I always thought it was spelled "Castor". Looks like it is either/or with the majority going with "caster". Learn something new every day.
I had my 86 GT alignment done a few months ago. It didn't change much but it was a little better. I didn't think it was bad to begin with but I had purchased 2 new tires and had never had the alignment checked before. I have had the car for about a year now and it has been my daily driver. No major complaints with handling but I was hoping that the alignment would make it more stable at Interstate speeds. I generally cruise at 70mph +/- 4mph so obviously nothing crazy. Sometimes I will punch it up to maybe 85mph when passing to let someone behind me get around (does that make sense?).
Anyway, I know that the recommended spec for caster is 5 degrees +/- 2 degrees. That gives an acceptable range of 3 to 7 degrees. I think that means POSITIVE degrees and not negative (someone please confirm). I didn't get a printout at the alignment because the printer was broken but I did take a photo of the screen. My caster was 2.6 left and 2.9 right. Cross caster -0.3 degrees. (what is cross caster?)
These numbers are just outside the recommended range but "just barely" according to the tech who said it didn't make a noticable difference. Of course HE would say that! Was he right? Would messing with it at this point be wasted effort? I have the bolt and washer kit from TFS that I was going to use on my 85 project but maybe I should put them on THIS car? Especially since I will be driving about 60 miles a day on the interstate next semester.
I felt like I was getting pushed around more than usual yesterday. Maybe the wind was up. It WAS especially cold yesterday and we even had snow flurries. That made me think about front end lift and hood vents. Which would be more effective for giving it a solid, "planted" feel on the highway? Do both? Do one first and see? I have an extra hood that I could cut a hole in to try. Is a hole good enough or would I need to create some "ducting" to direct the air up and out? If I change the washers, will a "seat of my pants" evaluation be good enough or will it mess up the other numbers requiring another alignment?
Did you replace the stock rubber cradle bushings with aluminum yet? My Indy felt like it had a hinge in the middle of the chassis before I installed Rodney's solid bushings...
Did you replace the stock rubber cradle bushings with aluminum yet? My Indy felt like it had a hinge in the middle of the chassis before I installed Rodney's solid bushings...
No. It is just about all stock and original. Had 63K on it when I bought it last year.
Castor oil comes from a bean, whereas caster angle is part of your front-end alignment.
hehe
Anyway, yes it is considered positive caster when the steering angle is raked back. A chopper-style motorcycle is an example of extreme positive caster angle.
Increasing the caster angle will make the front end more stable at highway speeds. And it seems your Fiero's caster angle is pretty small. So it should be no surprise if your steering feels twitchy on the highway.
The long bolt that attaches the upper control arm to the crossmember will have 2 spacer washers on it. With those 2 washers, you can get 3 different caster angles:
-- Both washers to the front (smallest caster angle) -- One washer on each side -- Both washers to the rear (largest caster angle)
If you're going to be doing a lot of highway driving, I would suggest the third option, i.e. the largest caster angle. Oh, and a hood vent wouldn't hurt either.
[This message has been edited by Blacktree (edited 11-13-2013).]
I had some good success by drilling a series of holes under the headlights in the sheet metal. You can also vent into the fender wells and put a simple flap with one way action to vent into the vacuum of the wheel well.
The more expensive way is to cut your hood, but, it really isn't necessary,
That said, for venting the rad for more cooling, cutting the hood is the only good way. There are a few options for that. I currently have a Camaro cowling for mine
As long as the camber doesn't get knocked off(loosening the ball joint) the alignment should stay close. Of course, if you make a big change moving the control arms back, the toe changes a little. By the pic, it doesn't look it, but raising rear ride height reduces Caster. Keeping the car level front to rear is best . Mine is all stock. 85GT. I seem to get "air" above 78mph. I had a more noticable wander feel from slight play in the rear bearings(OE). Really noticable when slightly stepping on the accelerator and letting up. Retorqued to spec with new nuts and haven't felt that in a while. But still get"air".
What is cross castor? I can see it is the difference in the two sides but why is it important? Is there a go/no go range that it has to be within? What are the effects of the cross castor being excessive?
What is cross castor? I can see it is the difference in the two sides but why is it important? Is there a go/no go range that it has to be within? What are the effects of the cross castor being excessive?
Jonathan
If the caster setting isn't close between the two front wheels, the front wheels will try to self center in a direction that isn't straight forward. Since most roads are crowned so the rain can run off, many times the settings side to side are tweaked to help make it easier to drive stright on a crowned road, but then on flat pavement the car will likely pull to one side.
Most street car alignments call for the front camber and caster settings to be adjusted to slightly different specifications on the right side of the vehicle compared to the left side. These slight side-to-side differences are called cross-camber and cross-caster.
