BF Goodrich Tyre Test
LRM heads to the USA to test Bfgoodrich’s next-generation off-road tyre – the BFG Mud-terrain KM3 – on the infamous Rubicon Trail
LRM heads to the infamous Rubicon Trail to put the new BFG Mud-terrain KM3 through its paces
IF YOU’RE going to test an off-road tyre, you need to do it properly and there’s nowhere tougher on rubber than California’s punishing Rubicon Trail. So, that’s where we headed to assess the end result of six years of intensive development by Bfgoodrich. Back in the early 1980s, BFG introduced an unconventional tyre that would forever change the way we thought about off-road traction. They called it the T/A Mud-terrain. It was the first such tyre with an aggressive tread design, deep voids and radial construction. The impact was such that in the following years, nearly every tyre manufacturer in the genre would introduce a variant of Bfgoodrich’s original design. In 1984 the company rocked the four-wheel drive community with a 35-inch version, a massive tyre for the time. Veterans of the Rubicon scene like me were ecstatic.
This new miracle tyre provided extra ground clearance, and at low air pressure its soft sidewall deformed like a warm marshmallow. However, it was also susceptible to pinching, tearing and punctures.
During the following decades the tyre underwent several revisions, ultimately appearing as the KM2 in 2007. With technology moving at light speed, the company’s engineers returned to the drawing board using CAD systems and consulting with chemists, as they spent the following six years developing the fifth-generation T/A Mud-terrain They called it the KM3.
Is this the best off-road tyre ever made? Well we were to soon find out as we headed back to California to test this latest variant on the Rubicon’s unforgiving granite – some of the most brutal terrain a tyre will experience.
NVH
Noise, vibration, and harshness (NVH) on tarmac are a tough nut to crack for an aggressively-treaded off-road tyre, but we had plenty of time to assess this as most of our miles were spent driving to and from the trail.
But first, what causes NVH? Noise is caused by voids in the tread block creating turbulent air: the larger the void the more noise. Meanwhile, a tyre’s roundness (or lack thereof ) and carcass design is a major contributor to vibration and harshness.
In addition to core construction, other contributing factors include how true the mould casting is, equal distribution of material during the moulding process, and post-production trimming. If done well, the tyre will be round. When combined with the proper rubber compound, it will be more predictable and track better.
En route to the trail on the tarmac, we found the KM3 to be surprisingly quiet at speed (for a mud terrain) and showed
On the Trail
If you are going to hit a rock or fixed object at speed, the general rule in desert racing is to place it squarely on the centre of the tyre, because the tread block is more resilient to harsh impact than the softer sidewall. But stuff happens, and when you do clip a sidewall or pinch it in low pressure situations, it needs to be tough. The KM3 utilises Coregard Max, a three-ply sidewall design and rubber compound that is more resistant to splitting and punctures – according to Bfgoodrich, it’s sidewall is 27 per cent tougher than the previous version.
The first testing phase included racing in UTVS on a highspeed track through the Sierra Nevada mountains, but a better evaluation would be on the Rubicon, where we slipped behind the wheels of two Defenders – a 110 and a 90.
On the dirt roads leading to the trail, step out, or side skip, was limited and lateral grip in the corners was positive. But what really impressed us was how tough this tyre was when we put it up against the Rubicon’s unforgiving granite.
At 15 psi, the tyre deformed like an inverted mushroom, conforming to the terrain and increasing its footprint on the tractive surface. Macro and micro keying under these conditions was excellent. The wraparound directional sidewall tread, which BFG calls ‘Traction-armor Sidewall
Sculpture’ was able to grip steep side hills like a hyena on a gemsbok’s tail, refusing to let go. Not withstanding cool buzzwords, the KM3 performed exceptionally well.
We would have liked to put the KM3S through more mud, the bottomless soupy gumbo type, but we did find areas of water and light mud. The shoulder, along with ‘mud-phobic’ bars placed in the outer voids (apparently they hate mud) was effective at clearing debris and providing additional forward force. Overview
Overall, the six years Bfgoodrich invested in the development of the KM3 has paid off. Their 45 years of desert racing experience has provided proper insights as to the abuse a tyre will receive and how to address the various challenges that come with it.
They’ve improved upon an already good tyre, addressing traction and sidewall toughness while enhancing NVH and on-road manners.
The KM3 will be on sale this summer via a phased introduction. There will be 20 sizes on sale in the UK by the end of the year, covering 15- to 20-inch wheels, with several dimensions available immediately. By early 2019, there will be 42 sizes on the market, 21 of which are new. Our initial impressions need further vetting so stay tuned, as we’ll be mounting a set for a proper long-term evaluation.