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Author Topic: does air pressure affect tyre traction?  (Read 13663 times)

paul.fr

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does air pressure affect tyre traction?
« on: 29/01/2008 01:25:00 »
Which has more traction, a type that is inflated to the maximum pressure that it can take, one that is inflated to the stated pressure or one that is underinflated?


 

Offline JimBob

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does air pressure affect tyre traction?
« Reply #1 on: 29/01/2008 02:29:46 »
Since there is more rubber interfacing with the surface, an underinflated tire will have more traction. In drag racing, where the fastest acceleration and speed is needed over a 1/4 mile distance, "slicks" are used for the most traction. Slicks are flat, without tread and are made of a softer rubber to give maximum traction. Motorcycle tyres also take advantage of this, especially the "crotch rocket" type that Italians love to race on their winding roads - and often get killed thereby.

A motorcycle racing tire can be seen in this example from http://www.webbikeworld.com/Motorcycle-racing/news/2008-world-superbike-kagayama.htm


« Last Edit: 29/01/2008 02:34:43 by JimBob »
 

Offline lightarrow

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does air pressure affect tyre traction?
« Reply #2 on: 29/01/2008 08:29:37 »
Since there is more rubber interfacing with the surface, an underinflated tire will have more traction. In drag racing, where the fastest acceleration and speed is needed over a 1/4 mile distance, "slicks" are used for the most traction. Slicks are flat, without tread and are made of a softer rubber to give maximum traction. Motorcycle tyres also take advantage of this, especially the "crotch rocket" type that Italians love to race on their winding roads - and often get killed thereby.

A motorcycle racing tire can be seen in this example from http://www.webbikeworld.com/Motorcycle-racing/news/2008-world-superbike-kagayama.htm



Much less killed this way than how hamburgers kill americans...
 

Offline chris

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does air pressure affect tyre traction?
« Reply #3 on: 29/01/2008 08:55:57 »
But what's the answer - a flat tyre or a hard tyre in terms of traction?
 

Offline lightarrow

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does air pressure affect tyre traction?
« Reply #4 on: 29/01/2008 19:57:03 »
But what's the answer - a flat tyre or a hard tyre in terms of traction?
The OP asked about "the maximum pressure that it can take, one that is inflated to the stated pressure or one that is underinflated?"

I would say the right one, neither too hard nor too flat. Too hard or too flat = bad traction. At the maximum pressure the tyre is too hard for a good traction, so it's not. This is quite intuitive to understand: there isn't enough area of contact between the tyre and the road. About too flat is less intuitive, but let's make an example in a limit condition: if the road is wet, the tyre must have a good contact with the road; if it's too flat it can make acquaplaning because of the low pressure of the tyre gum on the road (because the area of contact increases). In the same way, if it's too flat, with a dry road it could not make the maximum friction and so not be appropriate for the maximum traction.

Now the question is between inflated to the stated pressure or underinflated; well, it depends what do you mean with "stated pressure" and how much underinflated and for which veichle and purpose and the kind of tyre and its age. In my road bike, for example, I inflate tires a little more than stated when they are new. For a car, I would say it's better slightly underinflated. For a motocross bike in a very dirty track it's better much underinflated.

About "slick" tires the advantage is not only to have more area of contact, but also to have less rolling friction.
« Last Edit: 29/01/2008 20:04:28 by lightarrow »
 

Offline JimBob

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does air pressure affect tyre traction?
« Reply #5 on: 30/01/2008 02:12:46 »
Dear Doc,

Since there is more rubber interfacing with the surface, an underinflated tire will have more traction. In drag racing, where the fastest acceleration and speed is needed over a 1/4 mile distance, "slicks" are used for the most traction. Slicks are flat, without tread and are made of a softer rubber to give maximum traction. Motorcycle tyres also take advantage of this, especially the "crotch rocket" type that Italians love to race on their winding roads - and often get killed thereby.

A motorcycle racing tire can be seen in this example from http://www.webbikeworld.com/Motorcycle-racing/news/2008-world-superbike-kagayama.htm




Please note I said nothing about how severely underinflated.
« Last Edit: 30/01/2008 02:19:28 by JimBob »
 

lyner

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does air pressure affect tyre traction?
« Reply #6 on: 09/04/2008 21:23:53 »
The problem with underinflating a tyre is that it overheats and shortens its life drastically. It may be ok if you're drag racing but, for running around town and going up the motorway it's not a good idea.
 

Offline turnipsock

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does air pressure affect tyre traction?
« Reply #7 on: 09/04/2008 23:43:26 »
an underinflated tyre will roll over onto the sidewall so will have virtually no grip at speed. If you were stuck in a sand dune, letting the air out of the tyre would be a good bet.

These guys that I spotted at the filling station in Cumbernauld, might have tried letting the air out of their front tyres and driving to the air pump.



If you take a slick racing tyre and run it on low pressure, then the middle part of the tyre will make no contact with the road.
« Last Edit: 09/04/2008 23:45:10 by turnipsock »
 

Offline syhprum

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does air pressure affect tyre traction?
« Reply #8 on: 10/04/2008 08:27:05 »
The problem with running an underinflated tyre is the increased movement of the wheel relative to the tread that leads to handling difficulties.
This is of course more apparent with deep tyres than low profile
 

Offline graham.d

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does air pressure affect tyre traction?
« Reply #9 on: 10/04/2008 09:35:50 »
Underinflation, compared with manufacturers recommendations, may give improved traction but I suspect there is a lot of compromises. Underinflation leads to more flexing, overheating, increased wear, handling difficulties (if too soft) and a tendancy to "walk" out when cornering, increased fuel consumption and lowering of maximum speed. There may be a few more. It will be something that can be practically optimised for a specific activity, like drag racing for example.
 

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does air pressure affect tyre traction?
« Reply #9 on: 10/04/2008 09:35:50 »

 

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