Hi all,

I've been hanging around the scene for a few years, though my project is still in the planning stage. originally it was to be a custom based on the MR2, but recently it has evolved to a new donor - the Mazda MX5. The reasons being that this car is (IMO) simpler, has all-round independent wishbone suspension already (don't have to fabricate these parts and they suit a low profile body) and it suits the shape of the car I wish to base the body on (Aston Martin AMV8). In fact if you overlay these two cars (early model MX5 and AMV8 scaled down) the cars line up almost perfectly.

I apologise if this is the wrong place, but I have a few questions!
1) Are there any good links to exisiting MX5 based projects?
2) Any photos or measurements of the MX5 chassis and important mounting points etc would be great!
3) I have heard that the Ginetta G20 is/can be Miata based. Any good G20 build sites around?

Any other information greatly appreciated. Please let me know if i am in the wrong place, or if there are other useful resources.

Shoutout to Steve Graber - It's Pea from the MR2 forums from way back

[Edited on 2/1/06 by envy]

Keith Tanner....wrote a locostMiata book..."How To Build a Cheap Sports Car

Plenty of pics and info on his site

http://www.cheapsportscar.net/

Flying Miata....based in the US, google the name and see what you come up with...performance parts plus other stuff...

Thanks for that. I had heard about Keiths book, but the website link is great .

The shop manual for the Miata/MX5 includes a number of fundamental dimensions that can be used to ensure the unibody is straight. Are you planning on fabricating a spaceframe and simply installing the front and rear subframes from the MX5 inside? That would certainly be easy enough to do as they mount with just a few bolts.

Keith

I could put some pics of the mx5 underside up; my dad put his in a ditch recently and showed its belly nicely

I used an MX-5 donor. Have a look at my website. Also look at BobC's website. He's been a huge help to me.

--Chris

Hi guys,

Thanks for all the info!

Keith - Yes, building a spaceframe to take the front and rear subframes is exactly what I plan to do. I found great photos of the rear subframe on your site from the dissasembly of your donor, but wasn't aware that there was a front subframe assembly also? I plan to make the initial build as simple as possible, so bolting these assemblies on would be awesome.

Blueshift - Some photos of the underside would be great!

Chrisf - I will check out your and bobc's site.

Thanks all for the great responses.

Yes, there's a nice front subframe/engine cradle. The two are joined by the Power Plant Frame, an aluminium girder. You can actually make an almost-driveable car out of just these parts, you just need some way to support the top of the dampers! There's a nice photo of the lot here. A nice spaceframe to join it all together would eliminate a lot of hassles when building your car!

Keith

Wow! That is amazing! That has just made my day. I can see my car on the road much faster than I thought possible!

It may seem like 'cheating' to use so much of the MX5, but it will be my first project of this type, and i didn't want to just build a kit.

Is it all models of the MX5 that have this assembly? Which model should I aim to purchase as the most suitable donor? My aim is reliability and ease of maintenance over speed/power...

They're all basically the same when it comes to the chassis. Reliability is all pretty good. The best choice might be a 1994-97 model with the 1800cc engine for a bit more power and a stronger rear end. The engine is slightly longer but otherwise the packaging is the same. Still the 1990-93 1600cc cars are a good choice and quite common. There are a lot of parts that interchange. The 1999 and later cars are a little bit more complex mechanically but the biggest concern there would really be the cost of the donor.

I think you'll be busy for a long time on the body so you might as well get the chassis done as soon as possible!

Thanks for the info. MX5's are pretty common here in New Zealand - in the form of Eunos roadsters as well as mazda MX5 brand. I'm hopefull I can pick one up with extensive body damage but an intact PPF and running gear.

Here is a mockup of the AMV8 concept scaled down to overlay an NA MX5 (Miata). You can see that it lines up almost perfectly. The only copncern I have is the hight of the engine and front shocks fitting under the low hood.

If anybody has any photos of any part of the PPF or subframes, they are all much appreciated.
Rescued attachment envy_mx5_views.jpg

I have a set of subframes sitting in the shop right now. Let me know what sort of things you want and I'll take them for you. I don't have any PPFs except for those on the cars, but I can get a shot of them in situ. Not much to see there, just a big C-channel girder.

That would rock. Basically just some semi-hi-res shots of the subframes from various angles so that I can see clearances and mounting points and start designing the basic chassis around these.

I don't need exact measurements and things yet. I will probably get a donor and strip it back before I design the chassis proper to fit it.

Thanks very much!

I found this excellent scan:
High resolution PPF from side view

Photos from above angles would be great to see the approximate location of the mounting holes/bolts etc.

I'll see if there's anything good in the shop manuals too. I think there is. It might take a couple of days, the scanner needs to be installed.

No problem at all Keith. It's not urgent Thanks very much for doing this!

Good thing it wasn't urgent, but I think you'll like this.

Front and rear subframes on PDF - from the factory manual, including mounting points.

I have the full setup in the shop right now as you can see, so if there are any particular photos you'd like now is the perfect time.

How to make a Locost out of an MX5 almost instantly!

Thanks a lot for that Keith! Do there happen to be any pages in that manual with actual measurements? That may be asking a bit much

As for photos - a closeup of each 'corner' for reference would be nice, and perhaps one from as close to top down as you can get from the back and the front. Anything else would be a bonus!

I appreciate this very much.

I know what you mean about the quick build using the MX5 PPF whole! I am hoping that will be the case with my build but I very very much doubt it will be as strigh forward as all that!

the engine and shock tops will fit under that lower bonnet line. there's a good couple of inches clearance in there.

however - your head wouldn't fit under that lowered roof! unless you're some kind of midget.

My photos of the mx5 in the ditch aren't as good as I hoped, this is the only one of the underside:



high res version here

[Edited on 22/1/06 by blueshift]

Thanks blueshift. The seats will be bucket seats and the driving position reclined slightly too, so that will help.

How high is the top of the drivers head in a 7 ?

quote:

---

Originally posted by blueshift
your head wouldn't fit under that lowered roof! unless you're some kind of midget.
[Edited on 22/1/06 by blueshift]

---

Quite a bit lower in my case.

Here are some measurements of suspension geometry, I do not have dimensions of mounting points. Those are 17" wheels in the picture above. Might be time to get some subframes of your own if you want enough accuracy to start planning a frame.

http://members.cox.net/enderw88/miata.htm

Hi Keith,

Thanks for the link. That is definately the next step (getting a donor) I have been asking around the New Zealand MX4 list to see where/how much etc...

I wouldn't have thought you're more than 2-3" nearer the floor of the car in a locost.. I could be wrong. maybe should take some side-on photos of mine with the door open?

Some progress - my wife and I have purchased our first home, which has a garage Its only a single car garage but its better than nothing and means I can start thinking about purchasing the donor soon.

Thinking of a space frame chassis which will replace the mx5 chassis/body (and keeping as much of the rest of the mx5 as possible) is it a good idea to first plan members which will connect the major mounting points and structural members, and then triangulate those?

If so, main mounting points and considerations include (please suggest or add more):

- Front and rear sub frames
- Dampers
- Engine mounts
- Floor/Seats
- Seat belts
- Windscreen
- Roll bar
- Door hinges and latches
- Hinging for GRP body shell or hood/trunk

Any others?

Have you finished this yet?
You should!
Must have a bit of equity in the house by now, time to restart the project.
Ill build one if you do.