Braking and turning in - Trail Braking

[Jersey Tom]

Correct. Ideally at apex you'd hold constant speed.

[volarchico]

What I found very interesting was that in the more prominent braking zones, such as Turn 1 and 4; and when Mark was very clearly trail braking; the G-meter reads constant the whole way; basically having the same net acceleration, just that it shifts in direction from the car's longitudinal axis, onto the lateral.

I think you'll find the onboard telemetry they display on TV is highly filtered, so even if that looks like a constant g force, it's probably not...

[raymondu999]

I'm not sure I buy into that; as the graphics are provided by FOM and not the teams. However, I just realized that there is a bit of lag in the meter so that could explain it. The "traction circle" graphic isn't lagging, but the "meter" is.

[volarchico]

When I said "filtered", I didn't mean blocked or altered by the teams. I meant mathematically filtered. As part of data acquisition, it's important to filter out the noise, but doing so takes away some of the data. It's smoothing out the spikes and noise at the expense of having a slower refresh. From what I saw in the video, it seemed that any "max/min" type value got stuck and displayed for much longer than reality would create.

[raymondu999]

Do forgive the rubbish music at the video, but I found this video which had something I thought was rather interesting:
[youtube]http://www.youtube.com/watch?v=YWWsYZ3lSa4[/youtube]

If you watched at 0:51, Seb does this pumping action with the brake pedal - what purpose would that serve?

[timbo]

If you watched at 0:51, Seb does this pumping action with the brake pedal - what purpose would that serve?

It's a game, and he is trying to outbrake the rival. I'd not analyze that much.

[beelsebob]

If you watched at 0:51, Seb does this pumping action with the brake pedal - what purpose would that serve?

The same purpose as pumping the breaks in your own car serves when your wheels locks - it gets them rotating again and gets you grip.

[raymondu999]

I didn't see the brakes lock; but could be just the bad video. I thought it was a different take on trail braking, that's all.

In any case - I had a track day in Sepang with my friends; and Into T1 I tried the "classic" line - braking straight; then taking a circular line at constant speed; then changing to a trail braking line; but taking a slightly late apex at T1. Dear God - I shaved my braking distance by some 40%.

Done with a GT-R

[Caito]

There shouldn't be that much difference. 40% seems way too much to me. You were probably braking early. Was the apex speed the same in both cases?


IMO very little to read on vettel's video, he was just about to crash the car in front..

[Belatti]

Its not the brake pumping what called my attention, but the "are you nuts" gesture he did to Webber at Turkey 2010

Seriously now, that is called "human ABS"

[timbo]

I didn't see the brakes lock; but could be just the bad video. I thought it was a different take on trail braking, that's all.

Most certainly no.

In any case - I had a track day in Sepang with my friends; and Into T1 I tried the "classic" line - braking straight; then taking a circular line at constant speed; then changing to a trail braking line; but taking a slightly late apex at T1. Dear God - I shaved my braking distance by some 40%.

Done with a GT-R

I'm envious=)
Yeah, trail braking yields a lot, but be careful not too cut your braking distance too much.
In my practice with Ferrari Virtual Academy I found that I often settle to a line with late breaking point (later than recorded Alonso's trace) but that costs dearly on apex speed and exit. I had to fight against my instinct to brake earlier and carry more speed into the corner.

[andylaurence]

Here's some data from my data logger showing one random corner from last season. The lateral G (blue) is stacked on top of the longitudinal G (red) whilst everything is normalised to positive values. Other than normalising for positive values, this is raw data.


Braking starts at about 12.9 seconds in pretty much a straight line. I take an initial bite at the steering at about 13.5 seconds, resulting in a peak cumulative G of over 1.5G. I assume I had some problem (brain fade?) on turn-in as lateral and longitudinal G both dip at about 14 seconds, but I'm soon back on the brakes a bit harder and on the wheel again. Note how I don't get off the brakes properly until the apex at 16.5 seconds and I'm on the throttle immediately at 16.6 seconds. Cumulative lateral plus longitudinal peaks at over 2G, which is plain not possible with just lateral or longitudinal forces. The peak braking force was 1.24G and peak lateral force was 1.82G, yet the peak of the sum was 2.2G.

Less said about my driving the better

[raymondu999]

Mark Hughes published a piece on driving styles in the latest Autosport - and this is how he describes (in his usual fantastic prose form) trail braking:

In the days of high-grip tyre-war Bridgestones, Michael Schumacher used to love to overlap the braking and cornering phases into slow-to-medium-speed turns. Alain Prost used a similar technique. They would begin the turn slightly earlier than the geometric ideal, turning only gently at first and maintaining a lot of momentum. As they loaded the outer front tyre under combined braking and cornering, so they would then begin to release some of the braking force, allowing the tyre to build up more cornering load, and the rear would begin to pivot itself gently around that outer front. The braking kept the fronts from building up lateral grip too quickly and transferring the cornering load too suddenly to the rear, keeping that rear end tamed while still benefiting from the direction change it was introducing to the car.
It required great sensitivity to make it work, but it potentially allowed you to have your cake and eat it; the high entry speed of the understeer-type driver, but with the early direction-change completion of the oversteer-type driver. But it required the tyres to cooperate, needed a nice flexible sidewall to blend the braking with the cornering.

[raymondu999]

When you're trail braking, as most f1 drivers do nowadays, you often see inside fronts locking, and people always seem to say it's always better to keep them both rolling under braking. Surely then under braking you're limited by the front inside? Which by definition has less grip than the outside front, with weight transfer.

There has to be a crossover point surely, where a corner becomes so tight it's better to not trail brake to the apex and straight line is better for braking? Might be better (from a pure laptime perspective) to just lock the inside front, in fact (if the corner is so tight that the outside front has over twice the grip of the inside front)

[N12ck]

If you watched at 0:51, Seb does this pumping action with the brake pedal - what purpose would that serve?

The pumping action I only use when I'm racing if I lock up, it allows the tyres to turn a little bit then brake, stopping you from going off the track, it means you can brake later and get away with it