Tyres, grip and why Mikey won.

The Citadel - Essential References for Esk8
#1

So another epic track day in NL last weekend. Great turnout from all across Europe. We had dudes from Czechia, Germany and even NZ in attendance. We were privileged to have @xsynatic there as our celebrity guest of honour. It was also really interesting how few of the people I met were actually aware of this forum - blows my mind. But yeah, lots of different forms of vehicle doing the rounds and all with (at least) one thing in common: we were all sliding all over the place (like this and like this).

You can see in the first link there that the track is quite shiny along the racing line. It was also really dusty and quite sandy in places.

Track days are normally extremely physical because of the huge forces you’re constantly managing, but in this case, the forces were kept relatively small because you couldn’t go in so hot. But trying adapt the technique, weight distribution, throttle/brake balance etc. to the slippery circumstances so you could make it into, around and out of the corner without breaking away turned out to be equally tiring.

So mad props to @esk8manbabes for humiliating the rest of us with a win that put him 2.5s ahead of 2nd place (and 9.5s ahead of me) in the Esk8 AT category.

He and I were racing very similar setups so it would be easy to conclude that he is the more skilled racer. There’s no way I’m going to accept that explanation though so I’m zeroing-in on the one key factor that differentiated our setups: the tyres.

I was running practically fresh Evolve 175s. He was running brand-new AliExpress 200mm ATs. My tyres had a nice fat contact patch. His had a fairly narrow contact patch. The rubber compounds felt more or less the same. Certainly his weren’t as hard as the usual Ali AT fayre.

Conveniently enough, Mikey also weighs a bit more than me so I can put these two factors together and conclude that, since mechanical grip is a function of pressure and Pressure = F / A, he just had more grip. Case closed!

But alas it’s not that simple. For a start, he also did really well in the Street/PU category whereas I could barely complete a lap. Secondly, it turns out that rubber’s coefficient of friction actually reduces with pressure due to plastic deformation and tearing. Plus it begs the question: why would race cars (and LandSurf customers) choose to have such wide tyres if it didn’t improve grip?

So I wanted to open this thread to get more informed expert insight. Is there a way to determine the best tyre for your weight, setup and track surface? Is there a point at which you’re actually better off with a narrower tyre than a wider tyre? What else can be done to adapt to more slippery conditions and to prevent another humiliating defeat? :wink:

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Reinventing the wheel
#3

Tire Efficiency
So how do we achieve maximum traction? When we add weight to a tire the traction goes up, but not linearly (in a straight line). According to skid pad tests, it drops off pretty quick. Traction does not increase in proportion to the weight that is added.

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As weight is added to the tire, it will get more traction than it did with less weight on it. This much is true. But here is the catch, to gain that traction, weight had to come from somewhere.

Fundamental Truth Maximum traction in the rear is achieved when both rear tires have the same amount of weight on them, and as much weight as possible is transferred to the rear.*

A larger foot print will change a tires efficiency.
The larger the foot print the more weight it can hold before efficiency falls off.

That being said with a lighter rider, a wide contact patch to a point will give up grip to a narrower tire. Finding that sweet spot you need to factor your contact patch, tire compound and weight loading.

The weight on a race board is constantly shifting around, it is dynamic , it is not static (constant, still, not changing). We know that weight is going to transfer from the front to the rear, then we can assume that we will need to start out with, in the static state, more weight on the front and less on the rear than what we want to end up with on entry and middle of a turn. The question is how much.

Through durometer changes we can dial in our front to rear grip balance. Something we discovered early on when tire testing. Harder duro in the front softer in the rear.

I would say the winner here has a heavier rear foot than most, doing a better job of balancing the front and rear grip.

In the end “Grip is King”. You are only as good as your contact patch.

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#4

@MoeStooge and @brown5tick this is an excellent breakdown on tires and was a wonderful read. Thank you.

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#5

Cant we just say softer is better grip as long as the tire doesn’t rip?

