Hey everyone

I am researching using a miata/mx5 rear end on my honda S600 build.I intend to use a F20c or similar motor.
This is to replace the existing chain drive or live axle option. I am basing this rear end off similar builds in RWD minis , other small convertibles etc.
The front end is acceptable but I am open to suggestions ! HERE is an image of the design (sitting upside down)

So , school me abit about using another cars subframe + IRS setup....

1.Using an entire MX5 rear end - If the suspension is kept as is and the carrier area of the subframe is simply cut and narrowed to suit , will this keep the geometry ?

2.The honda S600 rear tracking is 1128mm and the mx5 (1st gen ) is 1430mm. Pending wheel offsets and widths I can narrow the subframe 151mm either side of center and shorten the driveshafts to suit and it should be a good start right ?

Ill shoot some more questions about this soon

thanks for any input ! Ben

*edit
My aim is for the Honda to be a little lighter and alittle more power , but equal or better handling than a 1st gen MX5.

[Edited on 20/8/16 by bennjamin]

It sounds like quite a logically Locost idea, it might be worth checking if any other Mazda's had the same CV/splines joints but were narrower trackr so you wouldn't need custom driveshafts.

Instead of chopping and welding the original subframe using it as a template to make a new narrower version might be better as the one I had was quite crude.

If you are going down that route would the simplest option be to use the entire MX5 drivelibe with a shortened propshaft and PPF? It's not F20c power but it would still be quick and fun. It would be the quickest route to getting the car on the road.

Annoyingly I have just chucked a surplus MX5 rear subframe in the tip.

Was just thinking about Geo' narrowing the frame and keeping the same wishbones to give a narrower track won't drastically affect the geo, I think the notabke blhange would be to slightly lower the roll centre. But seeing as how you are using the Geo' in a completely different car it's going to feel totally different anyway.

Apart from lowering the static roll centre, it can potentially screw up dynamic location of the roll centre (ie. the roll centre moves about significantly as the suspension moves).

This in turn means that the weight transfer is shifting about as the suspension moves during cornering, which can make the car feel rather unpleasant and squirrelly.

You may get away with it, but personally I prefer to do a proper suspension analysis (using one of the readily available geometry programs) to ensure that the roll centre remains constrained to within a couple of millimetres of the same position relative to the sprung mass, throughout its working range.

300mm = 1ft is a huge reduction in track I can't see the Mazda final drive casting with its wide mounting lugs fitting in, a Sierra or Freelander diff casing might be a better candidate. However it isn't clear from your post if the car is the live axle or the rare chain driven trailing arm version, if live axle really it might be best to leave the axle geometry alone. Honda are of course famous for using anti-clockwise on many older models so it would just be matter ensuring the axle rotation is the correct to match the engine.

If you really want to go IRS you could go Locost style IRS or the simpler Strut or Semi-Trailing arms. You might even have room for a de Dion.

Sorry Bennjamin... I only half read the original post, so I didn't really register that it was you and your S600 we're talking about (it is indeed the chain driven trailing arm arrangement we're talking about, BT).

I really shouldn't be replying on forums that early on a Sunday morning... my brain doesn't get into gear until about mid-day!

I Agree that you'll have some fairly serious packaging problems, with the Mazda diff and subframe, in a car as small as the S600.

I'd definitely be looking for the easy option of a suitably narrow live axle, if I were you.

Ford Anglia 105e axle would be an option for a clockwise engine.

Or MG Midget: rear track is 1138mm, versus the Honda's 1128mm (Anglia is 1162mm).

More modern stuff like the little Japanese vans and Jeeps might be worth checking, too.

Invert the axle, if the engine spins the 'wrong' way?

Thanks for the replies everyone.

I need to put this through a program or a scale image to work out more sense.
I have advised my fabricator and he agrees about using the standard subframe as a template for a tubed narrowed replacement. This should give more room for the OEM diff or an alternative.

FYI this car came as a chain drive setup - the later S800 came with a 4 link but is impossible to find parts for. So I'd thought to give it a IRS end similar to the front.

Lets see how it goes. Will keep you updated !