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Mk2+ MX5 With A SSC Chassis.
Big T - 30/11/21 at 01:11 PM

I am after a bit of help regards a donor vehicle, I am a little stumped and am hoping someone can give me a bit of a nudge in the right direction. Over the past year or so I have been collecting a pile of parts, documents, tools and so on to start my own build at some point in the future once time allows.

I am intending on building the chassis to the Haynes Roadster plans with the alterations as dictated in the Saturn guide. However this is based upon the Mk1 Mx5, obviously at the time the Mk1 was plentiful and cheap, that unfortunately isn’t the case anymore and the mk2/2.5/3 are more in budget. My concerns are however, how compatible with the later cars are the SSC alterations? I fully understand that anything is possible given the right amount of time and money however I am after a relatively trouble free build following a well trodden path of many before me.

I had a friend a number of years ago attempt to build one on the SSC plans with a MK2 and I’m from what I recall he mothballed the project due to so much being incompatible. However I don’t know if that was his lack of patience or if it was genuinely because it was such a ball ache to make it work.

I understand that the front hubs are different from the early to later model mx5s so I am very sceptical as to if the later hubs are compatible with the SSC arms.

Has anyone built a Haynes based chassis with a mk2 or later MX5? If so was it more trouble than it was worth?

Any pointers would be fantastic.

Thanks.

hughpinder - 30/11/21 at 03:01 PM

Some info here:

https://www.locostbuilders.co.uk/viewthread.php?tid=205845

regards
Hugh

rconey01 - 30/11/21 at 05:57 PM

Hi,

I am currently building a chassis for my MK2.5 mx-5, building to the ma7da regulation (ish) with the saturn rear end.
As far as I know, you can use the front uprights, you will have to make your own wishbones to pre-set your desired castor, also the mx-5 steering rack is too long so unless you get it shortened an escort rack will drop straight in with some extenders on the arms. This mitigates bumpsteer as the chassis was designed for the escort rack. Im not sure about the Haynes chassis though, Im using the ron champion plans and the saturn rear end.

Any questions just ask, I may have already thought about them.

link to thread - http://www.locostbuilders.co.uk/viewthread.php?tid=218927

Cheers

Mike Wood - 30/11/21 at 08:37 PM

Maybe a useful picture: https://completekitcar.co.uk/2021/07/05/haynes-roadster-rolling-chassis/

Cheers
Mike

Big T - 1/12/21 at 08:08 AM

Thanks very much for the additional information, links and photos, it’s all incredibly helpful and massively appreciated.

The main reason I am interested in using a later MX5 is so that I can adhere to the point system and eventually apply for an age related number plate, with ropey Mk1s knocking on for nearly £2k in a useable state, it kind of defeats the appeal of this project for me. If I can utilise as many parts as possible from a sub £500 mx5 and reduce the amount of independently sourced parts then I will be very pleased. Thank you for the note on the steering rack, looking online escort extensions seem to be readily available, however I may well have a punt at making my own!

Following that link I’ve seen the following reply.

quote:
Originally posted by big_wasa
Mk2 / 2.5 Rears are a little wider than mk1's adding somthing like 11mm in total to the rear track.

Mk2 / 2.5 Fronts have the steering arm around 7mm higher than mk1's. Said to be an advantage on a haynes roadster.


I am more than happy with +11mm overall on the rear and if the fronts are the same geometry wise with the only difference being related to the steering arm location that’s also fine with me.

And following a link from that link… I came across this bundle of info, it honestly amazes me some of the information people manage to retain on this site! This is incredibly helpful.

quote:
Originally posted by indykid
all uprights are interchangeable, '89-'05, only the hubs have the reluctor rings added and the upright may have a mount for the sensor

the calipers for 235 (1.6) and 255mm (1.8) discs are the same, only the carriers change.

one minor point, if you fit 1.6 calipers to 1.8 carriers, you need to swap the carriers n/s to o/s and vice versa to keep bleed nipples at the top, because the large and small slider pins are reversed. if you need a spare caliper in the future, you either need to swap in pairs, or get one to match the other side, 1.6 or 1.8.

