{"id":9161,"date":"2018-05-14T04:36:37","date_gmt":"2018-05-14T11:36:37","guid":{"rendered":"https:\/\/speedsecrets.com\/?p=9161"},"modified":"2018-04-28T22:11:27","modified_gmt":"2018-04-29T05:11:27","slug":"q-can-you-define-load-sensitivity-vertical-load","status":"publish","type":"post","link":"https:\/\/speedsecrets.com\/q-can-you-define-load-sensitivity-vertical-load\/","title":{"rendered":"Q: Can you define “load sensitivity” & “vertical load”?"},"content":{"rendered":"

Q: <\/strong>“<\/em>Could you possibly explain more about the definition of ‘load sensitivity’ and ‘vertical load’ if possible? I understand if there’s more weight on a tire, it can produce more grip. That’s why we try not to trail off the brakes and unload the front tires too fast. But I’ve seen graphs showing that the coefficient of friction decreases with more “vertical load.” This sounds\u00a0contradictory to what we drivers try to do. Would be great if you could help clarify the meaning of these terms\u00a0“load sensitivity and vertical load.”<\/em><\/p>\n

\u00a0<\/strong>A: <\/strong>Vertical load is sometimes used to refer to what is also called weight transfer. Technically, we should talk about load transfer (rather than weight transfer), and that\u2019s what\u2019s going on when we brake, corner and\/or accelerate. When we brake, we transfer load from the rear of the car to front, pushing those front tries harder into the track surface. When we do that, these tries gain grip \u2013 they have more traction than if we took load off of them.<\/p>\n

Yes, that\u2019s why we don\u2019t want to snap our foot off the brake pedal when entering a corner. Doing that quickly unloads the front tires right when we want to them to change the direction of the car.<\/p>\n

Vertical load is also used to describe the load that is put on the tires from the car\u2019s aerodynamics. More aero downforce puts more load on the tires, and they gain grip. And that\u2019s really the most accurate way of defining vertical load \u2013 the load that is vertically pushing down on the tires.<\/p>\n

Okay, now to your comment about \u201cgraphs showing that the coefficient of friction decreases with more vertical load.”When a tire has more load on it, it gains grip. But it also has to do more work. Without going into a huge amount of physics about the way rubber tires interact with a track surface (if you want to learn the details of this, read Paul Haney\u2019s The Racing and High-Performance Tire<\/em>book \u2013 get it at http:\/\/www.insideracingtechnology.com\/booktiredescrptn.htm<\/a>), understand that the more load on a tire, the more grip it has, but it\u2019s not a linear thing; as it has more load put on it, it doesn\u2019t gain the grip as fast as the workload the tire is having to deal with increases.<\/p>\n

I created a video called Why Smooth Is Fast<\/a> that explains this with an easy-to-understand analogy. You can watch it here: https:\/\/youtu.be\/vPrN7zBNZvQ<\/a>.<\/p>\n

Load sensitivity\u2026 Actually, I\u2019ve heard it used in more than one way, but when it\u2019s referring to the tires it\u2019s usually talking about this relationship we\u2019ve just talked about \u2013 the tires are sensitive to load. I\u2019ve also heard it used by drivers when talking about the overall handling balance of their cars. In this case they\u2019re saying that the car\u2019s handling (whether it\u2019s understeering or oversteering) is sensitive to the load on the front or rear, and that\u2019s causing the car to respond with some handling issue.<\/p>\n","protected":false},"excerpt":{"rendered":"

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