Don´t know how many people saw the moto gp race from Estoril in Portugal but you would have seen people riding 200 + bhp bikes on slick tyres in the rain - Carlos Checa ( Ducati ) discribed the experience of 300 kph in these conditions as " interesting " , which sounds like the understatement of the year .
Now how does this relate to cycling ?
Now most of us use tyres that are slick in the middle but may have tread on the shoulders - ever wondered why ?
When the bike is upright there is enough " texture " in the road surface for the water to be squeezed out from under - unless the roads been painted and the texture filled with paint of course - so why the tread on the shoulders ?
Now this is where we go back to motorcycles - go take a look at a high performance motorbike´s tyres : notice how little tread there is - and most of that is on the shoulders of the contact patch .
What´s happening is that the tread is causing the tyre to " squirm " or deform more when the bike is leaned over than it would otherwise effectively causeing the rubber to run hotter than it would otherwise - ie a dual compound tyre but with just one compound : hard in the center but softer when leaned ( or rather hotter , but it´s the same effect ) This is also why it´s a good idea to slightly lower tyre pressures in the wet to allow the tyre to run hotter and hopefully generate a bit more grip - the rain is acting as a coolant and causeing the tyre to fall below it´s nominal operating temperature .
Needless to say a dual compound tyre should be best but treading does allow tyre manufactures to achieve a similar effect at reduced complexity - in fact Continental use this effect on their top of the range tyres as well so it must have something going for it and all without increasing rolling resistance or making the shoulders of the tyre more vulnerable to cuts and tears - something that does happen with dual compound tyres : I don´t wear out tyres , I have to throw them out due to shoulder damage .
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Slicks and tread .
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- 29 April 2005
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- el Ingles
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Interesting comments. I'm no tire engineer, nor am I anywhere close to a MotoGP starboy. But, I do ride high-performance motorcycles. It's my understanding that the tread on the sides of my Pirelli Diablos (and similarly, on MotoGP rain tires), serves to channel water out from under the tire, to prevent hydroplaning. I've never heard of the tread being used to generate additional heat in the tire or being used to deform the tire. I'm not saying it's necessarily wrong, I've just never heard it before.
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friedmikey said:
Interesting comments. I'm no tire engineer, nor am I anywhere close to a MotoGP starboy. But, I do ride high-performance motorcycles. It's my understanding that the tread on the sides of my Pirelli Diablos (and similarly, on MotoGP rain tires), serves to channel water out from under the tire, to prevent hydroplaning. I've never heard of the tread being used to generate additional heat in the tire or being used to deform the tire. I'm not saying it's necessarily wrong, I've just never heard it before.
moto gp rain tyres are something different : intermediats are often cut slicks - sometimes cut more one side than the other to keep that side warmer - and this is why rain tyres fall apart when it drys , the movement of the tread blocks causes the tyre to overheat and with out water to reduce the temperature of the " rubber " it delaminates or turns to kibble .
I think if you look at your pirelli´s you´ll find that there is more tread on the shoulders , where you are unllikely to hydroplane than in the center - it takes some getting used to this idea , I only recently noticed on my tyres this lack of tread at the center ( 125 cc scooter ) but I´ve no trouble with the rain or puddles at all , other than an allergy to white paint and manhole covers .
ps do read about a guy who bought a Contach and said that until the tyres warmed up it handlled like a " puppy on lino " -
And I always thought the softer material to the side of dual-compound tires was for better traction during cornering (i.e. where softer shorter-life material is OK because you spend a lower %age of time cornering on that tire surface).
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RC2 said:
And I always thought the softer material to the side of dual-compound tires was for better traction during cornering (i.e. where softer shorter-life material is OK because you spend a lower %age of time cornering on that tire surface).
That's what it is for. Grooved tread isn't designed to generate heat, but is instead designed to minimize tread squirm, minimize heat build up, all while maximizing the channeling away of water.
Rains are typically fragile tires, given that they are usually constructed of a softish compound, and they have lots of tread squirm. Cut tires (or intermediates) are used when conditions are changeable, are short of full on rain.
What tire is used where is a funny thing. It's a fairly common thing to see guys on slicks in scattered sprinkles or on a track that is spotty moist. Those guys are quickly screwed iffin the track goes full wet. At the same time you might see guys out on full rains. Those guys are screwed if the track starts to dry: they have to hunt for puddles to keep the tires cool.
Picking a tire is part of racings black magic. Funny aside: when supersport racing started here in the US, it did not allow for the use of slicks. Tires had to be DOT approved tires. It just so happened that Dunlop got DOT approval on their D368 tires, and those became the tires of choice for nearly all supersport racers. Funny thing is that the D368 was actually an intermediate GP rain tire.
I've done a race or two on slicks (Bridgestone soft compounds).....and tire behavior was dodgy at best.
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Car and motorbike tyres operate differently to bike tyres in that they actively channel water away for increased contact.
This is not possible on bicycle tyres, so it's all about contact area for traction. More tyre in contact with the wet road, better the traction. Any grooves on the tread are a marketing "security blanket" for buyers.
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alienator said:
...Funny aside: when supersport racing started here in the US, it did not allow for the use of slicks. Tires had to be DOT approved tires. It just so happened that Dunlop got DOT approval on their D368 tires, and those became the tires of choice for nearly all supersport racers. Funny thing is that the D368 was actually an intermediate GP rain tire...
An aside to your aside: I had Dunlop D364s on a CBR900RR I used to own. I don't know if they were similar to the 368, but man, I loved those tires. They certainly looked like an intermediate tire.
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friedmikey said:
An aside to your aside: I had Dunlop D364s on a CBR900RR I used to own. I don't know if they were similar to the 368, but man, I loved those tires. They certainly looked like an intermediate tire.
.....they were D364's. The Percocet caused me to add 4. Intermediates they were....and their performance got worse and worse as supersport bikes got more power. Their sidewalls were just to flexy for the heavy (compared to GP bikes) street/supersport bikes. Muy sticky rubber though. I preferred, better, Bridgestone slicks and Michelin TX(various models) supersport tires. Someone had to stand up against the Dunlop Collective.
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i only ever use these...
http://www.vittoria.com/index3.asp?pagina=http%3A//www.vittoria.com/prodotto.asp%3Fid%3D16&lingua=en
i think they embody both technologies - dual compound, and 2 different treads, the outer being specific to the direction of the wheel, to do the best possible job of using centrifugal force for disipating surface water.
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robkit said:
i only ever use these...
http://www.vittoria.com/index3.asp?pagina=http%3A//www.vittoria.com/prodotto.asp%3Fid%3D16&lingua=en
i think they embody both technologies - dual compound, and 2 different treads, the outer being specific to the direction of the wheel, to do the best possible job of using centrifugal force for disipating surface water.
Water really isn´t a problem on a cycle
contact patch about 550 sqmm for 70 kg
mini car contact patch about 100 - 120 sq cm per wheel for less than 1000kg or 2,5kg - 2,08 kg per sq cm compared to 12,7 kg per sqcm .in other words there is more than enough pressure to squeze the water away via the " texture " in the road surface so the only reason for tread on the shoulders ( particularly when the center is slick ) is to increase squirm and raise the tyre temperature thus creating a dual compound like effect with a single compound .
re motocycle tyres : years ago michelin produced a tyre for 250 - 350 cc bikes called the S41 this was also used for racing but with different compounds the S41PZ2 and the S41PZ4 - lots of people , me included , used the racing PZ2 on the front of a road bike to get a bit more insurance in the rain ; identical tyres just different ,ie softer , compounds . was it legal ? it was never an issue - simpler times . 😎
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