In short. Before a track day, check three things that organisers rarely spell out: tyre pressures set by the tyre maker's track procedure and not by guesswork, brake fluid that is fresh and has a boiling point well above the legal minimum, and wheel nuts tightened to your car maker's torque with a torque wrench and checked again during the day. Tyre makers who publish track advice tell you to start at the car maker's road pressures, adjust only when hot, and go back to the road pressures once the tyres have cooled. Before you drive home, the tyres must still meet your country's road rules: 1.6 mm of tread in the UK, 1.5 mm in Australia, and in the US whatever your state sets (Pennsylvania's inspection, for example, rejects less than 2/32 in).
What the organiser checks, and what it leaves to you
Organisers write short lists. The UK organiser MSV Trackdays asks that a road car meet "MOT minimum standards for road use", that tyres be in good condition with pressures checked, that brakes have "plenty of wear left on the pads and discs", and that the towing eye be fitted before the sighting laps (MSV Trackdays). It also asks you to remove everything loose from the car, sometimes the spare wheel too, and to switch off the car's emergency e-Call feature for the day. In the US, the Porsche Club of America's advice to driver education participants adds a torque wrench, a tyre gauge, spare pads if yours are near half worn, and spare brake fluid for a multi-day event (PCA).
None of this says which pressure to aim for, at what temperature a fluid boils, or when to check the nuts. Those answers are in the makers' documents.
| Item | What the organiser or club asks | What the maker documents add |
|---|---|---|
| Tyres | Good condition, pressures checked, warm them up (MSV) | Start at the car maker's road pressure, adjust hot, reset cold before the road (Michelin, Pirelli) |
| Brake fluid | Spare fluid for multi-day events (PCA) | Boiling points by grade (FMVSS 116); change interval per the car maker (ATE) or 2 to 3 years (Brembo) |
| Pads and discs | Plenty of wear left, check through the day (MSV); spares if near 50 % (PCA) | Disc below its stamped minimum thickness fails a US state inspection (Pennsylvania) |
| Wheel nuts | Torque wrench in the kit (PCA) | Car maker's torque, crosswise, in stages, verify after 50 to 100 km (EUWA) |
| Wheels and kerbs | Not mentioned (MSV); take the plastic caps off locking nuts (PCA) | Repeated kerb strikes can damage the tyre and its carcass: inspect after each run (Michelin) |
Comparison compiled by the Onyx Forged design office from the pages listed under Sources, read on 16 October 2026.
Tyres: the pressure procedure
Start at the road pressure, adjust only when hot
The two tyre makers whose track tyre pages we read give the same structure. Michelin, for the Pilot Sport Cup 2 R, says to begin with the inflation pressures recommended for road use, bring the tyres up to temperature, and "after a steady run of laps, check and only then adjust" (Michelin). Pirelli, for the P Zero Trofeo R, says to start at the vehicle maker's pressures, run a warm-up of about 20 km (the distance depends on the car and track), then check and reset if over the target, at each stop (Pirelli).
Michelin also publishes figures for that tyre: a best operating pressure between 2.3 bar (33 psi) and 2.7 bar (39 psi) hot, depending on car and track, with some cars needing more; it does not recommend running below 1.9 bar (28 psi) cold, and for track longevity it strongly recommends a cold minimum between 2.0 bar (29 psi) and 2.4 bar (35 psi). These figures are for one tyre. Other tyres have their own data, and the car maker's own track advice, where it exists, comes first. The road pressure for your car is on the door pillar or in the handbook: see our guide to tyre pressure.
Why a hot reading is a different number: our calculation
At a roughly constant volume, the absolute pressure of the air in a tyre (the gauge reading plus atmospheric pressure, 1.013 bar) rises in proportion to its absolute temperature. Applied to Michelin's figures, with the tyre set cold at 20 °C:
| Set cold | Reading hot | Air temperature this implies |
|---|---|---|
| 2.0 bar (29 psi) | 2.3 bar (33 psi) | about 49 °C |
| 2.0 bar (29 psi) | 2.7 bar (39 psi) | about 88 °C |
| 1.9 bar (28 psi) | 2.3 bar (33 psi) | about 60 °C |
| 1.9 bar (28 psi) | 2.7 bar (39 psi) | about 100 °C |
Calculation by the Onyx Forged design office: T hot = 293.15 K × (p hot + 1.013) / (p cold + 1.013). Volume is assumed constant; real tyres grow slightly, so this is an order of size, not a measurement. None of the sources we read publishes air temperatures inside a tyre on track.
