Your 'grip budget' - how do you drive it?

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L2SFBC - Robert Pepper - auto journo

3 жыл бұрын

#circleoftraction #frictioncircle #kammscircle #circleofforces
If you want really understand driving techniques and traction aids then you need to understand grip. And a good way to do that is to understand the Circle of Traction, otherwise known as Kamm's Circle, the Circle of Friction and other names. In this video I explain the Circle, how it works with understeer and oversteer, and use examples from racing and 4X4s to show how grip can be modelled and understood. This video is foundational and there will be further videos on topics such as skid recovery using the concepts explained here.
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Пікірлер: 42

@midas8729 3 жыл бұрын

This channel is seriously underated. Driving school shall teach this to everyone.

@L2SFBC 3 жыл бұрын

Thanks, pleas share :-)

@stevedeardorff 6 ай бұрын

Nice explanation, I like how you work the concepts into the video with the fuzzy circle then the different size circles

@L2SFBC 6 ай бұрын

Thank you very much! Please share :-)

@dsitum Жыл бұрын

I'm impressed by the amount of practical information shown here

@allanhugh2044 3 жыл бұрын

Very well explained, I am sending links to a couple of people who will benefit from this.

@L2SFBC 3 жыл бұрын

Thank you!

@overlandready 2 жыл бұрын

A nice simplified version of what actually happens. My only bugbear is the use of "oversteer" and "understeer". Both of these are characteristics of steering design dynamics, what you are using them to describe is loss of traction aka skidding. To correctly understand oversteer and understeer you have to look at the fundementals of design of the steering and suspension of the vehicle - the factor of oversteer and or understeer of a vehicle does not change no can a vehicle oversteer and understeer in it's design. There is also neutral steering. How you measure neutral, oversteer and understeer is setting the vehicle at a set speed around a set curve and the known projectory is where the vehicle is expected to travel - neutral steer. If the vehicle turns tighter - oversteer as the vehicle is oversteering and if the vehicle doesn't turn as tight as expected this is understeer - neither are loss of traction and or skidding. Your slip angle chart is derived from oversteer and understeer tests, not from skid tests. skidding is a result of tyre design and composition not vehicle design and build.

@kathyl67 Жыл бұрын

Informative and well explained :)

@JAMBi93 Жыл бұрын

I saw a lot of materials explaining traction circle and that one is the best one for now. That chanel should has 500k subs at least.

@L2SFBC Жыл бұрын

Thanks please share and help me towards that target!

@orange2540 5 ай бұрын

Excellent video

@L2SFBC 5 ай бұрын

Thank you very much!

@trungvungoc4092 2 жыл бұрын

Your video is very helpful and here is the Kamm graph, explaining the dynamics of the tire. In Vietnam, studying for a Master's degree at Hanoi University of Science and Technology has been thoroughly explained.

@L2SFBC 2 жыл бұрын

Thanks! Where is the graph?

@ina7084 2 жыл бұрын

How helpful. I am here because my car tried to kill me on a roundabout and it's become icy which isn't the norm for where I live. I found out by this that my fwd car is prone to both oversteer and understeer considering how dramatic the weight shift is from accelerating to the back (front part of the car rapidly lifts up in the air) and from letting off the gas or breaking to the front (car dropps from above and sinks). It's like driving a boat and a nightmare. Also it has a tendecy for the front wheels to spin when taking off because it has an insanely reactive first gear (still getting used to it). Death on wheels.

@L2SFBC 2 жыл бұрын

What car is it?

@ina7084 2 жыл бұрын

@@L2SFBC Kia pride 1.3 I don't know which year. This car isn't normal. It literally rocks up and down when driven. But that might just be its age and some mechanisms within responsible for holding the front of the car down being worn out (don't know much about that). Wish I could show how it looks.

@nickjennings8317 3 жыл бұрын

Very interesting.

@nicolasbednarz9085 3 жыл бұрын

great work! Now i know exactly how i ended in the ditch of a muddy road. :D

@L2SFBC 3 жыл бұрын

And how was that?

