Grip in the wet

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pangolin
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Grip in the wet

Postby pangolin » Fri Feb 08, 2013 09:19 am

From article on the frontpage:

http://www.bikeradar.com/news/article/michelin-rolls-out-three-new-pro4-tires-36376/

The Michelin Pro4 Grip clincher

The Pro4 Grip has a few features designed to keep you rolling in the wet. Sipes are cut into the tread, not to clear water as many might think, but to increase pressure and therefore grip by reducing the contact patch of the tire. Margadonna gave the analogy of a football player with a size 14 shoe and a little girl with a high heel; "the girl's heel is putting more pressure on the ground because the contact patch is much smaller," Margadonna said.

Of course a soft rubber would squish and negate some of that benefit, so a higher-durometer rubber is used.

Grip in the wet, Michelin claims, is 15 percent better than the regular Pro4.


Wut. I get pressure increases as area decreases. But I thought more tyre on floor would = more grip. Pressure would decrease of course, but I assumed the extra area more than made up for that.

Hmm. Perhaps they are referring to an ideal world with no road debris. Whereas, with a few little stones around, a lower pressure tyre would be ok (mould around the grit / stone whatever, and still touch the ground) but a really high pressure would hit it, be in contact with only the obstacle, and slide out.

Thoughts?
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iPete
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Re: Grip in the wet

Postby iPete » Fri Feb 08, 2013 09:50 am

Michelin claims blah blah blah sales speal blah blah

I picked up the new Pro4 'endurance' when they came out, they proved anything but.

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meanredspider
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Re: Grip in the wet

Postby meanredspider » Fri Feb 08, 2013 09:51 am

Yes - it's very complicated because the "simple" rules of friction don't apply when you add a fluid "lubricant". The simple rules don't really apply to tyres anyway but that's a whole other story...
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DonDaddyD
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Re: Grip in the wet

Postby DonDaddyD » Fri Feb 08, 2013 10:02 am

Vorspruntecnik (I think that's how you spell his name) usually has the correct and absolute answer to these types of things....
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Veronese68
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Re: Grip in the wet

Postby Veronese68 » Fri Feb 08, 2013 10:56 am

I'm with Pangolin. My understanding is that knobbly mountain bike tyres are not so good on a wet road as there is less rubber in contact with the tarmac. A narrow road bike tyre has to be doing an unachievable speed before aquaplaning is a risk. Therefore that sounds like a triumph of marketing over reality.
The above may of course be nonsense.

t4tomo
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Re: Grip in the wet

Postby t4tomo » Fri Feb 08, 2013 11:03 am

Well in the snow in cars you are much better off with a narrow tyre than a wide low profile one, the higher pressure / narrower contact point presumably gets to contact, rather than skate on a film of water / snow.

that said, its very difficult to play fooball in high heels.

Is Margadonna a football playing chararcter from the argentine version of the Simpsons?
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The Rookie
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Re: Grip in the wet

Postby The Rookie » Fri Feb 08, 2013 12:16 pm

Friction is indepenadant of surface area as GCSE physisc tells you....

Sipes work by creating an edge that grips against protrusions from the surface, winter tyres have lots of sipes to do this, but overheat in summer as the extra tread block moevement heats the tyre up.

Using a high durometer rubber seems to offset the benefits of the sipes leaving you back where you started from.

Most Michelin tyres seem rubbish in the wet (car, M/C and bike!)

Danlikesbikes
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Re: Grip in the wet

Postby Danlikesbikes » Fri Feb 08, 2013 12:19 pm

pangolin wrote:From article on the frontpage:

http://www.bikeradar.com/news/article/michelin-rolls-out-three-new-pro4-tires-36376/

The Michelin Pro4 Grip clincher

The Pro4 Grip has a few features designed to keep you rolling in the wet. Sipes are cut into the tread, not to clear water as many might think, but to increase pressure and therefore grip by reducing the contact patch of the tire. Margadonna gave the analogy of a football player with a size 14 shoe and a little girl with a high heel; "the girl's heel is putting more pressure on the ground because the contact patch is much smaller," Margadonna said.

Of course a soft rubber would squish and negate some of that benefit, so a higher-durometer rubber is used.

Grip in the wet, Michelin claims, is 15 percent better than the regular Pro4.


Wut. I get pressure increases as area decreases. But I thought more tyre on floor would = more grip. Pressure would decrease of course, but I assumed the extra area more than made up for that.

Hmm. Perhaps they are referring to an ideal world with no road debris. Whereas, with a few little stones around, a lower pressure tyre would be ok (mould around the grit / stone whatever, and still touch the ground) but a really high pressure would hit it, be in contact with only the obstacle, and slide out.

Thoughts?


I think what they are trying to say is as the bike & rider weight remains the same by reducing the contact area of the tyre the downward force increases onto the road therefore increasing the grip. Which is correct if the tyre compounds were similar or harder on the smaller contact patch version to compensate for the extra downward force.

However I would think that the compound of rubber itself would be more important along with the design of the tyre to aid water dispersion.

IMHO the jury is still out.
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meanredspider
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Re: Grip in the wet

Postby meanredspider » Fri Feb 08, 2013 12:39 pm

The Beginner wrote:Most Michelin tyres seem rubbish in the wet (car, M/C and bike!)


Their (car) winter tyres are superb in snow, however. I've run them on several RWD Mercs and I couldn't be happier.

Sipes also work by shedding snow.

Shouldn't get too hung up on GCSE physics either because it doesn't really work for tyres.
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Big_Paul
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Re: Grip in the wet

Postby Big_Paul » Fri Feb 08, 2013 20:24 pm

Their Pilot Road 3 M/C tyres are very good in the wet, they have the sipes, so I suspect they've went sipe-happy!
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leeefm
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Re: Grip in the wet

Postby leeefm » Sat Feb 09, 2013 17:15 pm

I think the main thing to note is that static friction - as mentioned above - does not rely on contact area. Kinetic friction, however, does show a dependency on contact area. When a tyre rolls, it could be said that it operates in the static friction regime. This isn't entirely correct as it will operate in the kinetic regime to a certain extent; especially when the tyre loses grip and slides. I can only assume that this is what they are talking about, especially in the wet when you tend to slide a bit more. So when this happens, area can make a difference... (As above, let's not even think about lubrication because of the rain)

But on the question of "are we listening to Michelin hype?"; all I know is that companies want you to spend your hard earned readies with them... If only you could try before you buy :|

nation
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Re: Grip in the wet

Postby nation » Sat Feb 09, 2013 22:34 pm

Big_Paul wrote:Their Pilot Road 3 M/C tyres are very good in the wet, they have the sipes, so I suspect they've went sipe-happy!


There was a big thing in Bike magazine a while back with their test rider getting knee down through standing water.

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roger merriman
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Re: Grip in the wet

Postby roger merriman » Sun Feb 10, 2013 01:02 am

A hard compound tyre with snipes? plenty about, most if any do not get rave reviews about their wet weather grip...

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