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.. :nono:

[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/showpost.php?p=1757015&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/showpost.php?p=1757015&postcount=117
Hey, that was kewl! :niceone:
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! :niceone:
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.

[CookMySock]

anecdotally, I heard (one of) the pilot powers is the only tyre that will wheelie in the wet.

Michelin is been the uber elite road tyre since ages ago. We were putting them on our performance citroens (digressive suspension!) thirty years ago - any other tyre felt like meatballs. It was funny pulling out and passing V8's with our 2.2 litre cars mid-corner - them to blow us off on the straights, and we toast them again in the bendies - never to be seen again.

Michelin FTW!

Steve

[Sketchy_Racer]

Ok putting it in a racing situation, I only lost 3 seconds a lap when it was pissing wet than when it was dry around manfeild on the 250. There is more grip than many would believe in the wet.

Wet - http://motorsport.sportimage.co.nz/main.php?g2_itemId=58538&g2_imageViewsIndex=1
Dry - http://motorsport.sportimage.co.nz/main.php?g2_itemId=9817

Not a huge amount of difference really!

[beyond]

Ok putting it in a racing situation, I only lost 3 seconds a lap when it was pissing wet than when it was dry around manfeild on the 250. There is more grip than many would believe in the wet.

Wet - http://motorsport.sportimage.co.nz/main.php?g2_itemId=58538&g2_imageViewsIndex=1
Dry - http://motorsport.sportimage.co.nz/main.php?g2_itemId=9817

Not a huge amount of difference really!

That's pretty bloody good actually :)
Won't find me getting my 1400 over like that in the wet. :oi-grr:

[FROSTY]

Don't do a lot of rocket science myself.
What I do know is the 125gp guys use double thickness knee scrapers when wet racing. That limits the dangle angle

[Badjelly]

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

This is the sort of question for which you can either have a simple, but approximate, answer or a more exact, but much more complicated answer.

The simple answer (the only one I know) can be obtained if you make a few assumptions/approximations:

Road is level.
Rider keeps his/her centre of gravity in the plane of the bike.
Ignore "gyroscopic" forces, i.e. those required to change the direction of the axis of rotation. I think this should be OK except for really tight corners.
Assume constant speed and constant turning radius, i.e. consider that you've "settled in" to the corner.
Tyres are pretty narrow, so the contact patch is in the plane of the bike. (I think this might be the approximation that falls down first.)

Then the lean angle is given by a simple formula

tan(angle) = (lateral acceleration)/(gravity)
where "tan" stands for the mathematical tangent function.

You want proof? Geez, you don't ask for much do you? Go ask a real engineer like ocean1. It's simple trigonometry and I'm sure there are diagrams showing the balance of forces on the WWW somewhere.

This means that if you're going round a corner with a lateral acceleration of 1 g, then your lean angle will have to be 45 deg. Or conversely, if you're going round a corner leaning the bike at 45 deg (no leaning off the bike, mind you) then your acceleration will be 1 g. For 0.5 g, the lean angle is 26.6 deg (not 22.5 deg, because the tangent function isn't a straight line).

How does speed come into this? Well, for a corner of a given radius, the faster you go, the higher the lateral acceleration required to hold your line, so the more you have to lean. Or for a given speed, if you want to tighten your line you have to lean more. But speed as such doesn't enter into the formula.

I said this was simple but approximate. How approximate? Like I said, the assumption that the tyre contact patch is in the plane of the bike isn't very good at high lean angles on a modern bike with wide tyres. And neither is the assumption that the rider keeps his CoG in the plane of the bike. Still when you see Casey Stoner going round a corner leaning at (what?) 60 deg and hanging off the inside, you'd have to think he's achieving lateral accelerations somewhat more than 1.0 g. Which is pretty amazing to mere mortals like me, though not impressive compared with a single seater racing car which, due to its downforce, can corner at 3 g or something.

What angles do I corner at? I have no idea, but my chicken strips suggest I seldom get beyond 30 deg.

[Badjelly]

It's simple trigonometry and I'm sure there are diagrams showing the balance of forces on the WWW somewhere.

You'd think so, wouldn't you?

I finally found one on this page

http://tripatlas.com/Bicycle_and_motorcycle_dynamics

See the section on "TURNING", about halfway down.

The circle thingy towards the top, left-hand corner is the centre of mass of the bike+rider. The point in the middle of the graph is the centre of the tyre contact patch. Unfortunately, just to confuse you, the angle, theta, they've indicated is 90 deg minus what people usually call the lean angle.

[vgcspares]

Course in amongst all the trigonometry there's also the coefficient of friction to consider (loads bigger for soft sticky tires)

[Badjelly]

Course in amongst all the trigonometry there's also the coefficient of friction to consider (loads bigger for soft sticky tires)
The way the coefficient of friction fits in (according to the simple, approximate view of things) is that it determines your maximum lateral acceleration and therefore it determines the maximum lean angle you can support before you start to slide out.

