lowering question?

[375instroke]

Lowering does change the geometry in the sense that it moves the caster adjustment range in the positive direction, allowing more positive caster to be set.

I'm sure that bottoming out the suspension isn't helpful for handling.  Something bad must happen when the outer control arm stops moving, and the inside of the car starts pivoting on the outside tire instead of the roll center.

In a turn, when the outside tire moves up, the inside tire is pulled up also, thus lowering the entire front of the car.  Is this lowering also helpful for geometry and handling?  When the outside stops moving due to it hitting the bump stop, does that render the sway bar ineffective?

[Mike DC]

When you put the outside front wheel onto the bumpstop in a corner, it's equivalent to suddenly raising the spring rate on that corner by a drastic amount.  That works sort of like suddenly raising the swaybar rate on the front end.  It's like jacking the car up by that wheel all of a sudden.  It stops the body roll from increasing and throws more weight back onto the diagonally opposite rear wheel.
 
Some people like the handling effect of this.  But I think it has a lot more to do with "feel" than measurable stopwatch gains.  Any and all forms of suspension subtract road feel from the driver.  Putting the outside front wheel onto the bumpstop really lowers the amount of suspension action.  And it won't be pretty if you hit a bump in mid-corner because there is only the tire's air pressure & the rubber bumpstop remaining to absorb it.  Neither of which have any shock/rebound damping action.  They're purely un-dampened springs.




In regards to the whole front end height (average of both sides) being lowered for cornering, I think the main theoretical benefit is reducing the body roll w/o any additional suspension stiffening being used to achieve it.  For street cars like ours, IMHO the increase of negative camber is probably just as much of a real-world benefit as the reduced body roll.





Pro NASCARS have been playing with "big-bar, soft-spring" setups lately.  It means a stiff front swaybar and a soft set of front coil springs.  The result is that the outside leans into the corner and then the swaybar pulls the inside front corner down with it, so the entire front end spends the whole corner riding lower than it rides when there is no body lean.  

I think this setup has more to do with NASCAR's racing situation than what would be ideal in theory.  Their maximum front coil spring rate is rules-
limted, so the teams might decide that laying the outside wheel onto the bumpstop is a way to sidestep that rule. (Use the bumpstop to do the coil spring's job in the corners.)  The difference is that the BBSS setup means they can ride the bumpstops while also NOT leaning the body very far to get the outside corner that low.

Meanwhile they also benefit any time they can squeeze the whole car's ride height downwards just for aerodyamnic reasons.  Those cars spend half the miles of the race with the body leaning.  If all those miles are spent with the body riding an inch lower in front, that adds up to a lot of aero gain.    

[375instroke]

The lowered spindles do get the LCA to stay at a more downward angle, helping camber gain.  This is an advantage, but I still think the retained suspension travel isn't.  I'd raise the bumpstop to compensate.

[THE STIG]

Remember that when dropping the front, you may encounter tire clearance problems you didn't expect.

Also, you may want to get a re-alignment as the the geometry of steering/height/tires has changed.

Can't stress that enough, that's a great way to destroy tires.