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OK, even googelen en vond dit artikel dat eigenlijk het belangrijkste weergeeft:
Mechanisms of Tire grip.
Friction
Mechanical Keying
Adhesion
As they are made from deformable rubber, tires dont exactly follow basic friction theory. So to just say that F=mu*r is strictly wrong. Although it basically does follow this during the elastic range.
Tires only give grip when they are at the correct temperature. this is the most important thing you can remember about tires .
Tires are the most important part of the suspension, either they are designed to fit it, or the suspension is designed around the tire.
People who say wider tires make more grip because ''there is more rubber on the road" are wrong. They are both wrong that it makes more grip and that there is more rubber on the road.
When you make a tire wider, you alter the contact patch to be wider , but it reduces in length. So depending on sidewall stiffness, a wider tire can actually give less rubber on the road.
The main reason for tires being the size they are is actually heat management. Wider, low sidewall tires will cool better than narrow tall tires. If you can't get a tire up to temperature it will give no grip, if you get it too high you will cook the rubber and ruin the set of tires and loose all grip.
Back to contact patch, you can safely assume that contact patch stays roughly the same area with wide or narrow tires (as long as the load stsys the same). Narrow will have longer contact patches and wide tires will have shorter.
The reason why F1 tires are wide is primarily so that they don't cook (remember they arent just wide, they are fairly high sidewalled), but they tend to have wider contact patches because they will give better grip going round corners.
A wide tire will generate more lateral force per slip angle making cornering better. F1 cars DO NOT have wide tires for linear acceleration.
Conversely drag racers acutally use the tires not becuase of the width, but the tallness. As we know a wider contact patch gives better cornering performance, a narrow but long contact patch is what you want for linear acceleration.
So strangely, drag racers will actually be better with narrow tires. So why do they use wide tires? (remember the most important gip aspect of tires) Temperature! They want as longer contact patch as they can get, but need the width for cooling. (eith 4000+ horsepower you do kind of build temp rather well)
But if you look at the contact patch shape between say, an F1 car or drag racer. (both are considered to use wide tires). The F1 patch will be wider and shorter for good cornering, the drag patch will be longer and narrower (relatively) for good linear acceleration.
So to sum up: Wider tires are not always better. They dont always give better traction. It depends on the car, the situation, the conditions.
Eg. Rally cars use wider tires when on tarmac rallys, and use (surprisingly) very thin tires on ice rallys.
F1 cars used to use narrow tires until aero began to be used in the 60's.
Drag racers acutally want tall tires, width is there to stop the tire being destroyed.
TEMPERATURE!!!!
However a rubber tyre is a lot softer than metal, and a road is a lot rougher than a metal plate. Even at low loads the tyre deforms to key into the irregularities in the road, so increasing the load has a lesser effect. That's why you get the sub-linear dependance described in the Wikipedia article.
But this is only the start of the complexity. If you use a wider tyre the contact patch area isn't necessarily bigger. A wider tyre has a wider shorter contact patch while a narrow tyre has a narrower longer contact patch. The contact patch area depends on the tyre pressure, the deformation of the sidewalls and probably lots of other things I can't think of at the moment.
Anyway, if by "grip" you mean grip when cornering, the grip isn't just controlled by the contact patch area. When a car is cornering the contact patch is being twisted. This is known as the slip angle. The wider shorter contact patch on a wide tyre has a smaller slip angle and as a result grips better.
Two hypotheses for load sensitivity assuming area change isn't one are: thermal effects reducing grip of the compound and carcass deflection causing the tread slip angle to be different to the wheel's slip angle (Trevorrow 2006 Monash University Phd thesis)
Wider tyres are better in both these cases, they have higher in plane belt stiffness (less carcass twist) and the tyre is not being heated as much because it is in contact with the road for less time and cooling for longer due to the shorter patch.
The effect of pressure (and therefore area) on compound bulk temperature is a big effect - particularly with softer race compounds. Indeed it is perhaps easier to see these effects if you are dealing with race compounds rather than hard road ones.
En dit alles zie je dit jaar terug in de F1.
Naast minder downforce hebben ze ook iets smallere banden met als doel de bochtensnelheid te verlagen. En dat is gelukt.
Omdat daardoor de bandentemperatuur tijdens het rijden omhoog gaat is de coumpound (Mart dit is een "vergeten" aspect) harder gemaakt (en minder grip als gevolg) om de temperatuur onder controle te houden en toch nog heeft men tijdens het rijden alle handen vol om de banden niet te heet te laten worden. Dit zie je daarin terug dat zeker wanneer de banden al wat gesleten hebben ze het tempo moeten matigen om oververhitting te voorkomen.
Ik heb jarenlang gekart en ik kan je zeggen dat laterale grip (dwars op rijrichting) veel groter is met bredere banden. Teken op papier de contact afdruk van een smalle band en een brede band.
Dan zie je dat bij een smalle band in rijrichting deze de grootste wrijving oplevert dus meeste grip en de brede band in dwars richting dus meer grip in de bochten.
De door Mart gehanteerde formule gaat helaas niet op voor autobanden daar er veel meer andere factoren van belang zijn.
