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The MX5 Rallycross car

SpacSpac (@Spac) Canberra-ish.
edited July 2018 in Non-Volvo
History is that a mate bought this to turn into a rally car, but got divorced instead. He bought some MCA Red coil overs, replaced all of the suspension bushes, and did a few tidy ups, but basically didn't use it.

Eventually he got sick of looking at it and offered it to me for the price of the coil overs.
At first I declined, but then El Wifeo drove another mate's NB MX5 on the same day as the NA was offered again. And then we owned an MX5...



It is not a great example, but it is a solid base - leaky valve stem seals make it smoky on cold start up, the steering rack was buggered, and a few other niggles.
The real problem is that we had no idea what to do with it... I fixed the broken ignition lock and drove it around town, but it was sort of looking like a white elephant.

Then El Wifeo spectated at the Rallycross. She then announced that we should turn it into a RX car.
That's a dumb idea, because... um... shit - that's a really good idea, and it should be very competitive in the 1600cc class.

So then began another race car build.

First step was to swap the steering rack. I ended up swapping the entire power steering system because there were some weird things done to the old pump, and it had a shitty aftermarket reservoir.
Also removed the AC stuff from the engine bay.

Next was to strip the interior.

Had to drill out the rear mounting points for the seat;


Then I discovered that the matching pair of Velo seats aren't quite the same - one is about 20mm wider than the other, and that matters in an MX5.

The cheap seat mounts I had weren't helping things either, so I made a new one for the left hand side, that allows the seat to be moved leftward by about 20mm.3D2SJOOh.jpg

The actual bending of the 5mm aluminium was a challenge. The big sheet metal bender barely even touched it.
So I got creative with the hydraulic press. No actual photos but this explains how I did it:
Pretty happy with how it worked out, TBH.

Also wanted to move the steering wheel forward. Had an old boss floating around, so it met Mr Lathe for a bit.


  • SpacSpac (@Spac) Canberra-ish.
    Tomorrow I hope to get the seat mounting finished and the harness in.
  • SpacSpac (@Spac) Canberra-ish.

    Ebay 4x100 to 4x114.3 adaptor spacers came in 15mm or 25mm thickness. I get a bit nervous about the strength of the 15mm ones, and my calculations said that 24mm would give me the right offset with the +44 and +46 offset wheels that I have.

    Turns out that I was wrong. Despite not finding any faults with my primary school level mathematics, the 15x6 +46 wheels hung out nearly as bad as the silly original 15x8 do.
    Weirdly, the 15x6.5 +32 wheels with 205 tyres were the same!?

    I need to work out who is lying about their offsets, but the more immediate problem is to get a set of wheels that fit.

    So the 25mm spacers became 19.5mm spacers. S4mROpah.jpg

    Worst part of the job was bashing the studs in and out!

    Also finished the seat and harness mounting yesterday. I made my own life far more difficult by deciding to swap to the narrower Cobra seat rather than the Velo that was 99.99% installed...
    The positive is that the door doesn't hit the seat when you close the door now AND that's with the door trim refitted.

    CAMS have been irritating me about the cage spec. A few stupid rulings (IMHO), particularly:
    1) All Rallycross cars need a National Level rally cage. Rally cages differ from circuit cages because there are two people in a rally car, so I am buggered if I understand the logic of making a RX cage protect a person that isn't there.

    And Rallycrosses are run on short, tight circuits so the need for a full National spec cage is questionable. Even the outright RX cars don't see the speeds that a club race or rally car does, and they operate in the relatively soft environment of a race circuit (not a tree/rock/cliff/embankment lined rally stage).

    2) The Sainz bar (aka A-pillar support bar) must join to the front leg. It cannot mount to its own plate on the floor. This is contrary to the FIA (and the rest of the CAMS) regulations, makes the whole thing weaker and is harder to build.

    I need to stop sulking about those things, and just order the cage kit from Bond.

    Bought a lightweight hardtop. Need to sort myself out with getting it transported up here.
  • SpacSpac (@Spac) Canberra-ish.
  • SpacSpac (@Spac) Canberra-ish.

    Clearanced with a hammer.
  • Hehe in is still in.

    Cams regs are weird, particularity when it can come down to the opinion of a scrutineer on the day to some degree.
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