Newbie Handling Question

[merex]

My problem is somewhat hard to describe...

Driving in a straight line say about 40mph, if I turn, for instance to change lanes, it feels like the rear end is slow to respond. It almost acts like a tail whipping back in line. At higher speeds it is a very disconcerting feeling.

The car is an NSX, lowered maybe .5".

I just installed some coilovers and had an alignment. However, I am running different tire brands F/R. SO3's on the front and Falken Beta 451's on the rear. Could this setup be causing the problem?

Thanks

[Jakub]

Hi Merex,

Before we start on any possibilities on what the problem may be, perhaps you can tell what the status is of the springs, and anti-roll bars, dampers... You said you have coilovers installed, did these come with different springs, or are you still using the originals?

Jakub Zawada B.E. (Mech)
jakub@whiteline.com.au

Go Flatout with Whiteline Automotive

[merex]

Thanks for the reply.

The coilovers (HKS) came with pretty stiff springs, but they are progressive. I have fiddled with the damping (full soft/firm, most everthing in between) and the problem does not go away.

Not sure how stiff the sway bars are, as they were on the car when I bought it.

[Jakub]

Hi Merex,

From your original post, the description of the rear being slow to respond can be tricky to interpret. The "slow" reaction can be generally treated by increasing the stiffness of any of the components at the rear (springs, anti-roll bars, dampers), however this could leave the rear a little (more!) twitchy due to moving the handling towards an oversteer nature, which may disqualify this option.

Tyres could be a possibilty here. The rear tyres could have a "lower cornering stiffness" than the front, and therefore require time to react. This is always difficult to tell, as tyre data is rarely available. However it must be remembered that the rear will always lag behind slightly as the process of turning requires the front tyres to be steered, produce front cornering force, rotate the car, induce a slip angle in the rear tyres and then can the rear tyres provide cornering force.
Best way to find out is to borrow some rear tyres which are the same type as the front, or some fronts which are the same as the back.

Perhaps giving a little more grip to the rear in terms of handling balance, could stabalise the car. Increasing the stiffness on the front components can do this.

One final path to consider would be a more stable wheel alignment, something like setting a little more toe in at the rear. Is the car running aggressive camber?

Regards

Jakub Zawada B.E. (Mech)
jakub@whiteline.com.au

Go Flatout with Whiteline Automotive

[merex]

Thank you for the very informative post. I am going to have the alignment checked soon. Rear camber should be -1.5 and toe 4mm.

[Jakub]

Merex,

With the rear camber at -1.5 deg, and 4mm toe ("in" im assuming) im almost tempted to suggest reducing ths value to more neutral value (more neutral toe).

Another possibilty which Wojtek has given me is the rear suspension bushes may be giving too much complience. This is a problem which is also present in the s2000's (whippy tail).

Regards
Jakub