David Wilson talks wheel sizes

Carry too much speed and run too high a tyre pressure on the dirt and you can expect tyre failure on the stock rubber.

Is it a twenty-inch, maybe a nineteen, perhaps an eighteen? Nup, none of them. In the quest to stop the modern vehicle in the shortest possible distance, the world’s gone barking mad.

4W driving is something we do a lot of here in Australia, likely more so than just about anywhere else on the planet and because of that we should be demanding something better of new vehicle makers. Because they all know that ninety percent of 4WD owners don’t go bush, they fit tyres up as standard, in highway issue, paper-thin, with a uniform pattern, unable to carry much of a load and far from fit-for-purpose. Point them at a dirt road and you can almost hear the air escaping before the first puncture has been suffered. Whenever I’m testing a new vehicle it’s the auto equivalent of walking on eggshells. Back to wheel sizes. When you put a bigger brake on a vehicle you need a bigger wheel to go around it and an amount of space to clear the brake rotor and caliper to allow for errant rocks to rattle around inside the void without crashing into things. I get that bigger brakes makes a vehicle safer in an emergency stop, but what I don’t get, is a bigger wheel size that’s more to do with fashion. I recently read a post by a bloke called Ash on the Toyota Prado Owners of Australia

Facebook page. He tells the story of a recent trip to Alice of some family friends in their 2021 Kakadu. They suffered a couple of catastrophic fails on the dirt and wondered why on a big, beefy 4WD, the stock Dunlops weren’t up to the job? Given that the family were then stuck in Alice (because no-one carried nineteens) he pondered what might have been a sensible alternative?

The post on the Toyota Owners of Australia Facebook page says it all.

Prado, from what I’ve been able to glean, in this late 150 series, run rotors measuring 338mm front and 312mm rear. Add the caliper overlap and you see why they list the seventeen inch as the smallest wheel option, it’s a big assembly. Toyota have had four different wheel and tyre packages available in this model and they all run out to around 775mm rolling diameter. It’s a pretty standard size for most 4WD buggies in this medium/ large category, offering the right balance gearing-wise. It’ll have a modest ground clearance, still be able to accelerate away from a set of lights briskly and carry a light load (on the bitumen). Those choices are: • 265/65R17 112S fitted to a 7.5Jx17 wheel • 265/60R18 110H fitted to a 7.5Jx18 wheel • 265/55R19 109V fitted to a 7.5Jx19 wheel • 265/50R20 107V fitted to an 8Jx20 wheel The tyre that failed was the nineteen inch and it’s woefully inadequate for any gravel, anywhere, anytime. The load index is pathetic (109 = 1,030kg) and the speed rating is absurd for this country (V = 240km/h) and as they discovered, unobtanium outside of suburbia. If you’re going to buy a Prado for a bush excursion, make sure the placard on the car lists the seventeen-inch option, because then you’ll have choices, the other wheel diameters are full of compromise. That’ll likely mean you’re buying a poverty pack GX or a GXL and that, to me, is a good thing because the change you’ll save from the top-spec Kakadu gives you a tonne of spending money at your local accessory house to fix the suspension too. In a seventeen you could opt for the same size as original, but this time rated Light Truck (LT) and it’ll come with a massive increase on load index (and this gives you puncture resistance). It’ll read LT265/65R17 120R. That 120-load index = 1,400kg (Vs 112 = 1,120kg) of capacity and that ticks my 4WD tyre benchmark box. If it’s not 120 rated or greater, pass it over, and if you were wondering about the speed rating, R = 170km/h, is plenty fast enough for Aussie highways. There’s another legal alternative and the one I prefer to use, LT265/70R17 121S. A

Whilst the size might look the same as the OEM 17” tyre fitted to a Prado the devil is in the detail. This is a proper Light-Truck 4WD tyre with a massive increase in carcass strength. You’ll struggle to put holes in it.

This is my preferred option; good wheel to brake clearance, deeper sidewalls and a ripper load index, the true barometer of tyre strength!

five percent increase in sidewall height gives a small increase in ground clearance which is always welcome and it won’t affect gearing much at all and rolls out at 805mm. It achieves my 120-rule with 50kg more capacity and that means it’s stronger. Importantly you’ll find it on most resellers' shelves. It’s worth noting that both of these will retain some degree of comfort, despite the carcass now being a ten-ply rating, because there’s 172mm/185mm worth of sidewall height respectively, affording flex where the bigger wheel diameters can’t. Bad luck if you opted for the twenty because a 50 series sidewall has only 132mm to absorb the bumps before the suspension goes to work. Might not seem like much, but it’s plain as day when you drive them.

The new rubber is an LT265/65R18 122Q and will take a beating and for those of you reluctant to change your new ute’s 18” wheels it offers a legal improvement.

The nominal diameter I reckon that works for most owners is quoted as 32” in American sidewall-speak. That’s a little over 800mm in Aussie sidewall-speak.

