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Old 08-06-2013, 10:52 AM
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Ron Sutton Ron Sutton is offline
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For Optimum Corner Handling ... You Need to Disengage the Inside Rear Tire ... To a Degree

Below is a good Youtube video, showing how the inside rear tire needs to "disengage ... to a degree" in race car cornering. The gentler the radius, the less it needs to disengage ... the tighter the radius, the more. You can learn a lot, just by watching the tires. Expand the video to full scene & watch the inside rear tires of the cars in front of the driver with the video. Freeze frame it if you need to see it better.

"Disengage ... to a degree" means we are reducing the load & even reducing the contact patch on that inside rear tire. This is critical to a good handling car on grippy tires & tight corners.

How much is right? The answer depends on many factors. The video of the Porsches shows the "degree" to be quite high. That's why I posted it ... so it was clear to see. The "degree" the Porsches are disengaging the inside rear tire is correct for these cars, but they have the engine in the rear, so they have to disengage it more than an evenly balanced, or front heavy car. The amount the Porsches are disengaging the inside rear tire in the video ... would be excessive for a typical P/T car with 50-58% front weight. But the concept is the same.

"To a degree" means we are not lifting the tire off the ground completely. We may not even be close. It simply means we are reducing the load & the contact patch on that inside rear tire.

"To a degree" also implies ... correctly ... that we want to control how much. This is key. If we do not disengage the inside rear tire enough, we struggle with a tight/pushy car. If we disengage the inside rear tire too much, we now have a loose car to deal with.

"Re-engage" means we want to "plant" the inside rear tire hard on corner exit ... to regain & achieve a full contact patch ... so we have 2 full tire's worth of contact patch for accelerating. This actually happens as the driver unwinds the steering wheel. "How much" is determined by suspension geometry, shocks, springs, etc.



There are almost ALWAYS exceptions to the rule. It is NOT critical to disengage the inside rear tire to a degree if
a. You can get the rear end to "glide" (think slight, controlled slide) around a tight corner (easier to do on hard tires).
b. The car has a complete open diff, like Formula Fords.
c. You're oval track racing & running staggered tires (outside rear tire a much larger diameter than the inside rear tire.)
d. The corners are not tight, but instead they are big sweeping corners.
e. The corner has significant banking.

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Ron Sutton

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Last edited by Ron Sutton; 12-07-2014 at 04:37 PM.
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