A harsh ride: PH Blog

XFR-S too firm says PH review - not so says Jaguar and off to Gaydon we go

No editor wants to receive a summons. But we got one off the back of our review of the Jaguar XFR-S. In it Nat Barnes said "if you were being polite you'd say the ride was fidgety and if you weren't at times it's verging on unbearable. Cat's eyes crash through the cabin and you feel every expansion strip. Make no mistake, it's so firm it sometimes makes an Audi feel compliant."

XFR-S very different in sinister grey/small wing

Jaguar begged to differ and requested our attendance at Gaydon to spend some time with Mike Cross in an XFR-S. No chore - Mike is always fascinating company and this was a friendly invitation rather than a gun to the head.

Mike and I have discussed the 'science of flow' thing before, his job basically being the articulation of subjective ride and handling nuances into hard data for the engineers. Tools for the job? A nicely sinister looking XFR-S in dark grey with the optional small wing, an XJR and a couple of hours to kill on the Gaydon test track.

In terms of differences over the XFR Mike asserts that the damper hardware and anti-roll bars are identical. The steel springs are up 37.5 per cent front and 40 per cent rear and the tyres are 10mm wider 265/295 front/rear over the XFR's with both cars running 20-inch wheels as standard.

Mike on hand to demonstrate the principle

Jaguar's high speed test track uses a section of the old V-bomber runway and speeds into the 170s are easily achieved, subsidence and other natural lumps and bumps meaning the wide, fast corners have plenty of unsettling surprises including a vicious dip at the entry to the 120mph left-hander at the bottom. Which the R-S falls four-square into and damps the return stroke without a quiver. In Mike's view we can tolerate a fair amount of vertical movement - sufficiently damped of course - but it's the porpoising into dips that really unsettles both car and driver.

High speed stability is one thing but here in the UK we're more likely to be driving at sub-60mph speeds on broken, bumpy roads not 150mph-plus on smooth Autobahn.

A tighter handling circuit with vicious bumps, potholes, simulated frost damage, harsh transverse ridges and 'noisy' tarmac is probably more representative and here a sense of Nat's issue with the ride does show. This is an exaggerated test surface but the fat tyres do steamroller over it, harsher bumps thump through and there's a definite jiggle factor most Jags smother.

So, basically, you need to wheelie your car...

But it's not brittle, the initial damper movement is smooth and even with the firmer springs you can feel full travel of the suspension being used. The XFR-S is not a light car but these violent weight transfers feel well contained. Simplistically it feels 'firm' but controlled.

We do the same in Dynamic mode, which basically narrows the window of the dampers and raises the lower threshold of the operating range. Now it really does feel pretty harsh, but that's the purpose of this test track. Then an interesting thing on a rapid-fire series of transverse bumps. And here the fore-aft damping keeps the car flat, despite the pile-driver impacts and rapid undulations. If you've ever ridden off-road on two wheels think of it as the difference between the nodding donkey sensation of rolling through a dip versus raising the front wheel, keeping your body level and 'pumping' through the compression - see here for an explanation!

When we switch to the more softly sprung and damped XJR it actually feels more unsettled through this same section, demonstrating 'firmer' doesn't always equate to 'less comfortable'. The XJR also feels like it's rolling onto its outside tyre walls on a high-speed right the XFR-S barely flinches at. In Dynamic mode the XJR feels a lot better. But does hitting the button actually raise the cornering limits?

Osteopath on speed dial? Your call

Mike answers thoughtfully, saying in a steady state no it doesn't. Nor does it affect the amount of roll under load, though it does change the speed of its onset and the transient behaviour on turn-in can be played with via the software and sensors. From the wheel that might mean a temporary firming of the rear dampers for a 'sharper' turn-in, something I could feel even from the passenger seat of the XJR.

Of course, we're talking 550hp mega saloons here. And if you wanted to transport that apocryphal box of eggs across a ploughed field - or around Jaguar's test track - and not end up with them ready scrambled you'd still use a 2CV, not an XFR-S.

Dan

[Sources: MPORA]

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MissChief

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