Riding at -5 °C: what actually changes on the bike

The same bike at 12 °C and at -5 °C does not behave in the same way. The rear derailleur refuses to drop onto the big sprockets, the freehub makes a soft rattling noise and sometimes lets go under load, the brake lever is hard for the first three pulls, and if you are on an e-bike the range on the display is a polite lie. None of that is a breakdown: they are components working outside their comfortable temperature range.

There is nothing mysterious about any of it. It is viscosity, a bit of thermodynamics, and the chemistry of road salt. Here is what changes item by item, in the order you will feel it over the first ten kilometres, and what to adapt so you do not spend the winter repairing things.

What the cold changes, item by item

Stiffened grease: the freehub that slips

This is the signature hard-frost failure, and it is frightening because it happens out of the saddle: you push, the pedal drops away into nothing, and you land on the frame. The culprit is the freehub body in the rear hub. The pawls are held out by small springs, and if the grease around them is too thick when cold, it stops them lifting fast enough to engage. The mechanism clicks, but no longer drives.

• The real cause is almost always grease that is too heavy: either a thick assembly grease put there for convenience, or old grease emulsified with water after months of rain.
• Correct practice depends on who made the hub. Some specify a thin oil in the freehub body, others a very fluid dedicated grease. Do not decide by feel: this is one of the rare places where "a good dollop of grease" makes things worse.
• The other greases stiffen too, but without dramatic consequences: headset, wheel bearings, dropper post whose return speed collapses. A bike that seems to be braking on its own for the first two kilometres is exactly that.

Cables and outers: water freezing inside

A derailleur that will not drop at -5 °C when it worked the day before is not an adjustment problem. It is water that got into the outer in the autumn and froze overnight. The inner cable is locked in a plug of ice and the derailleur spring no longer has the force to pull it back.

The fix is upstream, not at the roadside:

• Continuous, sealed outers on exposed runs, with ferrules and seals, rather than open sections that act as funnels.
• Replacement in autumn rather than in spring. A set of cables and outers costs £18 to £35 and takes an hour to fit; it is the most profitable job on the bike before winter.
• Cable-operated rear brake: same mechanism, with a genuine risk attached. If the cable stays stuck in the pulled position, you set off with a brake that is dragging.
• A bike brought into a heated room in the evening dries its outers out and the problem disappears. A bike that sleeps outside under a cover accumulates it.

Tyres: you really are losing pressure

It is not an impression. Tyre pressure follows the absolute temperature of the gas. Between inflating in a warm garage at 18 °C and riding out at -5 °C, you lose around 7% of the absolute pressure. In practice:

• a road tyre at 6.5 bar drops to about 5.9 bar;
• a mountain bike tyre at 2.2 bar drops to about 1.95 bar;
• a cargo e-bike tyre inflated to 4 bar goes down to about 3.6 bar.

On high-volume tyres that loss is rather good news for grip. On a narrow tubeless tyre it takes you dangerously close to the point where the bead unseats. The habit to build: check pressure outside, cold, and not as you wheel the bike out of the garage. And accept running 0.3 to 0.5 bar below your summer pressure on cold wet roads, to grow the contact patch. Compound choice matters at least as much as pressure, and it is covered in our comparison of bike tyres in cold weather.

Brakes: hard lever, delayed bite

On a hydraulic disc brake, the fluid thickens. The lever becomes firmer, the pistons retract more slowly into the caliper, and it is not unusual to hear the pads rubbing for the first few minutes. That is not a bleeding fault, it is viscosity. It clears as soon as the calipers warm up.

Two things not to confuse:

• Water in DOT fluid does not form a plug of ice. It is dissolved, and its effect lies elsewhere: it lowers the boiling point. That is a long-summer-descent problem, not a winter-morning one. It is still no excuse for skipping the fluid change interval.
• Rim brake pads, on the other hand, really do suffer. On a frosted or salted rim, allow one to two wheel revolutions before any real bite. Brake early, and give a test squeeze at the top of a descent.

Cold pads bite less, whatever the system. The first emergency stop of the ride does not happen in the same place as it does in July.

E-bike: the battery is the most sensitive part

A lithium-ion battery does not lose its capacity in the cold, it loses its usable capacity: internal resistance rises, voltage sags under load, the controller cuts out sooner. Between 20 °C and 0 °C, expect 20 to 40% less range depending on the pack and the power being asked of it. The range display does not know that in advance, and tells you after the event.

• Never charge a pack that has just come in from the cold. Below 0 °C, charging a lithium-ion cell plates metallic lithium onto the anode: it is irreversible, it eats into capacity and it degrades the safety of the pack. Let the battery come back to room temperature for one to two hours before plugging it in.
• Carry the pack indoors when you leave the bike outside during the day. A neoprene cover limits heat loss, but warms nothing up.
• Long lay-ups: store at around 40 to 60% charge, in a frost-free room, and check it every two to three months. The detail is in our article on e-bike range in cold weather.

Salt: the corrosion works while you sleep

Road salt does not rust your bike during the ride: it does it over the following 48 hours, by keeping a conductive film of damp on every surface. The points of attack are always the same: chain and inner links, cables where they exit the outer, spoke heads, steel bolts in aluminium threads, e-bike electrical connectors and lower fork legs.

Two actions are enough, and they do not take ten minutes:

• Rinse with lukewarm water at low pressure, never with a pressure washer near the bearings. Then dry, with a cloth or by riding for two minutes.
• Re-lube the chain after every wet ride. In winter a wet lube holds up better than a wax, which goes brittle and disappears into slurry. Reckon on re-lubing every 100 to 150 km, or after every salted ride. The full method is described in protecting your drivetrain from salt and rain.

The winter routine that holds

Nothing above needs special tools. In order, before the first frosts:

1. New cables and outers, ferrules and seals in place. £18 to £35 and an hour.
2. Check the lubrication of the freehub body against the hub manufacturer's specification, not against habit.
3. Switch to a wet lube for the chain and put the wax bottle away until March.
4. Check pressures outside, not in the garage, and drop them slightly on cold roads.
5. Clean and grease the electrical contacts on the e-bike, and bring the pack indoors every evening.
6. Get into the rinse-and-dry habit after every salted ride, even a rushed one: two minutes beats nothing.

The point that trips people up most often is the third one: which oil or which grease in which hub, and at what torque for the cone or the end cap. That depends on the exact model, and a generic figure does not help. L'Atelier's technical assistant gives you the manufacturer's specification from the make, model and year of your bike, bearings and drivetrain included.