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Thursday 10th January 2013


PH BLOG: KNOWN UNKNOWNS

Why car hacks have it wrong about ride comfort


Dreams of being a car designer meant my maths lessons were doodled away with drawings rather than working out long division or quadratic equations. More fool me. I've since grown to have a fascination with engineering and the 'grown-up' end of vehicle design and could spend hours being politely baffled by the likes of Lotus's Matt Becker or Mike Cross at Jaguar. What fascinates me in particular is how seat of the pants 'feel' can be turned into something that can be ordered from a component supplier, calibrated and bolted into a car's drivetrain.

British firms still rule for ride quality
British firms still rule for ride quality
Hanging out with Mike Cross recently was a perfect opportunity to address some of these nagging questions that loom like Donald Rumsfeld's known unknowns. Like, why is it cars with passive dampers seem to feel more natural than those with multi-setting adaptive ones? Talk to the marketing guys like BMW's Ian Robertson and they'll tell you these gizmos can give you a car that can both nail perfect 'ring laps and waft like a Roller when you're around town. Which is why cars like the M5 and M6 have a million different settings for dampers, throttle and even steering weight. And yet, in my experience, I've rarely encountered an adaptive system for steering or damping I'd choose over a well-judged passive set-up. So, am I just a Luddite?

In terms of suspension, perhaps not. "A passive damper probably always responds in a way that's consistent," says Mike Cross, "and I think probably what you need to do with an adaptive damper is make it feel as if the car is a little more controlled but try and do it in a seamless way so that the driver is not aware of the system working. If it's obviously doing something, in a way, we've failed."

'Stiff' can still be 'comfy', as our Megane proves
'Stiff' can still be 'comfy', as our Megane proves
And yet the bloke who's just spent a few hundred quid on the optional adjustable dampers still wants to feel something when he pushes that 'sport' button, right? A polite smile in response says a lot. And takes me back to a comment from Richard Attwood on a Porsche launch. As we headed out onto the track my reflex was to hit the Sport button on the PASM. "Don't bother," he growled. "It works better in the standard mode."

What of Chris Harris and his Jag XF's dampers taking time to 'warm up' on cold days? Cross says he'd be surprised if the ambient temperatures - even in the Welsh borders - would be sufficient for that to be a factor. Harris begs to differ. I'll leave them to have that chat anon.

And consider instead the simplistic notion often bandied about that a stiffer suspension set-up automatically equates to a 'sportier' one. That's our - as in motoring hacks - fault. "Comfort and refinement is really important to customers; it's sometimes less so with you guys," says Mike, going on to explain how a 'softer' car can often be the faster car on your typical bumpy British B-road.

Dan and Mike chat in a totally unposed fashion...
Dan and Mike chat in a totally unposed fashion...
As ever it comes down to tuning and calibration and making sure everything is working in harmony. Which is apparently how Renaultsport can get away with ostensibly fierce spring rates on cars like our PH Fleet Megane, the Cup chassis we've opted for running springs 38 per cent stiffer than even the regular 265's. Mike points out that the ride frequency won't have changed by as significant a figure and says we can tolerate significant and rapid vertical movement so long as pitch and roll are well contained. Which translates as that 'four-square' sensation of all corners of the car working together in unison that feels so satisfying. "They seem like very well sorted cars," he says, with particular praise for an Megane R26.R he had a go with. "They've clearly gone to a lot of trouble matching the damping to the spring rates."

The only thing this really proves is that perpetuating the myth that soft can't be sporty and stiff can't be comfy is over-simplifying a complicated engineering problem. Something that perhaps needs articulating more clearly.

Dan

 

Author: Dan Trent
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