No matter what kind of vehicle you drive or which tyres you choose, vehicle efficiency and safety are affected by whether your tyres are correctly inflated.
If your tyres are under-inflated, their rolling resistance increases. This means they need more energy or fuel to make them turn. Think about how difficult it is to ride your bicycle with under-inflated tyres. Tyres that are underinflated can reduce fuel efficiency by up to 4% - this is like adding another 8 cents per litre to your fuel costs. In battery electric vehicles, higher rolling resistance will likely affect your range.
Your vehicle’s handling, cornering, acceleration, braking and wet grip are all impaired if your tyres aren’t inflated to the right pressure. If you have under-inflated tyres you’re more likely to have a dangerous blowout.
When your tyres are under-inflated, the contact patch with the road surface is concentrated towards the two outer edges of the tread. This leads to rapid wear on the shoulders, and reduces the life of your tyres.
Checking your tyre pressure
- Different vehicles need different levels of tyre pressure. You can find the correct pressure for your vehicle on a plate inside the driver's door, the fuel flap or in your vehicle handbook. You can also use our tyre pressure tool.
- Tyres lose air pressure naturally - about 1 to 2 psi per month (3 to 6%). Check your tyre pressure at least once a month and before long journeys.
- Check the pressure when your tyres are cold - so when you’ve travelled less than 3 km.
- Use the free pressure gauges available at most service stations, or there are a variety of affordable pocket gauges.
- Check the pressure in all four tyres and the spare.
Adding extra pressure
If you’re carrying a full load of passengers or towing a trailer or caravan, increase your tyre pressure in line with the vehicle manufacturer's recommendations. If your vehicle handbook doesn’t provide this information, a rule of thumb is to add 4 psi (28 kpa or 0.28 bar) to the recommended pressure.
When you’re checking the pressure, check the condition and tread depth of your tyres. Bulges, lumps or cuts are all signs that your tyre may need replacing. Although 1.5mm is the legal minimum tread depth, the grip of tyres in wet conditions reduces more rapidly once tread is below 3mm.
Tyre pressure monitors
In-vehicle tyre pressure monitoring systems are becoming more common in new cars. They monitor the amount of air in your tyres and alert you when the pressure falls below a certain level. Look out for this feature when you’re buying a car.
How to choose your tyre pressure
Getting the right tyre pressure is simple, right? Pump your tyres to the range recommended on the sidewall and away you go. Turns out it’s not quite that straightforward.
Your tyres do a lot of things. They grip the road so you can steer and go forward. On a road bike, they provide the only significant suspension, cushioning you from bumps and holes. They have to be tough enough not to puncture too easily, but thin and light enough to roll well. All these things are affected by pressure, as well as the design and construction of the tyre itself.
When you sit on a bike, your tyres compress. If they compress too much, they’ll writhe and squirm on the rims, making the bike harder to control, increasing rolling resistance and putting you at risk of pinch punctures. If they doesn’t compress enough, the ride will be harsh and there will be so little rubber on the road that grip will be reduced. Somewhere in between those extremes, there must be an ideal compromise. How do you find it?
The happy medium
As well as pressure, how much your tyres compress depends on your weight, so if there’s an optimum pressure it will depend on your weight and the type of riding you do.
Engineer Frank Berto, who investigated this issue for Bicycling magazine back in the late 1980s, came up with a formula based on the weight on each tyre(link is external); he reckoned that the happy medium involved a tyre being compressed 15 percent of its height.
As a recreational and touring rider, Berto was probably more interested in comfort than speed, so this idea is controversial, because Berto recommends lower tyre pressures than most of us use.
Tyre drop is hard to measure, but Berto did a shedload of measurements, and plotted the pressure needed to give a tyre drop of 15 percent for a range of rider weights and tyre widths. Here’s a graph of his recommendations, showing the relationship between pressure and wheel load for each common road bike tyre size.
There are two important things to bear in mind here. The first is that the tyre width is measured not claimed. When Berto originally did his work on tyre drop there was a big problem with tyre manufacturers mislabelling their tyres because the easiest way to claim you had the lightest 23mm tyre was to mark a 21mm tyre as a 23mm. That’s improved, but some tyres are still wrongly marked; I recently put calipers on a nominal 28mm tyre that turned out to be just 26mm wide.
The other is that wheel load is per wheel. If you weigh 72kg and your bike weighs 8kg, then your tyres carry a total of 80kg but it’s not evenly distributed. The rear wheel carries more of the load, usually between 55 and 65 percent.
To determine the right pressure, you’ll need to measure the load on each wheel. Put a bathroom scale under one wheel and enough wooden blocks, books or old magazines under the other to level the bike. Lean very lightly against a wall to steady yourself and sit in your normal position on the bike. Get someone else to read the scale for you. Repeat the process with the scale under the other wheel.
If your rear wheel is carrying 44kg and your front 36kg (a 55:45 weight distribution) and you’re running 25mm tyres, then reading from the graph tells you that you want about 90psi in the rear tyre and 70psi in the front.
