Jump to content
• Advertisement

#### Archived

This topic is now archived and is closed to further replies.

# Car physics: tire pressure

This topic is 5645 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

## Recommended Posts

How does tire pressure affect grip level? Is there some good approx function, for example like best grip is at certain air pressure level (top of cosine function) and less grip on lover and higher pressures.
3D Racing Game Updated June 16 2003

#### Share this post

##### Share on other sites
Advertisement
Too much pressure will lose grip.

I think low pressure has better grip on looser surfaces, like dirt, but uses up the tires faster..

I can't remember exactly, but I think I learned things like this with the NASCAR racing series.

As for the formula, I dunno.

[edited by - Waverider on June 18, 2003 12:02:40 PM]

#### Share this post

##### Share on other sites
In a very simplified, "ideal" friction calculation, there''s no difference. Otherwise, here''s the deal.

Let''s say that your car has mass m kg. Gravity is g m/s. Now, the gravitational force between the car is, of course, m*g N.

Let''s say that the tire pressure is p N/m2. (yes, you can convert pressure to these units.) Since the pressure from the contact patches must be equal to the gravitational force (otherwise the car would sink into the road) the contact patches have, total, area m*g/p, and each tire has a contact patch of size m*g/4p.

Of course, that doesn''t give you a final equation; but it does give you the size of the contact patches, which will be useful in determining one.

How appropriate. You fight like a cow.

#### Share this post

##### Share on other sites
Well, I think I''ll take just approximation fuinction approach like this:
float tyre_pressure_fact(float pressure_at_20C, float temperature) {	const float max_p=300;	float p = pressure_at_20C * (temperature+273.15) / (20+273.15);	if (p<0) p=0; if (p>max_p) p=max_p;	return 1.0+cos(PI*p/max_p)/2.0;};

Should be reasonable start. Later I had to add some other effects that too low pressure causes.

3D Racing Game Updated June 16 2003

#### Share this post

##### Share on other sites
http://www.theuspits.com/news/race/index.html

This is a collection or articles hosted by a race sim site (don''t know if you''ve heard of the US pits or not), but it''s a phenomenal guide to car physics, and is also somewhat geared toward simulation developement. You will probably never need anything else.

#### Share this post

##### Share on other sites
Thanks!

I also found that tyre pressure affects slip angle. Higher pressure makes tyre''s slip angle (the peak point) smaller.

#### Share this post

##### Share on other sites
quote:
Original post by tmoneyksu
http://www.theuspits.com/news/race/index.html

This is a collection or articles hosted by a race sim site (don''t know if you''ve heard of the US pits or not), but it''s a phenomenal guide to car physics, and is also somewhat geared toward simulation developement. You will probably never need anything else.

yeah, that''s the classic Physics Of Racing Series articles (PHORS, phoarrr!!). Brian Beckman should be canonised as a saint

#### Share this post

##### Share on other sites

• Advertisement

### Announcements

• Advertisement

• ### Popular Contributors

1. 1
2. 2
Rutin
28
3. 3
4. 4
khawk
14
5. 5
• Advertisement

• 11
• 11
• 23
• 10
• 9
• ### Forum Statistics

• Total Topics
633648
• Total Posts
3013112
×

## Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

GameDev.net is your game development community. Create an account for your GameDev Portfolio and participate in the largest developer community in the games industry.

Sign me up!