Gary Hunt
You’ll probably have a favourite tyre brand and model, your old faithful, the one that hasn’t let you down with punctures … maybe a set for training and another for racing … maybe they were recommended by your mates in the bunch years ago, or perhaps you haven’t thought much about it, the last frontier between you and the road. They’re the ultimate component in controlling all your speed and power, and in reality the one most likely to suffer catastrophic failure, so you should consider tyres carefully.
Your shopping checklist may include things like ‘low rolling resistance but also provides great traction for braking and cornering on all surfaces’, ‘lightweight but puncture resistant’ and not such a tight fit on the rim that it’s impossible to change out on the road. And of course they shouldn’t cost the earth or wear out in the first few rides.
We have collected a sample of 32 tyres from across the Australian market both training and racing tyres to show what’s out there.
There has been a strong trend recently towards 25mm tyres from the incumbent 23mm, so much so, that many suppliers have had trouble keeping up with demand of the new models.
While designing wider tyres for the race and sportive market, several have extended their research to incorporate aerodynamic considerations in recent years. Zipp is one such company that carries out extensive wind tunnel testing and CFD engineering. You might recall their earlier Tangentes which incorporated surface dimpling to reduce drag and provide aero benefit. Now their 2015 offering has a redesigned tyre casing shape and tread pattern to deliver improved aero results. Bontrager have also looked at the aero properties of their tyres and incorporated ‘aero wings’ into their design with a small lip around the tyre casing that blends the tyre’s join at the rim for smoother airflow and less overall drag.
The factors that contribute to speed and traction properties of tyres are many and affected by changes to road surface, tyre pressure, tyre size and shape, rim width, rider weight … and the list goes on.
Switching to a wider tyre will bring some benefits; it’ll allow you to run lower pressures without risking pinch flats, and thereby improve comfort and traction.
However you don’t get to have your cake and eat it too; the positives gained in traction and comfort are offset to a degree, because when you lower the tyre pressures with these larger case tyres, you will increase the size of your contact patch proportionally and thereby increase the amount of casing hysteresis—the energy lost through flexing of the tyre. This will in turn increase rolling resistance which will reduce your speed for a given power input.
But, adding yet another factor to this complex equation, the lower pressures should also enable your tyre to more easily accept the myriad tiny obstacles your tyres roll over, like coarse roads, pebbles etc that with harder pressures equate to a multitude of tiny uphill sections. Allowing the pebbles to push into the casing as it rolls over, and not force the bike ‘uphill’ will see a reduction in power lost.
Wider rims too, are getting quite a deal of press about the benefits they bring and these are related to effectively making your skinny rubber wider. They will change the shape of your tyre profile giving a wider contact patch along with its benefits of lower rolling resistance and better traction, but they potentially also bring some detrimental factors—increased weight and higher aerodynamic drag. If you’re persuaded to invest in new wider wheels check they’ll fit before you dive in; some wheels and tyres may fit inside your frame and fork while you’re stationary, but rub while sprinting or climbing due to flexing of your wheels or frame.
So beyond a short wide contact patch, minimising the energy involved in deforming the rubber where it hits the road is a key consideration for manufacturers looking to make a fast tyre. This is where the discussion about how ‘supple’ a tyre is comes in. More flexible and compliant construction of the casing, tread, shoulders and sidewalls should mean less watts of power are expended to drive that tyre forward. The addition of puncture protection may add some bulk or stiffness to the tyre casing and increase its rolling resistance so your training tyres will likely be heavier and less efficient than pure race tyres.
While we used standard tubes for our review, if you are looking for maximum performance so far as speed goes, tubes made from latex are lighter and more supple and will promote faster easier rolling, though also bring potential reliability issues.
While these changes to pressure and patch shape seem marginal, after experiencing various tyre widths and brands on the bike, there’s no doubt they affect the ride considerably so far as comfort and traction goes. Detecting marginal gains in speed is a little more difficult to subjectively.
