Need help with front end drivability

[BDealer]

I have a 99 Cobra and cannot figure out why it seems that the front wheels have a mind of their own on less than perfect roads. I can be crusing along on the highway or creaping @ 2 mph. The front wheels will pull one way or another.

I've been told it may be "bumper steer" issues, but have not found any solid info on this yet.

New tires and balance all around with front end alignment...new pads and replaced front passenger rotor...77K and unsure of age of shocks...

There is a shudder above 65 with increased vibration when breaking at high speeds. Possibly needs front driver side rotor...but this shouldn't affect non breaking activity like regular straight line driving at any speed.

Any help? I'm feeling frustrated

 

[tomustang]

It could be a number of things, one thing it could be 'tracking' in which the tires follow the sagged in tracks due to too much riding on.

the shuddering could be the driveshaft

 

[BDealer]

I should have mentioned that the shudder is more pronounced when breaking from high speeds and seems to dissipate at lower speeds.

Road grooves are hell, but just regular interstate driving with minor imperfections keep me actively adjusting the wheel.

 

[duner]

Is the car lowered? If you still have the stock ride height it may not be "bump steer".

 

[BDealer]

Hey Duner,

The car is lowered...It doens't seem to "pull" to either side, just all over the place. I have new lower control arms, but haven't put them in because I want to make sure that this will fix the problem...or at least make it better. I've got +75k on it and I'm guessing new bushings are really needed at this time. I bought the whole arm, because I was able to get them at cost and it was just about the same as having new ones pressed.

Whatcha thinking it may be?

 

[TheCrazy1]

It doesn't seem to have enough miles on it to need front end work. Did it start after putting on new tires, or did you replace them hoping it would improve? I've noticed that some tires will kinda dart around on grooved highways and it's annoying as hell! Did the tire shop put the right air pressure in them?

 

[Dan98Covert]

B Dealer:
My 98 Cobra was also darting around. I found that putting poly bushings on the rack, and (oddly) the rear control arms helped a lot. I also installed caster/camber plates and set the caster to 5.5 degrees, that also helped. This seems to be somewhat common to these cars from what I've heard.

 

[BDealer]

New tires were put on it because they were worn badly...lots of miles...I replaced the back ones first, then the front ones. I went as wide as possible on the rear, but couldn't afford to get fronts at the time...I was trying to wait, but they were too dangerous and I had a long trip to make on them. So I researched and bought what I could afford at the time...They were installed at a dealership that I do I.T. work for by a trusted tech...balanced and put on the alignment machine.

You guys have me wondering...
Front: Kumho 245/45Z 17 95W
Rear: Pirelli P275/40Z 17 93W

Except for the darting around, they do drive nice though...even when it's wet.

Would the diff in tire size make a drivability difference? I have no bench mark because they were so badly worn when I got it.

Dan98Covert...did you install your caster/camber plates yourself or had it done for you? What was your cost. Got a wife that hates when I put $$$ into what she feels is an "old" car! She really doesn't get it, but I love her anyway!!! Although, she does like to go riding in it with me...eating a little rice for fun.

 

[97rmcobra]

B Dealer:
My 98 Cobra was also darting around. I found that putting poly bushings on the rack, and (oddly) the rear control arms helped a lot. I also installed caster/camber plates and set the caster to 5.5 degrees, that also helped. This seems to be somewhat common to these cars from what I've heard.

Interesting. My 97 does this. I thought it was "Memory Steer" which is cause by frozen lower ball joints. I feel like it was never there, I noticed it when I put the car back on the road after last winter. I checked ball joints, strut bearings, tie-rods, tire pressure, and did an alignment at my shop. I have poly bushings in the rear but problem is still there. I would be interested to try the rack bushings.

 

[COBRA90GT]

Is the car darting around just before you approach an intersection (presumably an intersection that has witnessed lots of heavy truck traffic)? The car could be darting around due to the "ruts/impressions" left in the pavement by the heavy traffic.

I have experienced my factory wheels/tires tramlining when I approach an "abused" intersection.

Tramlining explained in further detail: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=47

 

[BDealer]

Cobra90GT & Dan98Covert--Hey, this happens all of the time...when coming up to a light with ruts I need to wrestle the car sometimes...dangerous if I'm not paying attention. Similar situation when the road slopes...it's like the front end is "loose". Highway driving is OK as long as the highway is clean...otherwise I'm constantly adjusting.