· 3 min read
Winter storage: six mistakes that damage a sports car standing still
Four months without turning a wheel can cost more than a season of track work. What really degrades, and what's just folklore.
A car that isn't driven doesn't wear out. That's false, and it's probably the belief that costs sports car owners the most between November and March.
Here's what actually degrades while the car stands still, in order of what it costs to put right.
1. Flat spots on semi-slicks
A soft-compound tyre left motionless for four months on a cold floor deforms at the contact patch. Semi-slicks such as AR‑1, R888R or Cup 2 are far more prone to it than road tyres, their compound being designed to deform when hot.
A light flat spot works itself out after a few miles. A settled one never leaves, and feels like an imbalance that no amount of wheel balancing will cure.
What works: over-inflate to 44 psi for the winter and move the car a quarter of a wheel turn once a month. What works better: put it on stands, wheels off the ground.
2. Brake fluid keeps absorbing water
This is the least intuitive one. Brake fluid is hygroscopic: it takes moisture from the air through the hoses and the reservoir whether the car is driven or not, at 2–3 % a year.
Fluid flushed in September, in a car that hasn't moved all winter, has lost a slice of its safety margin by April. Lower wet boiling point, from the first session back — the one where you're relearning the circuit and braking badly.
The full detail is in the brake fluid guide.
3. The battery, and what it takes with it
A deeply discharged battery permanently loses capacity. On a modern car, the standby draw of the ECUs will flatten one in five to eight weeks.
A maintainer — not a charger, a maintainer, which regulates — costs less than a battery and incidentally saves you losing engine adaptations and radio codes.
4. Moisture, inside and in the fluids
An unheated garage condenses on cold surfaces: discs, chrome, the inside of the exhaust. Discs surface-rust within days — that comes off on the first braking, harmlessly — but corrosion of the hat and the calipers settles in.
Used engine oil holds acids from combustion. Leaving it four months in the sump attacks the bearings. Change the oil before storage, not after: the opposite of what most people do.
5. Fuel, but not the way you think
Petrol degrades in three to six months, especially with ethanol (E10). The real risk isn't "stale fuel", though: it's condensation in a half-empty tank, which puts water into the system.
So: full tank, less air, less condensation. A stabiliser is worth it beyond six months.
6. The handbrake left on
On a car left with the handbrake applied for months, pads can bond to the disc — especially if it was put away with the discs still damp. You pull away and tear the friction material off.
Leave it in gear, with chocks under the wheels. Never on the handbrake.
What's folklore
"Start it up once a month." Standing still, the engine never reaches operating temperature. You generate condensation in the exhaust and the sump without ever driving it off: worse than doing nothing. Either drive it for twenty minutes and get everything hot, or don't start it.
"A cover protects it." A non-breathable cover traps moisture against the paint. Indoors, use a cotton sheet; outdoors, a breathable cover or nothing.
Coming back, in March
Before the first outing: pressures and flat spots, brake fluid level and colour, battery voltage, caliper play and leaks, the date of the last flush. Then a first session without chasing a lap time — the tyres and you have both lost your touch.
StemmaPass handles this for you. Winter mode triggers itself when the car stops being driven, reminds you of what degrades while standing rather than by distance, and produces a spring restart checklist — for your car, with the real date of your last flush and the state of your consumables, not a generic list.