That’s probably lower than you’re currently running, so think of it as a starting point from which you can tweak the pressure until you get a feel you like. If the pressure comes out well below the minimum recommended pressure of your tyre, then you can go skinnier; if it’s well above, then use a fatter tyre if your frame will accommodate one.
As I mentioned, this approach is controversial. Another engineer, the late Jobst Brandt, author of ‘The Bicycle Wheel’ wrote in a newsgroup posting(link is external): “What Berto did not seem to consider is that hard cornering and rough pavement require higher inflation than comfort or other considerations might demand. Banking over to a maximum lateral acceleration of about 1g is not something that works reliably with a comfortably inflated tyre, nor is encountering rough pavement with breaks and patches in the surface.”
Brandt was also sceptical about Berto’s notion that front and rear tyre pressures should reflect the loads on them. He wrote: “I run my tyres at the upper end of pressure because snake bites are always a threat on mountain roads. When descending with hard braking, the front wheel carries the entyre bicycle, with the back wheel at lift-off. The same is true climbing while seated on steep grades where front wheel rise is close at hand.”
More recently, Bicycle Quarterly magazine did some tests that revealed there was no speed advantage in pumping tyres up very hard. It was already known that when measured on a smooth drum rolling resistance didn’t decline much beyond a certain pressure. But as editor Jan Heine discusses here(link is external) Bicycle Quarterly ’s real-world testing indicates that when tyre pressures get too high, there’s no further reduction in rolling resistance. Heine believes that you lose the suspension effect of the tyres and that’s enough to push the rolling resistance back up.
Where does this leave you and me then? I think there are four take-homes:
If you ride in a leisurely manner — a short commute, gentle pootling around the lanes — then you can afford to run quite low pressures for comfort.
At the other extreme, don’t bother over-inflating your tyres for races and time trials. Unless the road surface is glass-smooth you won’t get any advantage, and let’s face it where are you going to find a road like that in the UK?
In between, you should tailor your tyre pressure to your riding style and roads. Ride in flat country and on smooth roads? Go for the lower end of the range between the Berto 15% drop figure and the range marked on your tyres.
In the hills I’d follow Jobst Brandt’s advice for equal pressures front and rear if you like to descend quickly. I love to go downhill fast (it makes up for the fact you need time-lapse photography to observe me climbing) but a front wheel impact puncture at 50mph is high on my list of things I’m not keen to try, along with BASE jumping and being visited in hospital by David Cameron.
If you're not a demon descender, you can run a softer front tyre for comfort.
For many of these situations, going up in tyre size is also a good idea. Our Mat Brett explored the reasons for fatter tyres in a Trendspotting piece last year. It’s a convincing case.
To set your tyre pressure right you’ll need a pressure gauge. Track pumps usually have one built in, but they’re often not very accurate, especially if the pump is a bit old and has been kicked around the workshop floor.
A standalone gauge, properly looked after, is a better alternative. If you can find a sturdy, metal-bodied analogue gauge, grab it but digital gauges like these are more convenient.
What are the recommended tyre pressures for best performance on road tyres?
It is now widely accepted that over inflation of your bicycle tyre actually reduces yours speed as it requires the tyre (and whole bike plus rider) to rise and effectively climb over every small bump on the road, whilst this skittish motion feels fast it is actually robbing your energy, where as a tyre at a lower pressure would deform over the bumps. This is obviously quite different to a velodrome where the varnished wooden surface is extremely smooth, so riders will use around 160psi, but on the road most pro riders are using around 90-110 psi. This deformation over the bumps obviously uses a small amount of energy in the tyre carcass but recent tests show that this is significantly less than the energy required to lift the rider over the many millions of small bumps on the ride. Of course, very low pressures of less than 70psi on the road will most likely also reduce performance, we tend to feel that as low as you can reasonably go without causing yourself lots of pinch flats is actually the best option. With these kind of pressures you also have much higher levels of grip so you can lead on the descents and corners, plus you'll suffer less fatigue and keep riding faster for longer.
Key information regarding tyre and rim heat build-up during long periods of rim braking
As rim braking is undertaken your kinetic energy is dissipated through heat between the brake pads and rims. This heat is then transferred to the air and tyre which are in contact with the rim.
The longer and heavier the braking the more heat is dissipated into the tyre.
Warm days obviously accentuate this problem as all components are warmer to begin with and they are less able to conduct the heat away as the differential in temperatures is much lower between air and tyre/rim. Hot road surfaces will also add to the problem.
As heat builds in the tyre, the air temperature in the inner tube/tyre rises and hotter air expands, this increases air pressure. If this continues it can reach levels that that tyre/inner tube are no longer able to cope with and thus they fail. A tubeless tyre can suffer the very same issues.
This is an issue that rim braked bicycle wheels of all kinds are susceptible to, and thus there are some reasonable precautions you should follow:
- Recommend max 110psi as it has been widely accepted now that slightly lower pressures actually reduce rolling resistance. With tubeless tyres we recommend that you do not exceed 100psi, and we regularly ride our 23-25mm road tyres at 80-90psi as the rolling resistance of tubeless road tyres is very low.
