Loose front end / steering feel

[cburke996]

I've had an issue with my '01 TT for a little while now. The front end occationally feels loose and vague in regards to steering feel. The weird part is, it isn't always consistent. It usually takes some rough/uneven pavement at highway speeds (55-65+?) and all of a sudden steering feedback sort of gets more numb, and I can move the steering wheel back and fourth with somewhat of a lag in response. Another symptom that is probably related, is the steering wheel tends to have vibrations in it more than normal. I don't feel the vibration driving around normal roads, only highway speed.

In an effort to fix the issue, I've done the following (from oldest to most recent):

1. Rennline drop links were installed, this was not trying to fix the problem but worth noting.

2. I had new tie rod ends (inner and outter) installed by my shop, along with a full alignment to factory turbo specs. Had new rear tires put on (fronts are still healthy) and all wheels balanced. Once I got the car back, the problem still persisted.

3. Next step, I ordered new front control and track arms, OEM 996TT parts from Pelican. I installed them myself this past weekend, also put new front swaybar bushings in. Torqued everything to spec, except the ball joint and the chassis mount on the control arm. Couldnt get a socket on them, so I made them nice and tight with wrenches. Note: I tightened the control arm chassis mount with the car on the ground, so the bushing isn't stressed when it is sitting static.

This is where I am at now. The problem still persists, and I am getting pretty aggrivated by it. Now I'm asking the communitiy what my next step should be.

What I am thinking it *might* be:-steering linkage-rack mounting points-internal to the rack (Hope not! $$)-subframe mouonts/bushings-Front diff mount?-Strut mount (although it doesn't clunk or make typical bad strut mount noises)

Any input or thoughts? I don't want to just keep throwing money at it, and I am competant enough to do a lot myself. That said, I am not opposed to bringing the car back in. The hard part with that is, Sometimes the car feels OK (esp around town) so my shop might not see what I am talking about. But it is once you hit the bumps at highway speed that the problem surfaces. Then even on smooth pavement, it is like something gets upset and the car still feels bad for a while.

Thanks for taking the time reading my long post, I truly appreciate it.

Connor

Edited July 3, 2013 by cburke996

[Dus10R]

What size wheels? Stock or larger?

Vibration could be wheels and or tires, out of balance, broken inner steel belt, not N rated tires.

Suspension stuff is always hard to diagnose.

If you're running 19" wheels, that's the culprit.

[athena1111]

Hi. I was just wondering if you had any luck correcting your front end problem? I have an '01 Turbo with the same issue.

[DaveCarrera4S]

If you're running 19" wheels, that's the culprit.

huh? Lots of 19" wheels on these cars. Do explain.

[Dus10R]

The car was not designed around 19" wheels. Just because they fit and lots of 996 guys use them doesn't mean they work better. I tried using them once long ago against better advice, but the side effects were adverse at the limit and when I switched back to 18"s all those issues went away. Running 19" wheels on a car that was not designed around them changes the suspension geometry enough to not function properly. There are other reasons too. Car was designed for specific overall diameter and with the AWD system a specific ratio of diameter front to back. No matter what tire you fit on a 19" wheel you'll never match the OEM diameters. Plus generally when you increase wheel diameter you have to increase tire size, sidewall gets shorter, wheel weight goes up, tire weight goes up, wheel flex goes up, weight distribution of the rotating mass gets farther from center. So... Puts more stress on the steering, which changes the steering feel. Wider front tires, even by a small margin, doesn't allow the weight to transfer enough to the tire on the outside as the inside tire now has more grip too. Wider tires work well but only on a car with the suspension geometry that is set up for it. Shorter sidewall now means less tire flex which means the suspension needs to compensate or you risk loosing contact and possibly bending a wheel. Its just not a simple swap. Porsche had to make lots of suspension changes to the 997 to get 19" Wheels to work correctly.