Mechanisms of Tire grip.
Friction
Mechanical Keying
Adhesion
As they are made from deformable rubber, tires dont exactly follow basic friction theory. So to just say that F=mu*r is strictly wrong. Although it basically does follow this during the elastic range.
Tires only give grip when they are at the correct temperature. this is the most important thing you can remember about tires .
Tires are the most important part of the suspension, either they are designed to fit it, or the suspension is designed around the tire.
People who say wider tires make more grip because ''there is more rubber on the road" are wrong. They are both wrong that it makes more grip and that there is more rubber on the road.
When you make a tire wider, you alter the contact patch to be wider , but it reduces in length. So depending on sidewall stiffness, a wider tire can actually give less rubber on the road.
The main reason for tires being the size they are is actually heat management. Wider, low sidewall tires will cool better than narrow tall tires. If you can't get a tire up to temperature it will give no grip, if you get it too high you will cook the rubber and ruin the set of tires and loose all grip.
Back to contact patch, you can safely assume that contact patch stays roughly the same area with wide or narrow tires (as long as the load stsys the same). Narrow will have longer contact patches and wide tires will have shorter.
The reason why F1 tires are wide is primarily so that they don't cook (remember they arent just wide, they are fairly high sidewalled), but they tend to have wider contact patches because they will give better grip going round corners.
A wide tire will generate more lateral force per slip angle making cornering better. F1 cars DO NOT have wide tires for linear acceleration.
Conversely drag racers acutally use the tires not becuase of the width, but the tallness. As we know a wider contact patch gives better cornering performance, a narrow but long contact patch is what you want for linear acceleration.
So strangely, drag racers will actually be better with narrow tires. So why do they use wide tires? (remember the most important gip aspect of tires) Temperature! They want as longer contact patch as they can get, but need the width for cooling. (eith 4000+ horsepower you do kind of build temp rather well)
But if you look at the contact patch shape between say, an F1 car or drag racer. (both are considered to use wide tires). The F1 patch will be wider and shorter for good cornering, the drag patch will be longer and narrower (relatively) for good linear acceleration.
So to sum up: Wider tires are not always better. They dont always give better traction. It depends on the car, the situation, the conditions.
Eg. Rally cars use wider tires when on tarmac rallys, and use (surprisingly) very thin tires on ice rallys.
F1 cars used to use narrow tires until aero began to be used in the 60's.
Drag racers acutally want tall tires, width is there to stop the tire being destroyed.
TEMPERATURE!!!!
However a rubber tyre is a lot softer than metal, and a road is a lot rougher than a metal plate. Even at low loads the tyre deforms to key into the irregularities in the road, so increasing the load has a lesser effect. That's why you get the sub-linear dependance described in the Wikipedia article.
But this is only the start of the complexity. If you use a wider tyre the contact patch area isn't necessarily bigger. A wider tyre has a wider shorter contact patch while a narrow tyre has a narrower longer contact patch. The contact patch area depends on the tyre pressure, the deformation of the sidewalls and probably lots of other things I can't think of at the moment.
Anyway, if by "grip" you mean grip when cornering, the grip isn't just controlled by the contact patch area. When a car is cornering the contact patch is being twisted. This is known as the slip angle. The wider shorter contact patch on a wide tyre has a smaller slip angle and as a result grips better.
Two hypotheses for load sensitivity assuming area change isn't one are: thermal effects reducing grip of the compound and carcass deflection causing the tread slip angle to be different to the wheel's slip angle (Trevorrow 2006 Monash University Phd thesis)
Wider tyres are better in both these cases, they have higher in plane belt stiffness (less carcass twist) and the tyre is not being heated as much because it is in contact with the road for less time and cooling for longer due to the shorter patch.
The effect of pressure (and therefore area) on compound bulk temperature is a big effect - particularly with softer race compounds. Indeed it is perhaps easier to see these effects if you are dealing with race compounds rather than hard road ones.
En dit alles zie je dit jaar terug in de F1.
Naast minder downforce hebben ze ook iets smallere banden met als doel de bochtensnelheid te verlagen. En dat is gelukt.
Omdat daardoor de bandentemperatuur tijdens het rijden omhoog gaat is de coumpound (Mart dit is een "vergeten" aspect) harder gemaakt (en minder grip als gevolg) om de temperatuur onder controle te houden en toch nog heeft men tijdens het rijden alle handen vol om de banden niet te heet te laten worden. Dit zie je daarin terug dat zeker wanneer de banden al wat gesleten hebben ze het tempo moeten matigen om oververhitting te voorkomen.
Ik heb jarenlang gekart en ik kan je zeggen dat laterale grip (dwars op rijrichting) veel groter is met bredere banden. Teken op papier de contact afdruk van een smalle band en een brede band.
Dan zie je dat bij een smalle band in rijrichting deze de grootste wrijving oplevert dus meeste grip en de brede band in dwars richting dus meer grip in de bochten.
De door Mart gehanteerde formule gaat helaas niet op voor autobanden daar er veel meer andere factoren van belang zijn.
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