For vehicles set up to drive on the "right" side of the road, the right side is aligned with a little more negative camber (about 1/4-degree) and a little more positive caster (again, about 1/4-degree) to help the vehicle resist the influence of crowned roads that would cause it to drift "downhill" to the right gutter. Since most roads are crowned, cross-camber and cross-caster are helpful the majority of the time, however they will cause a vehicle to drift to the left on a perfectly flat road or a road that leans to the left.
Using cross-camber and cross-caster is not necessary for track-only cars.
[This message has been edited by fieroguru (edited 11-14-2013).]
More caster can effect feel at highway speeds BUT be warned that will negatively effect steering wheel effort, especially at low speeds and parking. And Fiero doesn't have PS to help you with that.
Toe can/will effect higher highway speeds. If you set any toe out on a machine then it will get worse as more speed. More speed then more toe load. Spec says ±x° tolerance but any −/out is bad on front the more speed/load. Spec was written for national highway speed, 55mph. Now some states have 65-75MPH really means most drives at 70-85...
Cross wind on a car get same problem has aircraft and everything else. Little/nothing you can do to the car will help. Big cross wind can blow over and ever flip trucks and RV.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
More caster can effect feel at highway speeds BUT be warned that will negatively effect steering wheel effort, especially at low speeds and parking. And Fiero doesn't have PS to help you with that.
True, but since I'm starting from less than 3 degrees, I have plenty of room to increase caster without hitting the upper limits. I think I'll mess with it this weekend.
In the 80s we would almost religiously set .25-.5 degree more camber on left side to make up for road crown. Seemed they were more consistent when grading roads before then. By the mid 90s, we noticed most of the newer roads and redone roads were all over the place. At least here in Maryland. PA. still seems more consistent. Now we try to get them as even as possible. Some old rule of thumb. Cars with tapered roller bearings(servicable) have slight positive camber to keep the straight load on the larger bearing. Negative camber puts more load on the little bearings. Cars with equal inner and outer bearings stay near 0 unless slight negative camber is wanted to preload the wheels in turns. Really old, 1 degree positive caster for non power steering to help with steering hardness. 3 degrees on power steering to help with higher speed control(counteract wander). You have to remember these were for like a 72 Nova. and when you don't have specs. Performance intended cars have more caster and more negative camber, but this does wear tires more. For toe it would be 1/16-1/8 toe in for rear wheel drive to have the toe go to near 0 as rolling force pulls wheels back. Front wheel drive would be 0-1/16 toe out to have them go near 0 under slight acceleration. Rear toe on front wheel drive is normally slightly toed in for the same reason as front toe on rear wheel drive. On adjustable rear wheel drive(Fiero) toe would be near 0. Because of the constant changes in accelerating braking and coasting, but can't hurt to have slight toe in
I'm having the same problem. My car feels really unsteady on highway speeds. It has new front inner tie rods. And whatever you do, do not go to Autozone for an alignment. I will be going back next week for the third time to get it fixed again. I'm not sure how it's possible, but they keep messing it up. The first time I forgot to get a print out, and the second time I got one. They said the alignment was way off. But now It still doesn't feel right. So back in I go! They said that they couldn't get one of the adjusters in the rear loose to align it. Which is hard to believe because they are 1 or 2 years old...
also remember that Fiero and many other cars have racks mounted in rubber/poly... To keep steal frame breaking Al rack shell.
Rack and tie rods aren't 100% straight at rest or driving straight in many factory setups. Again, Higher speed = higher toe load. Toe load affect these part and rubber will compressed more because the parts tries to be straight. As parts are pulled straight the more toe out in Fiero's case and car w/ rack in front of the "axle." (Steering behind axle, like 84-87 Fiero rear? then toe load is trying to bend the steering parts.)
Lower the vehicle by messing w/ springs or BJ Often won't help. The steering parts have more load and rubber rack bushings will compress more.
You can try using Old Fiero front toe spec or in between old and new. If you try... try setting front only first. Old toe is Front +0.15° ±0.05° Per Wheel Rear +0.15° ±0.1° Per Wheel (Source: 87 FSM)
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Originally posted by cmechmann: In the 80s we would almost religiously set .25-.5 degree more camber on left side to make up for road crown. Seemed they were more consistent when grading roads before then. By the mid 90s, we noticed most of the newer roads and redone roads were all over the place. At least here in Maryland. PA. still seems more consistent. Now we try to get them as even as possible.
Likely a good plan. While cross camber works on small streets/highways... Can, often does, cause problems 2-4 or more lanes of roads in one direction. When setup to drive straight in right lanes, can pull left much more when drive in lefts lanes because left lanes often have crowning to drain towards the center grass etc.
Many roads are like this... Drive right lane is OK but left lane make most cars pull left. Not just interstate... Any multi-lane roads often have same problem.
I started looking at the grading of the streets I regularly use. The majority are center crowned. I'll post my findings as soon as the mailman brings the washers and I get them on.
My parts came in. Here are the 3mm and 9mm washers as they come in GM's kit. Two kits required for the car. Going out to put them on then going for a test drive.
