Road bike pedal strike: the lean angle where the pedal touches down
There is no single lean angle at which a road bike pedal hits the road. It comes from four measurements on your bike. This page shows the formula Krengo uses, a worked example, and how to find your own limit.
This is a model, not a measurement. The numbers below are the defaults in the Krengo data field and are estimates. The field is not published yet: it has been tested on fictional data and in a simulator, not with a real sensor on a real bike. Pedal strike also depends on pedal shape, crank position and road camber, which this static model leaves out.
The geometry in one formula
With the bike leaned over and the inside pedal at the bottom, the pedal touches down when the lean angle reaches:
touch-down angle = atan( (bottom bracket height − crank length − pedal thickness / 2) / reach )Reach is how far the outer edge of the pedal is from the bike’s centre line. The top of the fraction is how high the pedal’s lowest point sits above the road when the bike is upright. The bottom is how far it has to swing sideways. Lean far enough and the two meet.
The limit is geometry. It does not depend on tyre or friction.
A worked example with the Krengo defaults
| Measurement | Default |
|---|---|
| Bottom bracket height | 270 mm |
| Crank length | 170 mm |
| Pedal thickness | 17 mm |
| Reach (pedal edge to centre line) | 125 mm |
The pedal’s lowest point is 270 − 170 − 8.5 = 91.5 mm above the road when upright. Divide by the 125 mm reach and take the arctangent: about 36.2°. The field warns 3° earlier, at about 33.2°.
Treat these as estimates for a typical bike. Your own bottom bracket, cranks and pedals will give a different answer.
Why the simple formula gives a much bigger number
A common shortcut, atan(270 / (170 + pedal)), gives roughly 55°. It has no sideways term: it pretends the pedal sits on the centre line. Real pedals sit out to the side, so they reach the road at a much smaller angle. The version above is the conservative one, and it is the one the field uses.
Measure your own limit
A measured angle beats a calculated one. Do this standing still, never while riding:
- Put the pedal on the side you measure fully down, at the bottom of the stroke.
- Lean the bike over until the pedal touches the ground.
- Read the angle.
- Type it into Pedal touch-down angle in the field’s settings. A value above 0 replaces the calculation.
The field can also store a calibration per bike profile. The steps are on the Garmin data field page.
Do not try for contact while moving, and do not sit on the bike while you measure. A loaded bike and tyre pressure can give less clearance than when it stands empty.
How the Krengo field warns you
The field shows CLEAR* on green while the model says the inside pedal is clear, and PEDAL NEAR on red at or near the limit. The asterisk means it is a model estimate. PEDAL NEAR stays on until you are 2° below the warning level for 0.4 seconds.
The screen redraws about once a second, so the colour can be up to a second late. Vibration and tone go out straight from the sensor’s five packets per second and are the fast channel, with a floor of about 200 ms from the sensor plus Bluetooth.
Read it as “you are in the zone”, not as a guarantee. CLEAR* never means safe.
What the model leaves out
- It does not measure pedal contact, and it does not know where the crank is. It assumes the inside pedal is down.
- Pedal shape and width, road camber and rider position change the real limit.
- Technique matters: keeping the inside pedal up and the outside pedal down gives more clearance. See road bike cornering technique.
Frequently asked questions
At what lean angle does a road bike pedal hit the ground?
There is no universal angle. It depends on bottom bracket height, crank length, pedal thickness and reach. With the Krengo defaults the estimate is about 36.2°, and your own bike will differ.
Why is atan(270 / (170 + pedal)) so much bigger?
It has no sideways term, so it ignores that the pedal sits out from the centre line. It gives roughly 55°, which is too optimistic.
Does the Krengo field detect that the pedal touched?
No. It estimates from geometry how close the inside pedal is. It does not measure contact or crank position.
Can I type in my own touch-down angle?
Yes. Pedal touch-down angle in the field’s settings replaces the calculated value when it is above 0.