- Suspension Design Targets
- Suspension Install
- Suspension Notes
Suspension Design Targets: If this was a coupe,
there would be plenty of shock/spring combos that would work well, but the
convertible chassis, even with additional bracing, can only handle so much roll
stiffness. The targets I was aiming for in modifying the suspension:
- Get the 'stance' as low as possible, level front-to-rear, while
being able to clear all the local speed bumps; a daily driver can't be
scraping everywhere. This would amount to a 2" front 2.5" rear drop from
the factory new height (car springs settle over time so newer cars are usually
higher)
- Reasonably comfortable, with a usable amount of wheel travel (not
on the bumps stops); many complain about the ride quality of their aftermarket
suspension, not realizing their car is bottoming out, creating a jarring ride.
- spring and shock rates high enough to prevent the lowered
suspension to bottom out in daily driving - to get this right they will have
to be adjustable for compression and rebound.
- suspension compression and roll stiffness not too high for the
convertible chassis (or the passengers)
- improved handling, reduced brake dive and squat
- avoid problematic polyurethane bushings in LCA pivot points, as
they don't allow the control arms to rotate as required, resulting in poor or
even dangerous handling characteristics.
- avoid rod-end type control arms, because of noise and maintenance
issues.
- use reliable, proven components wherever possible, designed for
long life and low maintenance.
- roll bar to provide additional chassis bracing and protection
should the car get the wrong way up. This bar would preferably leave
room in the back seats for the kids.
Suspension Install: After a lot of research, and
going on personal experience, here's what I installed:
- Subframe connectors (SFCs), welded under the car (I used my 220V
MIG) to improve the rigidity of the chassis.
- Front Springs: Suspension Techniques Speedtech springs, about 50%
stiffer than stock, have a 1.75" drop and a high enough rate to keep the car
from crashing into the bump stops. An additional 0.25" drop is obtained from
the adjustable spring perches on the front shocks.
- Front Shocks: custom valved QA1 shocks adjustable for compression
and rebound, as well as spring perch height, allow for required (essential?)
tuning of the shock rates to match the springs. The adjustable spring
perches allow a slight adjustment on the ride height. Note: the default
valving on the QA1 shocks (for the F-body) are intended for drag racing, but
like any component shock they can be revalved to suit almost any application.
- Front Sway (anti-roll) bar: 32 mm hollow 1LE factory bar with
polyurethane bushings and end links. Being hollow keeps the weight down
and the size is a nice compromise between handling and ride.
- Front Alignment: start with the factory specs for minimal tire
wear, but with 7 degrees of caster the wheel won't be as 'darty' on uneven
pavement.
- Rear Shocks: QA1 custom valved shocks adjustable for compression
and rebound.
- Rear Springs: Suspension Techniques Speedtech springs, with one
coil removed from each to give a slightly higher spring rate and height drop
(countering the slight height gain from the air bags).
- Rear Air Bags: A set of AirLift bags in the rear coil springs allow
me to adjust for spring rate and height, even for varying loads (people,
foosball tables, lumber, lawnmowers, etc). Individually valved for
better handling, the fillers are located under the fuel filler lid.
Eventually, I will install onboard gauges and a pump so I can adjust them on
the fly.
- Rear Control Arms: The factory 1LE race parts are proven
components, and are cheap (bought from the dealer when I ordered the car) and
) replaced the softer-bushing Z28 lower control arms (LCAs) and panhard
rod (PHR).
- Rear LCA relocation brackets: These provide additional axle
mounting points for the LCAs that allow for correction of the rear
control arm geometry on lowered vehicles, making for better traction and less
brake dive & squat. Installed with all of the LCA mounting holes aligned
perpendicular to the ground and the brackets parallel to each other so
that the axle remains positioned properly front-rear in the wheel well.
