|
Rear camber Fix
By: Chris on Feb 8 2004 1:40AM
I started writing this a while back. I believe it is comprehensive. look it over and let
me know if there are any stupid errors I missed. rear camber seems to be a common question
recently so I figured it would be a good idea to put it all in one spot. maybe someone who
has done the hole drilling method can add to this so that both techniques can be in one
document. if you guys think its FAQ worthy then I'll update it with some mode detailed
hole-drilling instructions for people that want to do it that way and clean it up and
repost with a proper title. look it over
Many Z31’s have excessive negative rear camber because of component wear, or the use
of performance springs. If your camber is beyond the limits, and you do not have springs
that lower your ride height then component wear is most likely a big part of the problem.
In this case it would be advisable to replace all the rubber components in the rear
suspension. This includes spring mounts (top and bottom) control arm bushings, and
crossmember bushings. The control arm bushings will have the most effect on camber, but
spring mounts should not be ignored. If any of these parts are worn out, then it is very
likely that you are in need of rear crossmember bushings as well. Although the crossmember
bushings should not have a direct and significant effect on camber, it is a very good idea
to replace these at this point.
If all of these components have been replaced, or if you use springs that effect the cars
ride height, and you camber is still out of spec then you will have to take a different
approach. This involves relocating the pivot point of the outer control arm to allow for
camber adjustment.
There is an easy way and a hard way to do this. The easy way is simple. You drill a new
hole for the bolt and hope that you get it drilled in the right place. Many people do this
and get their camber close to spec. I wanted mine to be adjustable, and I was also looking
for an interesting project one weekend. If you want a quick fix then just drill yourself
new holes and be happy, it’s that easy. If you are like me and like to make things
more interesting then follow the directions below.
The stock rear suspension only has an adjustment for toe. This is located on the inner
control arm mounting point in the form of an eccentric bolt (also called a cam bolt) and a
horizontal slot. This horizontal slot has metal plates welded on either side of it that
are shaped to allow the cam bolt to turn within the boundaries of the plate, to
effectively move the pivot point front to back. In order to make the rear camber
adjustable, we must reproduce this adjuster, except locate it on the outer control arm
pivot point, and turn it 90 degrees to allow for vertical movement.
In order to reproduce this adjuster, some new parts will be needed. The following parts a
required:
1. 2 inner control arm eccentric bolts with washers and nuts.
2. 2 inner control arm bushings. The new bushings are necessary because the eccentric
bolts will not fit in the outer control arm bushings. Therefore the outer control arm
bushings must be replaced with new, inner control arm bushings. More on bushings will be
discussed at the end of this write up.
3. Metal plates for the eccentric bolts to rotate in. since I had a spare rear
crossmember, I was able to cut off the toe adjustment plates and use those. If you do not
have access to a spare rear crossmember, then you will have to fabricate 4 plates that
function just like the plates on the toe adjustment. These do not actually have to be
plates, however. You can simply make some guides for the eccentrics to rotate within by
using 8 strips of metal, 1 on the top, and one on the bottom of each eccentric washer.
Either way, you will need to weld these on so that the cam bolt can rotate freely within
the boundaries.
Once you are ready to begin the procedure, start by removing the rear crossmember. Once it
is out, the metal plates must be welded in place. Be sure to position the plates so that
the holes will be extended DOWN. Once you are satisfied with the positioning of the
plates, weld them in place. It is important to remember that the further down you position
the plates, the more you will be able to make the camber less negative. I lined up the
tops of the slots in the plates with the tops of the existing holes. You can bring the
plates slightly lower if you feel that is necessary. I was able to get correct camber with
all new bushings, and ST springs, with the plates in the positions that I put them. Now
that the plates are welded in place, you need to grind out the original holes to match the
slots in the plates. Now clean the welds with a wire brush and hit them with some spray
paint to prevent rust, and keep them looking decent. The crossmember is now ready to be
installed.
The next step is to prepare the control arms. The only thing you need to do to the control
arms is to replace the outer bushings with new inner bushings. Again, this is because the
cam bolts will not fit in the stock outer bushing sleeves. There is however, another
reason for this. The outside of the inner bushing sleeves have notches etched into them.
