Well, that was an interesting thing for Hamilton to tweet…

Things that I found interesting:

(I’ll refer to everything by the distance around the lap, which is noted at the bottom. For example, Eau Rough is at 1200m or so)

1) Hamilton gains mostly under braking, rather than in the corners (300m, 2200m, 3000m, 6700m). I would have expected the cornering speeds to be noticeably different, but they are actually quite similar. Hamilton can just go that little bit deeper, and brake that much harder before the wheels lock, due to the extra downforce he was running. With each steep drop in the speed trace (second trace from the top), you can see that Hamilton is just a little later on the brakes.

2) Hamilton messed up the third corner in the “Les Combes” section (corner 9, 2600m). He has more downforce, so should be as fast or faster, but he must have had a moment there, as his speed drops mid-corner. Unfortunately, the data is obscured by what seems to be the steering trace. The slight correction of the steering seems to indicate that he understeered, as he only let up on the steering rather than going into opposite lock (either that, or he has superhuman reactions that corrected a slide so quickly that he didn’t need to get to opposite lock to save it… but I doubt it!). You can see that in that short downhill run to Bruxelles (2500-2900m), the speed traces are parallel, so he isn’t losing time because of the wing – it was just his poor exit from the corner that lost him at least a tenth or so, where he should have gained at least one or two tenths.

3) Hamilton destroys Button under braking for the final chicane… only to lose most of that advantage by killing his corner exit (6900m). While he was able to brake much harder (note the higher brake pressure he can apply without locking up, thanks to the added downforce – bottom trace, brake pressure overlaid with throttle position – 6600m), he probably ran wide mid-chicane, ruining his line on the exit. Because of that, Button go the better exit and clawed back much of what he lost in the braking zone.

4) Through the easy-flat corners (Eau Rouge – 1200m; Blanchimont – 6200m), they both lose the same amount of speed. Had this been a few years ago where Eau Rouge was almost flat, the data would have been much more interesting. While Hamilton would have had more drag, he may have had as much as a 10-15 km/h advantage exiting Radillion or Blanchimont. At some point, Button’s speed would eclipse Hamilton’s, but Hamilton could retain an advantage. It’s counter-intuitive, but sometimes adding downforce increases your top speed down a straight, simply because you exited the previous corner that much faster – what you lose from drag is more than outweighed by what you gain from increased exit speed. That’s why Le Mans cars are closer to medium downforce spec now, especially with the chicanes on the Mulsanne – the corner exits are very important.

5) Neither driver can trail-brake as hard into Bruxelles (2900m), due to the downhill nature of the corner shifting the balance forward, making the rear of the car “light” and twitchy. The braking trace shows that as they turn in, they are braking with about half as much brake pressure as the entry to Pouhon (3800m); this could be partly due to the lower speeds and therefore lower downforce, but by watching the cars through that corner, some of it has to be because they are all quite twitchy on corner entry.

6) It is worth noting that at near top speeds, there is little-to-no brake modulation, as the car has so much downforce, giving the tires so much grip that arguably the best brakes in the world still can’t lock the wheels. Note the braking into La Source (200m) – they are mashing the brakes, and then gradually easing off the brake all the way to the apex of the corner, mostly because they are losing downforce (and therefore grip) as they slow down. To avoid locking up, they must ease off the brakes as the limit of the tires gets lower and lower with the decreasing speed.

7) Both drivers seem to be quite smooth – a testament to the McLaren. If you look at the whole lap, looking specifically at the steering trace (third trace from the top), there are very few corrections that were made. Each steering input, Hamilton’s correction in Les Combes aside, it’s all very deliberate and consistent – no massive opposite lock moments chasing the car through the corner. Then looking at the throttle trace, I can’t see anywhere where they had to lift to correct for any wheelspin – clearly the McLarens are putting the power down quite well. It would be really interesting to compare to De La Rosa’s throttle trace, where I bet his steering and throttle inputs are far more erratic, for the simple reason that the HRT has less downforce, is probably twitchy in each corner, and is not able to put the power down nearly as well – therefore poor Pedro has to wrestle the car at the limit, rather than Jenson being able to finesse the car through each of Spa’s lovely sweeping corners.

Hamilton posted the photo because he was blown away by the differences between a high downforce wing and a skinny wing, likely magnified by his disappointment of being so far off the pace. That was obvious to me (and probably anyone that understands the trade-off between downforce and drag), but it was the few other details that I found much more interesting.