The calculation shows the trap. Suppose a tyre set at 2.0 bar cold reaches 2.7 bar hot and you let air out until it reads 2.3 bar, inside Michelin's hot window. Once it cools back to 20 °C, the same arithmetic gives about 1.68 bar (24 psi), below Michelin's 1.9 bar cold floor. Our reading: a hot bleed serves the session, but the tyre must not be left at that setting. Both makers' instruction to let the tyres cool and reset them to the car maker's pressures before you leave the circuit closes that gap, and the same cold check before the next day's first session avoids starting below Michelin's cold floor.
The Porsche Club of America's rule of thumb, about one pound per 10 degrees, holds if the degrees are Fahrenheit: for a tyre at 32 psi, 10 °F gives 0.88 psi by our calculation. The 5 to 10 lb gain it reports over a day means air 31 to 63 °C (57 to 113 °F) warmer.
Read the tyre, not only the gauge
Michelin says that wear reaching the sidewall markings is a sign the pressure is too low, and to raise it by at least 0.2 bar (3 psi). It gives a camber range for circuit use of -1.5 to -3 degrees, not more than -4, and says camber for road use must go back to the recommended road settings. Our guide to tyre wear patterns shows how to read shoulder and inner-edge wear.
Brakes: fluid, pads and discs
Why fluid matters more on track
Brake fluid absorbs water over time, and water lowers its boiling point. Brembo explains the consequence, which it calls vapour lock: the fluid boils under heavy braking, the vapour bubbles compress, and the pedal goes soft or, in severe cases, to the floor (Brembo). A track session puts far more heat into the brakes than road driving, which is why the boiling point matters here more than anywhere.
What the law sets, and what one maker publishes
In the US, the federal standard for brake fluid, FMVSS 116, sets minimum boiling points for each grade, dry and "wet". The wet figure is measured after the fluid has been humidified until a reference fluid beside it reaches 3.70 per cent water (49 CFR 571.116, S5.1 and S6.2). The container must state the grade and the minimum wet boiling point. Bottles sold outside the US can carry the same grades: ATE's flyer gives, for each fluid, its FMVSS 116 grade and its ISO 4925 class.
| Fluid | Grade | Dry boiling point | Wet boiling point | Margin over the grade minimum (dry / wet) |
|---|---|---|---|---|
| FMVSS 116 minimum | DOT 3 | 205 °C | 140 °C | — |
| FMVSS 116 minimum | DOT 4 | 230 °C | 155 °C | — |
| FMVSS 116 minimum | DOT 5 and 5.1 | 260 °C | 180 °C | — |
| ATE SL | DOT 4 | min. 260 °C | min. 165 °C | +30 / +10 °C |
| ATE SL.6 | DOT 4 | min. 265 °C | min. 175 °C | +35 / +20 °C |
| ATE TYP 200, "racing quality" | DOT 4 | min. 280 °C | min. 198 °C | +50 / +43 °C |
| ATE SUPER DOT 5.1 | DOT 5.1 | min. 265 °C | min. 180 °C | +5 / 0 °C |
Sources: FMVSS 116, S5.1.1 and S5.1.2; ATE brake fluids flyer 2025. Margins calculated by the Onyx Forged design office.
Two points follow. A grade on the bottle tells you a floor, not the fluid's real boiling point: two DOT 4 fluids from the same maker differ by 20 °C dry and 33 °C wet. And a "higher" grade number does not always boil later: ATE's DOT 4 racing fluid has a higher wet minimum than its DOT 5.1.
Which fluid your car may take is the car maker's call. ATE says to follow the vehicle maker's instructions and to change the fluid at the maker's intervals; Brembo says to consult the maintenance manual, and generally recommends replacement after 2 to 3 years for road cars. FMVSS 116 requires every bottle to carry the warning to follow the vehicle maker's recommendations when adding fluid. The standard requires DOT 5 to be labelled "silicone base" and DOT 5.1 "non-silicone base", so the two are not the same fluid despite the number: use only what the car maker specifies. Fluid older than its interval is the first thing to change before a track day; a fluid change involves the brake system, so have it done by someone qualified if you are not.
