For you real racers out there.....slip angles?
- Thread starter claythrow
- 21 comments
- 6,144 views
- 640
- Cali
- SocalsZHP
From wiki:
In vehicle dynamics, slip angle[1] or sideslip angle[2] is the angle between a rolling wheel's actual direction of travel and the direction towards which it is pointing (i.e., the angle of the vector sum of wheel translational velocity vx and sideslip velocity vy).[1] For a free-rolling wheel this slip angle results in a force parallel to the axle and the component of the force perpendicular to the wheel's direction of travel is the cornering force. This cornering force increases approximately linearly for the first few degrees of slip angle, then increases non-linearly to a maximum before beginning to decrease.
In other words, if you're driving straight and turn the front wheels 30 degrees to the left, and your car (skidding) only turns 20 degrees to the left, slip angle would be 25 degrees.
EDIT: Sorry, you probably already searched wiki for this, anyone else want to chime in?
In vehicle dynamics, slip angle[1] or sideslip angle[2] is the angle between a rolling wheel's actual direction of travel and the direction towards which it is pointing (i.e., the angle of the vector sum of wheel translational velocity vx and sideslip velocity vy).[1] For a free-rolling wheel this slip angle results in a force parallel to the axle and the component of the force perpendicular to the wheel's direction of travel is the cornering force. This cornering force increases approximately linearly for the first few degrees of slip angle, then increases non-linearly to a maximum before beginning to decrease.
In other words, if you're driving straight and turn the front wheels 30 degrees to the left, and your car (skidding) only turns 20 degrees to the left, slip angle would be 25 degrees.
EDIT: Sorry, you probably already searched wiki for this, anyone else want to chime in?
- 5,785
- Norman, OK
- McClarenDesign
Tires don't just grip when they're going forward, they also grip side to side, albeit not as well. Rolling straight forward, there's no slip angle, as the tire can apply full grip to rolling forward. In a drift, the drive tire isn't always pointing in the direction the car is traveling, but is still providing a certain amount of grip and ideally power (i.e. rear tires pointed into the turn, but the car still slides sideways or at an angle).
Simply, slip angle is the relation between the direction the tires are pointing, and the direction they are actually traveling.
Simply, slip angle is the relation between the direction the tires are pointing, and the direction they are actually traveling.
- 5,785
- Norman, OK
- McClarenDesign
The Apex book that came with the CE has a pretty good article about this.
- 2,083
- FreedomWeasel
If you're interested I'd look up the "speed secrets" books at a bookstore. I've got one of the auto-x ones and I believe the section on slip angle had some diagrams and the like.
- 103
- HuygensHeroes
Some decent responses here. I'll give it a go too. The toughest thing to grasp I think is that the tires can and do move laterally through turns. Imagine two arrows with a common origin at the center of a tire. One arrow points in the direction the tire is pointing and the other points in the direction the tire is actually travelling. Slip angle is just the angle between the two arrows, it's really as simple as that. The moving sideways phenomen is caused by contact patch deformation and is always happening in turns it's just a very small angle/deformation usually, until you start really pushing the tires grip limits. As someone sort of mentioned tires have an optimal slip angle that gives the greatest amount of friction that that tire can give, somewhere in the range of 5-8 degrees I think.
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- 298
- Gaylord Michiga
- 103
- HuygensHeroes
Akwaaba
Sort of, if you imagine taking the same corner exactly the same way at increasing speeds then as the speed around the corner increases the slip angle will increase until the tire passes its optimal slip angle then at speeds past that point it will quickly start losing grip and sliding more and more towards the outside of the turn. That is considering all things are equal though, which never happens in reality.
- 298
- Gaylord Michiga
So, in GT5, what can we do? Basically, adjust toe, go to a softer tire, and adjust camber. In real life, we would be adjusting caster, spring rate, weight distiribution, compression and rebound, axis of inclination, and a few other various angles on a corner by corner-(of the car) basis in order to get our car to turn as quick as possible thru a turn. In Gt5, we aren't allowed to make side to side changes, which would be very handy for tracks like Monza, Daytona, Indy (mostly rt hand turns).
- 103
- HuygensHeroes
snowxdadx3
Good point, all of the adjustments that can be done to the suspension; camber, toe, springs, dampers, the main point of all that pretty much boils down to keeping the contact patch as large as possible for as much time as possible during a race (of course there are other considerations like straight line stability, tire wear etc. but ideally maximizing the contact patch in all situations is the goal). I believe this relates to the slip angle in that, when the optimum slip angle is reached and the contact patch is maximized then technically that tire is generating its maximum cornering force possible (disregarding the effects of aerodynamics and weight transfer).
