Tyre stretch info
Posted: Sat Jul 26, 2014 6:06 pm
Just seen this on another forum and thought it'd be useful since a couple of you are taking about stretch
[QUOTE=StandardFried;655215]
This is formed entirely from research and talks with many different drivers of various Motorsports. It is my understanding but not my opinion and is VERY BASIC with the sole goal of making it simpler to understand.
Due to once again many post/threads about tyre stretch how to/is it safe etc., being followed up by comments like "stretching tyres is dangerous even the smallest bit of stretch can super lethal" instead of commenting on each individual thread I will explain the BASIC difference between stretching of tyres vs "correct fitment".
It's really a horse a piece, and doesn't do all THAT much (obviously depending on the level of stretch), But...
Stretching the tire takes up the sidewall flex it would normally have, resulting in a more rigid tire. Stretched tires have a lot less give due to the removal of sidewall flex, and are more likely to lose their grip in hard driving situations. But the other side with a straight wall, while having more flex and giving more feedback as to when it's going to lose grip with a more comfortable ride.
Firstly what is the purpose of a tyre sidewall you say? Tyres are designed with this magical thing called a sidewall which apart from holding it all together is a major handing component in every tyre. Its responsibility in safety and handling aspects (which are the aspects we are discussing) is to increase lateral stability. In general, the lower the aspect ratio a tyre has, the higher its performance level will be. This is due to the fact that tyres with a lower aspect ratio tend to have better lateral stability. Whenever a car turns, its tyres must overcome the lateral forces that are generated. Tyres that have a lower profile tend to have sidewalls that are stiffer and shorter. As a result, such tires are better able to resist these cornering forces.
So let’s begin with a squared off wall (see example - http://grandmighty.com/wp-content/uploa ... ltires.jpg and http://grandmighty.com/wp-content/uploa ... itment.png)
ok so making this as simple to understand as possible when you are driving normally i.e. from point a to point b in traffic your tyre sidewall is doing almost nothing apart from holding in air, but say you were to go to a track an smash out laps in your awesome Proton powerhouse, you would notice that as you are begin cornering harder and harder you will feel the car 'roll' on its tyres and you could feel the gradual loss of grip allowing you to corner right on the limit of your tyre time and time again without actually breaking traction. The other major purpose of the tyres sidewall when driving aggressively is to transmit the torque applied by the drive axle to the tread to create traction.
Now moving onto tyre stretch. ok so let talk about small stretch to begin with not ridiculous hellaflush I am stance god stretch (see example - http://grandmighty.com/wp-content/uploa ... tretch.jpg) so in terms of driving around from point a to point b you won’t notice any major difference apart from a much more spine shaking ride. However take the car to the track and again you won’t notice much difference UNTIL you start trying to hit those corners faster and faster. No because you stretch out the sidewall you stiffen it up dramatically, and you completely loose the tyre 'roll'. Because you no longer have the tyre roll you completely loose that gradual loss of grip feeling, and it is replaced by a sudden snap. The car will be cornering normally at pace with good grip, then snap grip is gone and the car will slide or oversteer. Why would anyone want that you say? Welcome Drifting. What is the drifting? Intentional oversteer, causing loss of traction in the rear wheels or all tyres, while maintaining control from entry to exit of a corner. Although of cause it is possible to drift on a ballooned tyre however it take a lot more power or inertia to break traction and to maintain the drift. (See drifting example - https://www.youtube.com/watch?v=SKWJGHe ... Q&index=24).
Now moving onto the next level of stretch (see example - http://grandmighty.com/wp-content/uploa ... dtires.jpg) this amount of stretch is where it can become dangerous. If you take your car to a track with the intentions of lapping it with tyres stretched like that you wouldn’t even be allowed on the track, and if officials let you on they should be shot. With your tyres like that it puts immense pressure on the tyre bead to hold onto the rim, and the chances of a debead become quite high (debead example - http://cdn.speedhunters.com/wp-content/ ... G_0053.jpg). Any to minimal sidewall pressure can cause a debead which can be very dangerous and can be lethal but again you could be lucky and get away with it for a long time as long as you checked your tyre pressures etc. and drove reasonably gently most of the time.
So hopefully that clears up some things for you but to conclude the only difference you will ever see between tyre stretch and squared off tyres is a stiffer ride and a much more erratic loss of grip. Thankyou for reading and I hope this helps further your understanding of tyre stretch.
-Kim[/QUOTE]
[QUOTE=Darren;655986]You forgot to mention that there is an even higher chance of debeading if the stupid looking stretch tyres are combined with stupid amounts of camber.
