Why cyclists crash in corners
A corner asks three things of a bike: enough grip, a lean angle the tyres can hold, and a pedal that stays off the road. When one of the three runs out first, the rider goes down. Knowing which one is closest is most of cornering well.
About the numbers. The angles on this page are Krengo’s model values for a typical road bike, shown so you can see how the limits relate. Your bike, tyres and road will differ. The field itself is not released yet; sources are linked at the bottom.
Three limits, one corner
Crash studies of cyclists who fall without any other vehicle involved point to the same short list: a slippery surface, riding too fast for the situation, and loss of balance. Skidding is one of the most important mechanisms, and curves and turns are where the tyre has to produce sideways force on top of everything else.1 Seen as mechanics, that gives three separate limits that you can reason about one at a time:
- Grip: how much sideways force the tyre can hand over before it slides.
- Lean: the angle the bike has to take to follow the corner at your speed.
- Clearance: how far the bike can lean before something other than the tyre touches the road, usually the inside pedal.
Grip: the tyre has a budget
In a steady corner the tyre supplies the sideways force that bends your path. Lean angle, speed and radius are tied together by the standard simple model θ = atan(v² / (g · r)). It is not worked through in the sources below; it is the textbook starting point. The same corner takes the same lean whatever the surface, but the surface decides whether the tyre can deliver it. The simplest friction limit is tan θ = μ, where μ is the friction coefficient between tyre and road.
With the assumed values in Krengo’s grip scale, that limit is about 42° on dry worn asphalt (μ 0.90), about 31° on wet asphalt (μ 0.60) and about 27° on gravel (μ 0.50). Those μ values are assumptions with wide ranges, not measurements of a road. Braking, bumps, painted lines, wet leaves and oil use up part of the budget before you lean at all, so the real limit is lower than the model line.1
Lean: speed and radius decide
You do not pick the lean angle; the corner does. At 30 km/h on a 15 m radius the model gives about 25.3°, the same worked example as in the glossary. Enter a faster speed or a tighter radius in the calculator and the number climbs quickly, because speed enters squared. Entering a corner at a speed you cannot hold is how riders end up needing more lean than the grip or the clearance allows. How the bike gets into the lean in the first place is countersteering.2
Pedal strike: the geometry limit
With the inside pedal at the bottom, the pedal touches the road when the bike reaches a fixed angle set by bottom bracket height, crank length, pedal thickness and how far the pedal sits from the centre line. With the Krengo defaults (270 mm, 170 mm, 17 mm, 125 mm) the model gives about 36.2°, and the field warns 3° earlier, at about 33.2°. The full formula and a way to measure your own limit are on the pedal touch-down page. Unlike grip, this limit does not depend on the surface.
Which limit comes first
| Surface | Grip limit atan(μ) | Pedal warning | Pedal touch-down | Closest limit |
|---|---|---|---|---|
| Dry worn asphalt, μ 0.90 | ≈ 42° | ≈ 33.2° | ≈ 36.2° | Pedal |
| Wet asphalt, μ 0.60 | ≈ 31° | ≈ 33.2° | ≈ 36.2° | Grip |
| Gravel, μ 0.50 | ≈ 27° | ≈ 33.2° | ≈ 36.2° | Grip |
The useful reading: on a dry road the pedal tends to be the first limit, which is why it can be a warning you hear before the tyre has anything to say. In the wet the order flips. The grip limit falls below the pedal limit, so the tyre can let go at a lean angle where the pedal is still clear. A pedal warning that never comes is not a sign that the corner is safe. This is a model comparison with assumed values, not a prediction for any particular ride.
What helps in practice
- Slow before the corner, not in it. Braking mid-lean takes grip from the sideways force the corner needs.
- Look through the corner. Early sight of surface changes gives time to take a line around them. See road bike cornering technique.
- Inside pedal up, outside pedal down. It removes the pedal limit from the list and puts weight on the outer tyre.
- Treat wet, leaves, gravel and paint as a lower budget. The grip scale shows how the same lean uses more of it on a worse surface.
- Know your own pedal limit. Measure it standing still; the steps are on the pedal page.
Krengo reads the lean angle and puts the three limits next to it as estimates. It does not sense the road. The grip scale explains how the colours are built, and the FAQ covers the rest.
Sources
- Review on single-bicycle crashes in the recent scientific literature, Transport Reviews (2022). doi:10.1080/01441647.2022.2055674. Used for the main causes of single-bicycle crashes (slippery surface, speed, balance, skidding in curves). Read as a search summary on 5 October 2026; the publisher blocked full-text access, so no figures are taken from it.
- J. Fajans (2000), “Steering in bicycles and motorcycles”, American Journal of Physics 68(7), 654–659. doi:10.1119/1.19504. Background for how a bicycle leans into a turn.
The friction limit tan θ = μ and the simple lean formula are standard textbook models and are not taken from either source. The angles in the table are Krengo’s own model values: the grip scale’s assumed μ and the pedal defaults on the linked pages.