I am happy to report that this mod made a huge difference in handling! The car feels much better. More solid, more planted. Much less twitchy at interstate speeds. Feels like a modern car now. Very happy. I do not feel any NEED to add an extractor vent to the hood at this point. Not saying I would never do it but if I do, it will just be because I want to and not to solve some basic problem. I ran it up to 85 MPH and it felt great. Very confidence inspiring. I highly recommend doing this.
The work itself was pretty easy. Neither the bolt nor the nut were corroded or stuck to the bushings. I was trying to jack up the lower control arm to find a "sweet spot" that would allow the pivot bolt to slip out. A sweet spot like that doesn't exist. The reason for this is that there is a constant pull against the upper control arm by the weight of the hub, the caliper, and the brake disc. I figured this out on the first side and that made the second side that much easier and faster to do. I was also a little worried that releasing that bolt would allow something to spring loose and mash my fingers or hit me in the face. There is nothing in there that can do that as a result of removing the pivot bolt. Safe and easy, no worries. The factory lube on the bolt, whatever it was, was a bit sticky and that made sliding the bolt out a little harder but it wasn't like metal on metal friction. When I put it back together, I put some Never Seez on the bolt to make sure it would come back off again and wouldn't fuse to the bushings. I didn't put any on the bolt threads for fear of it backing off. As I was putting the second wheel back on, it hit me that I should have taken pictures. Sorry.
Between the bushings of the upper control arm, there is a spacer that is about 4 inches long. The washers add the remaining 12 mm that is needed to span the distance between the two bushings. From the factory, there are two 6mm washers. One on each side of the 4-inch spacer. I replaced the stock washers by placing the 9mm washer toward the rear of the car and the 3mm toward the front. Additional castor can be had by putting both washers toward the rear. Of course if you want that, you don't need a 3 and 9mm washer kit. You can do that with the original 6mm washers. That might be too much to be comfortable in low speed manuvering.
They wouldn't have shown anything you don't already know. It is VERY straight forward. Just a bolt, a nut, some washers, and a spacer. Take note of how the parts are lined up on the bolt and put them back on the same way except for the new washers.
EDIT: I found this pic on another thread. The bolt to be removed is the foot long one that runs from the shock to the brake line in this pic.
The brake line bracket 10mm bolt has to be removed and the line carefully bent down slightly to get a socket on the head of the bolt. The torque for the nut when putting it back together is 66 ft-lbs for 84-87 cars. The bolt and nut size is 18mm.
Jonathan
[This message has been edited by Boostdreamer (edited 12-04-2013).]
Yes, that is the driver's front. The head of the bolt goes to the front of the car and the nut goes to the rear. It is one long continuous bolt all the way through both upper control arm bushings and it passes behind the spring perch. In the area between the bushings and behind the spring perch, the bolt runs through two 6mm washers and a spacer tube. The washers and the spacer are what allows the bolt to be tightend against something. Without those pieces, you would just be putting a spring type tension on the bushings by squeezing them together. The washers and spacer make it a strong and solid member.
So when you take the nut off and start sliding the bolt towards the front of the car, the first thing that will drop off will be two thin washers that the nut rests against. As you pull the bolt out more, it slips through the rear bushing of the upper control arm. Next, it pulls through one 6mm washer, then the spacer tube, then the other 6mm washer. Stop pulling the bolt at that point. You don't need to completely remove it. Push it back in about a 1/4 inch and put the 3mm washer on. Then thread it through the spacer tube. Then put the 9mm washer in place and push the bolt back through the rear bushing. Put the two thin washers back on and then torque the nut. You may want to put something on the threads to keep the nut in place. I did.
I have the same air problem at 75 to 80 mph. New tires, did shocks, then alignment at sears. Car handles great except at those speeds. Ordered new ball joints and rubber control arm bushings and sway bar bushings. Will order spacers Too. Thanks for your writeup really helps me try to solve problem. Will continue working on it. THanks everyone!
I've re-located the washers on my '87 GT front upper control arms to increase the caster angle. Along with poly bushings front/rear, and aluminum cradle bushings, I have noticeably less "squirmy' feel at the rear of the vehicle.
Before changing my washers, I could steer on the highway with my fingertips. "Could" is not really the right word, "had to" is more appropriate. I had to keep light pressure on the steering wheel for fear of too much input. Now I have to hold the wheel and turn it where I want it to go. Really much nicer feel now.
I'm currently driving about 100 miles a day, five days a week for work. About 95% of my driving is on the interstate. With such a high percentage of my miles and time on the highway, I would be better off with the caster set to the max. All 12mm on one side for maximum caster.
The more highway miles you have to drive, the more caster you will want. You'll have to decide where you want that balance to be. As mine is, it is still nice to drive around town and agressively in tight corners and turns. I enjoy this kind of driving when I can get it so I don't know if I'll change my caster to improve my highway driving.
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