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KYB AGX shock install, September 9 & 11, 1999

Last updated 11/12/99

It was time to replace my stock shocks around the 52000 mile mark, and I chose the KYB AGX shocks that I've read about recently on the net. I think these shocks are relatively new compared to the other after market shocks that have been available for some time for the Miata (Tokico Illuminas, Konis). The compression and rebound rates on the AGX can be adjusted by a single adjustment, 8 position knob on the side of shock body. The knob adjusts both compression and rebound at the same time, with 1 being the softest setting, and 8 being the hardest setting. It has been said that these shocks are similar or the same as the adjustable shocks sold by GAB which are priced significantly higher.

After some searching on the Internet of various KYB dealers for ones who sold the shocks at the lowest price, I settled on General Automotive in San Bernadino, CA. After speaking with one of the sales crew, Charles, I managed to get an additional 10% off their very low price ($83.89+tax per shock regularly) after getting 4 other SOCALM members together for a large group purchase. Since their store was local to where I lived, I could save on the shipping costs by driving to their store to pick them up.

The shocks are model 741016 for the rear and 741015 for the front (#01). In addition, I bought a set of shock boots also. These were KYB model SB108 (#02). If you go to the KYB site and look at their online catalog, you'll see that KYB recommends these shocks for 90-97 models only, and it's not recommended for R package cars. Perhaps the R package sits a little lower than the stock? Anyway, these shocks don't have an adjustable spring perch like the Konis, so perhaps putting these shocks on an R package makes the car sit at a stock height. Additionally, these shocks don't have mounting tabs used for ABS brake systems.

Out on thew web, I found several sets of instructions for installing the shocks:

All three had similar instructions for installing the rear shocks. But for installing the front shocks, I ended up using the great directions written by Robert "JTBob" Holland from the San Diego Miata club site. It didn't involve any hammering and it also didn't require an alignment of the front end. Bill Keksz posted a Koni installation tips article on the Miata Usenet newsgroup which also describes the technique.

Rather than repeating Robert's writeup, I'll go over some highlights.

I ended up doing the rear shocks first, on a Thursday evening after I got home from work. Never having done a shock install on any car, I figured it would take about 4 to 5 hours to do the rears, and maybe a similar length for the fronts. I don't have the luxury of air tools, and I didn't have anyone helping me, other than my wife, Jeanne (who provided a welcome leg to push down on the lower A-arm for the front shock install).

The only real difficult part of the rear shock install was getting to the upper mounting bolts of the driver's side shocks. You have to remove the carpeting (#03) and metal shield (#04) that protects the area where the fuel hoses are (#05), and behind the hoses are the upper mounting bolts (#06). Being behind the fuel hoses makes it cumbersone to access.

The rear upper and lower A arms come apart very easily (#08, #09), and you take out the shocks and springs as a single unit (#10), compress the springs (#11) and replace the shock body with the new one (#12).

One surprise I got was that the boots that I bought were quite different from the stock ones (#13, #14, #15). It confused me a bit because the old and new bumpers were so different, that I ended up using the old boots on the new shocks. Fortunately, the old boots weren't torn.

After I put the rear shocks back into place, I didn't tighten down the the lower shock mounting bolts, or the bolt that connects the rear sway bar to the end links. I drove the car around a few miles, going over several speed bumps, and when I came back home, I tightened down all the bolts. Initially, when I first got the car off the jack stands, I measured the height of the car (from bottom of the fender lip, to the center of the weheel), and it was 1" higher than when I started the shock install. After driving around and letting the car settled, it was back down to the normal height for my car (13 1/2").

I began work on the front shocks on Saturday afternoon, just after the SOCALM ear plug fitting event. I had to move my K&N filter out of the way first (#16, #17) to get at the driver's side front shock. The separation of the upper and lower A arms begin with removing the lower mounting bolt of the shock (#18). Next, you stick a big screwdriver in the hole where the lower mounting bolt used to be, and then have the shock rest on it (#18). This allows room to get at a bolt that's lying vertically (#19). Remove this bolt (#20), and also another bolt that runs horizontally (2 views: #21 & #22). Together, these 2 bolts hold down a "tongue" which connects the hub carrier to the lower A arm. Once these 2 bolts are removed, you can pull out the hub carrier (#23 & #24) from the lower A arm, and you'll have lots of play to allow the lower A arm to be pushed down and the shock removed.

Both front boots were torn, so I ended up using the new KYB boots that I had purchased. After my confusion from Thursday in doing the rear install, I ended up just taking the old boot off and put the new boot on (#25 & #26). I pushed the new boot down the shock rod until the top of the boot was flush with the small perch on the top of the rod, then I cut out the metal washer from the top of the old boot (#27), and placed this between between the bumper and the upper mounting plate. Total time for the fronts was about 4 hours.

Once in place, the adjustment knobs are relatively easy to get to. The rear passenger side (#28) and the rear driver's side (#29) are easy to get too by getting down on your knees and looking behind the tires. The knobs for the front driver (#30) and passenger side shocks can be accessed by turning the wheel either full left or full right first.


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