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roush mustangs at mid ohio

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So although this is about mid ohio, what I want to point out is the way the roush mustangs were handling on this course. (if you haven't seen the race go back and find it, or better yet, one of you super techies could pull out just the vids of the mustang handling and post it here). Like I said before they were running a ton of squat, easily lifting the inside tire on the corners. The commentators were making a big deal of how "two wheels corner better than one" but the fact is one of those cars finished (about 6th) overall, which, with the current rules package was pretty good IMO.
So..if you've seen the video, what do you think?
 
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"What's the problem?" ;)
 
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I find it odd that the commentators were stating that.
Any well setup strut car (front engine, rear drive also) would pick up the inside front during the on-power phase of a corner.
It's a compromise to deal with the limited camber gain in a macpherson strut design. So to fight off the onset of the undesirable positive camber, one runs really high front roll stiffness.

The alternative is to of course simply run more static camber to compensate for the lack of camber curve...but then you affect braking with too much camber. So most often with cars being raced with near stock-geometry (stock pickup points), you'll find this inside front wheel lift to be a phenomenon.

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WheelLiftRacecar.jpg


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blacksheep-1 said:
OK, so any reason why the Roush cars would do that? Basically, why were they tuned to handle in such a manner?

From my original response: "It's a compromise to deal with the limited camber gain in a macpherson strut design. So to fight off the onset of the undesirable positive camber, one runs really high front roll stiffness."

More reading on this here: http://www.e30m3project.com/e30m3performance/myths/Weight_Transfer/weight_transfer2.htm

So you'll find with strut cars that have near stock geometry settings, the front end is going to be much stiffer than the rear, for reasons described above and in the article. So you'll get what looks like a lot of squat...however, I suspect what is really happening is anti squat -- the rear digging into the ground. However, the weight transfer transitions quickly from forward to back.

Strut cars are *really* roll center challenged when lowered...so any strut car worth their weight is going to be lifting a wheel in certain situations :)
 

isrboss

This pic is from the race. Not sure how stiff in the front, but by the looks of this pic, soft in the rear.

The car driven by Shelby finished 5th.

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isrboss said:
This pic is from the race. Not sure how stiff in the front, but by the looks of this pic, soft in the rear.

The car driven by Shelby finished 5th.

988645_616292715062236_744102115_n.jpg

Precisely.
Stiff front + soft rear. Notice the front is still fairly stiff, as in the image you show, there is barely any bump travel induced during this roll movement--even when tripoding.

With a very high front roll stiffness, you'll have a car that turns in sharply. So to account for what magic happens mid and late corner, you'll need a softer back end to be able to put the power down earlier. It's pretty common setup practice for strut front end cars (which happen to be rwd).

That rear is realllllly soft during roll though - notice that the rear wheel would probably contact a stock length bump stop at that range of suspension movement. I think such a soft back end during the roll phase is indicative of a lowered rear roll center...thus, the soft back end during roll.

I know it's not the same thing, but you'll notice f1 cars tripoding, and those who are into the nerdy world of RC, pan cars also can tripod on high grip surfaces.
 

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