Shock Absorber and Spring Replacement

A Step-by-step Procedure for the Total Novice

By Bob Cohen

with tips from Pete Hodge - phhodge@bigfoot.com

Editor's Note: There is a good writeup on Miata Forum for Shock/Spring replacement on an NB Miata.

Shock/spring replacement can be a difficult and tedious task, particularly if the Madza-recommended (i.e., shop manual) method is used. However, a number of posts to the Miata.net have indicated that this operation can be performed without changing the alignment or breaking ball joints.  The following is a detailed description of my (first-time) experiences and problems encountered following the procedure that was originally posted by Sean Archer, and modified and/or further explained by many helpful netters, including Peter Balfour, John Bowles, Bill Cardell, Brian Dore, Tom Manson, and Mike Simmons:

1. Loosen the wheel nuts, then lift the car and support it on jack stands; see either the Maintenance section from Tips from the Garage Web page, the Mazda Shop Manual, or the Enthusiast's Manual for further details.  I found that a good light source was often helpful, and that lifting the car within range of a shoplight and it's extension cord was good insurance (if the car is lifted outside, and the wheels are off, it gets dark, and you're not finished, that might be a bit inconvenient - not that it happened to me, of course). Remove  the wheels.

Rear Shocks/Springs

2. To access the rear shocks, first remove the metal trunk guard that protects the fuel lines (left shock) and the spare tire (right shock).  Loosen the shock absorber upper shaft nut a few turns (it's more difficult to do this after the unit is out of the car) with a 17 mm wrench and extension, but DO NOT completely remove the bolt, or the spring will separate from the shock (which is dangerous, and probably impossible to rectify once it occurs).

3. Remove the upper mounting plate nuts with a 14 mm wrench and extension.  Be careful not to drop the nuts into the sheet metal around the upper mounting area, or they'll wedge into place against the body in a very tight area (especially the rear one).  I dropped one, and it took about 1 hour to retrieve it with a pair of curved needle nose pliers.  During the process, I learned that Pep Boys does not carry 14 metric flanged nuts.

4. Disconnect the sway bar's attachment to the lower A-arm linkage (14 mm socket), to allow the A-arm to swing out of the way in subsequent steps.  The sway bar can be removed either where it joins the A-arm, or at the point between the main (horizontal) sway bar and the curved link that fastens to the arm.  I suggest the latter approach - it was very difficult to reattach the bushing to the lower A-arm, much easier to reattach between the main sway bar and the A-arm link.

5. Remove the lower shock mounting bolt (and keep track of which way the head of the bolt is pointing so that it can be replaced in the same configuration).

6. Remove the bolt that joins the upper A-arm to the wheel hub (and again, keep track of how the bolt should be replaced).  This allows the wheel hub to swing downward, freeing up the shock/spring assembly, and allowing for easy removal.   There is a paint mark on the spring that should be used to return the spring to the same position after the unit is replaced (if the shocks are to be replaced and the old springs reused). Alternatively, place a piece of tape, paint, or otherwise mark the spring to allow for reorientation.

7. Recover the top mounting gasket (a thin, white plastic gasket between the top mounting plate and the frame).

8. Clamp the shock in a vise (if they're going to be replaced, no need to worry about damaging them in the vise; otherwise, protect the shock with wood or aluminum sheets placed between the shock and the vise jaws), and attach spring compressors.  Compress the spring until the top mounting plate is loose, and the spring can rotate independently of the shock. Remove the top shaft bolt (loosened in Step 2), the mounting plate, and the compressed spring.

9. Protect the replacement (or re-used) shocks in the vise as noted above, and reassemble the compressed spring over the shocks (if new springs are to be installed, then decompress the old spring and discard (sell?), then compress the new spring).  Place the top mounting plate over the shock/spring unit, and replace the top mounting bolt.  Make sure the unit is aligned correctly, with the spring seated properly against the shock absorber and the top mounting plate, then reinstall in the car.   Use the OEM paint marks or your marking tape, etc. to replace the spring in the same orientation that is occupied prior to removal.

