Car keep pushing......

[NSXDreamer2]

Hi, this is a question for all the experts or experienced drivers on here, I need help, I'm so confused.

Ever since I change my tires to 02 spec with Kumho MX (running 8" front, 9.5 rear), I felt like my car had much higher limit, but the car feels not as lively as before handling wise.

This morning I took my buddy to airport and his flight got delayed, with nothing to do and a camera... we head to the big shopping mall right by the air port and I suddenly had an idea of do a little AutoX speed handling test...

I was trying both first gear & 2nd gear turnings, the car definately acting weird for me, I shut off the TCS, and the car acts exactly like it had it on... It's pushing, then the tail start stepping out... in normal street driving, I would have correct it real quick then procced my driving line... This time for testing purpose I didn't counter steering and kept the constant throttle, and weird things happened: The tail probably stepped out for a feet, then the front seems like pushing out and correct it itself....
is that because the 215/40 tires are too narrow for 8 inches rim, then that was the result of the side wall height diff. from front & rear???

I was definately pushing the tires to limit, since when I stopped, the tires warmed up and sticky....

 

[nsxtasy]

Answers to the following questions may help provide an answer:

1. What kind of tires were you using previously? What brand, model, size? What size rims?

2. What size Kumho MX and what size rims are you using now?

3. How many miles are on the Kumho MX tires? (All tires usually need a few hundred miles for the mold release compound to disappear, before they grip the best.)

4. Have you checked your tire pressure to make sure it's correct?

 

[NSXDreamer2]

Ken! I know you will have answers for me.

1.91 Stock A022

2. front 215/40/17 with 8" and 35offset, Rear: 255/40/17 with 9.5" and 44 offset.

3. They are not brand new, I had more than 5000 miles on it... I just inspect the tires the other day, and they're looking good... (so looks like my alignment had been changed to the later model settings.)

4. Tire pressure was checked 2 days ago, and it's perfectly matched factory recommendation.

Now that I look at my friends' little movie of me doing the whole thing, after listening to the exhaust sound, I probably didn't really shut off the TCS, or maybe I starved the engine... I can definately hear the rpm dropped from the clip.(Which is when I experienced the front pushing.) I stopped doing the experiment immediately when I saw the gas guage was pointing at "E"... I hope I didn't hurt the engine by doing that.

 

[nsxtasy]

It sounds like it's due to a combination of two things:

1. The difference in handling between the stock OEM tires, and the aftermarket tires. That's exactly how most folks describe the difference - that the cornering just doesn't feel as precise.

2. The TCS, which kicks in and cuts power when the tires slip. On the street, it's usually a good thing; but when you're TRYING to do some hard cornering, it can upset the car's balance.

Try it next time with the TCS disabled. Any differences remaining at that point are probably just due to the difference in tires.

 

[titaniumdave]

Tire pressure

NSXDreamer2,
Check the tire pressure once you have the tires hot, pressure is a linear function compared to temperature. If you are runnning stock pressures you might find the tires lose traction pretty quick as the tires heat up and pressures increase, I find just 2-3 pounds makes all the difference between holding the line I want and having to catch the rear end as it steps out.

I try to never track my car with less than 1/2 tank of gas, for fear of sucking air in hard corners.

How do you like the Kumho MX tires? I am about ready for summer tires and I am considering those.