Incidentally, you'll hear often about driving "smoothly" and probably see pretty easily if you watch really fast drivers what that means (especially in a game like GT5 which eliminates a lot of the variables of racing in real life because they just can't be simulated easily). One of the reasons smooth is good, I would say, is that you will naturally be hitting those optimal slip angles more often and if you are a talented driver will pick up on where they are and how they feel and keep the car in that sweet spot through corners. To me "smooth" sounds like code for "don't overdo it with the slip angles" since no one would understand that. But like I said smooth is good for other reasons too.
- 5,785
- Norman, OK
- McClarenDesign
Correct, and depending on the car, stepping over that grip limit will result in either understeer (front tires beyond max grip) or snap oversteer (rear tires beyond max grip).
To better understand this, take a few spins in a practice session, and watch the replay. It's a lot more noticable from afar rather than during the heat of the battle. Also, in real life, it's pretty easy to replicate on a frozen parking lot (free from poles, parking blocks, other people) or while doing donuts.
To get the most from your car, listen to the tires. They'll let you know if you're doing a good/bad job, and they are perhaps the most important sound in the game.
research
Premium
- 847
- Ohio
- ecko_driver81
^ this is brilliant.
Also I agree with freedomweasel concerning the Speed Secrets series by Ross Bentley. Check out the reviews...
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HE1RO
(Banned)
- 527
- Oklahoma
- K_Beast_D
Soo its like "this" but then its like "that"? lol jk
Dont worry to much about it otherwise you will lose concentration on whats really important, and thats just practicing driving and messing around with different settings to eventually tailor your ride to your style of driving. The best way to learn something is to do it yourself.
HyugensHeroes comment on "smooth" is spot on. lol
Dont worry to much about it otherwise you will lose concentration on whats really important, and thats just practicing driving and messing around with different settings to eventually tailor your ride to your style of driving. The best way to learn something is to do it yourself.
HyugensHeroes comment on "smooth" is spot on. lol
ok, OP, not that this is all exactly correct. AND its very long. but there is ton of good info.
http://phors.locost7.info/contents.htm
edit: i forget the slip angle. basically what that is.... its the difference between the amount that your wheels are turned and the degree your car is actually turning. meaning your tires slip a little. so if your fronts are turned at a 45 degree your car may only turn at a 40. if you make the tires at a 50 degree, your car may only turn at a 35. creating a larger slip angle. kinda an over simplified explanation, but hopefully you get the point.
http://phors.locost7.info/contents.htm
edit: i forget the slip angle. basically what that is.... its the difference between the amount that your wheels are turned and the degree your car is actually turning. meaning your tires slip a little. so if your fronts are turned at a 45 degree your car may only turn at a 40. if you make the tires at a 50 degree, your car may only turn at a 35. creating a larger slip angle. kinda an over simplified explanation, but hopefully you get the point.
These are all great explanations....I think I may have gotten it.
So a tire will sometimes tell you it's slip angle is 5 degrees, this means that at the right speed, if you are turning 45 degrees, you will actually only turn 40 or so? And if you push the tires beyond the rated slip angle, your grip is no longer optimal?
One cool thing I would love to see in gt5 tuning is tire pressure.
So a tire will sometimes tell you it's slip angle is 5 degrees, this means that at the right speed, if you are turning 45 degrees, you will actually only turn 40 or so? And if you push the tires beyond the rated slip angle, your grip is no longer optimal?
One cool thing I would love to see in gt5 tuning is tire pressure.
- 103
- HuygensHeroes
What you are trying to get at here is the technical definition of oversteer and understeer. Oversteer is defined as the condition that the rear tires have greater slip angles than the front tires which means that the rear of the car is sliding to the outside of the turn faster (well of course you don't have to be in a turn to experience oversteer, this can also happen for example when you launch and the rear of the car slides, the slip angles at the rear are still greater than at the front so technically this also is "oversteer") than the front of the car. Understeer being the opposite condition. You imply that the slip angles are causing the condition of oversteer or understeer but that is not technically correct.
EDIT: actually if you check out Oversteer on wikipedia it does a pretty good job of explaining the differences there, much better than me anyway.
You are correct about the grip, if the tire is below its optimal slip angle then it will not be generating the maximum cornering force it possibly can. Unfortunately you still don't understand about the slip angle though. You and lav01 are confusing slip angle with yaw angle. Slip angle per se has nothing to do with the car itself, when we talk about a specific slip angle we are only talking about the angle that I defined above for a single tire, the difference between the direction that tire is pointed and the direction that tire is actually travelling. It really has no more meaning than that. It is much easier to see in a picture than to explain, I'll try and post a picture. And of course the picture didn't work, just google image "slip angle" the first result is perfect.
Another couple edits: was slightly wrong in my descriptions of slip angle and "sliding" and optimal slip angles so corrected. Still some other small problems in previous posts with my descriptions but they are more or less correct, too lazy to fix everything...
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