A mistake here will require cutting off the brackets with a torch and
reinstalling - new brackets if you can't re-use the old ones. The LCAs
themselves should be parallel to the ground or slightly raised towards
the rear mounting point for the best traction and handling. See
LCA relocation brackets
for further explanation.
- Rear Sway (anti-roll) bar: None. After a lot of tuning, I found
that the roll stiffness at the rear was too high for the chassis (too much
cowl shake) and removed the rear sway bar. The overall roll stiffness at the
back is still higher than factory due to the higher rate springs and the
airbags installed in them.
- Wolfe 4-point roll bar (purchased but yet to be installed), with my
own design front bars for ease of entry, will be completely padded for
occupant safety.
- See also:
Suspension notes:
(standard disclaimers apply)
I've included this page to detail some of the obscure or otherwise
undocumented aspects of upgrading these cars. This stuff worked for me, but be
sure to check out the other install references, some of which are on my
links page.
Shocks and springs:
- I used the instructions posted here:
members.aol.com/InjuneerZZ/HALEibch.htm. I found them to be very complete.
- Get an additional set spring compressors, as the rather long springs in
the front can be a pain if you run out of thread on the first set - and you
could be stuck without them.
- Two people make the front a lot easier;
- When installing HALs, buy an extra set of spring seats and modify them
beforehand(!). this will get your car back on the road faster. A jig saw
with a metal blade worked well, with a file to clean up the edges.
SFCs (connect the front and rear subframes; one on
each side):
- I used a combination of a 110V grinder and air powered die grinder to
grind the welding points free of paints and coatings. The powercoating is
surprisingly tough.
- all the surfaces got two coats of weld-through anti-rust primer;
- when done welding, another coat followed by rubberized undercoating to
protect the primer;
- As this was a convertible, I supported the car with jack stands on the
frame behind the front wheels and ahead of the rears. This allowed the frame
to 'droop' and the SFC's to be welded into place without the stress on the
chassis. when the wheels are again on the ground, the SFC's will be
'pre-stressed'. For a coupe, it's fine to have the car supported by the
tires.
LCAs (replacement lower control arms): Just
a bolt-in install, with both the chassis and axle supported.
PHR (replacement panhard rod): See
LCAs
LCA relocation (anti-squat) brackets: They have to be welded on, so I
was initially had warranty concerns. Then I said what the heck.
- I put the chassis of the car on to 4 jackstands;
- lifted the axle up and supported it with a pair of ramps;
- parking brake set, so the wheels won't roll;
- Loosen the front and remove the rear LCA bolts, and move the LCAs down and
out of the way
- remove the small brackets that support the parking brake cable on each
side. These are overkill (or 'superfluous'),
and can be removed by cutting the small weld at the bottom of the bracket. I
used a 3" air powered cutoff wheel; grind the area smooth when done and coat
with anti-rust primer. Using a "Weld-Thru" type primer is best
as it will not contaminate the weld area;
- bolt the LCA brackets into place with the supplied bolts through the top
(factory) holes, torqued tight enough to hold the bracket firmly (keep the
factory bolts for the LCAs); there should be a supplied tubular spacer inside
the bracket so the bolt won't bend the sides in;
- carefully align the brackets so the axle tracks true. I used a carpenters
precision level to match them vertically, tapping them with a hammer to move
them. If one bracket is out from the other, your car will 'dog track' down
the road. I had a four wheel alignment after, and it checked out fine;
- welded them on the top and inside as per the supplied (by GW)
instructions. I have a 220V MIG that I used for this;
- sprayed on a coat of anti-rust primer on the welds;
- bolt the LCAs in the the appropriate holes (the LCAs should be level with
the ground with the driver in the car), retorque the front and rear LCA and
upper bracket bolts. If you get a clunking noise soon after this install,
check these bolts. I waited a couple days and jacked the car up to retorque
them regardless;
- Put the car back on the ground;
- Consider having the rear end checked by an alignment shop.
Last edited
Saturday, October 11, 2003
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