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I have just received notice that my Chinese carbon fiber hardtop is going to arrive in 2 weeks! It will be interesting how well it fits and the general build quality. It comes with polycarbonate rear window but no rubber seals nor latches. I plan to re-use my soft-top front latches and side seals, and make up some side brackets to get around my roll bar as there is no access to the standard bolt holes. The rear will hopefully clip into the Frankenstein bolts and I'll need to make a rear seal or purchase one, but we'll see how that goes when it gets here and I do a test fit.

For anyone looking at importing a hardtop from China, I suggest sending me a PM as there are a few gotchas regarding shipping, port fees etc.

I believe forum sponsor "carbonmiata" is also importing the hardtop through his website. Not sure if it is from the same supplier.

Is CF top legal for road use?

Kev05 wrote:
Is CF top legal for road use?

How could it be more dangerous or safe than a soft top? In which case it'll be just as legal as, say a rear spoiler?

LOL Why wouldn't it be?

Carbon bonnets aren't often legal for pedestrian safety reasons (the theory being metal bends around them, carbon fibre or fibreglass cracks and leaves sharp edges to cut them)

Same reason that massive rear spoilers are not legal in some states (although, I'd suggest that if you've cleared the bonnet/roof to reach the spoiler you're already flocked)


the roof may come into that, but I very much doubt anybody will ever notice.
Easy solution, paint the hardtop and nobody will ever know it's carbon.

Bonnets are also classes as intrusion panels and therefore have to meet ADR requirements.


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Given the standard hardtop is fibreglass, with the carbon hardtop being mostly fibreglass with a carbon outer layer, I can't see it really being any different. Of course who knows with licensing and regulations theses days.

madjak wrote:Given the standard hardtop is fibreglass, with the carbon hardtop being mostly fibreglass with a carbon outer layer, I can't see it really being any different. Of course who knows with licensing and regulations theses days.

Common mistake here.

Assuming car modification laws follow common sense.

For your consideration
Soft top- "designed to have the equivalent strength of a steel roof against snow fall and to suffer no deformation from a sidewind force of up to 30KG" It was said not to leak in a typhoon.

Detachable hard top OEM ( DHT) manufactured from sheet moulding compound i.e. SMC- not fibreglass. " the process made it possible to fabricate a complex inner structure with a uniform outer thickness for a light and strong DHT. "With CAE analysis and various proto tests " the engineers arrived at the best combination of panel thickness and structure tho give them optimum strength and and lightweight. Final design was a two piece bonded structure with an outer panel tightly bonded with epoxy resin to an inner panel.

Anyone interested in the smc processes check it out.

The bottom line is the MX5 was engineered and tested by qualified people. Bear in mind that an OEM top would have to meet its design spec and furthermore be tested for durability- that would surely include hot and extreme cold cycling and strength tests. The comments raised about ADRs etc are quite reasonable- you don't judge a book by its cover and many products today are failing- see the recalls in newspapers for poor manufacture.

Personally I would think an original OEM DHT is a very nice piece of kit.

SMC is fiberglass.

Just in case you don't believe me the following is taken from

http://composite.com.au/cme-processes-m ... pound.html

SMC is a high strength glass reinforced thermoset moulding material which is normally compression moulded. It combines long glass fibre and unsaturated polyester/ phenolic/ Vinyl and Acrylic modified resins to produce a high strength moulding compound. These materials are usually formulated to meet performance requirements of the part to be moulded. CME manufactures these materials at our Bayswater plant in Victoria.




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Safety wise I doubt the hardtop will contribute much if anything during an accident. In either case, OEM or aftermarket, the hardtop will be smashed to pieces in any serious accident. It might stop an arm or something flinging out of the car and getting crushed but other than I doubt it will make much difference as a benefit or negative. It may have a little bit of benefit if the car rolls in a sand trap. I'm using it on a track car so it will see very little road use.

I'm getting a hardtop to stop the rain... A little bit of extra chassis rigidity and less wind resistance at speed will be nice and hopefully it will look nice too. We'll see.

BTW... has anyone made custom side clips to get around the cage? Any ideas other an offset aluminium plate and some screws into the base of the hardtop?

Just don't use the side clips.

The hardtop is perfectly stable without them.

I've had my hardtop for years now, it doesn't even have side clips on it.
Never had an issue

hks_kansei wrote:Just don't use the side clips.

Didn't actually think of that! I figured there would be too much side flex.

I'll leave it till I have it mounted then. Cheers

"there are DHT's that are made with polyester resin and glass fibre laid up over a mould but utilisation of the SMC process for DHT manufacturing was a world first"- reference Seiichi Omoto

SMC is not fibreglass and its not the same process.

Its reassures me that modern car making is approached based on engineering knowledge but then proved by test and trial and Mazda seem to have got it right with the remarkable MX5.

What! Your own quote says it's fibreglass!
Resin + glass fibre = fibre glass

Yes smc is uses different manufacturing process to hand wet lay up, vacuum bagging etc but the material is still fibre glass.


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