Hot laps: BMW 435i vs M3 winter tyre test 3Fri, 31 Jan 2014 00:00:00 -0800
By Ben Barry
First Official Pictures
31 January 2014 08:50
How much difference can winter tyres make to your car’s performance and safety?
In snowy conditions, choosing between winter and summer tyres is like choosing between crampons and slippers, but plenty of British winters pass with barely a flake touching the ground. So it’s understandable that most of us are reluctant to fork out for winter tyres.
Yet tyre makers claim there are benefits when temperatures dip below 7degC, especially when it’s wet. In other words, the conditions you’ll typically find during a British winter. Are we missing a trick?
To see for ourselves, we’ve come to Pirelli’s Vizzola test track in Northern Italy. The temperature is hovering at a few degrees above zero while sprinklers keep the surface greasily wet. It’s here that we’ll compare winter and summer tyres’ performance during 0-62mph standing starts, braking tests and full lap times.
But, there’s a twist: we’re equipping our BMW 435i with 18-inch Pirelli Sottozero 3 winter tyres and pitching it head-to-head against an M3 on its factory-fit 19-inch Michelin Pilot Sports.
The 4.0-litre V8 M3 has 112bhp on the 3.0-litre turbocharged 435i, as well as uprated brakes and suspension, so it should monster the 435i. But can the 435i’s Sottozeroes overhaul the M3’s performance advantage? Time to find out…
Pirelli’s figure-of-eight track has limited run-off, greasy kerbs and, as you’d expect, few straights. The M3’s going to need to carry its speed through the corners if it’s going to stand any chance. But it’s soon clear that the lap time is going to prove its biggest challenge yet.
It’s not that the M3 feels inherently unsafe, because when you travel at even relatively high speeds the Michelins still cut through standing water and find purchase, and when I induce slow-speed second-gear oversteer for fun, it’s easy to balance and bring back under control. The problem comes when you push for a lap time: the front tyres quickly nibble at their limits and slip into terminal understeer if you over-cook your entry. What happens at the rear is even scarier: dip into the throttle just a little earlier on corner exit and there’s snap-oversteer. Brake hard and the M3 quickly becomes unsettled, especially on the downhill sections where the back end wants to step out.
It means that when you drive just a little faster, things become exponentially scrappier, and when you keep things neat to hit all the apices, it feels embarrassingly pedestrian.
I trickle around in fourth gear, only shifting to third for one corner, meaning any advantage the M3’s DCT ’box might have is largely lost. The best I can do is a 56.32sec.
The Sottozero-shod 435i is on another planet and so is my confidence. You can actually see the extra water the tyres are clearing from the surface once you repeat a lap, and I immediately feel comfortable throwing the 435i more aggressively at corners and working with the limits rather than feeling scared of them – because slip, when it happens, is progressive and controllable. I also change gear more, shifting between second, third and fourth, plus I brake harder and press the throttle to the floor on corner exit much like I’d do if it were dry. The fact that I can get up on those greasy kerbs and straighten some of the corners without fear of an accident further slashes the lap time.
After several attempts in the 52s, I dip to a 51.91sec on my fifth and final lap. The M3 holds a large performance advantage, but the 435i can pull off a lap that’s nearly 4.5sec faster. It is a frankly massive winning margin and one for which the winter tyres must take full credit.
By Ben Barry