- #1
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I was just curious to how tyres work in the rain. How does the tread shift the standing water so the tyre can have traction? Any information would be appreciated.
Can Unequally Spaced Blades Reduce Noise in Radiator Fans?
In summary, the tread of a tire serves to deflect water and prevent aquaplaning. There is a trade-off between tread design and tread life, with narrow tires performing better in wet conditions. Circumferential grooves and lateral grooves work together to drain water and provide contact zones. Tread patterns vary and are designed to balance performance and appearance. Unequally spaced blades on radiator fans can reduce noise if balancing is addressed.
- #2
pallidin
- 2,209
- 2
The varied geometric shapes of a tires tread serves to deflect the water into raised "channels" between these geometric shapes.
The challenge is that these shapes must have sufficient surface area, else they would wear down quickly.
So, there is a trade-off. Yes, you could design a tire that is extremely optimal in rain, but in so doing, it might have very poor tread life.
I suppose they strike a happy medium.
The challenge is that these shapes must have sufficient surface area, else they would wear down quickly.
So, there is a trade-off. Yes, you could design a tire that is extremely optimal in rain, but in so doing, it might have very poor tread life.
I suppose they strike a happy medium.
- #3
brewnog
Science Advisor
Gold Member
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The first most significant feature is a tread. You can have the stickiest compound in the world, but if you have no tread, wet weather performance will be rubbish. As you know, tread patterns break up the layer between the rubber and the tarmac so that aquaplaning is discouraged.
As a tyre rolls over wet tarmac, a 'wedge' of water forms in front of the tyre. If the tyre rises up on this wedge, contact between the tarmac and rubber is broken, and aquaplaning occurs. By breaking up the surface of the tyre such that there are channels for this water wedge to infiltrate, the tyre is less prone to rising up on the wedge. For a similar reason, (like-for-like) narrow tyres perform better in very wet conditions, - the tyre is less prone to 'floating' up onto the wedge of water.
More detail: Circumferential grooves (going 'around' the tyre) act as channels to drain the wedge, and to some extent, store this water. Lateral grooves, - going side-to-side across the width of the tyre - drain this water from the circumferential 'grooves' to the tyre edges. At 100km/h, an average tyre in average rain needs to shift something like 6 litres of water per second to maintain contact. New wet tyres have massive grooves in the centres which can displace huge amounts of water, - something like 10 litres per second, but these wear very quickly in the dry. Circumferential 'ribs' provide contact zones, particularly for cornering. Small, shallow dimples around the shoulders of the tyre increase surface area to allow for more efficient cooling. Sometimes a 'void ratio' is specified, which quantifies the amount of non contact/ contact area across the width of the tyre, - for a slick tyre this ratio will be 0%, for an off-road mud or snow tyre this will be much higher, perhaps 40%?
More detail still: Tread patterns vary for a number of reasons. Simple block-shaped treads fundamentally work well in muddy and wet conditions, but are prone to rapid wear of the front and back of the block on dry tarmac. Regularly spaced grooves are avoided because they set up harmonics which can cause hefty vibrations.
Finally, asymmetrical tyres will have more large blocks on the outside for cornering stability, and smaller blocks on the inside for heat dissipation and water displacement.
As a tyre rolls over wet tarmac, a 'wedge' of water forms in front of the tyre. If the tyre rises up on this wedge, contact between the tarmac and rubber is broken, and aquaplaning occurs. By breaking up the surface of the tyre such that there are channels for this water wedge to infiltrate, the tyre is less prone to rising up on the wedge. For a similar reason, (like-for-like) narrow tyres perform better in very wet conditions, - the tyre is less prone to 'floating' up onto the wedge of water.
