Mercedes' tyre woes continue in Barcelona

Sky Sports F1's Mark Hughes on Mercedes on-going tyre struggles, why they want backwards in Spain, and how the characteristics of Monaco could suit them

By Mark Hughes.   Last Updated: 15/05/13 10:30am

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Lewis Hamilton was distraught on Sunday evening in Barcelona, struggling to comprehend how he could have finished 12th in a race without incident or drama with car that he'd qualified second.

"I just don't understand what it is," he admitted. "It's obviously something to do with the tyres and how we're using them. But it didn't seem to matter whether I drove fast or slow there was just no grip from either end of the car. It's one of the strangest feelings I've ever had in a car."

It was the latest manifestation of the Mercedes team's struggle to get the car not to degrade its tyres faster than those around it, something it has struggled with since the introduction of the Pirelli control tyre in 2011. The difference is that this year, the W04 is the fastest thing around in qualifying.

At Barcelona, Nico Rosberg notched up the team's third pole from the opening five races (and had it not rained at an inopportune time in Malaysia qualifying, it's likely that score would now be four from five) and was joined on the front row by Hamilton to give the first Mercedes front-row lock-out since 1955. But even more than Rosberg's descending drive from pole to ninth in Bahrain, Hamilton's in Spain underlined how serious the tyre use problem is.

Bahrain and Barcelona are two of the toughest tests of a tyre, albeit for very different reasons. Bahrain's punishing combination of relentless low-speed acceleration zones, one of them immediately after repeated high speed lateral loads, with extreme track temperatures makes rear tyre heat degradation a serious problem.

Barcelona's challenge comes from a combination of two key long, fast corners (turns three and nine) with a traction-demanding final sequence. Turn three sees the cars at super-high and unrelieved lateral g loadings for around seven seconds, the longest anywhere on the calendar. So if you have an underlying problem with how your car is using its tyres it will become amplified at these two tracks.

The symptom of the Mercedes problem is that, left to the car's own devices, the rear tyres will run about 20-deg C too hot. There are things the team and the drivers can do to keep tyre temperatures down, but at these tracks even they were not enough to prevent a temperature threshold being crossed, beyond which there is no bringing them back.

Rosberg managed it better than Hamilton - mainly by lifting off massively through turn three for the whole race - and his initial pace was around 5.5s off what it could have been were he not having to keep the tyres alive (based on his qualifying pace and the fuel load of 150kg needed at the start of the race).

Rosberg's first stint pace at the head of the field was around eleven seconds slower than his pole time and the effect of the race fuel load accounts for approximately half of that. His second stint pace was even slower, when taking account of the lightened fuel load, his third only marginally faster.

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By contrast, once Alonso got clear air at the front of the field in the Ferrari, he was able to lap within around 3.5s of what would theoretically have been possible. The Ferrari could, in other words, run at about 2s per lap faster than the Mercedes without damaging its tyres.

But the Ferrari could not run the tyres for very long. "We could not have done a competitive three-stop," said Ferrari's Stefano Domenicali. "We saw that in Friday practice." At a certain point the rears would eventually go past that critical temperature threshold.

This happened before the stint length necessary for a three-stop and hence Ferrari committed right from the start to a four-stop. The difference, though, was that up until the moment (about 14 laps) that the Ferrari's rears got past that threshold it could be driven relatively quickly - much harder than the Mercedes was allowing Rosberg to do. The Merc's tyres could only be kept under that threshold by driving much slower.

At some circuits the difference between a three and a four stop race is considerably in favour of a three stop. The way that the time loss of the extra stop balances out against how much of a harder pace you are able to do if your stints are shorter determines this.

At Barcelona there just happens to be very little difference in theoretical race time between a three stop and four (between two and four seconds in favour of a three, according to most team simulations). Therefore on this occasion, Ferrari's need to four-stop did not unduly hurt it and Alonso was able to lap at the pace necessary to make a four-stop work.

At Mercedes, even a four-stop didn't work - as Hamilton demonstrated. The tyres overheated early whether pushed hard or slow. When they overheat in this way they can still be driven; they are not physically wearing away. Instead, they just become slow.

For Barcelona, Mercedes had a new drum arrangement around the rear wheels designed to take more heat away from the rim and brake calipers - heat that tends to get transferred through to the tyre. It clearly wasn't enough. For Monaco the team is hoping to introduce another, as-yet secret, feature that it hopes will be much more effective in that endeavour.

Monaco, however, is relatively undemanding of a tyre, with no fast corners and almost all of them short duration. Combined with how the Mercedes' excellent mechanical grip allowed Michael Schumacher to qualify fastest there last year, Alonso is expecting the Mercs to again be on the front row - and with nowhere to pass, they may be able to stay up front, or somewhere close. But that will not necessarily mean their tyre heat problems will have been solved.

For that, we really need to wait until the next fast, long corner track on the calendar - Silverstone.

MH

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