Undersealing an MX-5 which does not get driven during winter?

I took delivery of my ND2 during September and has been in storage since late November last year. The local council started gritting the roads earlier than expected which resulted in cancelling the underseal treatment.

I’m now having second thoughts whether I should rebook the treatment especially when the car does not get driven during winter?

I recently watched the following Mazda Miata Documentaries and was surprised at how clean the NA, NB and NCs looked underneath without any additional undersealing but those cars are probably owned and maintained by Mazda USA:

If you intend keeping the car long term then yes it’s a wise move to get it protected. Great getting it done now as I guess it’ll have no rust and maybe not much muck underneath either to remove.
That in itself should make the job easier and more likely at less cost.
If of course like some owners you either move it on after you’ve had your fun or are wanting the latest model in around 2 years ask yourself, is it worth it and let someone else worry about rust that may appear.

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Thanks Mick. I would like keep the car for as long as I can since it’s my first brand new car as well as being the 30th anniversary model. Embarrassingly, it currently has less than 100 miles as I wanted do the underseal treatment straight after having it detailed but the local council disagreed.

Does rain contribute towards chassis corrosion/rust?

I would like to drive around Europe sometime however, it would be impossible to do this on just dry roads.

The US cars by and large seem to stay amazingly clean underneath as you say. The culprit in the UK is road salt/gritting. Even a summer only car can pick up the dry residue which will then lodge in the nooks and crannies and become damp with the resulting corrosion. If you intend to keep the car and preserve it’s future value, function and saleability I would strongly advise a good underseal and chassis injection with quality materials. The real cost of prevention is small compared to that of remediation.

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If I had a brand new MX5 I would get it treated regardless. This year especially the grit stuck around visibly until well into April. If you are having to wait until it’s all gone you are giving yourself a very short season to use your precious.
I have heard that MX5 restorer are now doing a clear underseal. If i had known about that then that’s what I would have gone for. The black stuff makes it very tricky to see how the chasis is coping underneath, there could be rust forming from the inside out underneath the underseal and I would not have a clue till it was very far gone

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Mine has only done 50 miles since November 19 :frowning: so I wouldn’t be embarrassed.
Buying a new car then putting in away would really get to me, you must be very patient waiting until now👍
Yes as above posts say get it done, don’t forget inside the rails/sills etc.

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Thanks for your replies everyone :+1:

@BrilliantBlackBirdy: I had not considered the colour of underseal to be an issue and thanks again for mentioning it. The place I had initially booked with offers a choice of either Dinitrol or Bilt Hamber.

I’ve had to be steadfast with not being able to drive it whilst in storage. I learnt the hard way with my previous car, a Honda Civic Type-R (FN2) which was used throughout the year. The amount of rust underneath was appalling and much of the metal surface was flaking off as well as rust seeping through the rear arches :frowning:

Hi Jonathan, I noticed when cleaning my newly acquired 3 year old Icon that where the sill covers finish at the rear wheel arch, the amount of mud that had collected there was very disconcerting, I know the car must have been driven down a farm track or they had gone green laning in it as it was quite muddy underneath, but all nice and clean now. Anyway because of this I removed the sill covers and the dirt can get down the covers about 6-8 inches and it stays there, so I cleaned it out and Waxoyled the full length of the sill, so you might want to think about that as any muck is going to get in to what I think is a bit of a design fault.

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To be fair, in some parts of the US, the corrosion can be incredible (Rust belt cars). They use a salting gel there, which is very aggressive (some bridge collapses have been linked to it). We mustn’t forget we also have an essentially maritime climate. In Japan, salt is not used everywhere, but Mk1s, Mk2s, and now Mk3s are showing up over there with body rust, but the undersides looking very clean. That tells you there is two causes of rust; whatever is on the road peppering the underside, and then the effects of humidity in non-draining areas (sills). Japan also has a maritime climate.

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I had mine done with Dinitrol when it was10/11 months old and had only done 900 miles, when it was up in the ramps they cleared out all mud and road debris before undersealing, key for me was making sure it was cleaned AND dried before the dinitrol was put on, should be links to the photos I put on elsewhere in the forum

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21 February in body styling, my technical skills aren’t good enough to provide the link!
Cheers
Mark

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Hi WR,
How did you remove the sill covers please? I have looked and it was not obvious how they come off. It would be good to get in there and give it a good seeing to!!!
:heart:

Regarding Bilt Hamber products, they are not the cheapest but they have an extensive range which are great for diy. The large aerosols are easy to use and come with application tubes that will easily enter the numerous chassis access holes that mazda provided. They have a “clear” product UC which adheres nicely and is unobtrusive. UB is the black equivalent and S50 is the cavity wax.

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As per the above posts - as it sounds as if your car’s going to be a “keeper” my advice would be to have it treated, even though you don’t intend to use it during winter.

As identified above, there are other causes of corrosion besides the main culprit (road salt). My car was treated when new & while I do use it all year round because I wouldn’t be happy about the potential mechanical consequences of leaving it standing for months at a time, I don’t take it on wet salty roads so its winter runs are limited to dry sunny days.

During spring, summer & autumn it’s been driven in some appalling conditions - torrential rain on the motorway & also on roads with a lot of standing water.

Its over 8 years old now & still in lovely condition underneath. As others have pointed out, mud will accumulate underneath so it’s important to hose out the mud traps when cleaning the car - something I’ve always done since I got my first car.

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Thanks again for the replies and I will book the car in soon for its underseal treatment :+1:

How much does it cost to have done?

From what I’ve seen, prices vary from £300 to £600. The cheaper end will not have much preparation and is done in a shorter time whereas the higher end will have considerably more preparation and takes several days.

I paid £456 to have mine done in March 2012

I had both mine (2015 ND SE-L Nav & 2019 ND 30AE) done shortly after purchase, for the cost involved (£400/£500) is negligible when compared to the cost of the cars new.