Basic Auto Mechanics – Week 8 Steering and Suspension

Steering and suspension is what this week’s class was all about.  It seems that classroom time has pretty much gone out the window with no time being spent in the classroom setting.  The class has also shrunk down to about 4 guys, 3 of us are pretty serious about paying attention and learning the material and another guy that comes every week but seems disinterested.  The class is pretty good for beginners so I am kind of surprised that the class did not stay strong the whole way through.

This was a crash course on steering and suspension and we spent the first session of the class discussing tire wear.  We were shown the wear bars on the tire tread and told that if they are visible across the whole tire that the tire should be replaced.  The teacher stated that the penny trick is pretty much bunk and that you should just read the tread wear bars to make a determination on whether or not to replace the tire.

The common wear patterns that were explained to us are below:

  1. Center wear – This is caused by the tire being overinflated, making the tire like an inner tube with only the center touching the road.
  2. Outside wear – Caused by an underinflated tire, the tire would be concaved with only the outer edges touching the road.
  3. Inside wear – Too much negative camber, only the inside of the tire touching the road.
  4. Outside wear – Too much positive camber, only the outside of the tire touching the road.

There is another type of wear on a tire as well; I believe it is called scuffing.  It’s when the tire is not tracking straight down the road and is being dragged.  This is due to the toe setting on the alignment.  You will be able to feel the wear on the tire; it will be smooth one way and rough the other when dragging your hand across it.

Of course you cannot talk about tire wear without talking about the alignment.  This was what we went into next.  We talked about camber, which is the measurement of the lean in or out of the wheel.  When the wheel is leaning top out, that is positive camber.  When the wheel is leaning top in, that is negative camber.

Caster was mentioned as well, this is the angle forward or backwards the wheel is set from the top of the shock tower; at least that is the way I understood it.  This allows the car to track straight down the road and is the setting that allows your steering wheel to come back to center after making a turn.

We also talked about the toe setting of the wheels.  This is the measurement of the front wheels either being angled towards each other or away from each other.  Toe in is when the wheels are pointing in towards each other like this: / \ and toe out is when the wheels are pointing away from each other like this: \ /.

After talking about the toe settings, we went into talking about the steering system.  We had a cut out of a typical rear wheel drive vehicle on a bench to look at.  We were shown the inner and outer tie rods and the adjustment sleeve that allows you to adjust the toe settings.  The tie rods are connected to the center link which is linked to the steering box buy the pitman arm.  So, the steering works like this:  the steering wheel is turned which swivels the pitman arm which makes the center link move back and forth.  Since the center link is connected to the tie rods, and they are connected to the spindle, the wheels move back and forth and allow you to steer.  This is the system that would be in use with a Saginaw steering box.

There is another type of system call a rack and pinion steering system.  This consists of a gear that is attached to the end of the steering shaft which is in contact with a grooved rack that moves via the gear that is in contact with it.  The inner tie rods are connected directly to the rack and typically do not need replacement.  If they do, the rack is not far behind.

The teacher mentioned that you can tell when the rack and pinion is going bad by the steering starting to bind.  This will be when you release the steering after a turn and the wheel does not go back to center by itself, you will need to manually move it back.  We were also taught that when you replace the rack and pinion system you should flush the power steering pump so you don’t put all that dirty, metal filled fluid, into the new rack and pinion system.  If the power steering pump is cheap enough, he stated he might just replace it!

The last thing that we went over was the shocks and springs.  I was tasked with removing the shock from the demonstration unit and I did.  I was slightly nervous because of the spring that was still loaded in between the upper and lower control arms, but was assured that the spring would remain loaded because of the spindle that was still in place.  I am more familiar with strut assemblies so I asked because I was unsure.  The shock came out with ease, there were only 3 bolts.  The teacher demonstrated the way the shock actually works.  It compresses fast and releases slow.  This motion keeps the front end from getting damaged over every bump.  We were shown the bushing dimples that go in place a certain way to keep the shock aligned correctly in the hole which keeps it from hitting the edges of the hole.

We talked about springs and how they manage the ride height of the vehicle.  We were shown how the ends of the spring sit a certain way in their perches.  He went into measuring ride height, you would do this  by measuring from the top part of the wheel fender to the center of the wheel hub.  He stated that if this is out of spec, that the springs would need to be replaced.  At this point I asked about lowering a vehicle, he stated that he did not like lowering cars but if you were to do it, there is a right way and the other way.  You could cut the springs to bring the ride height lower, but you would have to do it smartly and cut it so that the spring would still sit in its perches correctly.  He didn’t even mention buying aftermarket springs.

We briefly went over strut assemblies and what they looked like.  He showed us a loaded strut cartridge which has the entire unit assembled and ready to go when you get it.  He stated that this is the way to go when replacing the struts because you get all new hardware and you know that everything is good.

This class what quite informative, he went over a lot of things really quickly, as you can probably tell by the non-stop information dump in this post.  It was a crash course but I took notes and paid pretty close attention.  I learned quite a bit since I am pretty unfamiliar with RWD vehicles and the demonstration unit was from a RWD car.  There’s only one more week of this class and it will be two weeks from now.  When I’m writing this it is November 20th 2014 and next week is Thanksgiving.  December 3rd will be the next and last class.




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