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Sound Insulating Sheets And Rust.

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#1 SolarB


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Posted 03 May 2017 - 12:12 PM

The Mini's coming off the road for a major re-furb soon and this will include my first attempt at sound insulation.

The self adhesive sheets look like a sensible option but I'm wondering about water getting under the sheets on the floor and promoting rust. My Mini seems better that many for staying dry but I have visions of the floors rotting out in a few years after water has crept underneath the sheets.

I've seen some sound deadening paste that would probably solve this problem, has anyone used a paste on their floor panels before applying mats on top?


#2 nicklouse


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Posted 03 May 2017 - 12:28 PM

your floors will already have insulation "sheets" on them.

#3 SolarB


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Posted 03 May 2017 - 03:00 PM

No insulation (new floor pan a few years ago). Not sure when Leyland started applying the insulation but my '72 Mk.III never had insulation.

#4 roberts


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Posted 03 May 2017 - 06:56 PM

I installed Dynamat throughout the interior of my Mini (every single panel covered by a trim panel - including the floor, sides and roof) when I was 18 ish, after reading all about it and listening to mates (with modified cars) who had installed it. It was very new back then (around 2002 ish) and had only just arrived from America.


I massively regretted it pretty much instantly...


1) It didn't reduce road noise, the Mini is the shape of a brick - so if you drive at anything over 60mph it makes no difference to the air smashing against your upright windscreen (which is what creates a vast majority of the noise).


2) When driving my sound system sounded no better (it was better when I was parked up... but how often do you listen to music when your stopped, unless your at a red light, in a traffic jam etc.).


3) I'm now in the process of the restoration and removing it was the worst job I've ever had to do (I actually got the apprentice to do it a few years ago, so what I really mean is... it looked like the worst job in the world).


It did reduce panel vibration though... but personally I actually like rattles and vibrations with old cars, if you want a car that doesn't rattle or vibrate, get something modern.


I would like to add that I have since plastered one of my cars (a Civic VTi I had about 6 years ago) and we also recently lined the entire works VW T5 with a closed cell foam... both worked brilliantly, but both are modern vehicles with flat panels. My experience with the Mini was that it didn't work in the real world - it worked great when your not moving, which basically meant it made no difference to the experience of actually driving the Mini. Whereas with modern cars, it does reduce road noise and improve the driving experience (if you want your car to be quieter from the inside).


If you do want to go ahead and do it we (here at Optimise), would recommend the sheets of closed cell foam (not the foil faced product)... it's what we use on the van linings and it works brilliantly. Depending on your budget either go for a general closed cell foam or if you have money to burn go for the closed cell foam Dynamat product (I'm not sure what they call it sorry).

#5 SolarB


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Posted 04 May 2017 - 08:03 AM

Many thanks for the detailed reply.

The car has a horrible low frequency drumming noise experienced by the rear passengers. It's very localised and when driving I can only hear it if I lean my head a few inches further back than normal. I suspect it's the stainless RC40 exhaust but a switch from the traditional rubber bobbin exhaust hangers to the more modern rubber loops has made no difference. The car has no bitumen like insulation pads on the floor or rear seat base and as it's a MK3 has a solid mounted front subframe.

I'm not aiming for Rolls Royce sound levels, just an elimination of the drumming and a general lowering of the other noises. After reading your reply I'm now leaning towards:
Dymat like pads on the rear seat base and back.
Dymat like pads in the front and rear foot well areas.
Layer of closed cell foam under all carpeted areas.
Something (type TBC) on the engine bulkhead (inside, not engine bay side).

#6 jamesquintin


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Posted 04 May 2017 - 02:22 PM

​I'm am currently in the middle of restoring my MPI and I am getting the original shape sound reading panels made for my car. Hopefully I can get more made and start selling them. I've got the templates, just need to source some decent material...

#7 greenmini1275


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Posted 04 May 2017 - 06:01 PM

I'm in the process of fitting sound deadening to my car, so far I have filled the speedo binnacle with closed cell foam, which actually makes a difference on a centre binnacle car. Next in going to be doing the dash area on the inside and then the engine side bulkhead. I'll be going for the closed cell foam, probably 10mm think all over everywhere that you can't see. I'm hoping my wife will be happy with that.

#8 vx220


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Posted 05 May 2017 - 12:11 AM

There's a guide here...


To prevent drumming/vibrating of panels you want the butyl/foil stuff (silent coat is popular) and give any panels that vibrate a 25%-30% coverage by area. It's not twice as good with two layers, so don't bother. It is more effective in one large sheet rather than several small pieces!

To really kill road and tyre noise that comes through panels, you need an MLV barrier layer. This is heavier, and actually blocks noise (Closed Cell Foam doesn't block sound, neither does dynamat type stuff). You do need the CCF however, as it stops the MLV buzzing against the floorpan.

Wind noise is just about untreatable, as said above. Worth checking door seals and fitment though, as this can have some effect.

#9 vx220


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Posted 05 May 2017 - 12:14 AM

Couple more points...

Unlikely to get water under deadening sheets, as you heat them to seal them down.

If possible, worth an extra layer or two of CCF under people's feet. Apparently structurally borne vibrations coming up through your feet and legs are as annoying as airborne noises

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