Your questions answered: why are new car wheels so darn big?

In this edition of Your Questions Answered, Robbo looks at why carmakers are going big on wheels, and why we don’t have to put up with it. He also looks at the thorny issue of spare wheels in many new EV’s and talks of towing with Toyota Prados.

Got an automotive question but you don’t know where to find the information you need? Never fear, email us here at editor@carsales.com.au.

Answer: Hi Jon, thanks for the note. Kia’s cool-looking electric van looks likely to hit Australia in the second half of next year with the brand confirming that it’s initially bringing in the cargo-only version.

There’s already a PV5 in Australia, which appeared at the recent Sydney Electric Mobility event.

The PV5 is expected to have front-wheel-drive mechanicals based off the EV3 and is the first in a line of Battery Electric Vehicle (BEV) vans and people movers that will come out of Korea.

Sometimes the car won’t unlock when I touch the handle – usually when my phone and smartcard are in the same pocket. As soon as I move the phone to another pocket, I can unlock the car.

This proximity problem suggests that the phone can interfere with the car key signals. – Lawrie

Answer: Thanks, Lawrie, that’s interesting. Many times I’ve wiped a hotel room key after leaving it in a pocket near my phone!

We can also follow up on Emma’s query about her troublesome GWM Haval key. After stalling her for a while, the local dealership finally coughed up for a new fob, and Emma’s entry dramas are now a thing of the past.

Answer: Hi Stanley, we can’t give you a definitive answer on this one, but we reckon it’s a 50-50 chance, given the current line-up.

The Tank 400 – which we’ve actually driven  – fronts up as a bold and brassy take on the Jeep-esque Tank 300, with strong off-road as a bonus. However, it’s only offered with a turbo-petrol drivetrain, which is at odds with its 4x4 aspirations. The Tank 300, of course, comes with a choice of three drivetrains but there’s no real point of difference, for example, a third row of seats. Besides, if you want a seven-seater, the Tank 500 is ready and waiting…

Wedging it into a growing local GWM line-up could prove challenging for the brand when it comes to price and positioning. Does it want to risk confusing the walk-up from the Tank 300 to the Tank 500? I can see both sides of the argument. It’ll possibly steal sales from other Tanks, whereas, having it in the line-up may also bring more people into the showroom.

Why are wheel sizes growing in combination with less tyre tread on the road IE more meat, less bread in the sandwich?

Locally, our roads are very average, with many potholes etc, all of which create bumps particularly with the larger wheels. – Bill

Answer: Aaah, Bill, you are a man after my own heart. I have long argued against the modern trend of larger rims and low-profile tyres for the very reasons you raise.

The tyre’s profile, or aspect ratio, is the height of a tyre’s sidewall expressed as a per cent of its width across its tread face. A 55-series tyre, for example, has a taller sidewall than a 40-series tyre.

Tyre sidewall height is crucial when it comes to ride quality and bump absorption. In fact, think of it as part of the car’s suspension package. A taller sidewall offers more compliance at the expense of response – a shorter sidewall provides more stability at the expense of ride.

The answer to your question is simple, fashion currently dictates that larger wheels look cooler. Ultimately, it’s a self-defeating trend. Larger-diameter rims weigh more, lower-profile tyres are more expensive, and the combination makes for a firmer ride overall that’s hard to avoid.

However, there’s generally nothing stopping you from fitting a smaller rim with a taller tyre profile to your new or used car, particularly if a smaller wheel came on your car as a factory fitment. I dropped two rim sizes on my personal car a year or so ago (from 20s down to 18s), and I’m more than happy with it.

I would advise seeking input from your local tyre store or car dealer first, though. Brake caliper clearance, tyre width and vehicle load rating all need to be considered before laying down the credit card for a new set of wheels.

We have a 2020 Toyota Prado with a lot of extras, which has a tare weight of around 2.7 tonnes with everything on board. We’ve bought a small 18ft caravan with a loaded weight of about 2.4-2.6 tonnes. Should we be worried about towing it? We have a GVM upgrade but no GCM change. If it can’t, we’re thinking of a Mazda BT-50 SP or Chevrolet Silverado ZR2 as a replacement. – Jackson

Answer: Hi Jackson; we’ve done a tow test with the 2020 Prado and it came up pretty well.

What concerns me is the 200kg weight range you’ve estimated – it could mean the difference between a smooth tow and a stressful trip. The only way to know is to run the car and van across a weighbridge to get an exact read on your gross combined mass, and – just as crucially – how the van sits on the tow ball. This will largely dictate how well it will behave behind your car.

The 2020 Prado received a power bump, which will help on the open road. At the end of the day, it’s still a 2.8-litre four-cylinder diesel, so the more you tow, the slower she’ll go. The BT-50’s 3.0-litre is well regarded, and that extra 500kg of tow rating will help – but can you live with a dual-cab after having a Prado wagon? Same caveat for the Silverado… it’s a big rig, as well. Good luck with your quest!

Hopefully you have picked up on the fact that there is substantial regional interest in moving to EVs with the caveat of having the option of carrying a full-sized spare.

I am proposing to complete my order of the Zeekr 7X performance vehicle [21-inch rims as standard/TR]; its AWD and air suspension are very desirable traits for our vast country. The concern is what happens when an inevitable wheel fails on our potholed roads?

I would also be very happy to have 20-inch wheels to assist storage of the fifth wheel so I can roam further. These are offered in other markets so hopefully it would not be too difficult to offer them in Australia.

Sadly, the numerous stories of vehicles needing to await a flatbed truck are widespread and the obvious need to be self-sufficient is not really acted upon by most manufacturers.

Here is an opportunity for Zeekr to positively respond to consumer feedback. There is a vast currently untapped regional market who will potentially reward such a sensible move. – Grahame

Answer: Hi Grahame, thanks for the note. A quick perusal of the specs of the Zeekr 7X Performance reveals 21-inch rims are fitted as standard. However, the entry-level Long Range is equipped with 19-inch rims.

If tyre security on poor country roads is your priority, I would bet dollars to donuts that a 7X Long Range owner would swap for your Performance wheels in a heartbeat, if the dealership wouldn’t assist first.

I’d be surprised if the dealer couldn’t help sourcing a fifth 19-inch rim as well. The taller profile of the 19-inch tyre will offer more compliance and rim protection and a much-improved ride thanks to the more compliant sidewall profile of the tyre.

If you’re looking for factory-spec 20-inch rims, though, then it may be a matter of waiting until Zeekr’s accessories catalogue comes on stream.

I couldn’t find any images or details about the wheel well size under the boot floor, but there are several aftermarket space saver rim options available.

The views stated in this advice column are advisory only. Questions may be edited for clarity and length.

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