Installation Instructions for Tein Flex into an MX-5 NC

[Charlie Brown]

I purchased some Tein Flex coilovers and went searching for some installation instructions from the Tein web site but found that they were only in Japanese and therefore no help at all apart from a little diagram that showed if you adjust the height on the shock body by 15mm, the difference at the centre of the wheel is 10mm.

So after quick chat with Chris Gough on how he installed them in his race cars, I went about installing them and decided that I should write it down as I go to help others in the future that may want to install coilover shocks.

Time for removal and replacement: It took me around 4 hours to do the work the first time (some bolts that had been done up with an air gun and were decidedly hard to undo), 2½ hours the second time.

Here’s the removal instructions:

The front:

• Jack the car up on both sides and place on floor stands.
• Remove the wheels
• Remove the tower bracing and loosen the three nuts holding the top of the shock absorber.
• Remove the 17mm nut at the bottom of the shock absorber, leave bolt in place in the control arm.
• Undo the bolt that holds the ABS line to the inner body work and unclip the ABS line from the plastic guard liner.
• Remove the 17mm nuts from the two bolts holding the upper control arm. Just leave the bolts holding the arm in place.
• Remove the 17mm bolt from the bottom control arm and disconnect the shock absorber.
• Remove the three nuts previously loosened from the top of the shock absorber. The shock absorber is now free from the bodywork but still contained within the upper control arm.
• Remove the two bolts from the upper control arm and pull the control arm away from the bracket. Tie the upper control arm off to prevent strain on the ABS line. See picture below.



• Pull the shock absorber down, push the bottom of the shock towards the rear of the car to clear the lower control arm. Now tilt the top of the shock forward to clear the guard and remove it.
• Replacement is the reverse of removal and will be easier because the Tein setup is shorter than the original shock unit.

Note: There needs to be a drill a hole in the top of the tower brace to allow access to adjust the damping screw. I drilled a 12mm hole and then inserted a short length of reinforced plastic hose over the damping screw. This hose protrudes out of the tower brace and allows the damping to be changed easily. You could also drill a smaller hole, say 3mm, to enable an Allan key to be inserted directly into the top of the damping screw.

The rear:

• Jack the car up on both sides and place on floor stands.
• Remove the wheels.
• Remove all the trim panels and the fuel line guard in the boot to allow access to the top of the shock absorbers.
• Undo the 17mm bolt connecting the bottom of the shock absorber to the lower control arm.
• From underneath the car, remove the single bolt that locates the top hat of the shock absorber to the bodywork. See picture below:



• Remove the two nuts inside the boot attached to the shock absorber, see photo below, and disconnect the bottom of the shock absorber from the lower control arm.



• The shock absorber is now free from the body but contained within the rear suspension control arms.
• Remove the 17mm bolt connecting the upper control arm and pull it away from the body of the car. See photo below:



• You can now remove the shock absorber.

• Once out (have a beer, you deserve it) replace in the reverse order, though it will be easier because the Tein setup is shorter than the original shock unit.

When fully assembled and back on the ground, check the height of the car front and rear measuring from the centre of the wheel vertically to the lip of the guard.
Stock height is approximately 385mm F / 370mm R, I’d suggest you adjust the height to 345mm front and rear initially. After a few weeks you can decide if that height is suitable for your driving conditions.
You adjust the height by unlocking the bottom ring nut with your “C” spanners, disconnect the shock from the lower control arm and turn the shock base in to lower the car or out to raise it. Don’t loosen the ring nuts at the base of the spring and adjust because this will affect the preload. Note the preload should be just enough to capture the spring on full suspension droop.

Adjust the damping on the top of the shocks to the same “click number” front and back. Start with 10 clicks off full hard. Wind it clockwise till it stops then count the clicks as you turn it anti clockwise towards soft. Don't refit boot liner yet.

Over the next few days experiment with the damping until your desired setting is determined. I've ended up with 12 off full hard front and 13 off full hard rear.

