 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Pontiac / Pontiac Fiero / June 2005alignment specs?
I have a problem with straight line stability at highway speed, 70 mph. My car is an '85 Fiero GT automatic. Deteriorated bushings in the passenger side upper control arm were causing the car to pull to the right whenever a bump was hit. I replaced all the control arm bushings, upper and lower, with Prothane bushings plus all 4 ball joints. The sway bar bushings were also replaced with Prothane. A 4 wheel alignment was done afterwards. According to the shop printout all adjustments are in spec. The handling in town is much better and cornering is great. On the interstate at 70 it's down right spooky! The technician called it "darty". The wheel bearings have been replaced since I bought the car and have no play in them. Air pressure is 28psi on all 4 tires. The rack doesn't appear to have any slop in it. The tie rod ends also feel solid.(I believe the tie rod ends and ball joints had been replaced at some time before I bought the car.) I ordered a new steering damper but neither I nor the alignment shop think it's the problem. All of this brings me back to alignment specs. I remember reading a posting by Bob of "Backyard Engineering" that camber should be set at -1 instead of the stock 0 to +1 and wondered what the basis of this difference was. Sorry for being so wordy. The more info I can give, the more likely someone will have an answer. Nothing like a comprehensive question to resist a stupid answer! :) A higher caster will tend to increase straight-line stability (at a trade off of higher turning effort usually). Some/most shops will tell you that the caster is NOT adjustable. If so, time to find a new shop. There are washers on the upper shaft bolt totaling 12mm (IIRC), and they can be shuffled back & forth to adjust the total caster. Just for the fun of it, I'm going to jam them all in the back to max out the caster and see how it drives! I don't care about steering effort... I've got strong arms. :) >I have a problem with straight line stability at highway speed, 70 > mph. My car is an '85 Fiero GT automatic. [quoted text clipped - 19 lines] > Sorry for being so wordy. The more info I can give, the more likely > someone will have an answer. A little toe-out will do wonders, if you like meandering. Lightens up the steering and gently chews the inside edge on the tires. Front should be more sensitive, but rear could do it as well... Nothing like 4 wheel alignment! > Nothing like a comprehensive question to resist a stupid answer! :) > [quoted text clipped - 29 lines] > > Sorry for being so wordy. The more info I can give, the more likely > > someone will have an answer. Factory changed the recommended setting middle of '87. -1 greatly reduces front end push, extreme understeer. If by 'darty' you mean front end moving abruptly this might be cause by improved front traction. If the rear end is making strange movements, feels like it wants to keep moving sideways on a lane change for instance, check the rear subframe where the tie rods are mounted very carefully, especially the drivers side. The frame can and does crack around the weld holding the bracket to the frame. Jack up the car, support it properly, and have someone else vigourously attempt to turn the rear wheel (left and right, not around). Get your head and a light in up close and watch for any movement of the rod or its mount. Check both sides. I have a picture somewhere of how bad the thing can crack and still drive normally at less than freeway speeds.  SignatureRobert W. Hughes (Bob) BackYard Engineering 29:40.237N, 95:28.726W or perhaps 30:55.265N, 95:20.590W Houston, Texas "The city with too much Oxygen" rwhughe@oplink.net > I have a problem with straight line stability at highway speed, 70 > mph. My car is an '85 Fiero GT automatic. [quoted text clipped - 19 lines] > Sorry for being so wordy. The more info I can give, the more likely > someone will have an answer. What tires do you have on all 4 corners? Miss matched or different tires front and rear can have a very negitive effect on a Fieros handling. My 85 Gt and my 88 Formula both are the same in this regard. I bought new rear tires for the 88 once and the shop that sold me them told me they were the same as the old ones. They looked the same, same tread pattern ect. The old ones were Cooper Cobra GTH, but the new ones were Cooper Cobra GT. The new tires didn't have as stiff of a sidewall and made the car exctremely darty and wanted to follow ruts alot. I sugest that you have the same stiffness tire front and rear or at least a stiffer one on the rear than the front. If the car reacts much slower in the rear than the front it will seem darty at hiway speeds. You can test this to some extent with your car. Bump up the rear tire pressure to about 40 psi and take a test drive. If it makes it feel better the tires are the culprit. What kind of tires do you have on it? Might want to think about those... I had many of the same problems on several different type of vehicles that I've owned over the years... and this was always the problem when it came to highway stability... -Arlie Bright www.fierostripes.com > I have a problem with straight line stability at highway speed, 70 > mph. My car is an '85 Fiero GT automatic. [quoted text clipped - 19 lines] > Sorry for being so wordy. The more info I can give, the more likely > someone will have an answer. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.