Mk 4.0 chassis corrosion

Note to moderators : Please leave this post where it is. My question will, I’m sure, be of much interest to prospective purchasers of the new Mk 4, particularly given the serious nature of the subject of my post. There has been only one response since you ‘buried’ my original post in the technical sub-forum…


Given the appalling lack of chassis protection and deterioration on earlier marks of MX5 (my 2008 NC included), does anyone know if Mazda has taken note of the plethora of complaints and actually galvanised the chassis of the latest MX5? I for one would not consider buying one if this fundamental expectation has not been addressed.

Check post by Drumtochty .  He did a complete strip-down and under-body protection job. with photos after this subject was extensively discussed a short while ago.

Would it not be a good idea to ask the question of Mazda themselves?


So how long do you expect a car to last? My 16 year old car is still good. Are you expecting to keep an MX5 as long as that?

There are loads of MX5’s from the 1990’s still on the road. How many  Ford, Vauxhall, BMW, Nissan, Honda  etc of that age do you see in comparison?

This is a pretty pointless thread in my view.



Pointless to you, perhaps, but not to the many people who have voiced their opinion about the appallingly poor chassis protection on previous marks of MX5. And yes, if I decide to buy a Mark 4, perhaps I will decide to keep it for 16 years or more… but this is not the point. The MX5 chassis protection - or lack of it - seems to have been one undesirable way in which Mazda has maintained the tradition of British sports cars of decades ago. No other cars in recent production, including other Mazdas, have suffered from this problem to anything like the same extent, as far as I’m aware.

when did you see the owner of a 12year old Land-Rover moaning it needed welding?

My 9+ year old NC has no rust

To be honest it will be of interest to a very small tiny minority of MK4 purchasers because most won’t be planning to keep the car for ever. And for those who set out to keep it they will probably take precautions now, or at some later date to preserver the car.

And the subject has been very well dealt with, and a solutions discussed already on this forum thanks to Drumtochty. 

They are not supposed to last!


MX5’s are cheap sports cars. You get what you pay for.

If one doesn’t like it, nobody is forcing one to buy it.

Nearly 25 years on …  with a bit of love and tlc.  and if the WB’s look a bit rough under the waxoyle , a further day’s refurb. is on the cards this winter… in summary if it’s a long term love affair , you will treat her nicely !!!




This is a wind up no ?  You might as well talk to a brick wall than complain to the boys in Horishima about galvanising the chassis. Wink




Just to prove that other car manufacturers are just as bad (and in a lot of cases far worse…), this was the front subframe of an eight year old Vauxhall Corsa with 67,000 miles on the clock that I had the misfortune to own a couple of years ago.

Yes, you did read that correctly. EIGHT years old. And thats without mentioning the failing hydraulic cam chain tensioner that involved a nine hour strip down and rebuild to repair, steering rack bushes made of cheese, an unhealthy appetite for lambda sensors, etc.

Yes Mazda’s do rust, have a look a first gen Mazda 6’s for example, but if you know there is a problem get the car treated and it’ll last for years.

And look at recent Mercedes Benz and BMW’s, some of those are truly shocking when you see the state of the bodywork.


@ boxerdog1

The insides of your alloys are an absolute disgrace!  

£22,000 is NOT cheap - of course about 25% of it is TAX (VAT and VED).

To spend £22,000 after paying income tax and NI, means earning the best part of £40,000 (if you pay 42% tax).

If I spend £40,000 of my income on a car, yes I do expect it to last a sodding long time. For Mazda to save a few quid on underseal is outrageous.

£22,000 is cheap for a car these days. You can spec up a small family car to easily £35,000, mini to over £30K. Heck my dad’s Volvo V40 R Design D4…£23-24K standard, £10K in options…

Plus furthermore as said above many people do not aim to “own” the car for a long time, because most of the new car market is being up held by leasing deals specifically PCP more than Hire Purchase. 

Hence why I put “own” because in so many cases people are not aiming to “own” the car, they want to have it for 2-3 years and change it in. In some cases it is far cheaper than buying used!

The amount of leasing going on in certain circumstances is undermining the used market look at the Golf R which initial purchasers are now at significant loss if they bought it outright as the lease deals were going for £300 per month, it still is cheaper to lease an R over a GTI…

Another “victim” of this is actually most BMW’s…M4’s with £20,000 off list and on lease for £500-600 per month, the practical car I am looking at 640D Gran Coupe M Sport loads on lease for 2 years around 10K per annum list of over £60,000 people were getting £17K - 20K off that list price and having lease of £350-400 per month.  The used market has been significantly damaged by these deals (hence why lease prices are almost double now and the deals are far less).

Plus how long is a “long time”? years or mileage? Most people could barely hold breath if you kept a car for more than 3-4 years these days…


I’ll get onto that right away !!!  



If I bought a new car I would expect to be able to own it in perfect condition for 10 years or more. Anything of lower quality I would regard as being a shoddy waste of money.

My rule of thumb is that deprecation of £1k per year is acceptable. This is only achievable if averaged over a long period.

(Major generations of MX5 have only been about every 9-10 years).



We are just a drop in the ocean in the MX-5 world compared with what Mazda push out every year. They won’t listen to us whinging about non existance of underseal so we have to do something about it ourselves, shouldn’t be like this though

Like others have said, I’ve had enough cars in my life that have gone rotten in just a few years, the worse a Ford Cortina, that had newspaper under the front wings holding the filler up

I’ve also had cars that have had not one spec of rust after 4-5 years (Skoda)

My first employer, I go back many years, had a Rolls Royce which I was fortunate to drive around on occasions, it was going rusty around the wheel arches, his Jag was about the same. I pointed this out to him as I also had to clean them so got up close to them, he got rid of both and bought a Merc. He crashed that and bought another Jag, they are just a tool to them that can afford, they are not bothered about what’s undersealed or not.

Were Jags and RR’s undersealed in the 60’s 70’s?

Perfect condition meaning no major work for up to 10 years? That surely is dependent on mileage and generally how it is used. So many cars have mechanical (usually drivetrain) and electrical issues these days that whilst the MX5 suffers with some rust issues during this this time I have found it somewhat easier to resolve…most cars are really only designed to last 10 years…


Although in fairness any car can be a lemon I know of at least one or two skoda Octavia’s that have had rusting sills.