Switching to wider rims with the same tyre size and pressure will increase the width of your tyre’s contact patch and shorten its length thus lowering the rolling resistance of your tyres. The longer your contact patch the thinner it will be—it must maintain the same area for a given pressure. The key point is the longer it is the more rolling resistance it will add.
Your tyre when loaded flattens at the contact patch.
Imagine this flat contact patch being an ellipse say 300mm x 100mm … long and thin—the same as this length of wood. If you push on the screwdriver’s handle along the length of the block, it will not easily roll. However if you turn the block 90 degrees so the ‘contact patch’ is very short and very wide, and then push, the block will roll easily. This is a crude comparison of the forces required to overcome your tyre casings’ resistance to deformation … more force is required across a longer section of tyre when it has a longer contact patch.
Here below are images of the tyres reviewed, followed by more detail of the test process.
Click here to view the full results in our Tyre Specifications Chart
To The Test
We conducted a rollout test and ran each tyre down our test track six times measuring speed and distance each tyre achieved. We repeated the test three times at 90psi and three times at the manufacturers’ recommended maximum pressure for each pair of tyres.
The test was completed outdoors on a calm day with absolutely no wind. The slightest breeze called a halt to proceedings twice during testing, but a high barometric pressure system prevailed and kept the air very still for the remainder of the time. The same bike, wheels, rider, pump, gauge, tubes, and start process was used to keep as level a playing field as possible. Rider position was also constant with every run starting from our start line at a dead stop, hands on the hoods, and elbows locked straight, and following a straight course till the stop, right pedal at bottom dead centre throughout with no pedalling input, just the constant force of gravity to get us moving.
Given their prevalence Mavic Ksyrium Elite S rims made a good choice as wheels for this review. They measure 15mm between the brake track so are on the narrow side of what’s available these days—of course the width of your rim will have a bearing on the effective tyre size, and indeed the measured width values we have listed.
The test track ran down a very quiet moderate, fairly dead, bitumened blue metal slope that would see us achieve as maximum speed around 30kph. The track then flattened allowing a roll out to about 180 metres before coming to a dead stop. We used a Cateye Velo 7 wired cycling computer to record the maximum speed of every run, and had the distance marked out along the roadside, measuring down to the half metre. A car passing the opposite direction was very rare but it voided the run, wiping up to eight metres from the rolled distance.
Our measurements showed very little variance for each individual tyre in its three runs in terms of maximum speed and distance recorded, though each run took only 20 seconds or so, and the implications of the difference over a longer ride could become significant. The distance varied by just over 8% from tyre with longest run to that with the shortest. Interestingly there was no difference in averaged speed between the 90psi and the maximum pressure bunches, though results for some individual tyres did vary.
So far as performance goes our review here deals with a very narrow band of parameters. One of our regular contributors Michael Hanslip reviewed a pair of Schwalbe One 25mm tyres a few issues ago, and while they did not see the highest rolling speed in the review carried out here, they impressed him so much in terms of ride feel, he said they were the best tyres he has ridden.
So while a tyre shines in one area it may fare less well in others … in some cases a grippy compound that corners like it’s on rails will mean it is softer and less durable or will achieve a lower top speed than if it were a harder compound. You might be more interested in puncture protection than top speed, or have a predilection for lightweight components and hang the expense. These facets are not mutually exclusive but changes to one aspect will have an effect on others.
I’d encourage you to do some research for yourself, preferably with newish tyres as, according to wheel and tyre guru Josh Poertner when we interviewed him during his time at Zipp, the aerodynamic performance in particular will decline as tyres wear and become flatter across the tread. Swap tyres with a friend, get a feel for how different tyres corner, compare roll out distance and speed for yourself and see what you prefer.
One thing is certain; tyres are one of the least costly ways to improve your bike’s performance.
Our thanks to all the brands for providing their tyres, and Schwalbe for providing spare tubes for the review.
