944 Handling/Cornering

[hoff944]

Let me set the scenario: I'm running my car at a high rate of speed on a sweeping curve through an area across from Nashville International Airport where the old terminal used to be. I like to do this here because if something goes wrong I have nothing to hit and no one is ever over there.(Sounds like I'm pulling an Ahmet right ) In this corner my back end got loose but it snapped back in line. I'm running 245's on the rear so this should not be normal. My front tires are 225 BFG Comp TA VR's and the rear tires are 245 BFG Euro TA HR's. I take that the rear is breaking loose because of the lower performance tire. What do you guys think? These tires came with the car and I'm planning on upgrading to Dunlop SP 8000's all the way around soon.



[This message has been edited by hoff944 (edited 08-21-2000).]

[LtUSMC]

I don't really understand your question. Your back end will always "break loose" *eventually* no matter what kind of tires you got or what kind of car you drive (F1 or otherwise). It's only a matter of how sharp and hard you drive. The 944 is not Godly. No car can withstand an unlimited turn strength.

What's important is that you practice to minimize the back eng slacking on you like that, so that the driver quality will near the vehicle's driving capacity.

IMHO, if you can turn so that the back end is just on the verge of slipping on you, yet maintain control, then that is the perfect turn.

[lm6y]

Welcome to the world of oversteer! LTUSMC is right, getting it right there on the edge of control is a blast! The only thing better is a four wheel drift!

[1.2gees]

Well done, 1.2gees junior!
Hehe...

Ofcourse the size of the tire is NOT the only variable... Better tires will make a differance, a stock 944 though, with the same sidewall height, and wider tires in the back WILL NOT oversteer, unless ofcourse induced by the driver.

If your car just started oversteering by itself, right at the limits of adhesion, well, there's a couple of things possible:

It COULD be bad sway bar bushings in the front sway bar, it COULD be an alignment, it COULD be low tire pressure in the rear, it COULD be bad shocks in the rear, not returning the full pressure on the wheel/tire as quick as the fronts did over a minor bump... So, it COULD be lots of things!

The thing is, a STOCK 944, with good tires all around, uniform tires, and so forth will NOT oversteer, ofcourse, unless induced by the driver.

My car as it is, with sport sway bars, bilstein shocks in the front, kyb sports in the back (with new bushings, save for the control arms in the front, which are busted!) handles nearly DEAD neutral. It's got 225/50/15 Yokohama AVS sports in the front, and 245/50/15 Dunlop Sport 8000s in the back, tire pressures, 40-42psi all around, depending on street/track driving.

So the big change here is the tires in the back, they DO loose a slight bit of agility, and ultimate feel at the limit, but that limit is raised very much by the tires in the back... I have a custom alignment, so don't want to comment on how this compares to your car, but a stock 944 that doesn't have anything major wrong with it will handle as close to neutral as most "spirited" drivers would want, leaning on the understeer.

The car WAS more fun to drive with stock tires, since the limits were easier to reach. If I didn't have the extra 10 or so (could be up to 25-30)hp over stock, I would NOT want the 245s in the back, cause throttle/brake induced oversteer is much harder, no doubt the former effected by the LSD.

Just some thoughts...
Ahmet

------------------
It's all the driver...

[hoff944]

I was just thinking that the front would break loose before the rear.

[1.2gees]

It should if everything else is in good shape.

Now that "everything else" includes tire pressures, which are likely at least part of your situation.
Ahmet

------------------
It's all the driver...

[Pilot_951S]

The end of the car that breaks loose first is determined by the way you enter, drive through, and exit any given corner. (within limits of course)

The character of that breakaway (abrupt or smooth) is generally determined by the tires, suspension components and the power delivery.

As an example we can use my Subaru Impreza 2.5 RS sedan. This car is notorious for its masive understeer at the limit, however an agressive trailbraking manuever can easily get the back end around. Similarly if I enter the corner slowly and attemp to accelerate through it the front end lifts and the car pushes to the outside.

In my 951S which is currently running 225/45-17 F, 255/40-17 R, zero toe with about 2.0 D neg. camber in front, and 3.0 D neg. camber in back, 1.5" lowered front, and 2.5" lowered rear, and about 350hp the car is very sensitive to throttle and brake input while turning.(so is any 944 really)

Anyway if I enter a turn too hot on teh brakes and I don't have enough traction left to turn the car with it will understeer pretty badly, however if I let up on the brake but continue to trail the throttle (meaning I'm not using it) the car will tuck in and turn, if I reapply the brakes a little bit the back end will start to swing out at that point. Now when exiting the corner if the front has been nicely hooked up from the turn entry I can feed the power in and the rear will slide ever so slightly in a beautifully controlled manner.

Basiclaly my conrering attitude can be adjusted using the brake and the gas in either car, but with the Subaru I am restrained by its basic handling behavior and with the 951 I am free to stethe car into the corner however I like. This does however require much mroe concentration on my part.

Now before I had my suspension set up on the 951 it was rather more of handful at the limit, it had a nasty snap oversteer that was very hard to predict and control. Part of that was due to the US rear ride height specification which is about 1-2 inches higher than optimal. In addition ot that mess the stock aligment settings of about 1 degtree toe in cause the car to understeer on inital turn in.

Anyway, what end is supposed to break first? Well as 1.2 says, that depends...

[hoff944]

My car didn't really feel at its limits though. It felt as if the rear tires were the only limit. It doesn't roll at all in the turns. I just didn't expect this in a long sweeping turn like what I was taking.

I know my tire pressure was okay because I checked it the night before at the rears both checked out at 36PSI which is what is recommended.

[This message has been edited by hoff944 (edited 08-22-2000).]

[Pilot_951S]

Considering it was a constant radius sweeper you rear end problem is either 1) applying more power than the car could handle at the speed you were going, or 2)your rear ride height needs to be lower, or 3) you have a worn suspension part (which could be on either end of the car).

as I said before it depends...

[hoff944]

Keep in mind the rear tires aren't near as good as the front which makes me think this is the problem. My 944 is still the best hanlding car I have driven.

[This message has been edited by hoff944 (edited 08-24-2000).]

[Pilot_951S]

You won't know until you change them