Wet/dry traction comparisons

[dpex]

Does anybody have any properly-tested data on tyre traction in wet conditions.

In this instance 'wet' means, "after the road has been reasonably washed with rain", not newly dampened roads.

Also, the factor of oil residue (road-centre/oils-spills) cannot be factored in.

I see in another thread a lean angle of over 50 degrees is possible in the dry, but doesn't say how much less an angle should be allowed for wet conditions.

Anyone got an answer of a data-base address?

[kickingzebra]

properly tested would be a loose term if you are referring to road riding?!
One can still drag ones knee on a race track on road tyres in the wet, it is just taking a decent risk...

[sharky]

On the Michelin website for Pilot Powers it states something like 50 deg dry and 40 deg wet. Look it up.

[racefactory]

I would also really like to know this. Good topic.

I like riding in rain but i don't know if i actually have to go that slow and not lean over that far. It would be really interesting to find out what grip is reduced by when it's wet and how far you can lean over and how hard you can brake.

[dpex]

On the Michelin website for Pilot Powers it states something like 50 deg dry and 40 deg wet. Look it up.

As a matter of fact I just, this very day, fitted a new Pilot Power Michelin to the front. Will do the rear after I've munted the current rear at the track on the 31st.

And you are right, Sharky. The sales Billy stuff says 51.9 degrees in the dry and 41.9 in the wet. Although the web graph shows almost identical performance in wet or dry.

But I can't see how just lean-angle alone dictates maximum parameters. Sure, speed must also become a factor at some point?

For example, if I cane around a round-about at 30ks, leaning 50 degrees, the inertial forces must be less than if I maintained the same angle of lean but at 35Ks.

But then I just thought of something. Maybe lean-angle and speed, relative to the radius of the cornering comes into play here.

But where does inertial force fit into the equation?

Gawd. I don't know! And I want to know. My parrot 'Arthur', says I 'have' to know, and he's one smart parrot..

[racefactory]

Yes that is also interesting- at lower speeds (lower inertia?) does that mean you can support a higher lean angle than if you were travelling at higher speed?

Sometimes i wonder about that vecause on a roundabout... somehow it feels way more hard to crank the bike over on there (low speeds) than cranking it over on a faster turn.

[beyond]

Ok, I'll go for the simple explanation.
We will work on 40% in the wet being your maximum lean angle assuming that in all instances the road surfaces are optimally wet according to the test data, bearing in mind that there is water running off wet, soaked wet and on we can go.

Lets say on a long sweeper you can lean 40% but on a roundabout which is a slow speed corner it's still 40%. Why?
Well you might be able to do say 70kmh around the roundabout to hit your max lean angle of 40% but on a tighter radius. On a real long sweeper you might hit 160kmh and reach your lean angle of 40% but it's a longer sweeper which spreads the sideways enertia.

i.e. There is no way in this wide world you are going to be able to do 160kmh through the roundabout so the speed effectively limits your enertial forces and radius of the bend limits your speed and therefore your lean angles.

In either case your enertial forces will be the same at there peak.
I hope that helps.

[sharky]

In simple terms grip in the wet is approximately 20% less than in the dry according to the information.

[racefactory]

In either case your enertial forces will be the same at there peak.
I hope that helps.

Oh yea, just clicked... they would be the same. But still... can you lean over further in the wet at lower or higher speeds?

[racefactory]

In simple terms grip in the wet is approximately 20% less than in the dry according to the information.

Only 20 percent? Thought it would be more. It certainly seems that sudden inputs yield greater consequences in the wet.. however I really do not know what absolute grip levels would be...

[Ocean1]

As a matter of fact I just, this very day, fitted a new Pilot Power Michelin to the front. Will do the rear after I've munted the current rear at the track on the 31st.

Coefficients of friction are slippery bastards.

In short, there's too many variables to predict reliably.

PPs have a good rep for wet grip, and I can tell you I was impressed with mine, as much for the progressive feedback as the traction.

The very tyres, at the angles in question: http://www.kiwibiker.co.nz/forums/sh...&postcount=117

[sharky]

Yeah I too would not take 20% literally. The purpose built tyre testing tracks in Europe have optimum conditions to enable the Tyre companies to be able to make these claims. They have water continuously flowing over the road that they never turn off, other wise fungi, moss etc would grow. Therefore the tarmac is well washed. On NZ roads you never know if there is some cow pooh/oil residue etc.. on the corner. Would I tip my bike over to 40deg in the wet..??? I don't think so!

[Hoon]

In simple terms grip in the wet is approximately 20% less than in the dry according to the information.

So simple that it's incorrect.

Grip vs angle relationship isn't linear.

i.e. the amount of extra grip required going from 0 degrees to 10 degrees is far less than what is needed going from 40 to 50 degrees.

I'll leave it to someone else to bust out the proof by math.

[vifferman]

The very tyres, at the angles in question: http://www.kiwibiker.co.nz/forums/sh...&postcount=117

Hey, that was kewl!
Of course, it doesn't allow for suspension compression reducing the clearance a tad (imperial, of course, seeing the Buell's Mrkn).

[beyond]

Hey, that was kewl!
Of course, it doesn't allow for suspension compression reducing the clearance a tad (imperial, of course, seeing the Buell's Mrkn).

Quite right, cos at higher speeds or on tight radius corners you have the weight of the rider and machine all working together to push down on the suspenders which means bits will probably be touching down well before the tyre manufacturers recommended maximum lean angles are reached.

The harder you corner and faster you go the more pronounced thsi will be. One of the reasons my GSX1400 is wound up to the max on preload settings.