'99 onwards (mk2), all cars got the 255mm discs, both 1.6 and 1.8

the 277mm 'sport' (and some other mk2.5 limited edition) discs have different calipers and carriers, but the caliper mount pitch on the uprights are identical between all years and models

235 and 255 rear calipers are the same across all models except the sport, but if you fit 255 discs to 235 uprights, you need to trim some of the stone shield away, same with fitting 277mm to 255mm uprights.


I think what confused me previously from googling, is it kept taking me to MX5 related forums, where to them, sensor mounts, ABS rings and so on are vital to the function of their vehicle and as such a Mk1 hub will not be interchangeable onto a later car due to lack of sensor mounts and ABS rings when ultimately to us, it is entirely irrelevant, as long as the geometry remains the same and I think this caused me some confusion.

Based on the above information I am confident that the later uprights/hubs will fit the Saturn arms.

I have a few queries about the steering columns fitment, however I am sure this is a hurdle I can overcome nearer the time. Regards diff arrangement I’m hopeful the Saturn plans will give me a nudge in the right direction and I can modify and make changes as and when needed for using a later diff if there are any differences across the range.

Thank you all very much for your incredibly helpful replies and inputs, it’s greatly appreciated.

hughpinder - 1/12/21 at 08:39 AM

some good info on diffs here - may be worth knowing when you are sourcing the donor.

https://beavismotorsport.com/guides-tech/differential-guide-for-miata-mx5/

Regards
Hugh

ianhurley20 - 1/12/21 at 08:56 AM

There are a series of videos by Tools n Track about the building of an MX5 Haynes which are amusing and informative. They even do a video about how to understand Glaswegian!

https://www.youtube.com/watch?v=7zdq-m6xq7k

cliftyhanger - 1/12/21 at 09:09 AM

The days of cheap MX5s is over, as the cats have so much value (were £750 scrap, which is why the cats are often stolen)

So unlikely to find one with original cat for under £1200 now. And if going age related, I think you will need the cat? Going for a Q plate makes life easier...

Big T - 1/12/21 at 11:24 AM

Locust reply 2


Thanks all very much once again for the extensive help.

quote:
Originally posted by hughpinder
some good info on diffs here - may be worth knowing when you are sourcing the donor.

https://beavismotorsport.com/guides-tech/differential-guide-for-miata-mx5/

Regards
Hugh


Thanks very much Hugh, I’ve had a very quick browse through that link and will have a proper read once I am home. I never realised there was so many options and combinations!

quote:
Originally posted by ianhurley20
There are a series of videos by Tools n Track about the building of an MX5 Haynes which are amusing and informative. They even do a video about how to understand Glaswegian!

https://www.youtube.com/watch?v=7zdq-m6xq7k


Thanks very much for the recommendation and the link, I will give it a watch and hopefully it’ll clear a few things up for me. I find build threads incredibly helpful for seeing things from different perspectives and also how builders have overcome certain issues.

quote:
Originally posted by cliftyhanger
The days of cheap MX5s is over, as the cats have so much value (were £750 scrap, which is why the cats are often stolen)

So unlikely to find one with original cat for under £1200 now. And if going age related, I think you will need the cat? Going for a Q plate makes life easier...


Sorry… have I read that right? £750 for the cat alone?!?! That’s insane!! I was weighing in large diesel cats for around £100 a few years ago and I thought that was fair money. I understand that the price of raw metals is increasing exponentially at the moment (I work in a position where steel costs are increasing significantly on a monthly basis) but £750 for a catalytic converter is bonkers.

I have found a couple of potential candidates, all under £1000, a few with an MOT which is ideal for a bit of a road test to confirm everything on the car is in a useable condition, some at around £500 but with stolen cats which is an obvious problem. Is there any possibility that an aftermarket “sports” style cat could be fabbed in to comply with emission regulations?

ianhurley20 - 2/12/21 at 10:15 AM

£750 does sound a bit high to me, a friends son had a new one fitted with lambda sensor Mk 2a two weeks ago for £320