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Kee Law October 29, 2007 8:44 PM

Wouldn't driver skill be a factor?  Are the laps done by different driver's, or do you keep a "stig" like tame racing driver for these occasions?

trackdemon November 2, 2007 9:57 AM

Blimey, those wet times are a bit strange.... not too suprised to see an RS4 up the top of the table (prodigious grip, 4wd, good power) but I find it hard to believe that the informal riegning champion of all weather ground coverage (ie the 911 Turbo) is dwindling at the back of the ranks.... behind an X5 diesel & Renault Twingo for gods sake!!!??

Whats going on Matt? We need to know.....

Matt Prior November 3, 2007 5:43 PM

We've had to be careful about driver skill, because if you just drive as fast as possible, you get big differences - even between the same driver on different days. The trick is to make the times consistent and repeatable.

Manufacturers and tyre testers use the same principles. You seek to find a consistently fast-ish level that all testers can operate at: regardless of whether we're totally on it, or whether we've had a bit of a rubbish night's sleep and a terrible journey to MIRA.

So that's what we do -- operate at about 80 percent, and on this principle we've found that different testers produce extremely similar times. Usually a car is tested by more than one driver anyway, which helps the consistency too. And as a control we'll go back and re-test a car some time after the original road test to make sure we're not subconciously getting quicker.

The eighty-percent rule's usually enough to push a normal road car's tyres and brakes to the brink of overheating after five laps or thereabouts, which is where we want it - approaching the limit of the car, and with a  bit of a safety cushion which means we're less likely to crash...

Which brings me to the 911 Turbo. A surprisingly disappointing time on first look, I'll admit. But the wet track gets consistently proper wet, and firmer-sprung 911s on focussed tyres have a bit of a problem with standing water. On merely crappy roads, bad surfaces, the odd puddle, they're fine, but the wet circuit's sprinklers absolutely soak the Tarmac.

Rawer 911s aquaplane quite early on the straight, and are none too reassuring under braking because the engine is out the back, which makes them more unstable beyond the limit too, now matter how good it is for traction. Sure, out of short low-speed corners, a 911 Turbo accelerates as quickly as anything, but the wet-circuit has lots of long, constant-radius bends with quick direction changes which, as they should, reward stability and controllability more than traction. Which is why the softer-sprung, narrower-tyred Carrera S is faster than the Turbo. And much, much faster than the GT3.

Casanova November 15, 2007 12:37 AM

How fast is my car around your test track?  Well, I drive a 205 XS like Chris Harris does {when he's slumming it!).  Could you get him to give that a spin round there?  Would be interesting to see how that (and other older cars) compares with the shiny new machinery.