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Driven5
Driven5 PowerDork
11/30/23 12:17 p.m.
jeffbob said:

Arguably, the reason the car becomes so unmanageable over bumps is amplified by any cross-weight imbalances...

While balancing the cross-weights may typically get 'close enough' to be in the noise for most cars and/or drivers, it only truly balances the handling for cars with a 50/50 L/R weight distribution. The further the car strays from that, the less effective looking at cross-weights becomes for cars turning both directions. The most equalized balance will actually be when LF/LR = RF/RR.

Andy Hollis
Andy Hollis
11/30/23 12:48 p.m.
Driven5 said:
jeffbob said:

Arguably, the reason the car becomes so unmanageable over bumps is amplified by any cross-weight imbalances...

While balancing the cross-weights may typically get 'close enough' to be in the noise for most cars and/or drivers, it only truly balances the handling for cars with a 50/50 L/R weight distribution. The further the car strays from that, the less effective looking at cross-weights becomes for cars turning both directions. The most equalized balance will actually be when LF/LR = RF/RR.

Yep.  I have a handy little spreadsheet I use to do those calcs for me.

Cross weights are a circle track concept.

racerfink
racerfink UberDork
11/30/23 4:28 p.m.

Harris Hill will definitely test your balance between stiffness and compliance.  I loved it after the repave, but it may be worse now than before.  Last time there, I had to really take the car right after exiting T3 (clockwise), otherwise the car would go airborne.  The car was setup very stiff, probably too stiff for the shocks.  I think something like 1000lbs up front, and 700 rear, but it wasn't my car, so thats how I had to drive it.  It would get a bad oscillation in Mustang if I caught the bump there.  I could go through Dam turn flat out though!

Andy Hollis
Andy Hollis
11/30/23 5:56 p.m.
racerfink said:

Harris Hill will definitely test your balance between stiffness and compliance.  I loved it after the repave, but it may be worse now than before.  Last time there, I had to really take the car right after exiting T3 (clockwise), otherwise the car would go airborne. 

Clockwise is now a mess.  While the number of bumps is smaller than before the repave, the amplitide is larger...especially the ridgeline exiting T2/T3 complex.  Going CCW allows you to diamond that turn and avoid the ridge to the inside.  The bump entering T7 CW are also nasty on the line making it hard to be consistent.  Going CCW, that becomes an accel zone so it's not so bad.  That's actually the key area I was working to improve with the dampers.

I rarely go CW anymore, especially when doing testing.  Hard to be consistent.  If I do, I drive the T2/T3 bit much tighter.  It's slower, but not so hard on the car.  Accelerating hard while cresting a sharp ridge is a recipe for breakage.

Andy Hollis
Andy Hollis
11/30/23 6:31 p.m.

Here's a clip of a CW lap.  I only track out to mid-track at T3 exit to avoid the worst of the ridge.  The back straight is dicey through the kink and T7 is a hot mess of bumps.  T9 is also now hard to keep your foot in it w/o the car stepping out.

 

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