Grip is something you have to estimate
A bike stays upright and under control because the tyres grip the ground. Where grip drops, a wheel can slide with very little warning, and a bike has only two small contact patches, so a slide often ends in a fall. You cannot measure grip by looking, but you can look for clues that suggest it may be low, then adjust before you reach the spot.
This article is about spotting the clues. How tyres and rain interact is covered in tyre tread and grip, and how to ride in rain generally is in riding in the rain. Here the focus is on what the surface itself is telling you.
Clues worth learning
Wet leaves. Fallen leaves, particularly wet ones, can form a slick layer, often hiding what is underneath. They tend to collect on corners, in gutters and on shaded paths, and can mask potholes or kerbs.
Metal. Manhole covers, drain gratings, tram or rail tracks, bridge expansion joints and steel plates over roadworks can be slippery, especially when wet. Rails and grooves can also catch a narrow tyre if crossed at a shallow angle, so they are generally best crossed upright and as close to square-on as is practical.
Painted markings. Road paint, including crossings, arrows, bike symbols and thick lines, can be slick in the wet. They often sit exactly where you brake or turn, so be gentle on them.
Shiny or dark patches. A glossy sheen on the road can mean wet, polished surface or oil. Dark, glossy streaks near junctions or at bus stops may be fuel or oil spills. Patches that look different in colour or texture from the road around them deserve respect.
Smooth, polished surfaces. Some paving, tiles, wooden boards and painted floors become very slippery when damp. Boardwalk decks are a good example, and boardwalk riding discusses them in more detail.
Mud and wet grass. Mud, wet grass and clay can be unpredictable. Wet clay in particular can be very low in grip. Riding across mud on the edge of a path or a verge is often slicker than it looks.
Frost, ice and snow. Cold, clear mornings can bring ice that is hard to see, especially in shaded spots, on bridges and in low areas. Black ice looks like ordinary wet tarmac. In winter conditions, assume that shaded or damp patches may be frozen, and see snow and ice riding for more on this.
Cobbles and stone. Cobbled streets can be uneven and slippery when wet, as described in cobbled streets.
Gravel, sand and dust. Loose material on top of a hard surface acts like ball bearings. A thin layer of grit on a corner can be as slippery as ice for a tyre.
Weather and timing clues
Surfaces are often most slippery in the first stretch of rain after a dry spell, when dust and oil mix with water. Morning dew, fog, and surfaces that have not yet dried after a shower can all lower grip. In autumn, damp leaf litter is a recurring problem. After heavy rain, look for silt and debris washed across the road, which may hide in dips and corners.
Using what you see
Spotting a slippery patch is only useful if you adjust. A few general principles:
- Slow down before, not on. Reduce speed early, in a straight line, while you still have grip to brake with.
- Keep the bike upright. Leaning and braking at the same time asks a lot of a tyre. Brake mostly before a corner, and keep the lean modest through slippery spots.
- Be smooth. Avoid sudden steering, braking or pedalling. Gentle inputs are less likely to break traction.
- Choose a better line. If you can safely go around a painted line, a metal cover or a patch of leaves, do so, but only if it does not put you in the path of traffic. A sudden swerve is rarely a good trade.
- Cross hazards squarely. When you cannot avoid a slippery strip, try to cross it with the bike upright and pointing straight, and avoid braking on it.
- Stay relaxed. Tight arms and a stiff body make it harder to let the bike move slightly beneath you.
Being ready for a slide is also useful, and skid recovery looks at what to do if one happens. If conditions feel beyond your comfort, walking a short stretch or choosing another route is perfectly reasonable.
Practising your eye
You can train your eye on ordinary rides. As you travel, pick out the shiny, painted or metallic spots and think about how you would cross them. In a safe, quiet place, you can also gently test how your tyres feel on damp paint or leaves at walking speed, with a helmet on and nothing around you. The aim is not to find the limit of grip, which is risky, but to get a feel for the difference.
Remember that you cannot always tell. Some slippery surfaces look perfectly normal, so treat unfamiliar wet ground with caution, particularly when carrying a load or riding at pace. If the surface surprises you, take it as information and ride the next stretch more carefully.