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#6

i prefer fully inflated (60psi) 8" Innovas (MBS Roadies) to most of the tires i have tried so far. They are grippy as fuck but also wear out really fast. I guess that’s the tradeoff with softer materials. I carve a lot but I don’t race, so maybe my use case doesn’t really apply here. I think if i was racing on them i’d be replacing them for every event.

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#7

Thas what racers do anyway. If not every heat.

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#8

Esk8 racers or traditional motorsports?

#9

Racers. All of em.

#10

This is interesting. One of the learnings I thought I’d come away with was that I was wrong to try to load up the rear through and out of the corner. My thinking was that I needed max downforce on the driven wheels to get more purchase to accelerate out, but what tended to happen was that it would still break-away and just catch me totally off-balance. I thought on reflection that getting my weight more centred to apply an even pressure across all four contact points would give me more overall grip and better composure if/when I broke away. Interesting suggestion on hard-front, soft-rear though. I’ll definitely try that.

I seem to remember that they had a tendency to distort? Maybe it’s those ribs-for-her-pleasure and/or that they’re quite thin but when you load them up through a corner, you get the sense that they’re shifting, like maybe the sidewalls can’t handle the shearing force? Maybe I needed to pump them up a bit harder. Dunno. I’ll give them another try!

Has anyone tried the LandSurf tyres? Are they truly a noticeable improvement or are they still firmly at the Peak of Inflated Expectations?

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#11

Let’s just go with this. :joy:
Good to hear he’s still going well. What board was he riding?

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#12

Too goddamn easy, Ben! Don’t fall into that trap! Always bear in mind “brown5tick’s Razor”, which dictates that the least obvious explanation tends to be most accurate.

Yes, indeed. He’s doing embarrassingly well. He was riding a DWII, DV6 Pro, 6374s, 4.2:1 belts, 12s Lipos and a set of physics-defying black magic tyres.

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#13

Well, no.

#14

What’s that? Am I being dim?

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#16

Sorry. MBS Pro 97 Dylan Warren 2.

#17

stretching them on wider rims certainly wouldn’t hurt either. I haven’t had them tuck yet, but i know what you’re talking about with the shifting sensation.

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#18

Yes, Kinematics can do that for you. :slight_smile:

#19

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#20

Relatively new. They’ve only seen the outside in my garden and a few km in Brussels. Next to that two more times at two other kart lev events for I’d say about 10 or so laps.

I was running them with 12s8p 40t on focboxes before and they just kept overheating.

At this event I could finally not worry about it. Pretty satisfied for now with the dv6 pro and lipo setup.

But yeah grip here was key for winning and I had all of it. Skills too :wink:

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#21

Interesting read for sure!
As someone who mostly race against the spandex 2 wheelers in town (I win every time :dancer:). Where the conditions are mostly shit. gravel, sand, wet leaves, snow, water, salt, dogs, cigarettes, chewing gum. You name it we def have it. How is your experience regarding the looser stuff. As that is what I normally loose traction on.

In my simple mind I feel like a wider & smoother wheel more easily skid across the surface. While a narrower wheel with a more aggressive thread pattern although less grippy but it doesn’t seem to skid on top of stuff as often.

Maybe more so at what point you want to move towards a more aggressive thread profile and how you deal with tire width.

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#22

With the short track races we host in New York, I’ve always had issues with traction on 8" kendas. Not on acceleration (I wish I had that much power), but on sharp turns.

I picked up a set of Newbee rims because I wanted to try stretching the kendas, but that ultimately didn’t give me a whole lot of extra traction either. It was noticeable, but it still felt sketchy on the really sharp turns. Strangely enough, I was only losing traction in the rear, so I tried putting the Qind 200x75 fatty tires on the back, and it has worked wonders. With a significantly larger contact patch in the rear, I was able to do full lean turns.

Since I was still using kendas in the front, I still had a very sharp turning radius and the difference was almost negligible. I was able to not worry about maintaining traction and I was only limited by the maximum lean of the trucks, which was awesome as I was able to lean very hard. I don’t know how this may change on a slick gokart track, but my experiences are on plain ol tarmac.

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