What is vMin? Minimum corner speed, explained

Why the slowest point matters

Through the middle of a corner you are traveling at or near your minimum speed, and every bit of it counts. At 50 mph you cover 22.4 meters each second; at 52 mph, 23.2. Over the slowest stretch of a corner that small difference adds up, and the extra speed is still there when you start accelerating, so you reach the next straight faster too.

vMin also reflects everything before it. Braking too early or too hard, turning in at the wrong point, or coasting between the brake and the throttle all show up as a lower minimum. That makes it a quick way to find which corners deserve a closer look on the full trace.

Reading it on a speed trace

Each corner on a speed trace has the same shape: speed falls under braking, bottoms out, and rises as you accelerate away. The bottom of that valley is vMin, and two things about it are worth reading.

• Its height. Compared with a faster lap at the same corner, a lower floor means less speed carried through the middle.
• Its position. If your minimum comes earlier on the lap distance than the faster lap's, you are usually turning in or apexing earlier. A minimum that comes after the apex often means a lift or extra braking in the corner itself.

The shape around it matters too. A sharp V means braking deep, turning quickly and accelerating hard. A rounded U means carrying speed through a longer, faster corner. Neither is wrong; they suit different corners.

When a higher vMin isn't faster

Lap time comes from the whole corner, entry, middle and exit, and the exit usually matters most when a long straight follows, because you carry that speed all the way down it. Sometimes the faster way through is to give up a little minimum speed for a later apex and an earlier, straighter exit.

LapLift's public laps show this at two tracks. At Lime Rock, the quickest third of drivers are mostly in quicker cars and carry about 3% more minimum speed than everyone else in a typical corner. At the Lefthander they carry 3% less. A faster car has no reason to be slower there unless its driver chooses a line that gives up speed, and the next corner, the Righthander, is where they get it back. At NJMP Thunderbolt's Turn 9, the slowest corner on the lap, the quicker group carries no more minimum speed than everyone else, and the largest gap on the lap comes at Turn 10, the corner it leads into.

So read vMin together with the exit. A corner where your minimum matches a faster driver's but you lose time on the next straight is an exit problem, and pushing for more minimum speed there can make it worse.

What a low vMin usually points to

When your minimum is clearly below a faster driver's at the same corner, the cause is usually somewhere on the way in.

• An overslowed entry. Lime Rock's own track guide gives a simple test for this at Big Bend: if you are off the brakes well before the apex, you braked too much.
• An early turn-in or early apex, which points the car at the exit too soon and forces a lift or more steering in the second half of the corner.
• A gap between brake and throttle, where the car coasts. On the trace it shows as a flat stretch at the bottom of the valley before the speed starts to rise.

Compare like with like where you can. Car differences change minimum speed in predictable ways: a car with 10% more grip carries roughly 5% more minimum speed in every corner, downforce adds most in fast corners, and extra power barely moves it. So against a faster car, look for the corners where the gap is smaller or larger than usual. The cleanest reference is a similar car on similar tires, or your own best lap.

vMin in LapLift

LapLift measures your minimum speed at every mapped corner of the track and scores it from 1 to 99 against the other drivers who have logged that same corner. The scores appear as colored dots on the track map, so you can see at a glance which corners cost you the most speed. Our guide to vMin corner scores explains how to turn them on and how to move a dot if it isn't sitting where you brake and apex.

The track guides for Watkins Glen, NJMP Thunderbolt and Lime Rock list the median minimum speed for every corner, which gives you a reference before you have uploaded a lap there.

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