You can now run 18″ wheels on your L663 Defender D300 and P400

Land Rover make some immensely capable 4X4s, but ever since the new generation kicked off with the Discovery 3 in 2005 the company has, sadly, fitted low-profile tyres to its vehicles which look good outside an urban cafe but compromise offroad capability and are prone to damage in the bush. And the new Defender L663 is no exception.

Now before I get into the problem and solution, here’s some terms so we’re all on the same page:

A “low profile” tyre has a small amout of rubber between the rim and the road, so a short sidewall. There’s no fixed defintion of “low profile” vs “high profile”, but on tyres around the 30-32″ overall diameter we’d say a 20″ rim would have a low profile, and a 17″ would be high profile. The lower the profile, the shorter the sidewall. Compare these two:

Now for offroading, the taller the sidewall, the better. That allows the tyre to flex and mould over uneven terrain, and it means you can drop air pressure without worrying about the rim damaging the tyre, or the rim hitting the ground. Reducing air pressure in tyres is one of the best ways to improve your offroad performance, be that driving in rocks, mud, sand or snow.

Here’s a Range Rover Sport 20″ rim, at road pressure, not dealing at all well with a simple rock. Notice how the tyre is crushed against the rim – this can lead to damage for both tyre and rim.

And here’s another Range Rover which had exactly that problem:

So why do Land Rover fit low-profile tyres to their vehicles? Answers on a postcard please, got me beat.

Anyway, if you are an offroader what you want is the smallest diameter rim you can fit; which means one of 17 or 18 inches, not 19, 20 or worst of all, 22.

Yet Land Rover insist on fitting their cars with huge rims. Most L663 Defenders, for example, come with 20″ rims with 265/60/20 tyres. These rim are far too large as they only allow a 163mm tall sidewall, and that’s before any weight is out on the tyre. In contrast, a 275/70/18 tyre allows another 25mm of sidewall, 15% more…and every millimetre helps.

Personally, I hate low-profile tyres on 4X4s and over the years have spent a lot of time explaining the problem. So I’m really pleased to see there’s a solution from Land Rover wheel specialist TuffAnt. They offer 18″ wheels to fit modern Land Rovers, including the Defender, so if your Defender doesn’t already run 18s then if you have a D200, D240, D250 or P300 just unbolt the old wheels and pop on a new of 18s. You could run Land Rover 18s, but carmakers charge a fortune for their wheels and Land Rover is no exception, so it’s cheaper to go aftermarket.

But there’s a problem with the Defender D300 and P400 – these vehicles run higher-power engines and have larger rear brake calipers than the other models. Which is a bit unusual, as normally the front calipers are larger than the rear. Anyway, 18″ wheels won’t fit on the D300 and P400 rears because of those large calipers.

So what TuffAnt have done is fit the calipers from another Land Rover product to the rear of a Defender, and that gives the required clearance. But..that’s a brake modification, and brakes are a critical safety item, so that change needs engineering signoff. Which is exactly what TuffAnt have done, taking their car to a test track for formal engineering certification and signoff.

The tests involved loading the Defender to GVM, and performing a series of high-speed consecutive stops in accordance with the Australian Design Rules standards.

Now that’s done, L663 Defender D300s and P400s can legally run 18″ wheels, provided that those wheels are TuffAnt, the caliper is provided by TuffAnt and fitted by an authorised installer (there will be one in each Australian capital city) who will then provide a modification plate. So, you can’t just DIY, and you can’t use any other kit to get the certification. If you do DIY then you’re running an illegally modified vehicle with consequent implications for insurance, or lack thereof. Oh and if you do swap rims, ensure they are load-rated to at least the original rim specifications, and the offset is within legal limits. Interestingly, you also need to put the Defender into “service mode” for th caliper swap! Don’t think that was necessary for a Series vehicle 🙂

So I think TuffAnt 18s for all Defenders is great news, as it’s a real disappointment to see capable vehicles like Land Rovers crippled with low-profile tyres. And another bonus is weight saving. I calcualted the weight of a 255/70/18 tyre running a TuffAnt alloy wheel and Goodyear Wrangler at 33kg, whereas the same Wrangler tyre but in 255/60/20 on a 20″ rim would be 39kg. So that’s 6k per wheel, or 5 x 6 = 30kg weight saving, or 30kg more payload. And, that weight saving is both unsprung mass as well as rotating mass.

Land Rovers are capable despite, not because of their tyres. Now you can fix yours! The kit isn’t on the market yet, but contact TuffAnt if you’re interested.

Wondering about changing tyres? Try my Tyre Size Calculator.

What are the pros and cons of low-profile tyres for 4x4s?

Want to know what tyre markings mean? Watch this:

New Defender Q&A