyre, running without an inner tube was most efficient. If you want to use inner tubes, it\u2019s better to use the non-tubeless GP 5000 clincher than the tubeless tyre. It will roll faster, and is lighter and cheaper, according to the site.<\/p>

Tubular tyres, like clinchers, have an inner tube. But the higher price of tubulars and their performance orientation means the inner tube may be latex, or occasionally TPU, as in the case of the Pirelli P Zero Race SL<\/a> tub, so their rolling resistance may be comparable to a clincher tyre with a latex inner tube.<\/p>

The cotton casing\u2019s higher thread count may also help to lower rolling resistance, but Bicycle Rolling Resistance found even the type and quantity of glue used and how long it had dried could affect the result, so it wasn\u2019t able to derive any definitive conclusions from its comparative testing of tubs.<\/p>

However, generally, the difference in rolling resistance between running tyres tubeless or with a latex or TPU inner tube is minimal, so you can pick and choose based on your own preferences.<\/p>

Tubeless setups also provide an extra element of puncture protection though, thanks to the sealant used to make the tyres airtight, which can be useful in many scenarios.<\/p>

How does rolling resistance vary with tyre width?<\/h2>
\"Tadej
Even pro road cyclists are riding much wider tyres now. George Scott \/ Our Media<\/span><\/figcaption><\/figure>

Our own Simon von Bromley performed a detailed test of two different widths of the Pirelli P Zero Race TLR \u2013 26mm and 30mm \u2013 to assess if wider tyres are faster<\/a>. The result was: it depends.<\/p>

Indoors, on rollers<\/a>, 30mm tyres required less power to maintain the same speed when both tyres were run at the same pressure.<\/p>

This is because, at equal pressures, a wider tyre deforms less due to the wider, shorter contact patch.<\/p>

When tyre pressure was adjusted to roughly real-world levels, however, the narrower tyre was more efficient.<\/p>

In theory, if you could perfectly adjust the tyre pressures in each width to offer the same-sized contact patch, the rolling resistance should be equal.<\/p>

In practice, the key takeaway is wider tyres do not roll slower than narrow ones on perfectly smooth surfaces, and may roll faster on rough roads \u2013 where greater compliance and grip is required \u2013 because they offer more suspension and a greater surface area for cornering.<\/p>

This is why many elite gravel racers are increasingly choosing ultra-wide tyres for gnarly off-road races such as Unbound<\/a>.<\/p>

As a result, you should pick your tyre size based on the terrain you\u2019re riding on and the objectives of your ride.<\/p>

Does rolling resistance matter for mountain and gravel bikes?<\/h2>
\"Santa
Mountain and gravel bike riders may be prepared to accept increased rolling resistance for additional grip. Alex Evans \/ Our Media<\/span><\/figcaption><\/figure>

The short answer is yes, but less so than for road bikes<\/a>. For many mountain bike disciplines<\/a>, and for gravel riders, additional rolling resistance is a worthwhile trade-off to remain rubber-side down on the trail.<\/p>

Tyres with lighter or thinner casings<\/a> \u2013 which usually equates to lower rolling resistance because they require less energy to deform \u2013 may also be more prone to punctures. For enduro or riding on hard trails and gravel, that may not be a compromise worth making.<\/p>

The one arena where an MTB rider might be prepared to trade some grip for lower rolling resistance is cross-country racing<\/a>, where the ability to cover more ground faster is an advantage, provided the route isn\u2019t too tricky. The same is true for gravel racers<\/a>.<\/p>

If your rides regularly take in a significant amount of on-road or smoother trail riding, a slicker, lighter tyre that rolls faster can make it quicker and easier to get to more interesting riding.<\/p>

But for most MTB disciplines and for gravel riding<\/a>, grip is a greater priority over low rolling resistance.<\/p>

Fastest road tyres 2024<\/h2>
\"BikerRadar\/CyclingPlus
We lab-tested the rolling resistance of eight tyres at Silverstone Sports Engineering. Gavin Roberts \/ Our Media<\/span><\/figcaption><\/figure>

If you plan to replace or upgrade the tyres on your road bike, our guide to the best road bike tyres<\/a> should help you choose. Our buyer\u2019s guide includes the 13 top-performing models we\u2019ve reviewed at BikeRadar, with considerations such as rolling resistance.<\/p>

We\u2019ve also been more scientific though, taking eight top-performing fast road bike tyres<\/a> in a size 700x28c to the Silverstone Sports Engineering hub to measure their rolling resistance on its bike tyre rolling-resistance rig.<\/p>

This consists of a motor-driven drum with a torque meter used to measure the tyre\u2019s resistance. There are more details of the protocol in the feature linked above. We also tested them in the real world to determine their ride quality, grip and how easy it is to set them up on your bike.<\/p>

Here are three tyres we found to offer the lowest rolling resistance of the bunch.<\/p>

As always, though, having the absolute lowest rolling resistance isn\u2019t everything.<\/p>

For example, although Challenge\u2019s Criterium RS tyres tested fast in the lab and offer superlative ride quality in the real world, they were a pain to set up tubeless \u2013 which might be a deal breaker for many riders.<\/p>

Pirelli P Zero Race TLR<\/h3>

SQUIRREL_TEXT_13087005<\/p>

\"Pirelli
The Pirelli P Zero Race TLR won our rolling resistance test. Ashley Quinlan \/ Our Media<\/span><\/figcaption><\/figure>

This Pirelli tyre had the lowest rolling resistance in our test, at 11.86 watts. The tyre was updated in early 2023, with a thinner carcass incorporating Aramid fibres and improved puncture protection \u2013 as well as offering a claimed reduction in rolling resistance.<\/p>

We noted the excellent ride feel and grip, although the tyre comes up quite narrow, with a rounded profile, which does affect handling slightly, although not comfort. At 310g in size 28mm, it\u2019s a little heavier than some tubeless tyre competitors too.<\/p>

Pirelli also recently launched the P Zero TLR RS<\/a>, promising lower weight and rolling resistance, as well as improved compatibility with hookless rims. We\u2019ve yet to test this new model, however.\u00a0\u00a0<\/p>