Pads and discs
MSV asks for "plenty of wear left" and suggests checking the brakes occasionally during the event; the PCA suggests bringing spare pads if yours are near 50 per cent. As a reference for what an inspector rejects, Pennsylvania's state inspection fails a disc below the minimum thickness stamped on it or the maker's figure, and bonded linings under 2/32 in at the thinnest point (67 Pa. Code § 175.80). Measure before the day, against the figure stamped on the disc or in the car maker's data; if the wheels come off for it, the car goes on axle stands, never on the jack alone. New pads fitted for the day need bedding in first: see bedding in brake pads.
Two habits from the PCA page: do not park with the handbrake on (it can stick to a hot drum), and use the cool-down lap to let the engine and brakes cool, braking as little as possible. MSV advises sessions of 15 to 20 minutes, after which, it says, "everything starts to overheat".
Wheels and wheel nuts
Torque: the car maker's figure, and a second check
There is no track torque. The figure is the car maker's: Porsche, for example, gives 160 N·m (118 lb ft) for the wheel bolts of the 911 (992) and 600 N·m for its central lock (Porsche bulletin 38/25). EUWA, the European wheel makers' association, asks for that figure, a torque wrench, progressive tightening "not in one go", a crosswise sequence, and a check after about 50 to 100 km on a new car and after every wheel or tyre change (EUWA ES 1.07, 3.5 to 3.7). The PCA page quotes a "typical" figure in foot-pounds; ignore any typical figure and use the one for your car. Our guide to wheel nut torque explains why friction, oil and seat type change the clamp load.
What we could not find: a wheel maker's or car maker's document that sets a re-check interval per track session. Many drivers check torque between sessions; EUWA's 50 to 100 km is the only distance we found in writing, and a track day often covers more than that. Our reading, not a maker's rule: the car maker's figure is meant for a cold joint, so a check on hot wheels shows whether a nut has moved, not a new figure to tighten to. If a nut has turned, find out why before going back out, and have it checked if in doubt.
Locking nuts, caps and kerbs
The PCA advises taking the plastic caps off locking nuts before a track day, because they can melt, and says standard nuts are preferable to locks for the day. If you keep locks, bring the key. Michelin warns that running over kerbs repeatedly can damage the tyre and its carcass, asks for a visual check after each run, and, after prolonged kerb strikes or a heavy off, recommends having the tyre demounted and inspected inside and out. A wheel that has hit a kerb hard deserves the same attention: look for cracks or a bent rim flange, and have it checked before you drive on the road.
Load, weight and clearance
A road wheel is marked with its load rating and the standards it was designed to; our guide to wheel markings shows where to read them. We did not find a published standard for road wheels that defines a track test, so we cannot tell you what margin a road wheel keeps on a circuit; ask the wheel's maker. If you fit larger brakes for track use, the wheel has to clear the caliper: see brake caliper clearance. What lighter wheels change is covered in our guide on unsprung weight.
The drive home: road rules by country
Michelin and Pirelli both say the same thing before leaving the circuit: let the tyres cool, reset to the car maker's road pressures, and check the remaining tread against the legal minimum. Michelin adds that you should switch the electronic aids back on and reset the tyre pressure monitoring system; MSV asks you to switch e-Call back on.
| Country | Minimum tread for the road | Text |
|---|---|---|
| UK (Great Britain) | 1.6 mm across the central three-quarters of the tread, all round | Construction and Use Regulations 1986, reg. 27 |
| US | Set by each state; Pennsylvania's inspection, for example, rejects less than 2/32 in in two adjacent grooves, and any tyre marked "for racing purposes only" | 67 Pa. Code § 175.80 |
| Australia | 1.5 mm in all principal grooves, across the contact width and round the whole circumference | Australian Light Vehicle Standards Rules 2015, rule 52 |
| Canada | Set by each province; we did not read the provincial texts for this guide | Pirelli's own guidance gives 1.6 mm / 2/32 in |
Table compiled by the Onyx Forged design office from the texts linked, read on 16 October 2026. US states set their own rules; check yours.
