Why tyre pressure matters for racing tyres – bar, psi and smart measurement on asphalt

Pressure that controls grip and temperature

Tyre pressure determines how much the tyre deforms and the size of its contact patch on the asphalt. Higher pressure generally produces a smaller contact patch and less deformation, affecting how quickly the tyre builds heat. Lower pressure increases the contact patch and deformation, which can speed up warm-up – but also allows more movement in the rubber. Both extremes cost grip over a session. The aim is an operating pressure that produces an even temperature distribution across the tread and consistent grip lap after lap.

Bar and psi – units you encounter in the paddock

Teams often work in both bar and psi. This makes it important to read, store and compare values in the unit used in the car, in the tyre supplier's documentation and on the tools in the paddock.

• Prisma HPM 5 offers a resolution of 0.001 BAR / 0.01 PSI and a pressure range of 0–7 BAR (100 PSI).
• HIPREMA 4 (both versions) has a measuring range of 0.0–5.0 bar with 0.1 bar resolution.

Tools that clearly display both bar and psi reduce the risk of misreadings and incorrect pressures.

Cold and hot pressures – the difference that guides setup

Cold pressures are the tyre pressures before driving, when the tyres have not warmed up. Hot pressures are the values the tyres stabilise at after running. The difference between cold and hot pressure is central to setup, as it reflects how much the tyre heats up and how the chassis, speed and weather affect pressure build-up.

• HIPREMA 4 stores cold and hot pressures, displays the difference immediately and records time/date/temperature. This makes it easier to identify the cold pressure needed to achieve the desired hot pressure in the next session.
• Prisma HPM 5 IR + tyre probe can store 4 or 8 tyre pressure readings (cold and hot) and link them to temperature measurements for a complete picture.

Driving in dry and wet conditions

Slicks on dry asphalt

Slicks have no tread pattern and support the car through a large, uniform contact patch. Tyre pressure affects how the shoulders and centre of the tread work against the asphalt. A balanced pressure helps the tread reach and maintain its operating temperature without overheating at the shoulders or cooling in the centre. Quick IR readings immediately after the in-lap provide a useful snapshot of surface temperature across the tyre.

Wet tyres in wet conditions

Wet tyres have a tread pattern to disperse water. Pressure choice affects how quickly the rubber reaches temperature and how effectively the tread pattern clears water. In rain, rapid warm-up and consistent water dispersal are often priorities, and wet tyres generally need a different pressure window from slicks. Combining IR surface readings with a probe in the rubber shows how the tyre's temperature actually develops through the tread.

Cold and hot weather

Ambient and track temperatures affect how much pressure rises during a run. Cool conditions can mean a slower build-up, while hot afternoons often produce a faster rise in temperature and pressure. Factoring in stint length also makes the cold-pressure plan clearer.

• Prisma HPM 5 can save both air and track temperatures in the same workflow as tyre pressure and pyrometer data. This makes comparisons between sessions and days easier.

Asphalt grip and track characteristics

High-grip asphalt puts heavy loads through the tread and often generates more heat, while low-friction surfaces require the tyre to work harder to find grip. Slow sectors with heavy braking produce different temperature profiles from fast, sweeping corners. This shows up in the pyrometer profile – for example, as warmer shoulders after a section of long, heavily loaded corners.

Measurement methods: IR versus tyre probe

• IR (infrared) gives a quick reading of tread surface temperature – useful as soon as the car comes in.
• A tyre probe measures within the rubber and helps reveal how heat penetrates it. This provides guidance on pressure, camber and how the tyre actually works under load.

Practical example: with a combined tyre pressure gauge and pyrometer, you can measure three points across the tread (inner/centre/outer) and compare them with the previous session. A hot shoulder edge may indicate that pressure or camber needs adjustment, while a cool centre may point to a pressure adjustment in the opposite direction.

Data workflow and decisions

• Measure and save cold pressures (bar or psi).
• Run the session.
• Measure hot pressures and temperatures using IR and/or a tyre probe at several points (inner/centre/outer) immediately after the in-lap.
• Compare the cold-to-hot pressure difference and the temperature profile across the tread.
• Record the data by track/session to find the right settings more quickly next time.

• HIPREMA 4 stores up to 50 measurements per race and displays the difference between cold and hot pressure directly on the screen.
• Prisma HPM 5 IR + tyre probe has a wireless app for export to Excel/PDF and Pit Stop Mode to save “Pit In” and “Pit Out” automatically.

Common pitfalls

• Changing pressure, camber and damper settings at the same time without logging them. Use memory modes and export functions for traceability.
• Taking temperature readings too late after the in-lap. Quick IR measurements provide more relevant values.
• Mixing bar and psi in your notes. Choose one primary unit and stick to it – or use gauges that clearly display both.
• Failing to account for weather and track temperature between sessions.

Tools for accurate measurement

• Tyre Pressure Gauge + Dual Pyrometer HIPREMA 4 IR+Probe – tyre pressure gauge with both IR and a tyre probe, stores cold/hot pressures with time/date/temperature, measuring range 0.0–5.0 bar, resolution 0.1 bar, maximum deviation 0.1%, IP55 and a backlit display with a light sensor. Stores up to 50 measurements per race.
• Tyre Pressure Gauge + IR Temperature HIPREMA 4 – tyre pressure gauge with IR temperature measurement in the same unit, measuring range 0.0–5.0 bar, 0.1 bar resolution, stores cold/hot pressures and the difference with time/date/temperature, IP55 and a backlit display. Stores up to 50 measurements per race.
• Tyre Pressure Gauge IR + Tyre Probe Pyrometer Prisma HPM 5 – 0.001 BAR / 0.01 PSI resolution, 0–7 BAR (100 PSI), measures 12 temperature points as well as air and track temperatures. Built-in IR with a 35° reading angle for quick measurements and a tyre probe for precise point measurements. Wireless app with export to Excel/PDF, Offset function and Pit Stop Mode.
• Tyre Pressure Gauge with Tyre Probe Pyrometer Prisma HPM 5 – combines a tyre pressure gauge and a probe pyrometer in one tool for pressure and temperature measurement.

Glossary

• Bar – a pressure unit commonly used in Europe.
• PSI – a pressure unit commonly used in English-speaking countries.
• Cold pressures – tyre pressures before driving, when the tyres have not warmed up.
• Hot pressures – tyre pressures after running, once the tyres have built temperature.
• Pyrometer – an instrument that measures tyre temperature, either at the surface (IR) or inside the rubber (tyre probe).