“Wider is quicker!” – They’ve been screaming it from the rooftops for some time, and it isn’t inconceivable to think about advertising and marketing departments from across the bike business having this printed on their workplace partitions like some kind of mantra to be repeated.
I mock it, however right here at Cyclingnews, we imagine there’s reality in it. But not ones to take the phrases of entrepreneurs at face worth, we wished proof, so we got down to get some.
We’ve been to the Silverstone Sports Engineering Hub a number of instances over the previous yr. We’ve examined bikes, wheels and helmets of their wind tunnel, and we have examined highway tyres on its Pedalling Efficiency Rig. So for the most recent instalment, we turned to gravel tyres for a lab check gravel tyre deep dive.
There’s quite a lot of dialog about what makes the optimum gravel tyre for any given race, and naturally, the reply will just about all the time be ‘it relies upon’. On the course, the climate, the terrain, your body, your dealing with abilities, even who you are using with.
It is determined by the course you are using, as a result of a rocky course will need a tyre that may clean out the roughness whereas dealing with the impacts, whereas a clean course will need one thing that rolls, properly, smoother.
It is determined by the climate circumstances, as a result of a muddy course would require extra grip, and doubtlessly extra clearance if the mud is prone to clog up in your body, whereas a dry course is usually grippy sufficient and clogging up is unlikely. It is determined by your common velocity, and whether or not you are using alone or in a gaggle, as a result of quick or solo riders will hit extra wind, and thus prioritise one thing with extra aerodynamic efficiency, whereas gradual riders, or these in a gaggle, needn’t fear fairly a lot.
It additionally is determined by the chance of getting a puncture, as a result of your light-weight race tyre would possibly prevent three watts in rolling resistance, however there’s nothing slower than standing along side the highway fixing the factor.
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As a outcome, we did not wish to simply spend a day testing a random cohort of gravel tyres to see which is quickest in our very particular set of circumstances. There’s no actual profit in figuring out {that a} Hutchinson Caracal – a race tyre designed for clean surfaces – is quicker than a Vittoria Terreno Wet, which is designed for reducing by way of sloppy mud.
Instead, we wished to provide the Cyclingnews subscribers some actionable perception each time they sort out the choice of ‘what gravel tyre ought to I run?’ – be that for a race, a long-distance journey, or every other off-road experience.
So we got down to reply the next three questions:
1. Is wider really quicker?
Quite merely, does a wider tyre imply a discount in rolling resistance? Because whereas a narrower tyre would possibly supply extra mud clearance, if you do not know how a lot quicker or slower it’s, you will not be capable to make an knowledgeable determination on whether or not it is well worth the danger.
As a outcome, we examined six Vittoria Terreno Dry tyres of the identical development and tread sample, in sizes starting from 31mm to 53mm.
2. What impression does tread make on rolling resistance?
If the terrain you are about to sort out is leaving you torn between two tread patterns, what number of watts are you prone to lose by selecting the ‘knobbier’ tread? Or do you have to simply change to the grippier choice to optimise for the muddy sections, secure within the information that your rolling resistance variations on smoother sections will probably be negligible? Again, with out the knowledge, you’ll be able to’t make an knowledgeable determination.
Here we examined two pairs of 40mm Pirelli Cinturato tyres. The first pair in 60TPI, and the second pair in 120TPI, with the one distinction between the 2 choices being the tread sample.
3. What impression does casing have?
Many gravel tyres are available in quite a lot of casing choices. Often this refers back to the TPI depend (threads per inch) however in lots of circumstances merely refers back to the stage of puncture safety constructed into the tyre’s development.
If you are not sure what TPI means, our TPI information will clarify the small print, nevertheless it’s typically accepted {that a} greater TPI depend is extra supple and due to this fact deforms extra simply over tough surfaces, however usually on the expense of sturdiness, which means doubtlessly extra punctures. The trade-off due to this fact is normally a query alongside the traces of “do I danger extra punctures to realize velocity?”
You cannot simply reply that query with out figuring out how a lot velocity you are prone to acquire, and so right here we used Panaracer’s Gravelking tyre, which is available in a ‘customary’, a ‘Plus’ and a ‘Race’, every with an similar (40mm) measurement, and tread.
The outcomes, which have been printed in our lab check gravel tyre deep dive, confirmed some attention-grabbing findings.
There was a particular trendline for wider tyres being quicker, nevertheless it wasn’t with out a few outliers. The aerodynamic implications are but to be examined, however it will stand to cause {that a} wider tyre is much less aerodynamic by dint of its elevated frontal space. From this inference, we are able to deduce that the majority riders – particularly slower-speed riders and even perhaps these inside a gaggle setting – as usually present in gravel races – would see a profit for going wider.
The check for tread and casing have been the actual surprises although. We’ll save the precise financial savings on supply for our subscribers, however each confirmed much less of a distinction than anticipated, which means you could possibly doubtlessly be gifting away velocity solely within the pursuit of it.
One factor that may shock no one, nonetheless, is that consolation on wider tyres is considerably higher. Part of our testing day included a stint of testing on simulated cobbles, and though that is extra an anecdotal conclusion than a data-driven one, using on cobbles with narrower tyres (we went as slender as 26mm) is just not an expertise I’d wish to repeat any time quickly!