Check the depth before you leave the circuit, not at home. A tyre that is corded, blistered or cut is not one to drive home on; if in doubt, have the car trailered or have the tyre checked before taking the road. Whether a track tyre is road legal at all is covered in semi-slick tyres and the road.
Your checklist
The week before
- Brake fluid within its change interval, of a grade the car maker allows; consider a fresh fill.
- Pads with plenty of wear left; discs above their stamped minimum thickness.
- Tyres: condition, age, tread, and the tyre maker's track procedure printed or saved.
- Wheels: no cracks or bent flanges; locking nut key located; plastic caps removed.
- Towing eye found.
On the day
- Cold pressures at the car maker's road values; tyre gauge and torque wrench in the kit.
- Warm-up laps, then check and adjust hot, per the tyre maker.
- Wheel nuts checked to the car maker's figure; anything that moved investigated.
- After each session: a cool-down lap, no handbrake, a look at tyres (shoulder marks, kerb damage) and at the brake pedal feel.
Before the road
- Tyres cooled, pressures back to the car maker's road values.
- Tread above the legal minimum where you live.
- Electronic aids, TPMS and e-Call back on.
If the pedal went long or soft during the day, do not drive home on it: have the brakes checked first.
Frequently asked questions
What tyre pressure should I run on a track day?
Start at your car maker's road pressures, then follow the tyre maker's track procedure: warm the tyres up, check hot, and adjust. Michelin gives 2.3 to 2.7 bar (33 to 39 psi) hot for the Pilot Sport Cup 2 R and not below 1.9 bar (28 psi) cold; other tyres have their own figures. Reset to road pressures once cool.
Should I let air out when the tyres are hot?
Only towards the tyre maker's hot target, as Michelin and Pirelli describe. Remember that a tyre bled hot will read much lower once cold: by our calculation, 2.3 bar at about 88 °C becomes about 1.68 bar at 20 °C. Reinflate before the road.
What brake fluid is best for track days?
The one your car maker allows, fresh, and with a high boiling point. The legal minima under FMVSS 116 are 230 °C dry and 155 °C wet for DOT 4; ATE's racing DOT 4 publishes 280 °C and 198 °C. The grade on the bottle is a floor, so compare the published figures.
Do I need to re-torque wheel nuts during a track day?
EUWA asks for a torque check after about 50 to 100 km after any wheel change; we found no maker document with a per-session interval. Check with a torque wrench to the car maker's figure, and if a nut has moved, find out why before going back out.
Can I drive home on track tyres?
If they are road legal and still above the legal tread depth: 1.6 mm in the UK, 1.5 mm in Australia, and your state's figure in the US (2/32 in in Pennsylvania). Pennsylvania's inspection rejects tyres marked "for racing purposes only". Let them cool and reset the road pressures first.
Should I take locking wheel nuts off for a track day?
The PCA says standard nuts are preferable and that the plastic caps on locks can melt. If you keep them, bring the key and tighten them to the same figure as the other nuts, with a torque wrench.
Wheels made for your car
Onyx Forged is a French brand of made-to-order forged wheels, designed to JWL/VIA standards. Onyx Forged does not recommend a size or an offset: the reference is your car maker's documents, and you can describe your car and design a set.
Sources
- Michelin, Pilot Sport Cup 2 R, recommendations for use; Pirelli, P Zero Trofeo R, product sheet.
- 49 CFR 571.116, FMVSS No. 116, motor vehicle brake fluids, S5.1, S5.2.2 and S6.2.
- ATE, brake fluids flyer 2025 and brake fluids page; Brembo, brake fluids for cars.
- EUWA, ES 1.07 (June 2020), sections 3.5 to 3.7; Porsche AfterSales, bulletin 911 (992) 38/25 (7 October 2025).
- MSV Trackdays: FAQ for booked drivers and FAQ for new drivers; Porsche Club of America, tips and techniques for DE participants.
- The Road Vehicles (Construction and Use) Regulations 1986, regulation 27; 67 Pa. Code § 175.80; Australian Light Vehicle Standards Rules 2015, rule 52.
All pages were read on 16 October 2026.
The Onyx Forged design office.