MWspeedshop.com

 PROGRESSIVE RATE SPRINGS INSTALL
WITH OFFSET STEERING RACK BUSHINGS

Written by Mustangworld.



Only advanced home mechanics should attempt this installation, you do it at your own risk.

We really liked this mod because it improved the performance and the looks of our 4.6L project stang. In the past we have run specific rate springs, Eibach springs and even the stock springs with 2 coils cut. We think we have found the best spring combo F/R with the best rate, a set of BBK Progressive rate springs ($215).

Here's our take on them. They are a very high quality part, powder coated to prevent rust. They are stiffer and lower your stang 1 inch in the front and 0.8 inches in the rear. They improve the handling of the stock Mustang tremendously. You can feel it on the first curve you drive. Nose dive is eliminated when braking. But the most important part of it all... The stang rides with the same ride quality as the stock springs... no bull. In fact, with these springs the stang stays much flatter in the curves and seemingly rides smoother over bumps than with the stock springs !

We are amazed at the stangs new ride. These are the springs that should have come stock with the Mustang. No creaks, squeeks or anything. There is a very noticeable improved handling feel with no added harshness whatsoever. The springs also work well with the stock shock rates (until you can get new adjustable ones).

Other springs we've used and liked :
We ran the BBK specific rate springs (blue coil) for about 4 years which has 9 coils in the front and we liked the overall ride. The ride was much harsher with these springs because they lowered the initial ride height 1 1/2 inches all around and they were specific rate (fixed rate). The tradeoff is on flat ground (race track) the stang handles very well. There is also a definite "slammed" or lowered look to the stang also and they only cost $169.

We ran Eibach springs for around 2 years and also liked the ride. They were comparable to the new BBK progressive we just got but we noticed Eibach using a few less coils and we did manage to bottom out in the rear a few times while using these springs. They are great springs, but we'd suggest going to Eibach custom springs dept. and get ones tailored to your particular Mustang driving style. They would probably win the race on the track, but the bottoming out on the street we didn't like too much. Other than a few places where we bottomed out, we liked the way it lowered the stang (around 1 1/2 all around) and it offered a better ride than a specific (fixed) rate spring. They offer the best ride for a 1 1/2 inch lowered stang. They cost around $215..

We ran Saleen Progressive rate springs for around 1 year. They seemed a bit stiff for a progressive rate spring. They had the feel of specific (fixed) rate springs for a slightly rough ride but not as rough as a true fixed rate spring. They did work well on the street, no bottom outs, and they lowered the stang around 1 inch all around. They cost $215 at the time.

Those were the spring sets we ran in the FOX4 '89 platform over the years and liked.

The V6 Mustang may require a unique set of springs. The front end is a different weight than the V8 stangs. Eibach sells a set of springs specially for the V6 stang. Other springs may work also. Ask about compatability with a V6 Mustang if this is your car.

This install is a set of BBK progressive (variable) rate springs in the SN95 platform. The only tradeoff with them is the fact that they don't give your stang a "definite" slammed look. They DO change the looks though, for us it looks perfect. Folks now have to ask if we lowered it, because it almost looks like a special edition Mustang with custom springs, it does not look "aftermarket" lowered with a spring kit. So if you want a "definite" slammed look, and it's the look that your after mostly, then a set of specific rate (fixed rate) springs may be what you want, they will lower your stang 1/2 inch more, the ride will be more rough but you won't bottom out with a fixed rate slammed spring.

RIDE HEIGHT FOR BBK PROGRESSIVE RATE SPRING (COMPARISON)
Stock front Stock rear
Stock ride height driver side.

Lowered front Lowered rear (passenger side)
Lowered ride height Front driver side, rear passenger side.

Photos above show 1 inch lower in Front. 0.8 inch (almost 1) lower in Rear approx. with BBK progressive rate springs. BBK specific rate springs lowers 1 1/2 inch all around (not shown).
.

Brief explanation of rates using BBK spring sets as an example:
Progressive rate (variable rate ) = slightly softer street ride, at the expense of ride height about a 1 inch slam all around. They improve the handling just as much as any other spring on the street, IE just as stiff when they need to be.

Specific rate (fixed rate) = 1/2 inch lower ride height over progressive springs at the expense of a harsher ride on the street. A definite "slammed" look.

Note that we are keeping the stock shocks (because ours are almost new). You may have seen kits that match the shock rates to a set of springs, etc. Don't worry about matching springs to shocks etc... we say that this particular spring set will work FINE with your stock shocks and struts until they eventually wear out. When they do, buy yourself a set of Monroe's, KYB's, Koni's, Tokiko's, or whatever suits you. For the street you don't need to get "nerdy" about matching the springs to the shock rates etc (despite what you may read). Most aftermarket shocks are adjustable allowing you to configure the rates how you want and even the stock shocks (if they are newer) run fine for the street with these springs.

