Tyre pressure can dramatically affect your ride - go too low and you’re at risk of repeated punctures, but riding with your rubber hard as a rock will cause the bike to skit over every bump in your path.
To be clear - the 'maximum' printed in the tyre side wall is exactly that - it's not the optimum, as has been a widely believed misconception for some time. The perfect pressure varies between individuals - factors include riding style, rider weight, expected terrain and weather conditions.
- PSI: Pounds per square inch, is the unit used to measure tyre pressure. A good track pump will show your pressure in PSI on a dial
To help us negotiate the sea of influential factors, we looked for an expert – and found one in Matthew Wakeford. Matt is an ex-professional racer, who started bike racing aged fifteen. Since retiring, he has worked as a mechanic on pro teams, in the SRAM Technical Centre, and he now manages Maison du Velo bike (and coffee) shop in Cranleigh (Surrey).
We discussed the factors involved, and the effect they have, eventually creating a chart of basic suggestions that you can work from. We've stuck to talking about clincher tyres - but you can think about going tubeless which might allow you to run lower pressures and avoid punctures.
What sort of riding are you doing?
Before you decide what width tyres to run, and how much to pump them up by, you need to examine your own riding and goals.
Matt told us: “Tyre pressure is important to different riders, for different reasons. If you’re racing or time trialling, and go too low, you’ll have more rolling resistance. That’s not what you want. But go too high and you’ll lack grip and the tyres will skit over the road surface. If you’re riding a sportive, or out training, you’re going to want a lower pressure - something more comfortable so you don’t have to spend all your time on a smooth gravel road. You can venture off on uneven roads and you’re not going to come back and find your neck is killing you. Commuters don’t need to worry so much about rolling resistance - the speed of getting to work is less important, most are going to be more worried about getting punctures and being comfortable."
Weight comes in to it too. A lighter rider causes the tyre to depress less against the ground, so they’ll need to run a lower pressure to get the same effect as a heavier rider, and vice versa.
What difference does the weather make to tyre pressure and grip?
Conditions are hugely influential. We’ve always known to lower tyre pressure in the wet, to allow for more grip – but Matt also explains that the amount of rain, and how long it’s been raining for makes a difference.
He explained: “Lower pressure means more surface area contact with the ground. You do get higher rolling resistance, but more grip. If it’s been raining for three days, constantly, the chances are most of the diesel and oil has been washed off the road. So if you’re riding around the lanes at home, you can probably drop about 10psi. If you usually run 100psi, 90psi is about right. If it’s just chucked it down, right before you go out, that usually brings more diesel up on the road. So then you might want to run them down a lot more – if you’d usually run 100psi, maybe look to run about 70psi. A lower pressure when it’s greasy and wet works better, and lighter female riders could probably get away with running down to 60psi.
How does tyre pressure affect puncture protection?
Whilst lower tyre pressure can provide more grip, it can leave you open to spending more time at the side of the road, fixing punctures.
Matt explains: “At a higher pressure, the carcass of the tyre will hold its shape better. So little flints and glass can’t get in, whilst at lower pressure sometimes they can. You’ve also got more contact with the ground, so there’s more chance of picking that stuff up."
So what do you do? You need to find a balance, a compromise that works for you: “It’s about getting that balance of pressures to avoid punctures and get grip in the corners. But if I had a choice between a puncture and crashing, I’d go with the puncture. In most cases the mild inconvenience of a puncture outweighs the chance of hitting the deck quite hard."
Choosing your tyre width
In recent years, wider tyres have become more ‘fashionable’ – even for racers. Wider tyres allow you to run a lower pressure and you should always adjust your chosen tyre pressure with this in mind if you opt for a new width.
Matt says: “When I first started racing, everything was 19mm tyres, pumped up to 150psi. We thought that was the fastest you were going to get. But you had to tip toe to the start line and it handled appallingly, you couldn’t lean over at all. Towards the end of my career wide tyres became popular and pressures started dropping. All the pros are using 25mm tyres now, and they wouldn’t if they weren’t faster – no matter how much you paid them."
So what are the benefits of a wider tyre? “Narrower tyres skip over stuff, you’ve got hardly any traction on them. A 25mm tyre depresses over the bumps in the road and so assuming you’re riding over variable UK roads, not the wooden boards of velodromes, it’s actually faster to go with the wider option."
But what about those enjoying ambles down country lanes, or commuting? The rise of disc brake road bikes, which allow more tyre clearance, means you can go wider. Matt says: “27mm or 28mm would be fine. You can run pressures a lot lower, it feels more stable. You loose some of the ‘zing’ and fast acceleration, but if you’re not jumping out of a corner and accelerating hard you don’t really need that."
Choosing your tyre style
Most road cyclists will swap over to winter tyres in the colder, wetter months, seeking an option with more puncture proofing. That usually means a harder compound, that doesn’t depress against the road surface so well, usually resulting in increased rolling resistance and a harsher ride.
Matt prefers to run the same tyre year round, looking to regular maintenance to prevent flats. He says: “You can usually get away with running a fairly racey tyre all year round. Riding the wrong tyre pressure is the biggest cause of punctures. Valves leak, tubes are porous, you need to pump them up regularly. When you get back from a ride, just wipe a cloth over the surface of your tyres to get rid of most of the grit. That one little bit of flint just stuck on the top, when you jump on your bike for your next ride, will just go straight in."
Tougher tyres made from a harder compound often come with a maze of grooves on the surface, and it’s common to believe these provide more grip. Matt disagrees and says: “There’s loads of myths about tyres. People often say ‘this tyre looks too slick’ – but often the grooves that look like grip are put on there for aesthetic reasons.. Some of the grooves disperse some of the water, but it’s really minuscule. A tyre with a softer compound will have more grip."
The tyre pressure chart for clincher tyres
To give you a starting point, we’ve created the following chart based on the three popular tyre widths. These numbers are a guide only – they’ll need further adjustment depending upon you riding, conditions and road surface.
You can run a slightly higher pressure in the rear tyre as you’ve got more weight over the back of the bike, and the front wheel is the one you really don’t want to slip out beneath you on a corner.
|All pressures are +/- 5psi, and expressed as front/rear||23mm dry day||23 wet or rough road surface||25mm dry day||25 wet or rough roads||28mm dry day||28 wet or rough roads|
|sub 50 kg||80/85||70/75||70/75||60/65||60/65||50/55|
|50 - 60 kg||90/95||80/85||80/85||70/75||70/75||60/65|
|60 - 70 kg||90/95||80/85||80/85||70/75||70/75||60/65|
|70 - 80 kg||100/105||90/95||90/95||70/75||80/85||60/65|
|80 - 90 kg||100/105||90/95||90/95||70/75||80/85||60/65|
|90 - 100 kg+||110/115||100/105||100/105||80/85||90/95||70/75|
Making adjustments: the basic principles
- Running pressure too low can result in punctures
- Running pressures too high will reduce grip and be less comfortable
- When road conditions are poor or it’s wet, you want lower pressures for a smoother ride and more grip
- The lighter the rider, the less they cause the tyre to depress against the road with their body weight, which is why lighter riders need to run lower pressures
- Racers should run slightly higher pressures, on narrower tyres – but not to an extreme, 25mm tyres are generally considered faster and more grippy than the traditional 23mm now
- If you’re riding sportives or commuting, a 25mm tyre is fine, but you probably want a lower pressure than a racer. You might find you get more stability and less fatigue with an even wider tyre – 26, 27 or 28mm – at a lower pressure
For more information on the basics of tyres, tubes and inflation, check out...