I just got done watching the Best of motoring Vol. 6, they go over a lot of points about the car. The differences in suspension and chassis rigidity VS the G35coupe (new skyline) is much more than I previously thought.

It has a lot of bracing on the bottum of the car that the G doesn't have, it is very very rigid, then they talk about the Front sway bar and talk about how this guy has NEVER seen one as large in diameter as the Z's (it is HUGE), I am not sure if he said the G has the front and rear strut bars, but looking at the bottum and the top of the car and hearing this review, it makes me wonder (along with stiffer suspension/springs).

Could the feather be an issue of the Z being so stiff that IF the measurements (alignment measurements) are slightly off, and it needs to be JUST RIGHT, since there is so little room for error (due to the stiffness and rigidity of the car and components)???

thoughts???

 

That's an excellent question to which I have an unexcellent answer...I don't know.

Really it seems doubtfull to me. First this feathering doesn't happen on everyones Z. Second, the feathering isn't happening to the rear wheels. Third, from a design perspective, you want the chassis to be perfectly rigid, but it would beat the customer to death.

However comma but...I honestly believe this unusual wear pattern we are calling "feathering" is a complex issue. Not due to just one thing. So it could be a factor. But, lets have a little fun and speculate a while (best done with 3.2 beers)

Let's speculate a while on my circumstances. Since the heel of the tread blocks are wearing faster than the toes of the tread blocks circumferentially around the tire, we have to start our speculation on what could cause this. To me it is either the tread composition is different across the tread blocks (tire issue) or somehow (magic) there is more force applied on the heel of the tread block instead of the toe. As the tire rolls forward, the toe of the tread block makes contact first and separates first. Let's assume it isn't a tire issue and press forward speculating about the forces.

Considering vertical forces on the tire, that would imply a variable frequency oscillation at a freqency X times wheel rotation. I didn't count the tread blocks, but lets say there are 20. Then this oscillation would have to occur at 20 times the rpm of the wheel. Meaning the oscillation frequency increases as the rpm of the wheel increases but at a fixed rate. For ease of discussion, lets assume 20X. Since my daily drive doesn't allow for much constant speed driving, that would imply it could happen across a wide wheel rpm range resulting in little wear all the time. Or it could happen over a narrow wheel rpm range / single wheel rpm resulting in a lot of wear for a little bit of time. In other words, either it is happening a little bit from 0-60mph or it happens a lot for that short stretch of 45mph. Now lets look at the road surface. The road surface varies from concrete, to mercadum, to asphault. Therfore the induced vibration level is never the same for very long. If it occurs at one magic speed and or road surface, then I (and a few others) must be the most unlucky SOBs on the planet.

So lets stick with the higher probability that it happens all the time a little bit over a wide speed range. The stiffness and response of the chassis and suspension would have to result in a 20X oscillation in the wheel at all speeds. Only considering the spring/mass/dampening system of the chassis/suspension, there might be a natural harmonic that occurs which indicates the chassis/suspension is the problem. If it is a natural harmonic, then that harmonic is independent of wheel rpm which would mean that you have to drive at a constant speed for the wear to occur in the same place on the tire all the time. Also, the chassis/suspension is non-variable and passive. Meaning it can only respond to an input and will respond the same way to the same input. But it will respond differently to different input. Since the road induced vibration is random (different inputs at different times), the response of the wheel/chassis/suspension will be random and not at 20X wheel rpm. So this indicates it is not caused by the chassis/suspension.

Ok, now I'm really getting a headache. I've managed to talk myself into it and out of it several times!

Now lets speculate on lateral forces on the tire. Outside of the obvious forces caused by cornering, I see lateral forces being caused by wheel flutter. Ever get a shopping cart where one or both of the front wheels flutters side to side? As you push the cart faster, the wobble frequency increases. Meaning as the rpm of the wheel increases so does the side to side flutter frequency IE back to the 20 X wheel rpm theory.

So the question is...what causes this flutter? And how do you stop it?


Enforcer

 

good lord!

I say it's the shocks and damping that somehow caused the tire feathering... So far, I have not heard anyone that have changed their shocks/springs has the same tire feathering problem, then again, no one can confirm that it doesn't exist anymore..

now I got a headache