Considering tyre pressure at the Tour de France
There’s a lot of talk about the tech on display at the Tour but there are little things every rider can do to optimise their performance on the bike. Pumping up your tyres is a basic act but there’s also a science to it.
The conditions in the opening stage of the 2017 Tour de France proved to be difficult for many and, alas, dangerous for some. Two star riders are out of the race – Alejandro Valverde and Ion Izaguirre, both victims of crashes on the wet roads of Düsseldorf on Saturday.
It prompted people to ask questions about how riders might manage themselves – or their equipment – better to limit the risk of crashing.
And so the topic of tyre pressure came up… again.
Often when rain falls before the start of a race, it’s not uncommon to hear the ‘psshhhhh pssshhh…’ of riders letting a little air out of their tyres. But this is modern, professional sport and such random acts based on feel are dated. When there’s so much attention to detail on a vast range of themes to maximise efficiency even the good old tyre pressure quandary deserves closer consideration.
“Tyre pressure is a topic of great interest,” said Simon Jones, the new high performance director at Cycling Australia, at the start of stage two.
The subject came up because I’d checked what Geraint Thomas raced with on his way to victory in Düsseldorf. Team Sky’s mechanic, Filip Tisma, told me: “7.2 to 7.3 bar”.
In terms of PSI, that equates to around 104.4 to 105.8… roughly.
But just because that worked for ‘G’, don’t expect it to be right for you.
Before his job with Cycling Australia, Jones worked with Team Sky. He managed some of the details that have contributed to the “marginal gains” of a team that is as pedantic as possible about all things relating to performance. And, as I’d learn during a discussion before stage two, tyre pressure is a topic he’s fond of.
“At Team Sky, the lengths that we went to to optimise and individualise the tyre pressures to each of the riders, to wet and dry conditions, was quite extreme,” Jones explained.
“As part of that process, I found a place in Finland, Wheel Energy, that specialises in this. I went up to see them and test rolling resistance, wet and dry grip… and we benchmarked every type of tyre at different pressures. Then, with that data, we created a matrix; like a decision-maker matrix – where, based off the weight and the weight distribution of the bike, you could optimise the tyre pressure depending on the racing objective, whether it be a time trial, a bad rough road surface, a smooth road surface, or a mountain.”
Simon Jones and Bradley McGee at the time trial in Düsseldorf.
Photo: Rob Arnold
Rain continues to fall on the 104th Tour de France. Wet conditions are again impacting the peloton as it races towards Liège in stage two. But it doesn’t necessarily mean that Geraint will have “7.2 to 7.3 bar” in this tyres today. There is a different bike, a different position, different road surfaces… all things that Sky consider when pumping up tyres.
“We got some methodology to say, ‘Well, what are the conditions like today? Who is the rider? What are the goals?’ And then used an appropriate tyre pressure,” continued Jones.
Gone is the notion of a rider just leaning over and easing a bit of air out the valves in the quest to find his optimal pressure. The lessons Jones learned in Finland are some he believes can be shared to the broader cycling community because everyone can benefit.
“You have to test your tyres because every tyre performs differently,” he said.
“We were finding that, with the Continental tyres and also ones that were slick, they performed really well in the wet. And, again, there was a bit of a sweet spot between a certain pressure – and it all depends on the mass of the rider. And it also depends on your weight distribution and how you’re set up on the bike.
“They will reduce tyre pressure by half a bar, not much. But we wouldn’t just go ‘psshhh psshh…’ and do it by feel. We’d actually measure it because it’s actually quite important to get it to that little sweet spot between grip, rolling resistance and stability. And obviously you’ve got to look at the road surface.”
Geraint Thomas powering along on the wet streets of Düsseldorf… and onward to a yellow jersey.
Photo: Yuzuru Sunada
The Tour moved from Germany to Belgium today, from a street circuit to some paved roads, some rough roads, some slick wet roads… and chances are Sky will select a different pressure and possibly a different tyre.
But it’s not motorsport and we’re not used to seeing commentary about the specifics of such stuff. But, says Jones, “I think there’s a lot of interest out there and I think we’ve got a role to share things which are not that confidential but people might find interesting”.
Two riders are out of the race and perhaps a little less (or more) air in their tyres could have improved their grip… but we’ll never know. As Jones conceded: “The streets in Düsseldorf are quite smooth so they’re quite fast.”
With the peloton now in Belgium, it’s a different situation.
“The funny thing is, if your tyres aren’t in contact with the ground, you fall off,” said Jones.
“That might be a bit of a crazy thing to say but if they’re too hard, you bounce. And you get this very, very high frequency bouncing which means your tyres aren’t in contact with the ground. So it’s actually really important.
“You’ve only got 2.5mm of rubber that connects you to the road so it’s quite an important 2.5mm and the tyre pressures are really important.”
Indeed it is. And even with all that goes into the trying to make things are effective – and safe – as possible, this is cycling. Incidents can happen. A touch of wheels, like what happened to Chris Froome with 30km to go in stage two, can bring riders down. And little does it matter if there’s 7.2 or 7.3 in the tyres. You also need a little bit of luck.
– By Rob Arnold