Correct fitment wins every time![/QUOTE]
[QUOTE=StandardFried;655215]
This is formed entirely from research and talks with many different drivers of various Motorsports. It is my understanding but not my opinion and is VERY BASIC with the sole goal of making it simpler to understand.
Due to once again many post/threads about tyre stretch how to/is it safe etc., being followed up by comments like "stretching tyres is dangerous even the smallest bit of stretch can super lethal" instead of commenting on each individual thread I will explain the BASIC difference between stretching of tyres vs "correct fitment".
It's really a horse a piece, and doesn't do all THAT much (obviously depending on the level of stretch), But...
Stretching the tire takes up the sidewall flex it would normally have, resulting in a more rigid tire. Stretched tires have a lot less give due to the removal of sidewall flex, and are more likely to lose their grip in hard driving situations. But the other side with a straight wall, while having more flex and giving more feedback as to when it's going to lose grip with a more comfortable ride.
Firstly what is the purpose of a tyre sidewall you say? Tyres are designed with this magical thing called a sidewall which apart from holding it all together is a major handing component in every tyre. Its responsibility in safety and handling aspects (which are the aspects we are discussing) is to increase lateral stability. In general, the lower the aspect ratio a tyre has, the higher its performance level will be. This is due to the fact that tyres with a lower aspect ratio tend to have better lateral stability. Whenever a car turns, its tyres must overcome the lateral forces that are generated. Tyres that have a lower profile tend to have sidewalls that are stiffer and shorter. As a result, such tires are better able to resist these cornering forces.
So let’s begin with a squared off wall (see example - http://grandmighty.com/wp-content/uploa ... ltires.jpg and http://grandmighty.com/wp-content/uploa ... itment.png)
ok so making this as simple to understand as possible when you are driving normally i.e. from point a to point b in traffic your tyre sidewall is doing almost nothing apart from holding in air, but say you were to go to a track an smash out laps in your awesome Proton powerhouse, you would notice that as you are begin cornering harder and harder you will feel the car 'roll' on its tyres and you could feel the gradual loss of grip allowing you to corner right on the limit of your tyre time and time again without actually breaking traction. The other major purpose of the tyres sidewall when driving aggressively is to transmit the torque applied by the drive axle to the tread to create traction.
Now moving onto tyre stretch. ok so let talk about small stretch to begin with not ridiculous hellaflush I am stance god stretch (see example - http://grandmighty.com/wp-content/uploa ... tretch.jpg) so in terms of driving around from point a to point b you won’t notice any major difference apart from a much more spine shaking ride. However take the car to the track and again you won’t notice much difference UNTIL you start trying to hit those corners faster and faster. No because you stretch out the sidewall you stiffen it up dramatically, and you completely loose the tyre 'roll'. Because you no longer have the tyre roll you completely loose that gradual loss of grip feeling, and it is replaced by a sudden snap. The car will be cornering normally at pace with good grip, then snap grip is gone and the car will slide or oversteer. Why would anyone want that you say? Welcome Drifting. What is the drifting? Intentional oversteer, causing loss of traction in the rear wheels or all tyres, while maintaining control from entry to exit of a corner. Although of cause it is possible to drift on a ballooned tyre however it take a lot more power or inertia to break traction and to maintain the drift. (See drifting example - https://www.youtube.com/watch?v=SKWJGHe ... Q&index=24).
Now moving onto the next level of stretch (see example - http://grandmighty.com/wp-content/uploa ... dtires.jpg) this amount of stretch is where it can become dangerous. If you take your car to a track with the intentions of lapping it with tyres stretched like that you wouldn’t even be allowed on the track, and if officials let you on they should be shot. With your tyres like that it puts immense pressure on the tyre bead to hold onto the rim, and the chances of a debead become quite high (debead example - http://cdn.speedhunters.com/wp-content/ ... G_0053.jpg). Any to minimal sidewall pressure can cause a debead which can be very dangerous and can be lethal but again you could be lucky and get away with it for a long time as long as you checked your tyre pressures etc. and drove reasonably gently most of the time.
So hopefully that clears up some things for you but to conclude the only difference you will ever see between tyre stretch and squared off tyres is a stiffer ride and a much more erratic loss of grip. Thankyou for reading and I hope this helps further your understanding of tyre stretch.
-Kim[/QUOTE]
[QUOTE=Darren;655986]You forgot to mention that there is an even higher chance of debeading if the stupid looking stretch tyres are combined with stupid amounts of camber.
Correct fitment wins every time![/QUOTE]
