Today we put more time into perfecting the Miata. The bump stops for the rear shocks showed up so that was the first order of business.
Removing the shock/spring assemblies means removing all the trim pieces from the trunk as well as unbolting the gold colored steel plate that covers the fuel lines in order to gain access to the top shock bolts. Once those were loose and removed we put the car up in the air (on the lift) and removed the wheels.
The anti-roll bar was disconnected, so was the lower shock mounting bolt, and then the upper control arm bolt so it could all be pulled down and the assembly could be removed.
With the Swift springs it was possible to undo the top nut and take the top parts off the shock so the new bump stops could be slid on to the shock rod. The new bump stops also had to be cut down by one hump as per the Swift instructions.
Both shock/spring assemblies were re-united with bump stops and returned to their place in the rear suspension. The bolts were tightened and the nuts for the anti-sway bar links were also fastened down.
While the wheels were off we put them on the Hunter balance machine again. There was a minimal vibration from the rear that I wanted to track down. Sure enough they were not only out of balance, they were out of round. Fortunately, the Hunter technology tells how to re-mount the tire in order to make the assembly as round as possible. Then they were dynamically balanced.
Then the front wheels were also removed because the stock flexible brake lines were going to be replaced with braided stainless steel lines. This results in a firmer feel at the brake pedal as the new lines don’t expand and flex with pressure to the degree that the stock ones did.
Since a lot of brake fluid was going to leak out during the lines swap it also was a good time to flush the brake fluid and we chose Ate Super Blue fluid.
We use a vacuum method of bleeding that allows us to keep the old fluid from contaminating the new fluid as well as eliminate air bubbles that would create a spongy feel.
After the new lines were on and new fluid was flushed through (including the hydraulic clutch) we changed out the fuel filter for a new one.
The owner and I had experienced at times when the engine would cut out and lose power, especially when the fuel tank was getting low. Since this car was ten years old and had been sitting idle a lot we figured that the gasoline was not only old, but had been subject to condensation as temperatures varied by season. This would be caught by the fuel filter, but it would also clog and impede fuel flow to the point pressure would cut out.
Changing out the fuel filter is a bit tricky. We are dealing with gasoline, after all. We had to release pressure in the system by first taking the gas cap off and then pulling the electrical connection to the pump relay. Then cranked and ran the engine until it would not run. That released any residual pressure, but there was still plenty of fuel in the lines.
We made sure that we had something to safely catch the dripping gasoline as we disconnected the lines to the filter. Then we moved the white nylon plastic clips to the new filter so the lines could be snapped on. Then we secured the filter’s clamp and covered it with the black plastic protector.
The wheels were bolted back on and the lug nuts were tightened to the proper torque before we took the car out for a test drive. Before we got more than a few feet we discovered that one of the new rear brake lines was touching the wheel so we put it back on the rack and were able to reorient the fitting with no trouble.
The test drive was fine with no other problems discovered, so it was on to the alignment rack.
We knew that the setting would change when we installed the Swift springs on the new Koni shocks since the ride height was lowered. We also were looking for an opportunity to add in additional caster to the front.
The rears started out with over two degrees of negative camber. That was much more than the car needed and would keep it from having the kind of rotation you would expect out of a shorter wheelbase car. We also wanted the total toe to be as close to 0.30 degrees as we could so we chose to set rear camber at negative 1.8 degrees. Moving to the front we found we could get almost six degrees of positive caster. That was really great to see. With a little less caster I could have gotten more negative camber, but in this application the caster was more of a priority so I left the front at negative 1.2 degrees and kept the “almost” six degrees of caster. Toe would be set at 0.30 degrees total like the rear.
Why so much emphasis on the caster number? Caster does a lot of different things for your handling and when it is set up to complement a suspension it can be a wonderful friend. If it is not, it can be unfriendly.
Caster will allow your steering to center itself easily after you are done with a turn. It will also add camber to the outside tire as you execute a turn. When you brake it can lessen nose dive and therefore weight transfer substantially. If you cannot achieve adequate caster you will start to lose all that helpful stuff.
With the alignment complete another test drive was in order.
It was a blast. Now the car really felt like the happy little convertible it should be. Corners could be pushed and the rear end controlled much more with the throttle. The steering felt even more connected with the tires. This car had really come together.
On Monday a set of FM anti-sway (anti-roll) bars were delivered and installed. These bars were just a bit stouter than the stock bars an offered adjustability as well. We were now anxious to and see how much flatter it would handle.
Now the car really woke up and handled like a pocket rocket. It made the most of the Bridgestone Potenza RE11 tires and the suspension really followed the contours of the road. This is one fun Miata!