@MadMatt4WD 3 жыл бұрын

Great info mate. really appreciate it. I filmed a video yesterday about traction and momentum which connect to this concept. Now about the use of my vehicle's image. I'm thinking $50 should keep me happy. 🤓

@L2SFBC 3 жыл бұрын

I'll pay that to the copyright holder then ☺

@MadMatt4WD 3 жыл бұрын

@@L2SFBC No flys on you

@cyclemoto8744 3 жыл бұрын

Thank you Robert

@L2SFBC 3 жыл бұрын

Hope it was useful!

@cyclemoto8744 3 жыл бұрын

@@L2SFBC I have an analytical mind so it was interesting to learn about the circle of traction concept. I will endeavour to think about this the next time I'm performing a technical off road climb (4wd...). Do you still work as a 4wd instructor?

@L2SFBC 3 жыл бұрын

on occasion

@MadMatt4WD 3 жыл бұрын

@@cyclemoto8744 Robert is a wealth of knowledge.

@cyclemoto8744 3 жыл бұрын

@@MadMatt4WD I think I have you to thank for introducing me to Mr Pepper

@ldmtag Жыл бұрын

Sorry for being an a&&, but front tires turn, and therefore the vectors don't really go front and side, they go perpendicular to the tires for cornering and in the same direction for braking and accelerating. And when the car slides, those vectors not necessarilly point where they originally were, like when no ABS braking they point in the opposite direction to where the car moves no matter the angle. And sliding grip is actually reduced... My point is: you explained what happens right before the sliding (or what would happen if you had ideal tires), but not during the sliding.

@bvward 3 жыл бұрын

Robert, in future, could you touch on left-foot braking to induce oversteer on tight corners (thinking rallycars)?

@L2SFBC 3 жыл бұрын

Yep!

@dhxl 2 жыл бұрын

It's my first video on the traction circle. I got almost everything, but now I have more questions, than before 😄 1. What if you modify your car and put wider tires? Will it improve traction, reduce or nothing will change? I've watched some other video about tires and now I'm confused. You look like someone who really understand the subject. 2. Is there a way to estimate grip force available considering tire load and its width? Namely I struggling to provide realistic-looking grip force for tires of a bus for a videogame. 3. If you lose traction, shouldn't the traction circle be smaller to regain the traction?

@L2SFBC 2 жыл бұрын

1. Wider tyres may improve grip depending on situation; specifically, track cars when cornering. However, the grip level is not related to the contact patch size which stays the same, just changes shape. More on this later. 2. That's a complex question; yes, but I can't help there, it's very complex modelling. I would suggest a simpler and better initial focus to be weight on tyre vs grip - more weight more grip, but it's not linear hence there is an overall grip reduction when cornering as the outside wheels gain less than the inside wheels lose. 3. No. The traction circle is available grip. If you lose traction, you need to reduce the traction demand to less than the traction available. It is possible the traction circle suddenly gets smaller - there is an example in this video or maybe the Oversteer Recovery one.

@dhxl 2 жыл бұрын

@@L2SFBC 🤔thanks. It will help a lot. I'll try to find some known grip vs weight values and start from there.

@dhxl 2 жыл бұрын

@@L2SFBC , there is one more thing that still bothers me after the night. If grip is reduced when load on tyre is also reduced (like here 11:20), then double set of wheels (like in some big trucks, buses and pick-ups) should give double amount of the reduced traction, right? The next problem that I need to solve is to find out the form of the curve. Whether twice smaller load result in less than twice smaller grip and thus greater grip overall. 🤔

@L2SFBC 2 жыл бұрын

No, weight is a big factor in traction so double wheels = half the weight on each wheel = half the traction. Except it's not quite that simple as there are other factors. But one important point = the effect of weight is not linear. Double weight on a wheel is not as much as double traction. This is why when cornering there is a net grip reduction.

@nicolasbednarz9085 3 жыл бұрын

Robert do you have any video about real, offroad uses of HDC or hill descent assist? thanks is it better than a carefull "manual" foot on the breake hill descent?

@L2SFBC 3 жыл бұрын

No but it's on the list to do. Yes it can be better.