Then head off to your wheel alignment specialist and get the alignment checked. Corner weighting is an option should you do track work.

Following the alignment you may need to fine tune the damping to suit your handling requirements. Assuming the handling is now neutral, firming up the rear induces oversteer as will softening the front. Refit the boot liner panels.

Additional information and tips:

You can access the top of the rear shocks to adjust them by just removing the centre panel in the boot.

Remember the Tein Flex spring rates are 7kg front (2.2 times stiffer than standard) and 5 kg rear (1.75 times stiffer than standard) which makes the ride a lot firmer and the car sits very flat through the corners using standard sway bars. Chris has found that it is not necessary to use heavier adjustable sway bars, such as the Whitelines, to control body roll and car balance. Tein Superstreet have 6kg front and 4kg rear springs.

Have a look at the Fat Cat site here for more suspension facts:

http://www.fatcatmotorsports.com/FRC_NC/FCM_MSDS_NC.htm

Plugging information into this table I found the roll stiffness for the various springs / sways combo’s is as follows:

Stock NC springs and sways: 1436.4 lb/ft
King springs and Whiteline sways set on soft: 2153.1 lb/ft
Tein springs and stock sways: 2526.4 lb/ft
Tein springs and Whiteline sways set on soft: 2941.0 lb/ft

So you can see that the Teins with the stock sways have 17% greater roll stiffness than my old King/Whiteline set up.

Updated 25 March 2010 following revalve.

[Charlie Brown]

I just revisited my post above and have a few additions and changes to make following the passage of time and life with the Tein Flex.

First up is the spring rate. The rates I showed above are for the Flex’s in the USA. The Aussie Flex comes with 5kg front and 4kg rear springs.

Next is the preload setting.
As indicated above, I had just captured the spring and therefore no preload on the advice of an NB racer. I was experiencing a very rough ride and backing off the damper firmness didn’t fix the problem. I was riding to close to the bumpstops. Had the springs been 7 & 5 it may have been different.

I managed to get the Tein Japanese installation instructions translated and found that there should be a minimum of 5 mm preload, so I put 10mm in the front and 5 mm in the rear and tried that out. It still hit the bumpstops, so I cut one rib of the bumstops both front and rear. Still no improvement.

So I installed a set of FatCat Motorsport bumpstops, increased the front preload to 15mm and the rear to 10mm and the resultant ride is now much improved.

[Regie]

Thanks for the guide cb....did my Coilover install in about 2 hrs yesterday

[sliq]

nice one regie. is it as challenging as the NB ones ? or about the same level?

[Charlie Brown]

At long last, I managed to get some Japenglish Tein Flex installation instructions that suit the US Flex configuration. Saves trying to translate the one on the Tein Japan site which I've found to be a little different for the US version.

Copied below are the three most important pages but remember, these instructions are for the Flex with 7kg front and 5kg rear springs. Australia, Europe and Japan get 5kg front and 4kg rear springs, so as the warning says on page 6, you will need to adjust your ride height to suit our "softer" springs. I've found that 335mm is about as low as you'd want to go for general road use. Any lower, expect problems with speed humps in supermarket parking areas.
Also back off the damper setting towards soft another two clicks.

[Guy_Coles]

Just as an addition to this, if you're putting STANDARD shocks with lowered springs back into the rear, you will need a trolley jack over and above stands.

As CB has said above, the standard shocks are longer than coilovers and need to be compressed to fit back on. Once you bolt the tophats in, the bottom of the rear shocks hang past the lower mounts by about 20-25mm. The trick is to get a trolley jack with a 40mm block and gently compress the shock and then use the wheels on the trolley (and a bit of muscle) to put it into position. You'll have to tap it off the trolley and onto the mount but once on it's fine. Definitely a 2 person job.

The Coilovers I've seen don't have this issue but if you're fitting lowered springs on standard shocks this can be a bit of a pain in the A$$ until you work out how to do it.

Thanks to Carbon Demon for the tip.