HORRIBLE front end push

[nhromyak]

I have a HORRIBLE front-end push, at slow and high-speed turns.

I am starting to think it's these tires - Bridgestone RE730s (205/55 - 16). They are 4 years old now, and are close to the wear bars, but appear to have another 10K in them.

I have the RE750s in the rear (245/45 - 16) with only 5K on them.

With the help of others on this board, I am running ~ 31 psi (was 29) in the front, and only 32 psi (was 38) in the rear. This has helped my front-end push in high speed turns.

BUT

When I make a simple U-turn, the front tires PUSH and scrub and feel HORRIBLE! If I give it a little more gas in the U-turn (more than 1500 rpms) it turns into a snow-plow and goes straight!

When backing-up, the front tires slip even worse, you can hear them grrrowling, not screaching. *sigh*


I just got an alignment done, and now I am at

LEFT
- 0.6 camber
5.9 caster
0.07 inches toe-in

RIGHT
-0.9 camber
6.2 caster
0.07 inches toe-in

I asked for about 1 degree negative camber.
Previously it was almost twice as much toe-in. So now, it feels much better, and has a quicker turn-in, but I am guessing these tires SUCK when they get this low on the tread, even though they have more wear to go yet. Disappointing...

The were wearing on the inside, presumably from too much toe-in.

Anything else it could be? More tire-pressure trials? Or are these RE730s just "sucky"?!?!?!

If it's the tires should I go and look for the RE750s or should I go after some Kuhmo ecstas?

I have some track tires, and as I recall, I had the same horrible front-end push. But that was three alignment settings ago.
Perhaps I should tried these again? Just to see if I still have the front-end push?

[Walko]

Before that question can be answered you would need to advise what sort of suspenion setup you have on the front and rear of the car as well as the type of car

Ie 911 SC .

Also have you got an LSD or locker diff or open diff.

Michael

[rdane]

How much air do you have in the tires?

[dickster]

i had the same symptoms with p6000's so i don't think its the tyres. i was told by my tyre shop that 911's do wear out the inside edges on tyres?

does yours plough in left and right turns?

[cstreit]

A major piece of this is likely tires.

...I would replace the fronts. For now, More toe-in means more understeer. This is good for the rear, not as good for the front.

In contrast, I run between 1/8" to 3/16"(!) toe OUT in the front of the racecar at certain tracks. You might try a zero toe setting.

[IROC]

Has this problem existing since you've had these tires or is this a recent problem? If it's a recent development, then maybe the front tires have just had it. If it's been there the whole time, then you need to address whatever is causing the problem.

In my experience, it takes alot of tire in the front of a 911 to really eliminate understeer. I've run 185, 195, 225 and 245mm wide tires in the front and I wasn't satisfied with the turn-in and lack of understeer until I started using 245s.

I think you might be shooting yourself in the foot somewhat with 245s on the rear and 205s on the front.

Chris is right about the toe also. I run zero toe in the front and I think it feels about right.

YMMV.

Mike

[nhromyak]

Thanks for the replies.

1) The car is stock. Bilsteins all around.

2) as outlined above, I am running ~31 psi in the front. 32 psi in the rear (cold).

3) This "push" has been there for at least last three years (as long as I have had these tires). Possibly since, I corner balanced and lowered the car (only 3/8" lower).

It presently sits at about 24 5/8" from the front lower fender-lip to the ground. The passenger side is at 24 3/4".

The rear is at 24 3/8"

4) The push and U-turn pushing happens in both left and right turns.

[dickster]

nick

it sounds very much like the condition mine has (mines an '86) however mine only does it in right handers. i have brought the topic up before and changed settings/shocks/tyres/bushes/t/bars/etc.

it is very frustrating because mine handles wonderfully in lefthanders - completely different animal. i have booked in to have the elephant front A arm bushes installed plus corner balance and alignment on 14th feb - will let you know if they cure the problem.

[450knotOffice]

Hmmm...so a little understeer is common with these cars, it seems? My Carrera is the only 911 I've driven and I have noticed that in high speed, power on sweepers the car will understeer quite noticeably. It's a little disconcerting when the car starts to push a little toward the outside of the turn, but of course a bit more steering input and all is well again.

I've got good alignment specs and S-03's with plenty of rubber left in them. I've got 205's front, 225's rear. I suppose the next tires should be 225's front, 245's rear.

-Scott

[nhromyak]

Dickster - Do you know what your alignment specs are on all four of your tires?

Slight understeer is expected and induced from the factory on the Carreras, or so I understand. I beleive this is a sway bar setting.
However, mine is COMPLETELY unacceptable.

I will put my kuhmo victor-racers on this weekend and see if I still have the push. I am afraid it will still be there.

[Bill Verburg]

You obviously need to apply massive amounts of power to the rear wheels

[rdane]

The reason I asked again on tires pressure is mine pushes when the tires are low.

With stock SC sway bars and 205/245 730s my car would understeer at high speed. Nothing like you have described though. 225s up front negated some of that. In addition late Carrera sways made my car very neutral. I also run 30/34 for air, 80% ZF l/s, Bilstein sports and 22/30 tbars, now with 225/245 SO3s.

camber front is -.90 / -.91
caster 5.36 / 5.28
toe 1.6 / 1.6

rear camber 1.74 / 1.71
toe 1.4 / 1.5

[nhromyak]

I tried going to 33 psi in the front, with no difference. It seemed worse during a slow U-turn.

*sigh*

[rdane]

I run 30 front 34 back.
Sounds like you have some hard tires!

[nhromyak]

Actually, my friend drove it and said mine seems to drive better (softer) than his with Kuhmo Ecstas.

[dickster]

nick

i had the aligment checked awhile back but nothing showed up-dont know the specs though i am afraid.

since then i have made lots of changes and the specs are way out. however the handling has remained the same. i mean even when i swapped the t/bars for 22/31 i was expecting some difference! but nothing!

i am taking the car to a well known wrench in the uk so fingers crossed.

[nhromyak]

It sounds like your caster is out of whack on one side there Dickster.

Good luck.

[gduke]

you mentioned that you lowered your car. the measurements to the fender lip aren't as accurate as thew one recommended in waynes 101 projects book(center of control arm - center wheel).

my car pushed and handled poorly when i first bought it. one of the remmedies to correct this was to raise the front end ride hight.

[stlrj]

Raising the front will bring your alignment closer to factory spec and reduce push while improving handling which, of course, is hard to believe but true none the less.

Factory spec for camber is as follows:

84-89 3.2 ........0 degrees

75-83..............0.5 degrees (positive)

When I took mine back to 0 degrees it handled much better and later set it to 0.5 it got even better with hardly any push or tire squeal during u-turns.

-Joe

74 w/86 3.2

[nhromyak]

Yah, I know it's supposed to 0 camber according to the factory specs.

I also know about the ride height specifications readings off of the center of the torsion bars, and center of the wheel bearings.

I was hoping to get better handling per Bruce Anderson's book.

I guess I should just deal with it until, I get it to a Porsche shop for a real corner balance and alignment.