Project Miata – part 3.5

I returned the Miata to the owner after completing part 3 (yes, really) and as part of the service we perform at Jim’s Garage we provide a write up of what was done and often some suggestions or advice.   The major recommendation was to see what could be done to make the ride less harsh.  It was an acceptable ride if you wanted to take the car on a road racing track, but on the street it was a bit much.  In particular the rear suspension would bottom out on road irregularities in a manner that was tough on passenger and driver alike.

I also recommended that a roll bar be installed.  This is a safety item that should be mandatory in convertibles and perhaps some sedans.  If ever this Miata turned turtle, the windshield would fold up and the result would be ugly. 

The owner and I did some research and he settled on a bar made by Hard Dog Fabrication.   While I tend toward a roll bar with cross bracing and plenty of strength, the bar the owner picked out was a single hoop configuration.   I went ahead a gave Hard Dog a call as I was concerned that this was primarily a cosmetic bar and that it would not provide any meaningful protection.  I was glad I did because the owner was able to point me to several photos of Miatas that had installed that very model of roll bar and had survived a roll over quite nicely.  Yes, a stronger braced bar would provide even more protection, but this bar was amazingly strong as a single hoop.  And the customer liked it.  My only insistence was that they also purchase padding for the bar.  I knew that in a skull meets bar contest the bar would always win – padding was not optional.

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It was also time to see what could be done to improve the ride and yet not lose the handling.  This is not often an easy thing to accomplish and in some cases pretty much impossible.   One thing that was clear was that the rear suspension suffered from a severe lack of suspension travel.  After some searching I found that Flyin’Miata had a solution.  It was a rear mount that added about 1.25″ of travel to the rear without affecting ride height.  That meant that we could still keep the car lowered and yet avoid banging the bump stops in the rear. 

Now we had to find the perfect shocks and springs for the street.  A combination that would provide a lowered stance, sporty feel, and yet enough compliance to be kind to your spinal column.  Bilstein has consistently designed shocks that provide excellent control and also a firm, yet civilized ride.  They are a gas pressure shock using a mono tube design and they are rebuildable.  They were my top choice.  There are many other brands well known to the Miata crowd – and loved by them.  This was not going to be a track nor an autocross car.  So adjustable shocks were not necessary – a disciplined ride was.

The car already had a set of springs that were way too high a rate for every day driving, but they were able to provide a ride height that really made the Miata look like the sports car it was.  I didn’t want to lose that.  I had always had good results with Eibach spring kits.  Their Pro Kit would drop the car about an inch from the stock ride height.  Other springs I investigated were more aggressive in the drop as well as increasing the spring rate itself.

My favorite source for shocks and springs is Shox.com.  I’ve dealt with them for several years now and found them very helpful in terms of valuable advice as well as carrying the best products available – all for a reasonable price.  They would have them to me by Friday.

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Anticipating success in sorting out the suspension I also recommended that we consider the most important part of a car’s suspension – the tires.  The current tires were Michelines that were designed to wear like iron and they road like it, too.  If the owner put 12,000 mile a year on the car that would be a factor, but reality was that it was a summer toy that was reserved for sunny drives with the top down.  It would never see the winter roads.

So we considered a tire that would provide tons of grip in the dry and excellent characteristics if the car did get caught in the rain.  When contemplating tires one should also consider the wheels.  One wheel that is a classic and really enhances the looks of the Miata is the Chaparral.  It looks just like the Minilite wheels I remember from the racing cars of the sixties.  It comes in a 15×7″ wide rim, which meant that we would look for tires in 195/50-15 size.  It is also the perfect offset of 38mm, which would mean that we don’t have to worry about rubbing or chaffing.

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The wheels were placed on order through Moss and they will be drop shipped from the factory.  For the tires I consulted Tire Rack.  They have the best selection and, if you get stuck, their staff is knowledgeable and very helpful.  My first choice was an “extreme performance summer” tire that was on back order with no outlook for fulfillment.  So I called up the Tire Rack tech and he recommended Bridgestone Potenza RE750’s.  What a fantastic recommendation.  They are a “ultra high performance summer” tire with very high marks in dry and wet cornering.

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We installed the roll bar on Friday and the Bilsteins and Eibachs today.  I took the car out for a test drive and could not wipe the smile off my face.  The ride was fantastic.  Just what I was aiming for.  Its handling was super yet the ride over pot holes and bumps was more than acceptable.  This was one sweet handling street car.  I can’t wait for the wheels and tires to show up!

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This entry was posted in Automobiles, Car Stuff, Care and Feeding, Modifying Cars, Servicing Cars, Sports Cars, Suspensions and tagged . Bookmark the permalink.

One Response to Project Miata – part 3.5

  1. markitude says:

    Jim,

    Fantastic write up of the project – neat to see all the components and the sources of the parts through the links to suppliers you thoughtfully provided.
    Thought you might like these two links. The first would be a good quality entry level to start and the second would be “institutional” level power for later.
    http://www.gtechpro.com/rr.html
    http://www.vericomcomputers.com/

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