- Long descents and heavy braking carry inherent risks due to heat build-up on the braking surface, especially in hot weather. It is advisable, on all clincher or tubeless tyre systems, to drop your tyre pressure by 10psi from your normal setting. Please ensure you remain within the recommended pressure by the tyre manufacturer. This will improve grip and resistance to high- tyre pressures due to heat build-up from braking.
- Stop regularly during long & steep descents to allow your brakes to cool. If you suspect your rims are reaching high temperatures during braking it is essential to stop riding for a period and allow them to cool before you continue. This is a reasonable and sensible action that all wheel, tyre and bike manufacturers would suggest.
30CARBON AERO DISC, 50CARBON AERO DISC, 30CARBON GRAVEL DISC - ONLY APPLICABLE TO WHEELS PURCHASED BEFORE DEC 2017.
The above wheels feature H-Lock Wedge (HLW) rim sidewalls and so please see further down this page for applicable maximum tyre pressures as they are different from those listed below for the rest of our range.
PLEASE SEE BELOW FOR INFO APPLICABLE TO THE REST OF OUR RANGE OF WHEELS:
Standard clincher tyre with inner tubes. Maximum pressure for using our wheels with clincher tyres with inner tubes fitted is 120psi, however we believe best performance is achieved at below 110psi for all riders.
Recommended Pressures are slightly higher than tubeless to prevent pinch flats:
Tyre Size - Front Pressure - Rear Pressure
60kg Rider 23mm - 95/100 25mm - 90/95 28mm - 85/90
70kg Rider 23mm - 98/103 25mm - 93/98 28mm - 88/93
80kg Rider 23mm - 101/106 25mm - 96/101 28mm - 91/96
90kg Rider 23mm - 104/109 25mm - 99/104 28mm - 94/100
If you start getting snake bite style pinch flats raise the above values by 5 psi at a time.
Maximum pressure for using our wheels with tubeless tyres set-up tubeless is 100psi, however we believe best performance is achieved at below 100psi for all riders Recommended Pressures are lower than clincher to reach the lowest rolling resistance and obviously pinch flats are not an issue.
Tyre Size - Front Pressure - Rear Pressure
60kg Rider 23mm - 87/92 25mm - 82/87 28mm - 77/82
70kg Rider 23mm - 90/95 25mm - 83/88 28mm - 80/83
80kg Rider 23mm - 93/96 25mm - 88/93 28mm - 83/88
90kg Rider 23mm - 93/97 25mm - 90/95 28mm - 86/91
The above is a starting point and you should bear in mind other variables then tweak the pressures to suit you, your riding style, roads, specific tyres and bike:
- Rougher roads may require a slight reduction in pressure.
- Adding load to your or your bike may require some slight extra pressure in the tyres (use the rider weight as a guide).
- Some tyres, especially puncture protection tyres with heavy duty sidewalls, can be stiff and require slightly lower pressures.
H-LOCK WEDGE (HLW) SIDEWALL WHEELS
These wheels feature our Hunt H-Lock Wedge (HLW) sidewalls which are similar in design to those found on Enve SES AR4.5 Disc road wheels and Stans Avion Disc road wheels. The Hunt H-Lock Wedge sidewalls have stronger impact resistance and lock the bead in place whilst allowing the tyre to reach a wider overall size reducing rolling resistance and providing more grip.
Hunt HLW wheels are designed for wide versatility and are compatible with a large range of tyres from 25mm to 50mm, please use tyres specifically designated as TUBELESS or TUBELESS READY constructed with CARBON BEADS. These tyres have predictable bead diameters and a strong bead construction. You can use an inner tubes with these Hunt HLW rims as long as they are used in tubeless tyres. Tyres constructed with Aramid/Kevlar beads are not suitable for use with HLW rims.
Suitable tubeless road, gravel and CX tyres are available from a huge range of companies including Schwalbe, Hutchinson, Panaracer, Bontrager, Specialized, Maxxis, IRC and many more. The Schwalbe Pro One 25mm tyre weighs just 255g, is tubeless ready and is Schwalbe's class leading clincher racing tyre.
Maximum tyre pressure for Hunt HLW rims is 100 psi when used with 25-28mm tyres. 100 psi is more than enough for any rider on road. Click here to listen to a podcast exploring the science of why lower pressures were found to be faster by pro teams. Maximum tyre pressures for other tyre sizes 30mm do not exceed 70psi, 33mm do not exceed 50psi, 35-45mm do not exceed 40psi, 46mm+ do not exceed 35psi. Please do not exceed the maximum pressure stated on your tyre.
Why is it important to check your pressures regularly?
Correct tyre pressure is vital to your safety on the road. Under-inflated tyres affect handling and grip, potentially causing irregular or unpredictable vehicle behaviour. They are also much more likely to suffer from a dangerous sudden rapid deflation, especially on high-speed motorway journeys.
By keeping your tyres at their optimum pressure, your running costs are also reduced. Under-inflated tyres require a bigger force to make them turn, so your car uses more fuel. Additionally, tyres which are not set to their correct pressure wear out more quickly.
So, to benefit from lower fuel bills, longer tyre life, increased safety and reduced CO2 emissions, make sure you check your tyre pressures at least once a month and before a long journey.