south yorkshire
didnt rain for a couple of days after i did it- may just need a re-coat!
Water Beading On The Roof - Pic
- Thread starter Ian_Mac
- Start date
Let me be the one to put my head up and be shot at, but something is wrong here :thumbsdown:
So the science (lifted from Z4 authors that know a bit about it):
The BMW roof is a multiple layer structure (I refer to the power roof as the manual is thinner and different structure) The outer is 3 layers of polyacrylonitrile fibers, polythene fibers and underneath a butyl rubber layer. Below this polyurethane film and then inside polyethersulfone. In simple terms the outer fibres (the bit you see) reduces noise, the middle is waterproof and inner insulation and soundproof.
Bottom line is that the outer layer is not supposed to be waterproof!!! - it's a permeable layer and you've just defeated one of the key features of how it all works.
Might look good for now but IMHO not a good thing to do to a roof that will cost £1000+ to replace, has to last 10 years + must be flexible and stay good looking.
BMW make a perfect roof protector, as do Ragtopp. These are the top products and the latter is endorsed by pretty much every softtop company and neither of them cause beading of any sort (I know as mine is well treated with it). Tent waterproofers are designed for that - waterproofing a tent, designed to last for a season and usually to stop leaking caused by touching the inside of the canvas (I'm a keen camper and use this stuff on my tents...)
All I can say is stick to the correct stuff and not spray £5 tent protectors on it when the correct stuff is not much more expensive and proven.
Fire away
So the science (lifted from Z4 authors that know a bit about it):
The BMW roof is a multiple layer structure (I refer to the power roof as the manual is thinner and different structure) The outer is 3 layers of polyacrylonitrile fibers, polythene fibers and underneath a butyl rubber layer. Below this polyurethane film and then inside polyethersulfone. In simple terms the outer fibres (the bit you see) reduces noise, the middle is waterproof and inner insulation and soundproof.
Bottom line is that the outer layer is not supposed to be waterproof!!! - it's a permeable layer and you've just defeated one of the key features of how it all works.
Might look good for now but IMHO not a good thing to do to a roof that will cost £1000+ to replace, has to last 10 years + must be flexible and stay good looking.
BMW make a perfect roof protector, as do Ragtopp. These are the top products and the latter is endorsed by pretty much every softtop company and neither of them cause beading of any sort (I know as mine is well treated with it). Tent waterproofers are designed for that - waterproofing a tent, designed to last for a season and usually to stop leaking caused by touching the inside of the canvas (I'm a keen camper and use this stuff on my tents...)
All I can say is stick to the correct stuff and not spray £5 tent protectors on it when the correct stuff is not much more expensive and proven.
Fire away
srhutch said:
are we not advocating auto glym as well tHen?
used Autoglym on other soft tops and never had a problem with it. Not sure if the set up on the z roof could cause problems. Autoglym is a car product designed for the masses so i can not imagine it would be a problem on yours. As with previous post - now time to get shot down!
I'm sure Autoglym is just as good as any other proper roof protector.
The 'garage' argument makes no snse. Unless in an airtight garage the roof will dry anyway. Left in rain outside for a week they don't rot either. Even with beading some water will get underneath. The roof should breathe as designed.
The 'garage' argument makes no snse. Unless in an airtight garage the roof will dry anyway. Left in rain outside for a week they don't rot either. Even with beading some water will get underneath. The roof should breathe as designed.
A car will take a considerably longer time to dry when indoors and not subject to wind or internal heating. Over the winter months I regularly put the Merc away on a Sunday afternoon then when getting it out the following Saturday it would still be wet. After a short drive it would turn almost white where the road salt dried on the body work.
As mould only needs to 2 conditions to grow, moisture and a food source (which is found on almost anything) I'd prefer to leave my roof with as little moisture as possible when garaged for a week.
But each to their own....
As mould only needs to 2 conditions to grow, moisture and a food source (which is found on almost anything) I'd prefer to leave my roof with as little moisture as possible when garaged for a week.
But each to their own....
Ian - I cannot comment regarding what you do with a Merc. I have no idea of the composition of it's roof.
On the Zed I don't have the same experience at all. Mine is a daily drive, gets completely soaked and garaged. It's is pretty much dry the following day, regardless. The only water on it is the larger beaded drops on paint that don't dry easily. Of course water can remain under the rear seal regardless, but that outside this discussion. Left outside in Winter a Zed roof can easily be soaked for weeks on end and aside green on the lower rear seal I've never heard of mould on a roof.
All I point out is that what you have done is to partially defeat the entire methodology of the roof design by BMW with a product not designed for the job and post it as information/warning to others to let them decide from a position of greater knowledge.
As you say each to their own, but I repeat that I see no sense in stepping outside using the appropriate purpose made products on the roof
On the Zed I don't have the same experience at all. Mine is a daily drive, gets completely soaked and garaged. It's is pretty much dry the following day, regardless. The only water on it is the larger beaded drops on paint that don't dry easily. Of course water can remain under the rear seal regardless, but that outside this discussion. Left outside in Winter a Zed roof can easily be soaked for weeks on end and aside green on the lower rear seal I've never heard of mould on a roof.
All I point out is that what you have done is to partially defeat the entire methodology of the roof design by BMW with a product not designed for the job and post it as information/warning to others to let them decide from a position of greater knowledge.
As you say each to their own, but I repeat that I see no sense in stepping outside using the appropriate purpose made products on the roof
Wow, looks like this has caused much debate - I didn't know that the roof was structured so well, I'm used to a Porsche which needed sealing all the time! (and it still leaked!)
I've decided to go down the official BMW cleaner route - I just called my local Sytner BMW here in cardiff and they have the cleaner for £6, the guy on parts said with the Z4 you don't need to apply a sealant.
Thanks for all your help.
Soj
I've decided to go down the official BMW cleaner route - I just called my local Sytner BMW here in cardiff and they have the cleaner for £6, the guy on parts said with the Z4 you don't need to apply a sealant.
Thanks for all your help.
Soj