CerberusM5 said:
Gansan,
Thanks for your insight between the 94 and 97 you experienced on the track. I have a 2004 with 225s on the front and 285s on the rear. The only suspension change I made was Comptech sport springs. I know that 60mm is probably more than the ideal ratio between the front and rear contact patches for the NSX, but the front end just gives up too early and its not related to the tires in my opinion. I think it's Honda's suspension tuning or lack thereof that is causing this frustrating understeer.
Even when the car was stock with the factory wheels and tires (215F/255R) it still understeered like a pig.
The car just pushes wide and scrubs off speed in tight corners. Using the throttle helps bring the car back in line somewhat, but not enough. This is the biggest complaint I have with my NSX and has tainted my experience with the car. :frown:
Although I cannot give a definitive opinion because I have not inspected your car in person nor driven it, here are the things that are influencing the handling on your car, based on your description:
1. You increased the front tire width by 10mm and the rear tire width by 30mm, increasing rear grip significantly more than the front. This is on top of the 10mm increase in rear tire width that Honda added in 2002, specifically to increase rear grip.
2. The additional width of the rear wheels (depending on the offset) increases rear track by a significant amount. This reduces weight transfer during cornering, increasing grip at the rear.
3. The Comptech Sport Springs are in no way designed for increasing oversteer. They are street springs that lower the car, that's it.
There is absolutely no way that any of the changes you listed would have improved your understeer situation. In fact they most likely made it worse. The tire situation alone is a tremendous change to the handling balance, no doubt about it. This kind of additional rear tire grip would be great for handling additional power (such as a supercharger), but not unless your power warrants it. Even with the justification of additional power, you would still end up increasing low speed understeer.
Why not make some changes that will help instead?
1. Decrease rear wheel width to match what you have in front. For experimentation, consider going back to the stock wheel sizes while you sort out the suspension.
2. Increase your rear sway bar diameter. Get the Zanardi/Type S rear sway bar. Do NOT upgrade the front bar. In fact, check the front one and return it to stock if it has been upgraded unbekownst to you (if you bought the car used).
3. Increase rear spring rate. This is similar to increasing the rear sway bar diameter, but is trickier. You would probably need to upgrade both the front and rear to get the balance right.
4. Increase rear ride height or lower front ride height. Speaking from personal experience, even a 3mm increase in rear ride height is noticable in decreasing understeer. This works by increasing weight transfer in the rear, decreasing grip. Unfortunately, this kind of fine tuning is only available if you have adjustable ride height suspension (i.e. "coilovers").
I hope this gives you ideas, or at least help you evaluate the current state of your car and understand why it is behaving the way it does.
Oh, and I apologize for hijacking this thread! :biggrin:
