KM3 Long Term Review

Sometime in 2018 depending on your market region BFGoodrich launched the KM3 a revision to the popular KM2 Mud Terrain tyre. Some bold claims on increases to performance. The 5 – 8 -27 mantra was part of the marketing.

The new model purported to be a cross-over tyre suitable for both All Terrain and Mud Terrain uses. Typically the ATs have a 75:25 ratio of block to valley within the profile and the Mud Terrains having a typical 50:50 block to valley profile. So what is this witchcraft? Is it any better and is it really a cross-over?

Compared to the older KM2 the tyre was claimed to have 5% better traction in mud, 8% more grip on rocks and 27% tougher sidewalls. A claim that the KM3 outperforms the previous generation KM2 in spades. Although 5% is hardly a spade full.

Having used the KM2 and KM3 extensively in Sand, Mud and Rocks I can say it performs better but 5% is a small amount. Is it noticeable, I think so. I switched my tyres at the Michelin Training Center in Stoke in 2018 and on the drive home I noticed an immediate difference in noise coming from the highway drive home. This is even though there’s no specific claims on the noise in the marketing literature. I’ll break this down later. The stability was improved no doubt due to the tougher sidewalls. So is it noticeable? Yes it is. I’ve now driven the length of Africa and I don’t drive in a straight line.

SAND
A Mud Terrain isn’t the best tyre to go into sand as that would be something almost like a racing slick. The less tread means the less disruption to the sand surface as so higher flotation. So you’d imagine a KM3 would be terrible. It’s not so. With sufficient deflation based on your vehicles weight* you can effectively “dig” your way across wide expanses of sand. I’m too heavy to go dune bashing but having travelled across the top of Mauritania in very deep sand to visit Ben Amera I can tell you it performs very well. With a worn older tyre I’d guess it gets even better as the blocks round off and so takes us back to the less surface disruption. My tyres were almost new and I got there and back with only a few incidents which of course are driver error and my vehicle weight.

I did not note that I had to drop my pressures any lower than normal but maybe I should have as the stronger sidewalls do seem to have an effect. I’m now on my second set of KM3 and more recently I’ve been experimenting with some lower pressures and it does seem to return dividends. However only you know how heavy you are and how low you can go.

*Don’t use a pressure figure your mates tell you works, figure it out yourself based on your individual weight. It’s important for all road surfaces. Your truck may be lighter or heavier than your mates.

MUD
Mud Terrains in mud do perform very well. Who would have thought that? You don’t need to keep as much momentum as you would with an AT like the KO2. This is one of the most important aspects. You can get yourself out of most situations with a KO2 if you have the momentum and you are an experienced driver. With a KM3 you, like me, can make more mistakes and still make it through. As I’ve said my vehicle is heavy and I’m not the best driver but to date we’ve not been stuck in Mud. The tyre seems to shed mud from the tread very well and cleans itself off quite quickly. So that’s 5 stars from me. Is it any better than the KM2? I honestly cannot tell if it is or is not but neither tyre left me stuck in the sticky stuff. I’ve had incidents but I wasn’t stuck. I’m confident in entering mud with this tyre and don’t second guess its capability, only mine!

GRAVEL and ROCK
What can I say about this. I’ve done tens of thousands of kilometres on gravel and rocks. I’ve truly gone places I should not really have been. The performance is outstanding. There’s some YouTube videos of me being silly one various mountain passes and trying to destroy my truck and my tyre. I’ve also noted even when new they don’t pick up stones as easily as the KM2. Significantly less in fact.

We recently succeeded in killing a tyre, I should say that. I can say that the wear of gravel is much greater than on any other surface. It really takes its toll. I’m at the physical limit of this tyre due to my axle weights and this is reflected in the pressures I need to run. Combine this with significant ambient temperatures here the tyres are working really hard. Recently I’ve ripped a tyre apart with a tear which is large enough to deflate it in a couple of seconds. This was a combination of low pressure and the age and kilometres on the tyre. My current, second set is starting to show its age and is due to be replaced. Older tyres are much more likely to suffer punctures. This is the way. More on this below.

HIGHWAY
It’s not a highway tyre but performs as you would expect on highway. It’s a confident tyre that passes this to the driver. It’s not as scary in the wet as some mud tyres but it still needs a change to your style if you are used to a road tyre or even an AT. The wet breaking is not brilliant but adequate. I’ve had my moments with emergency stops in both dry and wet and didn’t hit anything. I think that’s a good sign. The goats get everywhere as do the taxis in Africa and they don’t care if they’ve come out on you.

In the dry you can motor along like any other tyre. I mentioned the stability earlier and it’s not a bouncy wobbly tyre it just feels normal, probably due to the thicker side walls. With the tyre off the truck you can feel the difference from other brands with the side wall thickness. I suppose the wobbly bouncy feeling could change with larger sizes as I’m only running and 235/85R16.

PUNTURES AND WEAR
I’ve had two deflations in over 100,000KM. Both times this was at the end of the tyre life and once was a tec-screw roofing bolt. So that doesn’t really count as they’re designed to drill through steel. The other time I’ve mentioned above. I killed it myself and the tyre failed. What happened is hard to say but it’s ripped not sliced. Typically slicing happens in the wet. A wet tyre is much easier to slice. This was in the dry and very sudden in a not particularly difficult section crossing a dry river bed. However I was running sand pressures and giving it some power to come up the bank. The tyre had over 40,000km already and was a 4 year old. Hardly a big loss. It’s had a very hard but long life.

EDIT….
Additional investigation on the rip that was not the ultimate cause of the deflation. I need to speak to Michelin Technical about what happened. Watch this space.
END EDIT….

Chipping is still there but less than previous tyres I’ve had. I’ve got some chips as the tyres are old and I’ve spent almost a year driving on gravel tracks and pushing the truck up mountain passes. They are certainly significantly better than the original KO as that was awful with chipping and it’s much better than the KM2 they replaced and more like the KO2 in this regard. A significant thumbs up there.

Big block tyres wear strangely. See the photo. This is caused by high torque on tarmac type surfaces where the tyre contact patch is travelling at the speed of the vehicle but the tyre itself drags at different speeds through the contact patch. This causes the blocks to compress and then skip as they roll out of the contact patch. This is the same effect as if you are trying to file a piece of metal flat. You always end up with a high and low point on the edges. On tyres this creates highs or lows on the leading or trailing edge depending on direction. Different levels on blocks across the tyre is because the blocks are not all supported the same due to size and position on the tyre. The effect is exasperated at the edge near the side wall due to the differing load at that point and the potential for it to be hotter due to under inflation or heavy load as I my case.

Note the block levels and wear. Makes them noisier as they get older.

MY WEIGHT AND PRESSURES
Tyre
235/85 R 16 120 load index
Axle load
Max 1700kg Front
Max 2300kg Rear
Road – Highway Speed 70mph – 40psi Front / 65psi Rear
Cross Country- Maximum speed 35mph -33psi Front / 51psi Rear
Mud/Sand – Maximum speed 14mph – 28psi Front / 43psi Rear
Emergency – Maximum speed 5mph.– 24psi Front / 37psi Rear