Lowering: how does it affect the handling?

[MvM]

I want to put a new suspensin-set on my car. Currently it is lowered by about 3cm (1.2 inch). I will probably raise it to better cope with speedbumps and such, but I'm also looking at the performance side.
My first idea was that lowering will also improve you car's handling and maximum cornering because the center of gravity sits lower.
However, all your suspension beams will be pointing upwards even when standig still instead of just being horizontal. Second, the maximum wheel travel will be shortened.
So, will lowering your improve the car's handling, especially in turns or over bumps.
Won't the lowering negatively effect the toe-changes of the tires? And therefore acutally lower your maximum cornering speed?

 

[sjs]

You have hit on an often neglected issue. Suspension geometry can be adversely affected when simply lowering a car without altering the suspension mounting points. As you stated accurately, at rest your suspension is already part way through the normal range of motion so any geometry parameters that change with suspension travel may already be at or beyond their optimal point at rest, then as it compresses while cornering things only get worse. This can easily more than offset the minimal benefit of a very small drop in CG especially in a car like the NSX. An observable symptom of this adverse affect is the increase in “bump steer”, which is the kick or jerk you feel in the steering when you hit bumps with the suspension loaded under cornering. That can be more than just annoying.

But the news is not all bad. If at the same time you lower the car you also increase roll resistance with stiffer springs (and dampers to match) and/or bars, then the suspension arms don’t travel through as great of an arc and may actually spend more time in the “sweet spot” of the range. So conversely, extra roll resistance without modest lowering might not be ideal either depending on other factors. It’s always a matter of balancing the various pieces and settings and you would need to do some careful measuring and calculations to determine the optimal combination. With slightly stiffer springs and shocks you should not need to worry about the reduced available travel on a car lowered only an inch or so. The one thing we know is that Honda did all that for us given their target ride height and comfort level. But like many others I prefer it a bit lower and stiffer so the trick is to not screw things up too badly!

I’m very glad you brought this up because I’m hoping someone will take the time to do detailed measurements of the NSX so I can put them in a suspension geometry program and determine the real impact of such changes. I’ve got a friend who’s a wiz with the program if anyone would like to volunteer to do all the measuring.

BTW, in the old days (and today with my old 510s) we could correct for most of the problem by simply adding spacers to the bottom of the strut or not-so-simply raising the pivot point of the control arms.


[This message has been edited by sjs (edited 15 March 2003).]

 

[Hrant]

snip

I’m very glad you brought this up because I’m hoping someone will take the time to do detailed measurements of the NSX so I can put them in a suspension geometry program and determine the real impact of such changes. I’ve got a friend who’s a wiz with the program if anyone would like to volunteer to do all the measuring.


[This message has been edited by sjs (edited 15 March 2003).][/B]

This is great! Really!

The NSXPO 2003 Planning Committee is currently discussing the various possible topics for the tech seminars, and this same issue is being explored.

There are several levels of possible discussion in here ....... but ideally and in order to reach the widest audinece I think if it is "explained" in a non-too technical way (i.e., no vector forces on the tire, corner balancing, the physics of the center gravity and axes of rotation .... LOL!) we might all get more out of such discussion. Perhaps the focus ought to be on the majority of "us" who either as SJS said want it a little stiffer and lower ridde with all the handling assets of the NSX, and the occasional weekend trackers who are ou there to have fun ....... and not necessarily the diehard boy racers who have something to prove with timed laps, I would think the latter's needs and budget are quite different ......

 

[MvM]

sjs

Thanks for your (long) reply. At least you make me feel somewhat more comfortable about changing the setup of my car with the suspension I want.
You mention certain measurements to be taken. Which measurements are we talking about here?