Tyres and tyre pressure
Tyres are the cheapest change that transforms how a bike rides, and the component most people leave alone for years.
If you change one thing on a bike, change the tyres. They are the only part touching the road, they determine grip, comfort, rolling speed and puncture resistance, and a good set costs less than almost any other upgrade.
They are also where the most persistent myth in cycling lives: that harder tyres are faster. For decades riders pumped tyres to the maximum printed pressure believing it reduced rolling resistance. On real road surfaces the opposite is usually true.
Reading a tyre sidewall
Every tyre carries its size and pressure range moulded into the sidewall. You will see something like 700x28c or 27.5×2.1.
- 700c / 29in — the standard large wheel on road, hybrid and many mountain bikes
- 650b / 27.5in — a smaller diameter used on gravel bikes and many mountain bikes
- 26in — older mountain bikes and small-frame bikes
- The second number is width: 28c means 28mm; 2.1 means 2.1 inches
What width should you run?
Wider tyres have won the argument over the last decade. Where 23mm was standard on road bikes, 28mm to 32mm is now normal, and the reason is that a wider tyre at lower pressure deforms less over surface roughness, wasting less energy.
| Riding | Common width | Why |
|---|---|---|
| Road, smooth tarmac | 25–28mm | Fast without being harsh |
| Road, poor surfaces | 30–35mm | Comfort and fewer pinch flats |
| Commuting | 32–40mm | Puncture protection and pothole tolerance |
| Gravel | 38–50mm | Grip on loose surfaces |
| Mountain, cross-country | 2.1–2.4in | Traction without excess weight |
| Mountain, trail | 2.4–2.6in | Maximum grip and cushioning |
Check clearance before buying wider. The tyre must not touch the frame, fork or mudguards. A rough test: you should fit a coin edge-on between tyre and frame at the tightest point.
Tyre pressure: the part people get wrong
The number on the sidewall is a range, and the top of that range is a safety limit, not a recommendation. Correct pressure depends mostly on two things: how much weight the tyre carries, and how wide it is.
Too hard and the tyre skips over bumps instead of absorbing them — slower, harsher and less grip. Too soft and you risk pinch punctures and sluggish handling.
| Tyre width | Starting pressure | Notes |
|---|---|---|
| 25mm | 80–90 psi | Reduce for rough roads |
| 28mm | 70–80 psi | The modern road default |
| 32mm | 55–65 psi | Commuting sweet spot |
| 40mm | 40–50 psi | Gravel and towpaths |
| 2.2in MTB | 22–26 psi | Lower for loose or wet trails |
| 2.4in MTB | 20–24 psi | Tubeless only below about 22 psi |
How to actually find your pressure
Start in the middle of the range for your width and weight. Ride your usual route. If the bike feels harsh and skittish, drop 5 psi and try again. If you feel the rim through big bumps or the tyre squirms in corners, add 5 psi. Two or three rides will get you closer than any chart.
When to replace a tyre
- The tread centre has gone flat or square instead of round
- You can see the casing threads or a different-coloured layer beneath
- The sidewall is cracked, cut, or bulging anywhere
- You are getting repeated punctures with no cause found in the tyre
- Any cut deep enough to reach the casing — a boot is a get-home fix, not a repair
A bulging sidewall is an emergency, not a maintenance item. It means the casing has failed and the tube is pushing through. That tyre can blow out without warning. Replace it before riding again.
Tubes, tubeless and what the fuss is about
Inner tubes are simple, cheap and repairable at the roadside. For most riders they remain the sensible default.
Tubeless removes the tube and seals the tyre against the rim with liquid sealant that plugs small punctures as they happen. It allows lower pressures without pinch flats and is genuinely better off-road. The trade-off is a messier, fiddlier setup and sealant that dries out and needs topping up every few months.
If you ride mostly on road and puncture rarely, tubes are fine. If you ride trails or gravel and puncture often, tubeless is worth the hassle.
Three things that make tyres last
Check weekly
All tyres lose pressure gradually — narrow ones fastest. A weekly check with a gauge takes a minute and prevents most pinch flats.
Inspect while you check
Run a thumb round the tread looking for embedded flint and glass. Picking one out early prevents the puncture it would have caused.
Rotate if you like
The rear wears roughly twice as fast. Some riders move a part-worn front to the rear; there is no harm in it, but never move a worn rear to the front.
Common tyre questions
Up to a point, yes, and unusually for cycling the difference is measurable. Better tyres use suppler casings that roll faster and grip more, and better puncture belts. The gains flatten out well before the most expensive options.
Almost always something still embedded in the tyre, or rim tape that has shifted and is exposing a spoke hole. Check both carefully before blaming the tubes.
Yes, and some riders deliberately run a slightly wider front for grip. Keep both within your frame clearance and adjust pressure separately.
A little. A heavy protection belt adds weight and stiffness. For commuting that trade is usually worth it; for fast weekend riding it usually is not.
Very roughly 3,000–5,000km for a rear and double that for a front, but it varies hugely with surface, weight and compound. Judge by wear and damage, not mileage.
Got a flat right now?
The puncture repair guide walks through the whole roadside fix in eight steps.