All else being equal, tire width has no impact on patch size, only shape. - Discuss please. (Updtd)
11-18-2005, 11:54 AM
#1
AudiWorld Super User
Thread Starter
Join Date: Mar 2000
Posts: 7,148
Likes: 0
Received 0 Likes
on
0 Posts
All else being equal, tire width has no impact on patch size, only shape. - Discuss please. (Updtd)
I am saying that section width has no impact on the area size of the patch, just shape. Oversimplified example:
Narrow tire: patch size 7" wide 3" long 7*3=21 sq "
Wide tire: patch size will be 10 wide, but only 2.1" long, still only 21 sq "
Narrow tire: patch size 7" wide 3" long 7*3=21 sq "
Wide tire: patch size will be 10 wide, but only 2.1" long, still only 21 sq "
11-18-2005, 12:41 PM
#3
AudiWorld Super User
Join Date: Feb 2001
Posts: 11,579
Likes: 0
Received 0 Likes
on
0 Posts
Are you saying "section width has no impact on tread width"?
If so, then I'd say "maybe" at best... if you're saying tread width has no impact on contact patch, I'd have to disagree. Even with equal camber and pressure, a larger tire will dynamicly deflect and have a larger contact patch. Even the contact patch at rest will be slightly larger because the tire will deflect with weight; assuming you're running static negative camber.
Different size tires have different section and tread widths. Even similarly sized tires made by different manufacturers have differently sized section and tread widths. Wheel width is also a factor. Maybe clarify a little so we can discuss more on topic.
Different size tires have different section and tread widths. Even similarly sized tires made by different manufacturers have differently sized section and tread widths. Wheel width is also a factor. Maybe clarify a little so we can discuss more on topic.
11-18-2005, 01:40 PM
#4
AudiWorld Senior Member
Join Date: Mar 2000
Posts: 1,189
Likes: 0
Received 0 Likes
on
0 Posts
Simple physics
If a tire is supporting 1000 pounds, and it's inflated to 40 PSI, physics says you have a contact patch of 25 square inches.
I'm also interested in learning about this too, cause maybe physics of tires isn't quite so simple...
I'm also interested in learning about this too, cause maybe physics of tires isn't quite so simple...
11-18-2005, 02:24 PM
#5
Junior Member
Join Date: Nov 2000
Posts: 583
Likes: 0
Received 0 Likes
on
0 Posts
You are right it is not that simple.
You are ignoring the mechanical strength of the tire. Taking your concept further, that would mean that a tire at 0 psi can support no weight at all. Clearly this is not correct as the tire has structural strength without any air pressure. If you built the tire structure out of steel, it could support a lot of weight without any air pressure and adding 200psi would not change the foot print at all.
As a real world example, the contact patch on my race car tires changes very little between 20 psi and 3 psi.
As a real world example, the contact patch on my race car tires changes very little between 20 psi and 3 psi.
11-18-2005, 03:22 PM
#6
AudiWorld Super User
Join Date: Dec 2003
Posts: 7,152
Likes: 0
Received 0 Likes
on
0 Posts
Interesting topic Tomasz...
<center><img src="http://www.tirerack.com/images/tires/tiretech/35_series.gif"></center><p>Did a little reading and thinking...
What seems to make a wider tyre corner and turn-in better is that the pressure on the footprint of the tyre is more uniform. That way it deforms more evenly. A narrow tyre will have a longer and thin footprint which tends to change its pressure on the ground more as it rotates. So some of the footprint will be at the sliding limit for the tyre while the rest of the footprint will not be at that limit. The wide and narrow footprint will tend to deform evenly so more of the footprint can be closer to the limit.
This echos our experiences with tyres. Grandma's tyres will squeal a lot and break away slowly. Our tyres tend to have more of an edge to them.
Interesting thread on the link. :-)
Stephen<ul><li><a href="http://www.eng-tips.com/viewthread.cfm?qid=102250&page=1">wider is better? or not? size of contact patch arguement</a></li></ul>
What seems to make a wider tyre corner and turn-in better is that the pressure on the footprint of the tyre is more uniform. That way it deforms more evenly. A narrow tyre will have a longer and thin footprint which tends to change its pressure on the ground more as it rotates. So some of the footprint will be at the sliding limit for the tyre while the rest of the footprint will not be at that limit. The wide and narrow footprint will tend to deform evenly so more of the footprint can be closer to the limit.
This echos our experiences with tyres. Grandma's tyres will squeal a lot and break away slowly. Our tyres tend to have more of an edge to them.
Interesting thread on the link. :-)
Stephen<ul><li><a href="http://www.eng-tips.com/viewthread.cfm?qid=102250&page=1">wider is better? or not? size of contact patch arguement</a></li></ul>
Trending Topics
11-20-2005, 09:04 PM
#10
AudiWorld Super User
Thread Starter
Join Date: Mar 2000
Posts: 7,148
Likes: 0
Received 0 Likes
on
0 Posts
Picking up a bit...
Size of the contact patch can be calculated using this formula: Area = Load/Pressure. If a load of 1,000 lbs. is applied to a tire with 40 PSI, the patch will be approximately 25 square inches. This formula is independent of tires section width. Side wall and carcas sill also play a small role in the patch size. Run flat at 5 PSI will probably look the same as at 20 PSI. But this matters little as we are not talking about performance of grossly underiflated tires.
So, again going to our example above, we already know the patch size = 25 square inches. That patch can be long with a relatively skinny tire - dragster use this type of tires. Or, short and wide - race cars go that way. This ends up being a compromise between longitual and lateral acceleration forces / needs.
So, IMHO, and grossly oversimplified - wider tire will do better in corners but worse under braking. How wide is enough for a 3,400 S4 Track Car? (I do not know that... yet!)
So, again going to our example above, we already know the patch size = 25 square inches. That patch can be long with a relatively skinny tire - dragster use this type of tires. Or, short and wide - race cars go that way. This ends up being a compromise between longitual and lateral acceleration forces / needs.
So, IMHO, and grossly oversimplified - wider tire will do better in corners but worse under braking. How wide is enough for a 3,400 S4 Track Car? (I do not know that... yet!)