More detail: Circumferential grooves (going 'around' the tyre) act as channels to drain the wedge, and to some extent, store this water. Lateral grooves, - going side-to-side across the width of the tyre - drain this water from the circumferential 'grooves' to the tyre edges. At 100km/h, an average tyre in average rain needs to shift something like 6 litres of water per second to maintain contact. New wet tyres have massive grooves in the centres which can displace huge amounts of water, - something like 10 litres per second, but these wear very quickly in the dry. Circumferential 'ribs' provide contact zones, particularly for cornering. Small, shallow dimples around the shoulders of the tyre increase surface area to allow for more efficient cooling. Sometimes a 'void ratio' is specified, which quantifies the amount of non contact/ contact area across the width of the tyre, - for a slick tyre this ratio will be 0%, for an off-road mud or snow tyre this will be much higher, perhaps 40%?
More detail still: Tread patterns vary for a number of reasons. Simple block-shaped treads fundamentally work well in muddy and wet conditions, but are prone to rapid wear of the front and back of the block on dry tarmac. Regularly spaced grooves are avoided because they set up harmonics which can cause hefty vibrations.
Finally, asymmetrical tyres will have more large blocks on the outside for cornering stability, and smaller blocks on the inside for heat dissipation and water displacement.
- #4
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- 9
Thank-you both of you. That was excellent. 
- #5
DaveC426913
Gold Member
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Sunufagun. Lots of interesting info there, more than I ever knew about tires, but surely, this is by far the most interesting bit:
"...Regularly spaced grooves are avoided because they set up harmonics which can cause hefty vibrations..."
which explains one of the most curious aspects of tire treads - the complexity of the geometrical shapes.
"...Regularly spaced grooves are avoided because they set up harmonics which can cause hefty vibrations..."
which explains one of the most curious aspects of tire treads - the complexity of the geometrical shapes.
- #6
brewnog
Science Advisor
Gold Member
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DaveC426913 said:
It's not the only explanation. Looks are a major selling point, and it's quite a hard job to design a tyre which performs well, and also looks the part.
Interestingly, we're currently experimenting with radiator fans with unequally spaced blades, - it's looking like noise can be drastically reduced if we can address the balancing.
- #7
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- 9
brewnog said:
Well, good look with that. I've never thought about harmonics with tyres, fans and such like before. Puts a different perspective on things
- #8
Danger
Gold Member
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Hmmm... I saw a car fan once that had five blades, not equally spaced. Maybe that's what it was all about.
- #9
FredGarvin
Science Advisor
- 5,093
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Balancing and performance I would also imagine. I would tend to think that the blade profiles would not be the same. Interesting...brewnog said:
1. How do tyres maintain grip on wet roads?
Tyres are designed with specific tread patterns and rubber compounds that allow them to maintain grip on wet roads. The tread patterns are designed to channel water away from the surface of the tyre, allowing it to maintain contact with the road. The rubber compounds are also designed to be softer and stickier, providing better traction on wet surfaces.
2. Why do tyres lose traction in the rain?
Tyres can lose traction in the rain due to a combination of factors. One factor is the buildup of water on the road, which can create a layer between the tyre and the road surface, making it more difficult for the tyre to maintain grip. Another factor is the speed at which the vehicle is traveling - the faster the vehicle is moving, the less time the tyres have to displace water and maintain contact with the road.
3. How do tyre treads affect performance in the rain?
Tyre treads play a crucial role in maintaining grip on wet roads. Treads with deeper grooves and more sipes (small slits in the tread) are better at channeling water away from the surface of the tyre, allowing it to maintain contact with the road. Treads with a more open pattern also help to disperse water more efficiently, reducing the risk of hydroplaning.
4. Can tyre pressure affect performance in the rain?
Yes, tyre pressure can affect performance in the rain. If the tyres are overinflated, there is less surface area in contact with the road, making it more difficult for the tyre to displace water and maintain grip. On the other hand, if the tyres are underinflated, there is too much surface area in contact with the road, resulting in a higher risk of hydroplaning.
5. Are there any special tyres for driving in the rain?
Yes, there are tyres specifically designed for driving in the rain. These tyres are often referred to as "wet weather" or "rain" tyres and have treads with deep grooves and more sipes to improve water dispersion. They also have a unique rubber compound that provides better traction on wet surfaces. However, it is important to note that even with these special tyres, it is still important to drive cautiously and adjust your speed to the road conditions.
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