10. Lubricate the lower shock mounting bolt with molybdenum or similar grease, and replace the bolt.  Lift the wheel hub and replace the bolt joining the upper A-arm to the wheel hub (a short piece of wood to support the hub or a helper is nice; a little grease also can be used to lubricate the bolt).  Make sure the plastic gasket is replaced on top of the mounting plate (not that I forgot to do that the first time...), and thread the upper mounting plate bolts through the chassis holes.   Loosely reattach top mounting nuts, and replace the sway bar linkage bolt/nut.   Re-torque all nuts/bolts to specifications (see below), and replace wheel, spare tire, and metal trunk guard.

Front Shocks/Springs

11. From inside the engine compartment, remove the plastic dust covers from the upper shock mounting plates (they're loosely attached, and are readily removed).  To obtain easier access, the bolt that fastens the diagnostic connector and the associated wires to the sheet metal may require removal, to allow the wires to be pushed a few inches out of the way for access to the shock mounting area). 

12. Loosen the shock absorber upper shaft nut a few turns, but DO NOT completely remove the bolt (see items 2 and 3, above).  Remove the upper mounting plate nuts with a 14 mm wrench and extension.

13. Disconnect the sway bar to the links on both sides (this will allow the lower A-arm to drop sufficiently in subsequent steps).  Again, remove the sway bar at the point between the main (horizontal) sway bar and the curved link that joins the A-arm - this is the easiest point to reattach the sway bar.

14. Remove the lower shock mounting bolt.  As above, remember/record the original orientation of the bolt and nuts.  In ABS-equipped cars, a wire will be attached to the shock via a welded clip.  Carefully pry the clip away from the wire with a large flat-bladed screwdriver and remove the wire from the shock absorber.

15. Carefully step on the lower A-arm (it now can go down about 3-4 inches) and pull the top of the shock towards you (i.e., to the outside of the car).   This provides enough room to attach a spring compressor while the spring/shock assembly is still on the car.  Note the orientation of the OEM paint marks on the spring, or add your own paint or tape to indicate the original position of the spring, as noted above for rear shock absorber installation.  Then carefully compress the spring.

16. Push down on the upper mounting plate (compressing the shock; the spring is already compressed) and remove the mounting plate.  This provides another few inches of access. Save the white plastic mounting gasket.

17. Again push down on the shock piston rod.  This should provide enough room to move the top of the shock/spring towards you, then up and out of the car, while a helper steps on the lower A-arm (it's more difficult, but possible, to do it as a one-person operation).  If the shock becomes stuck in the lower mount, then gently prying it free with a large flat screwdriver may be helpful before the final removal.

18. Replace the shocks and/or springs as noted above in #8 and 9, but leave the spring compressor attached to the  (compressed) spring.  Reinstall into the car by reversing the above procedure:  step on the lower A-arm, and slip the unit back into place.

19. Lubricate the lower shock mounting bolt with molybdenum or similar grease, and replace the bolt.  Push down on the shaft of the shock, and replace the top shock mount.  Replace the nut holding the shock absorber shaft to the mounting plate.

20. Push down on the lower A-arm, and align the top mounting plate bolts in the holes in the chassis, and replace the mounting plate nuts.  Decompress the spring and remove the compressor.  Then replace the sway bar linkage bolt/nut, and re-torque all fasteners to specifications

21. For ABS-equpped cars, net.suggestions for reattaching the ABS wire to the shock have included:  a) ignore it; it's just to stabilize the wire a bit, it's not rubbing against anything, and there are two other mounts; b) fabricate a mount from a metal strip, and epoxy it onto the new shock; and c) secure it to the shock with a plastic cable tie.

22. Replace the wheel, and retorque the nuts as noted below (or to your specs).

23. Find a nice twisty road, and take that favorite turn at the speed where the rear end always would break loose a bit, but see if there's any more grip this time.  Repeat as necessary.

24. (Optional; note that step 23 generally isn't): Consider how much better the car would handle if new springs had been added as well as the new shocks, and when that procedure gets done how much easier all this should be the next time...