So what do you think is the coefficient of friction of a soft sticky tyre? I'd guess 1.2 or 1.3. I'd be very surprised if even a MotoGP qualifying tyre could get anywhere near 1.5.

[dpex]

I've done about 80Ks today, slowly scrubbing in the front Pilot Power. Despite my lack of significant experience I can say I can feel a significant difference in handling. Can't wait to get the back one on and scrubbed.

[racefactory]

Ok putting it in a racing situation, I only lost 3 seconds a lap when it was pissing wet than when it was dry around manfeild on the 250. There is more grip than many would believe in the wet.

Wet - http://motorsport.sportimage.co.nz/main.php?g2_itemId=58538&g2_imageViewsIndex=1
Dry - http://motorsport.sportimage.co.nz/main.php?g2_itemId=9817

Not a huge amount of difference really!

Wow some excellent posts here!!! Really enjoyed the read.

sketchy racer.. that's awesome... i guess it's not about how far you can lean in the wet (on a road bike clearances) but more about how much extra force you can put through the tyre while cranked over (acceleration and braking in turn) before it starts to slide as the coefficient is lowered.

[Flip]

Did an advanced riding skills course in the wet and some of the sports bikes were doing stoppies no problems on the wet track. My bike not do stoppies, do good bulldozer. The thing I picked up is there is heaps more grip than I expected but the effect of diesel or other crap on the road is a lot more noticeable. Also the bike locks up and skids quicker-easier by which I mean there was less notice it was going to happen and it was harder to release and re-apply the brakes. Before you ask yes a harley rider went on a skills course. Good reading the data.

[cowpoos]

My thoughts on this is that you guys are all reading to much info which isn't really going to compensate for lack of skill/experience. You just need to start doing miles in the wet.

You just can't rely on a mathmatical figure you read. its much more a case of having good feel for your bike in the wet. using comon sense to where you place your wheels,where you look. setting your speed correctly for the corners. relaxing...never rely on what someone tells you,or something you have read.





I heard (one of) the pilot powers is the only tyre that will wheelie in the wet.




nah you can do a wheelie on any tyre in the wet...I've done them on screwed slicks in the wet.
And rolling stoppies on a dirtbike on wet paddocks in the pissing rain.

Having good feel...knowing your bike well...having a couple of clues...you can create grip over and above what other people can find or believe they can find.

[sharky]

Well put Cowpoos. - I don't think people will be whipping out their protractors and calculators mid-corner in the pissing rain doing 100km/h+. Gaining wet weather riding experience is what is required.

[slofox]

What angles do I corner at? I have no idea, but my chicken strips suggest I seldom get beyond 30 deg.

Errrrmmmmmmmm.....yeah me too probably...

[ferriswheel]

It all depends on your breed of tyre
If got mates with Perelles n they havnt pushed there bikes hard enough on the wet to notice much difference
where as I have Bridge Stone Battlemax's on my bike and it scares the shit outa me in the wet
It feels like I have about 20 maybe 25% of grip in the wet verses dry

[scroter]

if you cant feel whats going on with your bike then your probably going too fast wet or dry, maybe not for the bike, maybe not for the tyres but definitly for you, no offence intended just a plain fact that most people think too hard about falling off in the wet and forget to relax and listen to how the bike is reacting. the biggest difference I find in the wet is that the grip levels can change from bad to worse and back again quite quickly in the wet where they can remian quite constant in the dry. survival instinct is a good thing but slow down and listen to the feedback your bike is giving you. safe riding.

[racefactory]

http://www.youtube.com/watch?v=7OOpE7fBw28 - check out THIS. A guy going hard with knee down in the rain WITH A PILLION also with knee down.

So i guess you can still get your knee down if you really want! How the fuck though? Even when you see wet races they somtimes very seldom get their knee down like that even with hardcore wet tyres.

I really want to know what does it feel like when your at maximum lean in the wet?? Obviously in dry tyres are more than capable of angles past footpeg scraping, but in the wet how do you know when you are at the point where it will slip if you lean further?

[sharky]

In that clip you notice the bike is not leant over very far at all, they're just hanging off like monkeys.

[racefactory]

In that clip you notice the bike is not leant over very far at all, they're just hanging off like monkeys.

I know what you mean at the latter section of the video mate but the bike is way cranked over for wet conditions. Granted at the end the pillion is hanging off big time but that is some serious lean still... at the begginning he's hanging off as much as anyone cornering that quickly.

[racefactory]

http://www.youtube.com/watch?v=se9DOJQyW00 Also the same guy doing it on an SV650.... fucking good wet skills...

[sugilite]

Wow, do you guys have gyroscopes on your bikes or what? :lol:

Yes, a road in perfect condition offers more grip than many would suspect. However, a wet road can hide a lot of dangerous slippery shit too...so prob best to keep this stuff to theory sessions me thinks.

I've raced many years at fickle weather manfield and I do know that the most dangerous time is when it has just started to rain, and the drops of water are beginning to join up on the way to making the surface fully wet...watch out!!!! (esp on hotmix surfaces) If the back end steps out in these conditions, you seldom get it back.