1. My model of MX-5 is: __NC 2.0 Sport
  2. I’m based near: __Sheffield
  3. I’m looking for technical help or recommendations on: __Rustproofing/undersealing

So I’m awaiting the final outcome of the MX-5 City undersealing thread with interest, but I think that whatever the outcome at this point, I won’t be going to them.

I’ve had a first close look under the body of my 2009 NC, and it’s looking pretty clean, and no surprises after the limited inspection I was able to do before I bought it (except for a slightly oily diff - probably more on that later in another thread).

I definitely want to treat/underseal the car to avoid future problems, but have a few questions for you kind folks to help me decide which way to go (or where to go).

  1. If I decide to pay to get it done, and MX-5 City is out of the equation, where else would you recommend not too far from Sheffield?

  2. If I’m right that there’s no more than surface rust, should it still be treated before undersealing, or just wire-brushed off?

  3. If I decide to do it myself, are there any recommended instructional videos? (I’ve seen the very helpful thread on, but ideally would like something a bit more detailed/idiot-proof)

  4. I’ve found something online about why you shouldn’t use rust converters here. saying that oil and grease will stop the rust preventer working. He does work mainly with Land Rovers etc, so perhaps less of a problem on an oil-tight(ish) Japanese car, but I’m curious whether this is just one guy’s bugbear, or a more widely recognised problem.

Thanks in advance for any and all help.


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I have the same car, just paid £480 to a garage who I trust to treat any rust and apply Dinitrol. I’m no mechanic but looking under the car with a torch it looks ok. Went with black finish so I could see it.

Try Carl at cbs autos in Nelson,he did mine,great job !

Having had my NC previously waxoyled by MX5 City who did a good job but didn’t remove the front wheel arch liners I am now taking the car to JR Classics at Askern in Doncaster for retreating. Whilst not the cheapest and there is a 3 month waiting list I have read good reports on the quality of their work. I will know for certain once the car is done in January.

I have touched up areas with Waxoyl underseal where the underside has caught and it is messy to use. So much so that I wouldn’t want to apply it in my garage as it is a devil to get any splashes off the concrete floor.

Eyup James, another Sheff/Rotherham owner here. Thinking of using the Lanoguard kit in the spring when it warms up a bit, so if you want to pair up and have an undersealing day let me know. Haha!
I was also looking at having it done at Askern until I saw their prices! I mean, how difficult can it be? Brush off the loose stuff and spray it all over the underside. Roll on summer heat.

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my thread is updated… have a look, avoid.

Thanks - not too far away. What did they charge (if you don’t mind me asking)?

Thanks - I did look at JR - but a bit too pricey for me.

Hoping to get mine done before then, as I’ll be using it over the winter. Will let you know how I get on if I do it myself. As you say, can’t be that hard (messy though).

Hi James,I can’t remember But I know he’s resonable

Carl at CB excellent, I used him for everything when i lived up there. Unfortunately too far away now

If you do it yourself you can take your time and do the work in stages. As others have said the problem areas are the sills , the rear wheelarch forward corners and the rear subframe. 90% of the underside may be dirty but is probably rust free.
The sills are easy to access by removing the scuff strips on the lower door aperture using the long application tube supplied with bilt-hamber dynax s50 aerosol. The rear bumper reinforcement attachment points are very likely to be rusty. Don’t be frightened to scrape off any lifted original underseal patches as the Mazda stuff peels and flakes particularly above the rear backbox on the frame rails. Bilt -Hamber UB aerosol is a translucent black-brown wax which sprays nicely and doesn’t drip too much. Some areas will need wire brushing and rust treatment before treating. If you need welding better off getting it done before application as it’s not made easier by cavity wax.
Good luck and enjoy your car.

I agree with the above and the areas you should look to first.
I’ve not bothered with the main underbody, the floorpan, it’s pretty well coated but have touched in where I’ve noticed peeling sealant. The length of the sills, the seam weld is my next priory, it looks pretty good TBH but a slight trace of surface rust here and there. I’m going to do the front arches too next year, not touched yet.
All jobs to keep me busy but for now I think it’ll be tucked up in the garage away from any winter road grime and salt.

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Had our 2012 Venture Waxoyled by MX-City last month, liners removed, photographs sent by MX-City showing each stage of the work, provided with a courtesy car for the day, pleased with the work



Oh dear!

Hi ChrisMK3
Just checking was your ‘avoid’ post about MX5 City or Lanoguard? I can only see posts about MX5 city on your profile. Just checking as I am considering Lanoguard as I want a lighter oily protection not a gloopy one (dry use only, in fact mot much use at all this year…).

See this thread: Undersealing at MX5 City in 2020


It was specifically about MX5 City… I’ve got no experience of Lanoguard though I hear good things about it.

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Re: CBS Autos Ecroyd Street Nelson BB9 7BJ 01282 697413.
I have been a customer of Carl’s for 10 years, in fact ever since
I took my first MX5 to him in 2010. Carl has expertly carried out a variety
of work for me on 4 different MX5’s. Work included Dinitrol treatment.
Carl is currently not doing bodywork restorations but he is doing rust
prevention treatments for all series of MX5’s.
Yesterday’s visit included a new under tray for the Eunos plus fitting the
Skid Nation indicator/day running light conversion kit.

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It would be useful for less experienced folks like myself to have a list of areas to avoid getting covered in underseal.