The air in the tyre carries the bike and the load. Too little air makes steering heavy, wears the tyre edges, heats the tyre and can let it come off the rim. Too much air makes the tyre hard, wears the centre and reduces grip. Check both tyres at least once a week, before a long trip and before you carry a passenger or a heavy load.
Safety
- Check with the tyres cold. A tyre that has just been ridden reads high. Never let air out of a hot tyre to reach the cold value.
- Stand clear of the valve when you use a high-pressure compressor. Fill in short bursts and check often.
- Never inflate above the maximum pressure moulded on the tyre sidewall.
You need
- A tyre pressure gauge you trust. Compare it with a second gauge now and then: roadside and fuel station gauges are often wrong.
- A pump or compressor with a chuck that fits the valve.
- A valve cap for each valve. The cap keeps dirt out of the valve core and is a second seal.
Steps
- Find the correct pressures. Look on the label on the chain guard, swingarm or under the seat, or in the owner's manual. Some bikes give a higher rear value for a passenger or load.
- Use the value for your bike. For reference, K-Light 125: front 190 ± 10 kPa, rear 210 ± 10 kPa, cold (about 1.9 and 2.1 bar, or about 28 and 30 psi). Do not use these numbers on another bike.
- Turn the wheel so the valve is easy to reach. Remove the cap.
- Press the gauge straight onto the valve, quickly and firmly, so no air hisses out. Read the value.
- If it is low, add air in short bursts and measure again. If it is high, press the valve core pin briefly with the back of the gauge and measure again.
- Repeat on the other tyre.
- Refit both caps, finger tight.
Check your work
- Both tyres are at the value for your bike and load.
- No hiss from the valves. Put a drop of soapy water on the valve tip: it should not bubble.
- Check again the next morning. If a tyre has dropped noticeably, there is a leak.
If it did not fix the problem
- Tyre keeps losing air: go to Tyre slowly loses air.
- Air escapes at the valve: Check and replace a tyre valve.
- Pressure is correct but the bike still feels wrong: Inspect tyres for wear and damage, then Bike pulls to one side or Steering feels heavy.
Reference values (K-Light 125)
| Item | Value | Source |
|---|---|---|
| Front tyre 90/90-17, cold | 190 ± 10 kPa | K-Light 125 manual, PDF p. 71 |
| Rear tyre 130/90-15, cold | 210 ± 10 kPa | K-Light 125 manual, PDF p. 71 |
| Check interval | At every scheduled service | K-Light 125 manual, PDF p. 51 |