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Haynes Roadster MX5 Extra legroom?
albertz - 29/1/19 at 08:17 PM

Hello, it has been a long while since I last posted here!

I built a book Locost with a Toyota 4AGE engine, registered in around 2008. The engine eventually swapped to a 2.0 Blacktop Zetec and then eventually sold the car around 2013.

However, I have recently been bitten by the bug again and this time I am in the very early stages of building a Mk2 MX5 Roadster (currently stripping down a 2003 Mk2 1.6 MX5). I can see that this is a well-trodden path and there is loads of info available. However, my specific problem is that I am very tall, around 6'5" and although I just about squeezed into a standard 'book' Locost I would like to try and build in a little extra legroom this time to make it more comfortable.

So, my question is, can I add 2" into the length of the cockpit area without causing myself too many problems later in the build? On my 'book' Locost I made the side panels myself so would probably do that again - as standard size panels would obviously be 2" too short. Is there anything else that is a fundamental problem with this approach? I'm not planning racing the car or anything like that, just enjoy building the car and a nice sporty car to drive once finished.

Out of interest what are the actual differences in overall sizes between the Roadster and the 'book' Locost, from what I have read it is 2" wider than the book version, is that the only size difference? I realise that the chassis is quite different in terms of suspension and things.

I would plan to add the 2" to either BR3/4 or BR5/6 - does anyone have any thoughts on this approach?

Also, final question, are the standard MX5 seats suitable for the car, will they fit? My donor has very good condition leather seats which I would like to use if possible.

Thanks
Andrew

JC - 29/1/19 at 09:38 PM

You could look at the various McSorley plans - mine is a 442 which is 4” wider, longer and 2” taller than a standard Locost. As I recall there were other dimensions too - admittedly for the Champion chassis rather than the Gibbs one tho...

Nickp - 30/1/19 at 06:27 AM

Best to try one first before over complicating things I reckon. I'm not small at 6ft+ and 16st and find mine plenty roomy enough with good legroom. I use composite seats though so anything bulkier would reduce the legroom slightly I guess. One of the things that would put me off making it bigger would be that the nice bodywork that you can get from the likes of Equinox will no longer fit

I think the dimensions of the Haynes are about right and anything bigger (like a Luego) starts to look silly tbh (just my opinion, sorry Luego owners )

Description
Description

[Edited on 30/1/19 by Nickp]

[Edited on 30/1/19 by Nickp]

Charlie C - 30/1/19 at 06:55 AM

Have you considered using a top mounted peddle box and moving it forward, so it pivots forward of the front cross member and panelling an extended foot well area? The MX5 clutch fork would be a tight fit and the steering column might need a bit of rerouting, but this might be easier than extending the chassie.

ianhurley20 - 30/1/19 at 09:35 AM

quote:
Originally posted by Charlie C
Have you considered using a top mounted peddle box and moving it forward, so it pivots forward of the front cross member and panelling an extended foot well area? The MX5 clutch fork would be a tight fit and the steering column might need a bit of rerouting, but this might be easier than extending the chassie.


I did this using MX5 parts - have a look at my build blog for photos and how I did it. I used the MX5 steering colum as well, worked out fine all round.

albertz - 30/1/19 at 12:56 PM

Thanks for the replies!

I did look into the 442 McSorley but was worried whether there were enough supplier still making bodywork for this size of car?

Unfortunately where I am located (Caithness) greatly reduces my chances of sitting in a finished Roadster.

I will definitely look into the pedal box changes as that sounds like a good idea to get a bit more legroom, every little helps.

I was hoping that by adding 2" into the cockpit area that it would only directly affect the side panel length, I intend to make my own panels so that is manageable and also the looks of the car, again a compromise I am willing to make for my comfort. Are there any other issues/problems that I am missing? As far as I can see the back end mechanicals and looks would all be identical and likewise with the front, it is just the bit in between that I wanted to lengthen slightly with me being so tall.

Any other thoughts on this please let me know. I am currently stripping down the donor and then it will be onto the chassis, so I am keen to get to the bottom of this quickly to avoid rework etc.

Thanks again for the help!

jps - 30/1/19 at 01:17 PM

quote:
Originally posted by albertz
I was hoping that by adding 2" into the cockpit area that it would only directly affect the side panel length, I intend to make my own panels so that is manageable and also the looks of the car, again a compromise I am willing to make for my comfort. Are there any other issues/problems that I am missing?


I would have thought you'd be right really - obviously everything running the full length of the transmission tunnel will need to be 2" longer (prop for example) and perhaps to retain the same level of chassis stiffness you would need to alter the triangulation? Depending on your proportions you may need to think about the fact that the gear lever and steering wheel will be 2" further away from the seat - but then I would think your height translates to have longer arms too!

The only other thought would be that the handling will be a little different as the wheelbase will be longer - and potentially it'll be easier to ground the car where there's a steep change in floor angle - i.e. coming off the kinds of ramps they have off a ferry or in a tight multi-story car park.

James - 30/1/19 at 02:48 PM

Having built a Locost +10% a great many years ago I can see very little issue with adding 50mm to the cockpit sides.

I suppose there's a little more chassis flex but if you look at the Cymtrix (Cymtricks?) chassis mods you can add a load of stiffness and reduce weight anyway.

Cheers,
James

coozer - 31/1/19 at 09:11 PM

How about putting a 'dent' in the back panel so you can move the seat further back and as said a top mount pedal box with dents in the front panel to gain the 2"?

If you want to add 2" to the cockpit length its not a problem, how about welding in a full cage to stiffen the whole lot up?

Or, build a Midlana.. uses MX5 suspension and ANY fwd engine and trans..

ianhurley20 - 1/2/19 at 01:41 PM

My vote would go for a Midlana as well