When it comes to tyre width, what we really want to know is: does size really matter or is it what you do with it that counts?

In the past, narrow tyres were the order of the day, but the modern peloton is bucking the trend and switching to wider hoops. Tyre companies are unanimous in their support for this increase in diameter, which they claim reduces rolling resistance and saves energy, as well as adding extra comfort. No longer does thinner mean faster.

It’s not just the tyre brands making the change. Bike manufacturers are also taking heed of the trend and fitting their machines with 25mm tyres as standard — instead of the formerly ubiquitous 23mm size. As a result, tyre clearances are expanding. Frames that were once too narrow for anything other than skinny race tyres now have room for fatter fitments.

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The root of this trend is found in the pro peloton. Nothing new there. On a long stage, it’s easy to see why comfort — increased with a wider tyre — factors so highly.

Getting a rider to the climax of a stage race in good shape helps them to deliver the knockout blow. If they’re spending the day feeling every road imperfection, fatigue is exacerbated — no matter how quickly they get to the business end, no matter how good their lead-out — their performance will be compromised.

Tyre

Sizeable benefits

At the extreme end of the scale, look at Paris-Roubaix, in which most teams use 28mm or 30mm-wide tyres. When deciding on tyre pressure, the weather conditions must be considered, and it’s not always easy to hit the sweetspot of comfort, speed and handling. The number-one priority is getting the rider and their bike to the finish in one piece.

Paris-Roubaix may differ wildly to the riding the majority of us do, but our tyre choice shouldn’t be any less considered. The contact points between our bike and the road are what keep us shiny-side-up, after all.

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A wider tyre has a larger contact area with the road beneath our wheels, adding a modicum of extra traction — a welcome attribute in wet conditions — and making pinch-flats less likely.

Then there’s rolling resistance.
The performance of a wider tyre is less compromised by lower pressures, compared to a 23mm tyre. But in a cycling world obsessed with aerodynamic advantages, surely wider is slower?

It’s easier to accommodate wider tyres on wider rims, thus avoiding detrimental effects on aerodynamics. On a narrow, 19mm rim, a bigger-profile tyre balloons, causing more drag, so that any advantage gained from the decreased rolling resistance is void by the increased drag. A wider, 23mm rim with a 25mm tyre allows the rim and tyre to sit flush with each other, thus making airflow far smoother.

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Counting the costs

Practically, there is one downside. Switching tyres is relatively cheap, but if it necessitates buying new wheels to get the most out of the shift, it suddenly becomes a far less attractive prospect. Pounds in the till to save watts on the hill? It just depends how far you are willing to go.

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Wider tyres: yes or no

Yes: Rob Scullion, Cambrian Tyres (UK distributors for Continental)

“25mm tyres have been proven in various tests to be more efficient than 23mm tyres. The 28mm GP4000S II is faster in the lab than the 23mm and 25mm version, but in the real world, aerodynamics come into play and hinder efficiency. With a smaller contact patch on the road, the 25mm is the perfect all-round package for speed, grip and comfort. It is the size all our race teams choose.”

No: Michael Hall, Zipp wheel development director

“The trend to move to a wider tyre comes with a slight advantage in rolling resistance over narrower tyres. A reasonable-performance improvement when going from a 23mm to a 25mm tyre would be a reduction in rolling resistance of 10 per cent or about three watts at 40kph. However, when evaluating the aero affects of such a change on Zipp Firecrest rims on a TT bike set-up, we found the opposite.”

Garmin leads the peloton in the 2014 Omloop Het Nieuwsblad

If wider tyres work for the pros, then they can work for us too

Our take

How far can we go before we turn our carbon race bikes into glorified Boris bikes? The key is striking a harmonious balance between rolling resistance and aerodynamics. The other factors — the reduced risk of pinch-flats and being able to lower tyre pressures for comfort and better handling — are a done deal. If 25mm is good enough for the pros, it’s definitely good enough for us average Joes.

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  • “A wider tyre has a larger contact area with the road” – I’m not convinced this is true, I think it will have a different shape, wider but shorter (at the same pressure – where all these resistances etc. must refer) – that actually means the tyre deforms less, hence the less energy used in deformation and hence better efficiency/lower rolling resistance.

