# Continental Grand Prix 4-Season rotating direction?



## Kickit (Aug 9, 2006)

This probably doesn't come up much in road tires but anyone know which direction these tires should be mounted? I'm sure it's not absolutely critical but it's not symmetrical and it's not marked on the tire or anywhere in the packaging or instructions.









http://www.conti-online.com/generat...and_prix_4_season/grand_prix_4_season_en.html


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## wim (Feb 28, 2005)

Technically, it doesn't matter. Any pattern you see molded into a bicycle road tire tread is there for marketing reasons only.

But if you care about tradition, mount the tire with the labels centered over the valve. If your tire has only one label, mount the tire with the label on the drive side, centered over the valve.


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## Kickit (Aug 9, 2006)

wim said:


> Technically, it doesn't matter. Any pattern you see molded into a bicycle road tire tread is there for marketing reasons only.
> 
> But if you care about tradition, mount the tire with the labels centered over the valve. If your tire has only one label, mount the tire with the label on the drive side, centered over the valve.



Yeah, the labels weren't much help since they are on both sides. I was just trying to mount them in the technically correct direction while being well aware that it doesn't make a hill of beans worth of difference.


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## ewitz (Sep 11, 2002)

Do you want them set up for wet weather cornering or low resistance?


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## Kerry Irons (Feb 25, 2002)

*Pointless*



Kickit said:


> I was just trying to mount them in the technically correct direction while being well aware that it doesn't make a hill of beans worth of difference.


Since it doesn't make a hill of beans worth of difference, then by definition there is no technically correct direction.


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## rogger (Aug 19, 2005)

ewitz said:


> Do you want them set up for wet weather cornering or low resistance?


Are you taking the piss?


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## ewitz (Sep 11, 2002)

rogger said:


> Are you taking the piss?


That depends, are you taking the bait?


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## 99trek5200 (Jan 26, 2007)

From the picture shown, you would want the tire to rotate counter clock-wise. That way the groves would tend to channel water from the center of the tire out to the edge. If it were to spin clockwise, water would tend to get pushed from the outside in toward the center which is not what you want.

You always want the groove at the center of the tire to contact the ground first as the tire rolls to help push water out.


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## Kickit (Aug 9, 2006)

99trek5200 said:


> From the picture shown, you would want the tire to rotate counter clock-wise. That way the groves would tend to channel water from the center of the tire out to the edge. If it were to spin clockwise, water would tend to get pushed from the outside in toward the center which is not what you want.
> 
> You always want the groove at the center of the tire to contact the ground first as the tire rolls to help push water out.



That's the way I have it, counter clockwise, for the reasons you've given. Thanks for the reasoned response. Of course the peanut gallery had to pipe in with their free thoughts as well.  There are lots of things on the bike that don't have any impact on the ride that are done just for the sake of doing it "right". E.g. tire labels centered at the valve stem as wim mentioned, or QR levers on the nondrive side, etc.


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## Mark McM (Jun 18, 2005)

*Wild, unfounded conjecture*



99trek5200 said:


> From the picture shown, you would want the tire to rotate counter clock-wise. That way the groves would tend to channel water from the center of the tire out to the edge. If it were to spin clockwise, water would tend to get pushed from the outside in toward the center which is not what you want.
> 
> You always want the groove at the center of the tire to contact the ground first as the tire rolls to help push water out.



Of course, all of the above is at best a "wild guess", as the poster is unlikely to have any actual data to back up his claims.

It has been shown over and over again that bicycle do not need sipes or grooves for wet weather traction, because bicycle tires can not hydroplane. In fact, most wet weather traction tests of bicycle tires have shown that complete smooth tires tend to have better wet weather traction than tires with patterned treads (smooth tires have better dry weather traction as well). The likely reasons for this is that the patterned treads reduce the area of road contact, plus the raised ridges in the pattern are more subject to squirm.

The biggest factors in bicycle tire wet weather traction are tread compound and casing flexibility (deformability).


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## 99trek5200 (Jan 26, 2007)

Mark McM said:


> Of course, all of the above is at best a "wild guess", as the poster is unlikely to have any actual data to back up his claims.
> 
> It has been shown over and over again that bicycle do not need sipes or grooves for wet weather traction, because bicycle tires can not hydroplane. In fact, most wet weather traction tests of bicycle tires have shown that complete smooth tires tend to have better wet weather traction than tires with patterned treads (smooth tires have better dry weather traction as well). The likely reasons for this is that the patterned treads reduce the area of road contact, plus the raised ridges in the pattern are more subject to squirm.
> 
> The biggest factors in bicycle tire wet weather traction are tread compound and casing flexibility (deformability).


Thank You Mark for your "Wild Unfounded Conjecture" on my knowledge, or lack there of, on tire design. A question was asked about a specific tire and I responded with a reasoned response as to why it would be better to have the tire rotate in one direction over the other. From my experience with many types of vehicle tires and as an engineer, I stand by my response. 

Be careful with a blanket statement like "bicycle tires can not hydroplane". Given a wider sectioned tire, a light load and enough speed, conditions could exist for hydroplaning to occur. Physics is physics my friend.:thumbsup:


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## rogger (Aug 19, 2005)

99trek5200 said:


> Thank You Mark for your "Wild Unfounded Conjecture" on my knowledge, or lack there of, on tire design. A question was asked about a specific tire and I responded with a reasoned response as to why it would be better to have the tire rotate in one direction over the other. From my experience with many types of vehicle tires and as an engineer, I stand by my response.
> 
> Be careful with a blanket statement like "bicycle tires can not hydroplane". Given a wider sectioned tire, a light load and enough speed, conditions could exist for hydroplaning to occur. Physics is physics my friend.:thumbsup:


"Enough speed" being the key words here. The NASA critical speed for hydroplaning in knots is equal to 9 times the square root of the tire pressure in psi. If the tire is pumped up to 110 PSI the sum would be (9*10.4480885) * 1.150779448 = 108.21101 MPH. You must be very fast.


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## 99trek5200 (Jan 26, 2007)

rogger said:


> "Enough speed" being the key words here. The NASA critical speed for hydroplaning in knots is equal to 9 times the square root of the tire pressure in psi. If the tire is pumped up to 110 PSI the sum would be (9*10.4480885) * 1.150779448 = 108.21101 MPH. You must be very fast.


Speed is but one variable, not the only one. Vehicle weight, contact patch, temperature and tread depth also effect the speed at which hydroplaning occurs. Speed of hydroplaning varies from the 9p^.5.

Lets say that 108 mph is the magic number for any tire pumped to 110 psi. The world speed record on a bike is north of 150 mph. So.... someone, not me, could experience hydroplaning on a bike. That is why I cautioned against a "blanket" statement.


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## rogger (Aug 19, 2005)

99trek5200 said:


> S
> 
> .... The world speed record on a bike is north of 150 mph. So.... someone, not me, could experience hydroplaning on a bike. That is why I cautioned against a "blanket" statement.


Hydroplaning on the Bonneville salt flats, yeah right.


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