My peeve with the prevalence of eighteeninch wheels in dual-cab utes is the paucity of quality tyre product. Up until recently there’s been precious-few choices, often just dressed-up passenger car pretenders with mild A/T patterns and retaining lowly 112-114 passenger load indices. I’m experimenting at the moment with a set of eighteens on my new D-MAX and running Toyo’s R/T (Rugged Terrain) in LT265/65R18 122Q. I’ve had the pattern before and they’re great, but the last time in a sixteeninch fitment (75 series) with near-200mm worth of sidewall and the difference is telling. Running the right pressure in both instances (based on the weight of the vehicle) at around 210kPa/30psi, you get a bit more thump on broken bitumen and dirt with the shallower sidewall seen on

New boots on the D-MAX and in 18”, something I’ve avoided in the past but this Toyo R/T has a load index that suits me fine.

Here’s a comparo between my old 16” Toyo OPAT II and the new 18” Toyo R/T. The deeper sidewall of the 16” offers more flex in really bumpy conditions.

the eighteen measuring 172mm, versus the 200mm on the sixteen. Less flexibility makes for more road shock. There’s plenty of pressure (no punintended) (and there’s a whole other story on “pressure” too) on seventeens at the moment. As road safety mandates overrule 4WD and off-road capability we’ll end up with wheel and tyre sizes that are the antithesis of what’s really needed for trouble-free dirt road touring. Brakes, they’re the problem … overrated!

The new home of UBCO bikes in WA 288 Welshpool Road, Welshpool, WA 6106 Phone: (08) 9351 9000 Email: sales@fredhopkinswa.com.au www.fredhopkinswa.com.au

We Want To Give You A Boost

Ford / Mazda Bravo 2.5L RHF5 B2500 TDCI Ford Ranger/ Mazda BT50 3.0 J97MU 115 Kw Holden Colorado RC 3.0 L Holden Rodeo <97 Holden Rodeo 98-2002 Holden Rodeo Isuzu Dmax Hyundai KIA / SANTA FE 2.2L CRDI TF035 Isuzu Dmax / Holden Colorado 4JJ1 3.0L Mazda CX7 Petrol Mitsubishi 4M41 TF035 early 3.2L Pajero Mitsubishi Pajero 4M41 Mitsubishi Pajero 4M41 RHF5 3.2L TT-VJ33 TT-VJ38 TT-VIGM TT-VI58 TT-VIBR $1350 + gst $1350 + gst $1350 + gst $900 + gst $900 + gst

TT-VIDW

$1350 + gst TT-49135-07310 $1350 + gst TT-VIEZ $1350 + gst

TT-K0422-582

$1350 + gst TT-49135-03410 $1350 + gst TT-VT13 TT-VT12 $1350 + gst $1350 + gst Mitsubishi Triton TT-49135-02912 $1350 + gst Mitsubishi Triton / Challenger RHV4 4D56 2.5L 100 Kw TT-VT10 $1350 + gst Mitsubishi Triton / Challenger RHV4 4D56 2.5L D-ID 100 Kw TT-VT16 $1350 + gst Mitsubishi Triton 4M40T 2.8L TT-49135-03130 $1350 + gst Nissan Navara 3.0L ZD30 D22 1411-9S00A 170 Kw TT-HT12-19D $1350 + gst Nissan Navara D22 2.5L RHF4H TT-VN4 $1350 + gst Nissan Patrol HT18 TD42T Y61 GU watercooled TT-14411-62T00 $1350 + gst Toyota CT20b 100 series 1HD-FTE TT-17201-17040 $1350 + gst Toyota CT26 80 series 1HDT TT-17201-17010 $1350 + gst Toyota Hi-Ace TT-17201-30180 $1550 + gst Toyota Hi-Ace TT-17201-30200 $1550 + gst Toyota Hi-Lux / Prado / Front runner 2.8 L TT-17201-11080 $1550 + gst Toyota Hilux 3.0 L 1KZ-TE CT12B TT-17201-67010 $1350 + gst Toyota Hilux 3.0L CT16VGT 1KD-FTV D4D TT-17201-30110 $1550 + gst Toyota L/Cruiser 12HT 1HJ61 TT-17201-68010 $1350 + gst Toyota L/Cruiser 1VD-FTV V8 twin turbo LC200 series TT-VB22 $1850 + gst Toyota L/Cruiser 1VD-FTV V8 twin turbo LC200 series TT-VB23 $1850 + gst Toyota Prado 3.0L CT16VGT 1KD-FTV D4D TT-17201-30160 $1550 + gst

Brand new highest quality | 12 months conditional warranty Each unit fully tested prior to sale | OEM quality and performance Trade and volume discounts if applicable

484 Great Eastern Highway Ascot WA 6104 m: 0418 922 018 | p: (08) 9478 2144 | f: (08) 9478 2166 e: sales@turbotech.com.au | w: turbotech.com.au