These notches allow the crossmember and the bushing to clamp together and remain
stationary when the bolt is tightened. I have found that the fastest way to get the old
bushings out is fire. That’s right, set them on fire and let them burn for a few
minutes. Once enough rubber burns away, the inner sleeve will push out easily, and the
outer sleeve can be cut away with a hacksaw. Once you remove the outer sleeve, be sure to
thoroughly clean the inside of the control arms bushing area. Use a wire brush, or
Scotchbrite to get this area as smooth as possible. To install the new bushing, leave them
in a freezer overnight. Then when you are ready to install them the next day, heat up the
control arm with a torch, take the bushings out of the freezer and tap them in with a
mallet. They should slide in pretty easily with a few good smacks.
Once both new bushings are installed it is time to put everything back together. Bolt
everything back in place, and don’t forget to use the new eccentric bolts. Once you
are up and running, get an alignment and you are all set. Don’t forget to tell the
alignment guy what you did. He may overlook it.
Other things to consider.
Cambers effect on toe adjustment.
If your camber was considerably off, then the alignment guy may have a hard time getting
the toe and camber to be in spec at the same time. The only way I can see to fix this, is
to take the crossmember back out, cut off the metal plates on the toe adjuster and re-weld
them either further forward, or further back, depending on which way they need to be moved
in order to achieve more adjustment. My right toe came back into spec, but my left toe was
nearly half a degree off, and at the end of its adjustment range. I have not done this
yet, but I plan to in the future. The degree of this problem may be related to the angle
of the new slot that is made for the camber adjustment. Another person who has done this
has suggested that the only way to keep the toe in line is to make sure that this slot is
perfectly vertical. I have also heard from another source that there is some math that can
be used to determine the exact angle of the slot. It involves some calculus which I suck
at, so you are on your own there.
Use of polyurethane bushings.
MSA (through Prothane) has recently made available full sets of polyurethane bushings that
include rear control arm bushings. In order to make use of these, you will need TWO sets
of rear control arm bushings (around 15 bucks each). This is because with this setup you
must replace 4 inner control arm bushings, not 2 inner and 2 outer like the stock setup.
Keep in mind, these polyurethane bushings do NOT come with new sleeves, so you will still
need to get the inner sleeves of 2 inner control arm bushings to use in this setup.
Drilling holes for Rear Camber fix
I was looking at my control arm brackets over the weekend, and it looks like there is
enough room to drill a hole for at least 1.5 degrees of camber correction in the existing
bracket.
Is this correct? Do I need to reinforce or weld a new support into the existing bracket
before drilling? Just drill the holes, no need to do any welding unless you mess things
up. Remember, that if you do not drill the holes exactly below the existing holes your toe
will not be right, and if you drill off to much you will not be able to adjust the toe
back into specs without repairs. There are two bolts that hold the suspension arm to the
crossmember. the one closer to the center of the car has off-center washers attached on
either end, and the bolt passes through slots in the crossmember bracket, not holes. The
offset washers are trapped between brackets, so as you rotate the bolts, the washers cause
the bolt to slide back and forth in the slot, effectively moving the point where the
suspension arm is mounted to the crossmember.
In the stock setup, the bolt that is closer to the outside of the car has no eccentric
washers, and passes through a hole in the crossmember bracket, not a slot. The
modification to create adjustable camber involves turning that hole into a vertical slot,
adding the brackets that trap the eccentric washers, and using the same eccentric bolt and
washers that are normally found on the inner mount. Basically, you make the outer mount do
the same thing as the inner mount, except it adjust up and down instead of front to back.
To make it permanent, all you would need to do is drill a new hole for the outer bolt.
I've heard that one bolt's width makes for about one degree of camber correction. of
course, you would be guessing as to how far to move the hole.
If you were to actually do the adjustable camber mod, all you would have to do is take the
whole thing apart, look at the inner mounts and say "okay, I am going to make the
outer mount look like that, but vertical instead of horizontal" then get out your
rasp, Dremal, MIG welder, what have you, and get to work. when you are done, all you would
need is to install the bushing and bolt that is meant for the inner mount in the outer
mount
|
|