The grip scale G1–G12: what the colours mean and what they do not

What G1–G12 means

Each step is a share of capacity. The model computes how much side grip the corner demands, divides it by an assumed capacity, and names the result:

utilisation = demand / capacity
demand      = tan( lean angle + margin )
capacity    = surface μ × level factor

100 % is the model limit you selected, not a detected slide. Below it you are inside the model’s margin. Above it the corner asks for more than the model assumes you have. The twelve steps are:

The word after the number groups the steps: ROOM (G1–G4), BUSY (G5–G6), NEAR (G7–G8), OVER (G9–G10) and HIGH (G11–G12). If the model cannot estimate, the tag reads UNKNOWN with an empty meter. That never means “safe”.

What the model takes in

Three things come from the ride and two from you.

• Lean angle from the sensor.
• Speed. Above 40 km/h the model adds 3° to the lean angle as extra margin.
• How fast the lean grows. If the lean angle increases by 10°/s or more, it adds another 3°. The base margin is 2°, so the margin is 2°, 5° or 8°.
• Surface, which you choose. Each surface has an assumed grip μ:

• Level, which you also choose. It is your own assessment of vision, line, body position and smooth braking before the corner, not a measure of how good you are. A higher level removes reserve from the model; it does not give the tyre more grip.

A worked example

25° of lean at 30 km/h in a steady corner, dry worn asphalt, level Settled. The margin is 2°, so demand is tan(27°) = 0.51. Capacity is 0.90 × 0.70 = 0.63. Utilisation is 0.51 / 0.63 ≈ 81 %, which is G6 BUSY. The same corner on wet asphalt (capacity 0.60 × 0.70 = 0.42) gives about 121 %, which is G11 HIGH. Same lean, same speed, different assumption.

When there is no estimate

The model gives no colour (UNKNOWN) when the sensor is still calibrating; the lean angle is invalid or 60° or more; lean or speed data is stale; the speed is under 8 km/h or over 100 km/h; the lean angle changes faster than 30°/s; or the surface is unknown. You get no number rather than a guess.

Why it is an estimate and not measured grip

Krengo has no way to sense the road. It measures lean and speed, and everything about grip is an assumption you pick from a list. Four things follow from that.

• The surface values are assumptions. The ranges in the table above are wide. For the 25° example on dry worn asphalt with level Settled, the assumed range 0.45–1.10 gives anywhere from about 66 % to about 162 %, depending on where the real μ falls. The colour uses the middle value.
• The level is your own call. The model cannot see how you ride.
• Many things are outside the model: tyres, water, wet leaves, cobbles, oil, braking and body position can all make the estimate wrong.
• 100 % is a line in a model. It is not the point where a tyre lets go.

Never treat green as permission to go faster.

Reading the scale without colour

Colour is never the only carrier. Every tag has four things you can read without seeing hue:

1. the G-number, G1 to G12, which is the order;
2. the percentage of capacity, where it fits;
3. a twelve-segment bar that fills one segment per step, so G3 is three segments and G12 is full;
4. a word: ROOM, BUSY, NEAR, OVER or HIGH.

Neighbouring steps can look alike, G1 and G2 in particular, and green, orange and red are hard to tell apart with some forms of colour blindness. Read the number or count the bar, not the hue. UNKNOWN is shown with a dashed outline and an empty bar.

What to do at orange, red or purple

The colour is a reason to look at the corner and at your inputs, not an instruction.

• Orange (G6–G7, 77.5–92.5 %). Most of the assumed margin is in use. Check that the surface and level match the day. If the surface is uncertain or the corner is new, ease the speed before the next one.
• Red (G8, 92.5–100 %). You are at the edge of the limit you selected. A small increase in lean or speed puts you over. Treat it as a clear signal to take speed off in similar corners until you know why.
• Dark red and magenta (G9–G10, 100–115 %). The model says the corner asks for more than its capacity. First check the inputs: a surface that is too optimistic or a level that is too high is the most common cause. If they are right, the corner was beyond the assumed margin.
• Purple (G11–G12, 115 % and above). Far over the model. Do not read it as measured slipping. It most likely means the assumptions do not fit, for example wet or loose road with a dry setting, or the real situation is well beyond the margin you chose.

In every case: adjust the surface and level to what you actually see, and ride to what you see, not to the tag.

Where you see the scale

The lean angle calculator and the ride analysis show all twelve steps. The Garmin data field uses the same twelve steps, G1 to G12, so its tags match the web one to one.