Creating the Mazda MX5 "Roomster" edition

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Creating the Mazda MX5 "Roomster" edition

Postby jass » Sat Sep 24, 2011 12:49 pm

It's easy to end up facing this adventure, if you are taller than average and decide to enjoy life driving lightweight, RWD and well balanced car offering go-cart feeling. There are not many options left out there, and especially if you want to stay away from the project cars like Escort, Kadett C or AE86.

Below is a summary of my experiences collected, trying my best to autocross in a stock limiting class and get myself in a very small car with 2 meters and a helmet. And most important - win:).

So here is the point:
1. We are 2 meters tall (well, I am...).
2. We want to race the MX5 (approx. 5cm. additional headrom for the helmet).

Before starting - are there actually any good news at all?
Yes, there are some very good news:
1. Bottom seat level is below the side skirt level. This says, the full height of the door flange opening can be used for getting in and out. And this offers more room than the average passenger car, where the seating level is much higher and limits the effective opening height.
2. There are some inexpensive basic measures to reach acceptable room for normal driving and racing.

Lets face the problems now:
1. Limited headroom with hardtop or softtop.
2. Very limited legroom, resulting to minor space to operate the steering wheel.
3. Limited sight to the front.

(safe maesures (green) to risky (red))

Creating headroom

1. Defoam the seats.
- Defoaming the seats gives you most headroom. Going to extreme you can gain up to 4-5cm headroom.
- Defoaming the backrest takes you seat approx. a centimeter to the back and improoves side support.
- Defoaming the head rest allows you to push the seat tighter to the stifening brace between the belt towers. It is a must to do if you are driving with the wind deflector, as by closing the soft top it is limiting the backrest travel.

Here is the write up to this with some pictures.

2. Going for aftermarket seats, only in combination with aftermarket seat rails.
After defoaming the stock seats it is difficult to find lower aftermarket alternative, as they are made from very thin metal shell and fall and utilize the space between the rails. You basically "seat on the rails".
Most aftermarket seats usually need additional adapter bracket on top of the stock rails and build up with thicker seat materials.
The stock brackets are 2,5cm (1 inch) high. The adjustable aftermarket rails I have found so far are not far from this if you considering the specific seat adapter, that builds up on top.
To get the most of an aftermarket seat you will probably need to sacrifice the adjustment of the seat and screw the adapters to the floor. Extreme version of it is flatening the floor and screwing them trough it.
Stock MX5 seats after defoaming offer 85cm height measured from seating level to the top of the head rest. Finding a seat for somebody with two meters is a challenge on its own, considering the backseat height (belt holes, rear impact protection) and the limited seat width top and bottom.

I had to race with the stock defoamed seats, as in my racing class I had to have fully adjustable seats. The option to for Elise seats was not attractive for the upper reasons.

3. Removing the sound insulation and knocking back the firewall shell.
You will win headrom by tilting the backseat more to the back. To do this:
1. Remove or push low down the insulation behing the back rest.
2. Knock back the firewall shell just behind the seat. It will hide behing the black carpet.
Doing this right will allow you to happy tilt the back rest by a click. And this is so much!

Creating legroom
The following pictures are showing the problem places best. A bone stock MX5, me driving.



1. Door pull
Idealy you will remove it all, and put a stripe to pull the door.
As my MX5 was this time also my prefered daily driver ... and as this time I was working as interior concept engineer for BMW I had to come with some smarter idea.


Here you can see more about this project.

2. Handbrake
You have right hand drive car - you should be happy.
You have left hand drive - just bend the handbrake. To do this remove the plastic covers and bend, until you feel comfortable. It will make the some big difference.

3. Steering wheel size
In case power steering is present best size for me is 30cm (as 28 is already too small).
Airbag is to be considered, when changing the wheel. If you have one and you want to keep it, there is the option to go for aftermarket airbag wheel like Raid Silverarrow.
Smaller steering wheel gives more room. Without offseting the wheel /quite a lot/ you will not be really able to race the car. This takes you to the next point.

4. Steering wheel offset
To move the wheel nearer you have to concider to remove the airbag, as there are no wheel/wheel spacers working with airbag wheels. Removing the airbag is on the one side safety issue, on the other makes the car illegal in some countries.
I took a decicion for me, that it is safer for me and to the others to drive without it, than a car on which I cannot turn the wheel fast with both hands?
On the picture at the end the wheel offset is what brings the most.

5. Steering wheel position
I need to mention this for just the record, as it is not recomended and does not bring that much for the risk taken. You can lift the wheel a bit by removing the thick metal plate (bracket) between the steering column and the cockpit frame. Expect approx. 5-6mm lift.
Unfortunately I have only this picture from this bracket:


Make sure not to remove or put in a wrong way the two spacers, which are alowing the steering column to dive down in case of front impact.

This is the result that you can expect after taking all leg room measures.


Front sight
- Remove the useless sun visor at least on the drivers side. It will make a difference.
Again, consider it has safety function, being in front of the hard A-pillar.
This is the replacement cap I fabricated to fill the emtpy gap - nice and functional interior light:


Sun visor light

As I couldn't fit by more in a MX5 NB/MK2, I went for the lighter NA/MK1 model with more interior room.
The write up on top is NA/MK1 related, thats why I am extending it with two more points for the NB/MK2:

Door pull
You know it well - it looks different - it is bigger. Coming with a smart replacement is more challenging/fun. If there is interest I can fabricate leather pulls for the NB/MK1 as well.

Moving the pedals to the front
There is a way to move the gas pedal bracket further to the front, which gives you more legroom Various write ups on the net about it, best to search google for "gas pedal mod miata".

There is so much information on the net about this, but I never saw a site summarizing it. Hope this can help somebody start on the fly and not from a scratch like I did.
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