  • hedgemagnet

    Have you actually seen the tread pattern on a 28mm Gravelking? It doesn’t have nubs. It has tiny raised dots on the centre band (which wear smooth after a couple of hundred miles) and a file tread on the shoulder. It’s similar to a Vittoria Open Pavé and is effectively one of their old road tyres which they renamed to cash in on the gravel boom.

  • Because you went and bought gravel tires and expected them to perform on the road the same as a road tire. That’s asinine. Of course they’re like syrup. The tire is breaking you each time one of the nubs touches the ground. In the gravel or dirt where the surface gives and is loose, that’s great because it affords you more grip. On the street those nubs are the worst thing ever. You’ve effectively doubled your rolling resistance.

  • The contact patch changes because of the width of the tire. The narrower tires contact patch is longer and thus spends more time contacting the road and braking the wheel through a longer period of friction because of its longer profile. The wider tire, being capable of carrying its weight load more efficiently under the same pressure, has a wider contact patch, but is much much shorter horizontally. In effect not only does it have a shorter profile, but its contact area volume is smaller than the narrower tires. All the while, you gain the advantage of having more lateral grip because its contact profile is much wider.

  • The contact patch changes because of the width of the tire. The narrower tires contact patch is longer and thus spends more time contacting the road and braking the wheel through a longer period of friction because of its longer profile. The wider tire, being capable of carrying its weight load more efficiently under the same pressure, has a wider contact patch, but is much much shorter horizontally. In effect not only does it have a shorter profile, but its contact area volume is smaller than the narrower tires. All the while, you gain the advantage of having more lateral grip because its contact profile is much wider.

  • Jamie Wafc Finch

    Becuse the sweet spot is 25mm, looks like you missed the boat on that one.

  • getoverit

    The article failed to say that a wide tire on a wide rim would still be less aero than a narrow tire on a narrow rim ( a dodge caravan is not as aero as a motorcycle). The bike and wheel companies want change so the public will end up buying replacement bikes and or wheels in a slow economy..l like to wait a year to respond..lol

  • hedgemagnet

    Well… I’ve just stuck some 28mm Gravelkings on, and with 130 tpi, 270 grams and having read all the guff about tyre deformation, hysteresis,and so on, I was looking forward to rolling along at least as effortlessly on the tarmac than I do with my collection of 23mm Fortezzas, ProRaces, and Conti Attack/Forcey kinds of thing – and bouncing around on hard dirt to boot. Well the off road stuff is good fun, but they’re like riding through syrup (one up from treacle) on the road, and feel only slightly faster than my nuke-proof Spesh Nimbus EXs

  • Will

    There is also the effect of vertical movement of the rider and bike. Every bump accelerates the rider and bike upwards and this motion uses energy. Wider tires have more give reducing vertical movements and saving energy. If you don’t believe this, just think of how much more difficult it is to climb a hill with rough tarmac than smooth – so much so you will find that you subconsciously seek out a smooth surface line to reduce that vertical jostle – because it costs you energy. So a soft ride can also be a fast ride if the roads are not great and the heavier you are as a bike /rider combo, the more this is the case. On the dead flat, as in a velodrome, narrow high pressure tires are probably much quicker. .

  • John Clay

    How can a wider tyre have less rolling resistance? Simple geometry says the opposite, as the contact area with the road will be greater for the wider tyre?

  • Jacob

    On the track you need to run 19mm or 20mm in order to achieve the right gear, this has little to do with aero or not

  • Mark M.

    Yeah, they do, but nothing higher than 220tpi, and at that point, why bother putting them on your $2500 wheels? Their “high-end” tire comes in 21mm and 23mm. No 25mm.

  • Andy

    Yes they do. 25mm

  • Dave

    A wide tyre on a wide rim is no more aero dynamic than a
    narrow tyre on a narrow rim. But the volume of air in a wide tyre and rim is
    much larger which reduces the rolling resistance on a rough road. Rolling
    resistance is not an issue on a track as they are perfectly smooth.

  • Mark M.

    Of course Zipp says no…they don’t make a wide tire.

  • Richard Braginton

    Last year i used veloflex 21mm dia tyres and they were definitely the best clinchers, i have used and the nearest to tubulars in a clincher, and i notice that attempts on the hour record at least two of them have used 19mm dia tyres pumped to huge pressures, so if the wider rim/ tyre combination is most aero why aren’t they using for the ‘hour’ when aero effect is most important.

  • Larry Ring

    I ride 23 in the front 25 on the back. Works for me.