Miata Upgrade: Coil-Over Upgrade
Part 1: Overview and Plan
The time has come for the Miata to get some serious upgrade love. The first thing I wanted to change about my Miata was the tired shocks and springs. The car felt good during normal driving, but when pushed exhibited confidence-shaking body roll. Add that to the fact that NA/NB Miatas have very little suspension travel and rock hard bump stops, it was time to make some changes.
My initial plans were this:
Replace stock shocks and springs with a reputable aftermarket alternative
Replace bump stops to gain travel and improve handling characteristics when transitioning from regular travel to bump stop contact
To expand on my plans, the replacement suspension needed to fulfill the following
Lower the Miata (goal is 12-12.5" fender to hub), bonus for height adjustability
Good match between shocks and springs to provide excellent handling performance
Good street manners (limit handling is priority one, but the ride has to be decent), bonus for adjustable dampening
With the guidelines set, I began my search. Due to the Miata's popularity, there is a massive number of aftermarket shocks, springs, and coil-over kits available. Pricing for these kits range from $400 to over $2,000. I wanted to keep my cost as close to or below $800 as possible. I won't go into detail, but I used the Miata.net and miataturbo.net forums for a few months trying to decided what suspension was right for me. I originally settled on the (as of this writing) unreleased 949 racing TECNA entry coil-over. It was targeting the entry-level coil-over market focusing on great ride quality and overall solid construction. With that in mind, I setup a craigslist watch to see if any used suspension components would become available while I waited for the TECNA's to become available. A few weeks later an ad was posted for "Bilstein shocks with ground control sleeves and springs".
Here is what I was looking at:
As with any craigslist item, there is a certain amount of questioning that needs to be done to figure out what exactly the person listing that item actually has. I wanted to know spring rates and how old the shocks were. The responses were strange. The lister stated that the shocks had only seen 7,000 street miles and a few track days. I would buy that, except for the amount of rust on the shocks. The answer to the spring rate question was very questionable. He quoted 600 in/lbs front and 63 in/lbs in the rear. At this point I knew the owner had no idea what this suspension was and his responses could not be trusted. For those of you confused at this point, 600 in/lbs spring rate is a little less than four times the stock spring rate (potentially too stiff for the shocks) and a 63 in/lb rear spring rate is less than the stock rear spring rate (unbelievably soft).
I eventually met the individual selling the shocks in person and got to take a close look at what I was dealing with. My observations are listed in the order I came across them:
The shocks are Koni adjustables and not Bilsteins (there was a Koni sticker and Koni imprints on all shocks) - GOOD
The front spring rate is 450 in/lbs, not 600 in/lbs - GOOD
The rear spring rate is 63 mm/kg (around 300 in/lb), not 63 in/lb - GOOD
The rust looks to be all surface rust and the shocks look to be in good condition. They all compress and rebound correctly. - GOOD
The shocks had stock bump stops that were cut and reused - BAD
After a good looking over and a few minutes of haggling, I decided to take a chance on the suspension.
Once home I decided to make a game plan around what I wanted to do to prepare the suspension for installation. I really just wanted to get rid of the rust, change out the bump stops and throw them on the car.
The next fours parts in this series will cover the following:
I will end the first part of this series with some more detailed pictures of the suspension before any work was done.
turnnoffyourmind
ellievsbear
2087
discoholicmusic
blakekathryn
izzy806
andulkaphoto