Torque Specifications (from the Mazda Shop Manual)

Sway bar links:  36-54 N-m (27-40 ft-lbs)
Lower shock mounting nut: 73-93 N-m (54-69 ft-lbs)
Upper shock mounting nuts: 29-36 N-m (22-27 ft-lbs)
Rear upper A-arm to wheel hub bolt: 46-67 N-m (34-49 ft-lbs)
Wheel lug nuts (OEM): 88-118 N-m (65-87 ft-lbs)
Shock piston rod upper nut: 29-36 N-m (22-27 ft-lbs)

Time Required

Rear shock, first time, no clue:  about 4 hours.
Rear shock, second and subsequent time: about 1-1.5 hours for both.
Front shock, after benefit of replacing rear shocks: about 1.5-2.0 hours for  both.
Someone with experience (i.e., Pete Balfour, Toronto Trillium club): both shocks, "a tad over one hour."

For questions, comments, or anyone I've left out or inadvertently forgot to give credit to, send email to robert_cohen@sdm.buffalo.edu .

Bob


Tips from Pete Hodge - phhodge@bigfoot.com

I installed new shocks over the past several days using all the information from Miata.net. In particular, I relied on Bob Cohen's instructions from the garage section and Bill Cardell's (of Dealer Alternative) detailed explanations of how to extract the front shocks without upsetting the existing alignment. Many advised that the replacement would go much smoother with a helper, but I had to do it alone. Thus, I had to come up with solutions to the problems of having not enough arms and or muscles.

1. The dust cap on the front shock mounts in the engine compartment are 2 1/4" in diameter. As mine had not been touched in seven years, I was unable to discern this fact, and spent too much time trying to pry off the entire top of the shock mount. Yes, you can put a little pinky fingernail in the dust filled and invisible groove and pop that sucker off. As someone on the list says....DUH.

2. Bill Cardell says to take the cotter pin off the castellated (my spell checker offered castrated for this one..:-)) nut on the upper ball joint, unscrew the nut a few turns and then smack the side of the steering knuckle.  The drawing and picture from his website were excellent, but on the first shock I was unable to determine when the ball joint had popped loose. I kept banging away for about 10 good hits with my mini sledge. Finally, I decided to start unscrewing the nut anyway, and presto, the ball joint had popped loose. Probably on my second hit... so the solution is to back the nut off about 1/4". Then when the ball joint pops, you will see it jump right down, and you'll know the hammering is over.

3. Still on the front shocks, I found it was impossible for me to pull the upper control arm down, pull the lower control arm down (taking care not to damage the brake line), and wrestle the shock out all by myself . An octopus I'm not. My solution after many unsuccessful attempts was to place a prop on the upper control arm to hold it in the down position. You must be very careful not to put undo pressure on the inside of the fender...we don't want any dents from below. First get a small rectangular block of wood about 2x3" and about 1/2" thick. You will also need a prop of about 13 1/2 ". I used a paint roller extension. Place the block on the inside of the fender, the prop against it and then push down the upper control arm far enough to push the prop into position. Presto, now all you have to do is worry about the lower control arm. Makes getting the shock out very easy. Keep the prop in position while working on the shock off the car and reinstalling will also be much easier.

4. On the back shocks, I had a similar problem. I was following Bill's instructions, but was not strong enough to push down on the control arm and weasel the shock out. After some thought, I decided to use the Miata's sissor jack. I placed it on the lower control arm on the car side of the end links. The handle faced the rear of the car. I started cranking away and the control arms went down nice as you could hope for. Once the top of the shock cleared the fender, I stopped cranking on the jack and lifted it right out. A baby could do it. The jack holds the control arm in that position ready for reinstallation of your new shocks.

Pete


The following tip was received from Phil Yasuhara

One tip for the fronts--in order to compress the springs enough to remove the shock/spring assembly without breaking the ball joint, I had to put the lower attachment under the shock spring mounting--no problem as it is shaped like the bottom of a half a spring but BE CAREFUL to insure it doesn't slip off!

