Feb 032015
 

A routine check up revealed an awful surprise.

Some people hate to go to the doctor’s office. They thought they are feeling alright there’s no need for a check up. Within this group of people, some are fearing the doctor might discover something they have been concerning about but don’t want to face the reality.

We believe in proactive care. Identify the problem, and face it in a positive manner. So we decided to take our MSM to see a podiatrist, the alignment doctor.

Yes, for the past few years, we thought the handling of our MSM was pretty good. By birth, the MSM got the double-wishbone suspensions all around, relatively low curb weight (2,529 lbs), low center of gravity, and from the beefy sway bars; 23mm front, 14mm rear.

Afterbirth enhancements include Tein Type Flex Control Master Coilovers; spring rates: 390 lbs/in (F), 340 lbs/in (R) vs. Stock’s 215 lbs/in (F), 160 lbs/in (R). The too heavy and too big 17-inch RacingHart wheels were swapped out for a set of 949Racing 6UL 15×9 wheels and also up-sized the tire width from stock’s 205 sectional width to 225, and still reduced 2.5 lbs at each wheel.

As expected, the ride is stiff, you can size the pavement cracks and amplitude of the bumps via your bottom.

We also thought it is our lack of skills and the natural disadvantage of short wheelbase making the MSM twitchy to drive at the limit. For that very last reason you’ve never seen any Miata in drifting competitions. We were having difficult times putting down power at corner exits without the tail snapping over without any prior warning; no tire squeal, no nothing; all of a sudden you are facing the oncoming traffic. To a point that we were scared to corner near its limit.

Not being able to drive the car at 100% is definitely killing our mojo. So we brought her to the podiatrist for a check up, and perform an alignment that we think is appropriate to achieve handling predictability at the track, decent driveability in the street, and yet keeping overall tire wear in an acceptable level while conforming to the current engine output.

We decided to go with the following setting: for the front, negative 2-degree camber, zero toe, max caster. Then for the rear, negative 2.5-deg camber, total 1/8” (or 1/16” per side) toe-in to combat corner exit power oversteer.

Once the car was hooked up on the alignment rack, the alignment was awfully off.

Some pretty messed up alignment, positive cambers in the front, and the significant differences between the rears. No wonder the car handles funny!!!

As the podiatrist starting to align the car, something is preventing him from getting more than -0.9-deg camber on the left front. The lower control arm ball joint wasn’t tighten properly, and stripped the threads on the lower bolt that connect to the underside of the control arm. So whoever the installed the Tein just didn’t do the job right – Amateurs!

That means we have been tracking the car with a loose left ball joint for these many years!!!

So we had to painstakingly replace the lower ball joint before proper alignment could be dialed in. The ball joint replacement was a 3 hour arm twisting expedition since we didn’t want to remove the entire lower control arm. The good news is the ball joint is hold in-place by bolts. Once the old ball joint was removed, the new ball joint popped right in without any drama.

We got the new ball joint and the associated nuts-and-bolts from a Mazda dealership, and $116.38 was the total damage.

NA01-34-550B – LWR BALL J – $ 78.65
9975-61-225H – BOLT, FLAN – $ 4.12
B001-39-037B – NUT – $ 10.92
H226-28-312 – BOLT, LINK – $ 13.08

We took the car back to the podiatrist. The final alignment setting:

We took the handling aspect a step further. A set of Racing Beat adjustable end links was also installed with the preload on the sway bars tuned out while I was sitting in the car. The stock endlinks were meant for stock ride height and since our car was lowered the stock endlinks were creating a preload on the sway bars which interfered with the spring rate; and potentially increased it. Also the connection between the left and right tires were more direct; almost acting like a live axle suspension. The former explained the stiff ride while the latter for the truck like roughness.

Now the car is more predictable. With the preload tuned out, the suspensions now is finally doing it job. We felt the suspension now has better compression stroke, and the chassis behaves more stable without the abruptness over bumps. We can now slide the car around at the track with new found confidence. LZG

Sorry, the comment form is closed at this time.