One thing we will also be installing in the future is a set of camber / caster plates, BUT with the SN95 stang for street use, the lowering springs we installed introduced a tiny amount of negative camber in the front wheels, which is actually a perfect amount we recommend for the street to improve your cornering without premature wear on your tires. The SN95 already has a great amount of caster built in also, so expect a great ride and improved handling with this set of progressive springs alone. You can buy the other parts when you get the money. Of course if you lower your stang more than 1 inch, then the off-set bushings and camber/caster plates become more necessary, they are also necessary if you road race your stang in competition for adjustability.

We've run our '89 without off-set bushings for many years with no problems. In the SN95 stang, we would have to give the off-set steering rack bushings an "optional" rating with this particular set of springs. This spring set only lowers the stang 1 inch. Also, in the 4.6L, the steering rack only has about 1 finger space before it hits the oil pan. The off-set bushings would raise the steering rack extremely close to the pan. If the engine mounts gave out slightly, it could pinch the steering rack. If you slam your stang more than 1 inch, then a way to off-set the steering rack may be needed. With the off-set bushings, the steering rack is lifted (not lowered), because the tie rods are in a natural down position, lowering the stang raises the tie rods slightly. The off-set bushings effectively lowers the tie rods by lifting the steering rack. Off-set bushings are to prevent possible "bump steer" conditions. We never had this condition while running non-offset bushings with lowered springs before, or it may have happened momentarily on only a few occasions. If you have the time and money, get them and install them. We say more for good measure in all Mustang applications.

On with the install !

OK... HERE WE GO!

1. Here's what we bought for a complete spring install (we're still keeping the stock shocks, they only have 13k miles on them!). The BBK progressive rate lowering spring kit $215. New urethane rear bump stop $11 and new urethane off-set steering rack bushings $24. These springs will fit all '79 - '98 V8 mustangs. Spring kit
2. Let's start in the rear (easiest). First, get your stang safely lifted and supported and remove both your rear tires. Disconnect your battery for safety and set the e-brake.. JAck up and secure
3. Next, remove the rear sway bar by removing the 2 bolts on each side that hold it in place. Remove rear sway bar
4. Completely remove the bar and keep it to the side of your work area. Keep track of it's orientation when you re-install it !. Sway bar removed
5. There are 2 ways to do this. Support the lower control arm with a jack and pre-load the rear spring slightly by lifting a bit on the lower control arm. Now, you can either un-bolt the top of the shock by removing the carpet in your trunk to gain access OR do what we did and remove the lower control arm bolt. One or the other. We didn't want to deal with removing the carpet in the trunk at this point. Support suspension w/jack
6. Either method you choose (after unbolting either the lower control arm as we did above OR unbolting the top of the shock) you can now lower the rear suspension with the jack. DO THIS CAREFULLY and SLOWLY as to prevent getting "boinged" by the spring. The spring will get loose and should virtually fall out. If not you can remove it after you lowered it all the way down. CAREFULLY lower it

7. Now lay in the new spring retaining the rubber boots. Align the "pig-tails" in the spring so the upper ones point to the driver side (may be different for a different spring set)..

Lay in new spring
8. Now simply jack the control arm back into place and replace the lower control arm bolt. OR if you un-bolted the rear shock at the top, you'll need to guide the shock into place as you lift and re attach the upper shock nut in the trunk area of your stang. Line up holes and re-bolt
9. Using our method, you may need to use a pry bar to get the lower control arm hole lined up with the hole on the rear axle. If you are on a flat level surface, you won't need to do this. Use bar if needed
10. Next remove the stock bump stop assembly. It looks like this. Notice the new bump stop is much lower to prevent a premature bottom out condition. You may also cut down your factory bump stop as well. Bump stops
11. Here's the location above the rear axle where the bump stop is located. It's held in place by three bolts. It's simple to remove / install. New bump stop in place
12. REAR SPRINGS. Look at the new progressive rate spring and the stock spring for comparison. Rear springs.
CONTINUED ON PAGE 2 ---->


Back to Mustangworld.com

Mustangworld Shop

MUSTANGWORLD.COM, the Mustangworld crest logo above and MOLLERNET are registered trademarks of MoLLER DIGITAL / DiscMEDIA INC. Copyright © 1986 - 1998 MoLLER DIGITAL. Some web elements on this site are copyrighted and are being used with permission from their respective owners. MUSTANGWORLD web elements may not be "re-posted" on any website anywhere in the free world without permission from MoLLER DIGITAL INC. All original graphics are digitally watermarked to aid us in copyright enforcement.
.