I have noticed that my speed on-ramps has been gradually going up as I know the car more. One question for all you experienced folks - how do you know you are reaching the limits of adhesion?

I've been doing "throttle on" driving through on ramps and get to the point where I can hear the tires starting squeal (Stock Eagle RS-A's). Is this point pretty close to the limits?

Another question I have is that what happens if I have to slow down suddenly? I am a little nervous that lifting off at that point will swing the tail out.

Thanks for your answers (in advance)

G35S AT / Ivory Pearl and Black

 

go to a deserted parking lot or somewhere else safe (I recommend an autocross track). push the car past the limits & learn to drive with the tail swinging. Learn how to control, steer, and recover the car during a loss of traction. It is relatively easy. Just takes practice and some expensive rubber. Thenyour confidence will be higher as you are approaching the limits. For example, I have lost the tail at 80 mph on the 3-4 shift before and was able to recover before bad things happened. this car will reward you if you push it to and past its limits.

Better Life thru Chemistry
Black on Black 03.5 Sedan 6MT - Goodyear F1 GS-D3's 225/55/17, Custom Intake Tube, HyperGround Kit, Magnaflow resonator.

 

It depends on the tires. Some tires have a very progressive break at the limit, and others break over very suddenly. Generally, you'll know that you're reaching the limit of adhesion of the front tires when further steering input returns less steering response than the previous increment of steering input. The tires might be squealing when this happens, or they might not. Another thing, are you leaving VDC on while doing these driving manouvres? (Please say yes) It wouldn't be too wise to experiment with the limits of the car on public roads imho, without at least being already familar with the basic concepts of chassis dynamics and adhesion. Have you considered a high performance driving school, or at least a good book on the subject? If you have to slow the car down when cornering at the limit, it could easily send the car into oversteer. ABS and VDC will try to help, but they can't do miracles. Be careful out there.

 

I have the VDC on and only try it on ramps with enough run off and no one else around so I do not think I am compromising the safety of others. Also, I am not going in at very high speeds - I prefer tight turns with enough runoff so even if the tail swings out, the speeds are not very high - no more that 50-60mph at exit of the turn and obviously slower through the turn.

I am however a little concerned if I have to slow down suddenly - say a deer emerging on the road. As you say, lifting off will likely cause the tail to swing out.

Bye the way, the whole issue of speed and oversteer is a little overrated - it is easy to induce a little rotation even at 20-30 mph on a slow corner (say a left turn on a 2 lane road). And that is fairly enjoyable, without, imho, being dangerours to anyone (as long as done on a deserted toad). Or am I wrong?

G35S AT / Ivory Pearl and Black

 

If you're creating oversteer at 20-30mph, it's power-induced oversteer, and lifting off the throttle will correct it, not make it worse. It's the high g-force turns at the limits of the tire's ability to grip where lifting off the throttle can make things worse.

On a freeway onramp, it's hard to say.. you're probably accelerating through the corner, so it could be squeeling from too much throttle as opposed to not enough lateral grip. With the VDC on, you shouldn't get into too much trouble. Don't depend on it to save you to the exclusion of all else, though.. VDC can't disobey the laws of physics.

Don't push new limits in traffic. Test your car on empty roads and parking lots, and local autocross events.

 

Tire pressures will certainly change the way the car reacts. What tires pressures are recommended for spirited driving? My car has crappy EL 42 Turanazas was wondering how I could gain maximum handling with the stock tires. I was thinking of fronts at 36psi and rears at 32 psi?

Thanks

2003 G35 Sedan 6MT
14.13 @ 99.55

 

When autocrossing, I run my EL 42's at 38 front/40 rear. They're being replaced soon with some real tires, though. [img]/w3timages/icons/smile.gif[/img]

Those pressures are too high for the street, though.. too rough over bumps in the road.

<P ID="edit"><FONT class="small"><EM>Edited by Ryoken on 04/18/04 12:35 PM.</EM></FONT></P>

 

ryoken,

I agree wholeheartedly. I would recommend tire pressures of ~40psi for front/rear for best handling and longer tire life.

For those of you who may be thinking this is counter-intuitive, well, I used to think the same thing. I learned to drive/road race about 25/20 years ago, respectively. Back then, tires would bulge when overinflated, causing a reduction in the tire patch and a reduction in traction... not to mention the fact that it would result in excessive center wear. So the goal was to reduce tire pressure so that the tire patch was maximized... or so the theory went.

