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Hello all. New to the forum, I have recently come into possession of an incomplete lightweight. It is at an early in the build and if I decide to have a go a it, will probably dismantle most of it and start again. Have read a lot about the structural problems and have seen the modifications done by GDC to achieve IVA. Would be grateful for advice on the following points.

1. Is it worth it, if I strengthen (as GDC has done) what chance do I have of passing IVA

2. Am considering fabricating from steel front and rear sub-frames and tying together with chassis rails to include engine, gearbox, diff and seatbelt mounts. Has this been done before? will it pass IVA?

3.Do I just give up on the design and find a second hand chassis and use the panels and parts to complete it

Thanks I advance for an advice.

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Use it as a donor for a another car with a proper chassis there are lots of part built and even unstarted kits out there that when complete will pass IVA and in the end cost you a lot less than the lightweight

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I think your approach will work, you will of course add weight.

An engineer mate of mine thought the wishbone mounts needed changing or sleeving with steel as the ally would go oval or crack.

I think it's great to take a difficult project and make it work.

Also find a way to make the diff removable, in standard form the diff on a Lightweight is boxed in permanently.

Edited by Snapperpaul
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Walk away or use it for parts for another build.


When GDC Finally got his cars, yes he got more than one through SVA, the diff started to twist and turn inside the monocoque and the way the diff is built into the car made it a pile of scrap tin foil.


Even Graham gave up and built a Zero, that must tell you something .

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Just remember it's the IVA examiner who will/will not approve your car for use on the public highway --- not some over enthusiastic optimist who loves our type of cars. Think very carefully before spending an awful lot of time & money on what may be a static model for the garden.


Having received a very vitriolic P.M from a member I wish to add that the post was a general reference to IVA testers & seven style enthusiasts NOT any one person in particular.

Edited by florin metal works
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There were quite a few fixes created before the problems showed up. One being a plate added to the diff area to spread the loads below the point where they would tear/rip/fold/spindle or mutilate in the stock design. Not too many people listened.


The problem with the lightweights alloy design was it was built like for lack of a better description a CAR! The problem was it needed to be designed and built like an aircraft. That means attention to how the fasteners are used ie seatbelts and the stupid rivets just to name a few. It also could be built much lighter and whole lot stronger and stiffer. A prime example of this is the area under the engine mounts. Instead of designing a proper structure or even using the right gauge material it is this built up layered "thing" loosely riveted together with a hunk of steel thrown in as an after thought. Thicker does NOT mean better! Of course nothing ties it into the side walls. Am amazed the few cars on the road haven't had the engines drop out or at least see fatigue cracking in that area from the flex.


If you are interested pm me. I did a analysis of the original as well as a redesign. I had just started mine with a GM 2.4 Ecotec with 6spd Suby irs etc before I had to move and lost shop space. If nothing else you should take a case of beer or two out to the nearest airport and talk to a airframe tech. Those are the guys who build part and fix things on aircraft. They will shake their heads when they see the "kit" and how it goes together.

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In the very early days of the lightweight there were proposed options of the kit being available in stainless or mild steel sheet as well as the ally option. Even Richard Stewart said the ally option was intended as a racing chassis and throw-away at the end of the season. It morphed rapidly to an ally road going version only. Anyone with an engineering background lost interest rapidly but a few people were suckered in and by the time all the predictable problems appeared many had invested to much money and time to back out. I had considered building the mild steel version and lost interest when it never appeared.

I doubt you would get one through IVA these days and IMO they should be failed as unsafe design and inappropriate materials, even with added strengthening. Useful only as a cheap donor and most sellers know that.



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Thanks for all your replies.

Decision made, will go with the chassis option and use it as a donor for the parts. Don't want to spend months building and modifiying only to end up not getting an IVA pass.


Am keeping an eye on e bay but if anyone knows of a chassis for sale in the south east I would be very interested



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  • 1 month later...

the lightweight is a weak chassis car, i defended it for

several years but eventual decided it was not good or even practical .my dif spun even with mods i had 190 horses .

an unmodified lightweight is a death trap in my opinion .swap the chassis out with a zero . the front shocks will fit the rear

you will need new front shocks .

the zero is far better than the lightweight .

scrap it like i have.

i feel a restoration coming on

regards graham

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