Also, since the stock and replacement (KYB AGXs) shocks were both gas pressure type, you can use wire to tie down the upper shock attachment after wedging a 2x4 above it to keep it compressed. It IS possible to hold the rear shock/spring assembly and attach the upper shock retaining springs on the rear--just get in a real friendly hug with your rear fender!


Alternate Method from Andy Hollis

Here's the easy way to replace the front shocks and or springs without messing up your alignment. Its also a whole bunch easier than splitting or unbolting the ball joints. Credit for this tip goes to Mazda Master Tech, John Long, of Mazda South in Austin, Texas. 

  1. Jack up front of car and place on jackstands at the side rail jacking points. 
  2. Remove front wheels. 
  3. Inside the engine bay, loosen center nut holding upper spring mount to shock shaft (14mm socket w/extension). Only back this off a few turns, not all the way. This helps get the spring off easier later. 
  4. Remove the 2 nuts holding upper spring mount to the body (14mm socket). 
  5. Remove upper through bolt connecting sway bar end link to sway bar (14mm socket and box wrench). Note which way the bolt goes. 
  6. Remove lower shock absorber mounting bolt (17mm socket and box wrench). 
  7. Loosen rearmost mounting bolt for front sway bar frame bracket until the back is flush with the backing nut (12mm socket with extension). 
  8. Remove upper control arm mounting bolt. Use 21mm box wrench on the nut and a 21 mm socket on the bolt head. Slide the bolt back through the big washer towards the sway bar frame bracket. Rock the a-arm up and down if the bolt is stuck. Once the bolt is all the way out of the a-arm, just leave it where it is. 
  9. Being careful that the rubber brake hose is not in tension, pry down on (or stand on) the hub or lower control arm until the top of the shock/spring unit can swing out clear of the shock tower. 
  10. Disassemble shock/spring unit using appropriate spring compressor. Be VERY careful!! 
  11. Reassembly is the reverse of disassembly.

Note: Do not tighten mounting bolts for sway bar end links, shock lower mount or upper control am while the car is in full droop. Once everything is back in place but not tight, place a jack under the lower arm as close to the hub as possible. Jack up until the car just starts to come off the jackstand. Now tighten those mounting bolts. You should also torque the shock shaft upper mounting nut at this time.


Alternate Method for Cars With Shorter Springs from Justin Mitchell

If you have aftermarket coilovers with shorter springs and adjustable shocks, there is a much easier way to remove the coilover assembly from the car.

This method only works if you have shorter springs which become uncompressed while the car is in the air. After jacking up the car, see if you are able to move the spring around by hand. If so, then you are golden. If the spring is compressed and cannot be moved by hand, then this is unsafe and will not work.

  1. Jack up the car, put it on jackstands, and remove the front wheels. 
  2. Adjust the shock's rebound setting to full stiff. If the shock has adjustable compression, set it to full soft. Later, when you compress the shock by hand, it will prevent the shock from decompressing too quickly. 
  3. Loosen the shock center nut, located at the top of the shock tower. This will make make it easier to remove later.
  4. Remove the lower shock mounting bolt (17mm).
  5. Remove the 2 upper shock mount nuts (14mm).
  6. Completely remove the shock center nut, located at the top of the shock tower.
  7. At this point, your shock assembly is partially disassembled. In order to get it to clear the upper control arm you need to remove the upper shock mount and spring. Press down firmly on the upper shock mount to compress the shock as far as possible, then remove the upper shock mount from the shock. Remove the spring the same way.
  8. Now, that the clunky stuff has been removed from the shock, compress the shock rod all the way and remove the shock from the car.
  9. Reassembly is the reverse of disassembly. Be sure that the shock is set to full stiff (rebound, not compression!).

 


Back to the Garage

19 October, 2006



[Home] - [FAQ] - [Search] - [Sponsors] - [Forums]
[Garage] - [Clubs] - [Contact Us] - [More...]
Copyright ©1994-2014, Eunos Communications LLC
All rights reserved.