However, with modern (high performance) tires, manufacturers use threads such as kevlar and other non-stretchable products in the tire's windings to prevent this bulging. Because of this, we can run higher pressure in our tires and maintain our tire patch (with a very minimal change in patch length that is more than made up for by the following benefits). This is good because higher tire pressures: (1) increase sidewall stiffness for faster turn response; (2) stiffer sidewalls have less "roll", maintaining the tire patch; and (3) reduced heat load in the tire, decreasing tread changes during driving and extending tread wear.

Anyway, higher than (Infiniti) recommended tire pressure can result in a major benefit in handling. Also, I didn't find the change in ride that bad.

As for the squealing by the Goodyear RS-A's, in my experience with those tires, this definitely indicates that the tires are at their limit and a dramatic reduction in traction is about to occur. Again, my experience and perception is that the Goodyear's have a higher overall traction limit, but when that is exceeded the tires have a notably reduction in traction until they "hook up" again. The Bridgestone EL42's have a slightly lower traction limit, but are much more progressive at the limit, maintaining their traction while "squealing" louder. Overall, I prefer the EL42's.

Scott

 

so can I run 38 psi front and 40 psi rear all the time? I mean on the streets for everyday driving.

are there any cons to that? i could care less about ride quality...i have the 350z suspension anyways, and its bad enough...a bit worse wont matter.
will overinflating reduce my tire's life expectancy?

G35S 6MT / ts ecu / 350z springs & struts / jwt popcharger + z-tube / stillen dual exhaust / 6-wire ground kit / soon: kinetix high flow / ssr intake manifold

 

nuttyprof,

I kept my EL42's at 40psi and got 32K miles before replacing them. We replaced them with over 1/8" of tread, enough for at least a 2-3K more miles before I would have been legally required to replace the tires (http://www.tirerack.com/tires/tirete...eplacewhen.jsp). There were no treadwear irregularities when I replaced the tires, so I would say that, based on my experience, increased tire pressure (to within about 5psi of the tire's maximum pressure) will increase treadlife.

Here is some information from the tirerack.com site:

http://www.tirerack.com/tires/tirete...vs_dryperf.jsp
http://www.tirerack.com/tires/tirete...vs_wetperf.jsp

Hope this helps.

Scott

 

<blockquote><font class="small">In reply to:</font><hr>


As for the squealing by the Goodyear RS-A's, in my experience with those tires, this definitely indicates that the tires are at their limit and a dramatic reduction in traction is about to occur. Again, my experience and perception is that the Goodyear's have a higher overall traction limit, but when that is exceeded the tires have a notably reduction in traction until they "hook up" again. The Bridgestone EL42's have a slightly lower traction limit, but are much more progressive at the limit, maintaining their traction while "squealing" louder. Overall, I prefer the EL42's


<hr></blockquote>

I think I better check this out in an empty parking lot. I can pretty muh make the tail swing out (or car rotate) at will.. but it is always been at low speeds. This on-ramp business (where the tires were squealing) was a mixture of a fast turn and power; if I am in fact near the limit (precipice), I better watch it before I fall off.

G35S AT / Ivory Pearl and Black

 

You sound pretty new to higher perf driving. Take it easy for a year and get to know exactly whats up with your car before you risk anything. I can take my car through situations now that i never could when i got it just for the simple fact its like a glove on me now and could never be until I got intimate with the cars balance, feel, reaction, traction (which changes), at many different situations and scenarios. This car is very forgiving within it's limits but you want to know where they are or you'll go way over them and never know where to calm down.

2003.5 DP Sedan (Everything but Nav)
Injen CAI
10 Wire Hyper-Ground
Polk Tweeter Upgrade (EX-3500)
Crawford Plenum (V4)
H-Liner Sound Deadening
Shock Sensor
UR Crank Pulley

 

SixFive, am new to high perf rwd for sure. Have owned stick, front wheel drive cars and also have done my share of biking (motor). It is kind of interesting to see how different things become important in different classes of machines. WIth the stick, fwd cars, you just don't have the power (the types I drove) where you could factor in engine power into the equation. The focus was more on ensuring keeping the engine on the boil etc.

With the G, there is so much power available, many things start become a decision of the type - should I brake or out-accelarate, use the steering or dial in some more power.After almost 20k miles on it, I still love everyday I am out driving it. It is almost like my bike (which I sold a few years back).

G35S AT / Ivory Pearl and Black