Aston Martin DBX
A switch to lighter wheels has improved our Aston SUV’S ride quality
WHEN DID WHEELS GET SO BIG? THOSE of us of a certain age will remember when 15-inch alloys were considered large, and if you had 16s you were talking about a serious diameter-to-width ratio, with a low-profile tyre thrown in for good measure. If you can call a 50 profile ‘low’, that is. But then 18s quickly became standard fare, 19s optional (the BMW E46 on its optional larger wheels was full Speed Freaks in overproportion for me), and then we blinked and the 20s arrived, with the world going big-rim, lowprofile-rubber mad. But why?
Well, cars are getting bigger so that they can pass ever-more-stringent crash tests, while the technology being squeezed into each new model requires more room, too. The inevitable result is bigger cars and, in turn, suitably sized wheels to make them work visually.
All of this means there are thousands of chassis engineers crying themselves to sleep at night as they try to fathom out how they can control all that unsprung weight hanging from each corner of their new car. The average weight of a 20-inch tyre is up to 15kg depending on the load rating. For a cast wheel you can add at least another 10kg depending on its design and how strong it needs to be for the role of the car it’s been designed to fit. For the DBX’S 22-inch Ribbon design wheels don’t expect much change from 35-38kg per corner.
In selecting the Ribbon wheels for JYD not only did I incur the wrath of evo’s car design critics but I had inadvertently handicapped the DBX’S Gt-like ride quality, a standout feature when I drove the model at its launch. A ruffle had appeared in the smoothness of the ride compared with those launch cars, with poor surfaces making themselves known in the cabin more frequently than expected.
Thankfully Aston Martin’s head of engineering, Matt Becker, knows more about these things than I do and suggested we tried the lighter – by around 3kg per wheel – Sport design wheel and drop the tyre pressures by 0.2bar. That second bit of advice is because the Pirelli P Zero only has one recommended pressure on the DBX that covers both high-speed and full-load running, yet the former is not something I’m going to achieve on the M11 between Cambridge and London, and even my family’s inability to pack lightly won’t trouble the DBX’S maximum load weight.
Anyway, the result is that the evo DBX has taken on the full gangsta look with its set of matt black Sport wheels, but they, and the small drop in pressures, have also brought a marked improvement in ride quality. There’s now more consistency on poor surfaces and less lowspeed shuddering – on the heavier wheels it could occasionally feel like you were driving over Belgian pavé – while high-speed ride, stability, grip and precision aren’t impacted one bit, so it’s a job well done all round.
Date acquired April 2021 Total mileage 6347 Mileage this month 2430 Costs this month £0 mpg this month 19.9