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Discussion Starter #1
Hi all,
I have recently took delivery of my 12C in January this year, the car has been more than an awesome experience. I live in a city state and the car has to negotiate a lot of humps. The car has no problem going over most irregular road surfaces but it would often scrape lightly over those narrow and high humps. So I sent it to the dealer and they raised up and pointed to a pair of aerodynamic plastic part that is about 40mm in height mounted to the underside of the chassis tub towards the front and another pair in the rear. Only the front pair is scrapping the humps. I tried to circumvent the issue by setting the chassis settings from 'Sport' to 'Track' mode to stiffen up the suspension but it still scraped occasionally but thankgoodness the part is not damaged as seen from the picture I took of my car. I heard that many owners have provided feedback about theirs being damaged and cracked and several had the front pair removed altogether.

Can anyone explain the aerodynamic benefits of this particular part?
Will it make a huge difference if it is removed?
Thanks in advance.
 

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Hi all,
I have recently took delivery of my 12C in January this year, the car has been more than an awesome experience. I live in a city state and the car has to negotiate a lot of humps. The car has no problem going over most irregular road surfaces but it would often scrape lightly over those narrow and high humps. So I sent it to the dealer and they raised up and pointed to a pair of aerodynamic plastic part that is about 40mm in height mounted to the underside of the chassis tub towards the front and another pair in the rear. Only the front pair is scrapping the humps. I tried to circumvent the issue by setting the chassis settings from 'Sport' to 'Track' mode to stiffen up the suspension but it still scraped occasionally but thankgoodness the part is not damaged as seen from the picture I took of my car. I heard that many owners have provided feedback about theirs being damaged and cracked and several had the front pair removed altogether.

Can anyone explain the aerodynamic benefits of this particular part?
Will it make a huge difference if it is removed?
Thanks in advance.
The only thing that I've heard RC33 about those little thingy's is it diverts air around your tires. I'm not sure if it has any other significance to the performance or enhancement of the car. Cheers......??
 

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Many or most of these get damaged,the scrapping is as extreme has suggested,its the 2 front rubber moulding that creat the noise,not what you are pointing out.These can be replaced at mimimum cost,but they are designed for high speed track work for the balance of the car with airflow,its the mclaren attention to detail,but its unlikly to cause any problems except to the extreme track junkies on the limit:)
 

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Hi all,
I have recently took delivery of my 12C in January this year, the car has been more than an awesome experience. I live in a city state and the car has to negotiate a lot of humps. The car has no problem going over most irregular road surfaces but it would often scrape lightly over those narrow and high humps. So I sent it to the dealer and they raised up and pointed to a pair of aerodynamic plastic part that is about 40mm in height mounted to the underside of the chassis tub towards the front and another pair in the rear. Only the front pair is scrapping the humps. I tried to circumvent the issue by setting the chassis settings from 'Sport' to 'Track' mode to stiffen up the suspension but it still scraped occasionally but thankgoodness the part is not damaged as seen from the picture I took of my car. I heard that many owners have provided feedback about theirs being damaged and cracked and several had the front pair removed altogether.

Can anyone explain the aerodynamic benefits of this particular part?
Will it make a huge difference if it is removed?
Thanks in advance.
I have the same issue whenever I go into the carpark at work. I spoke to McLaren Singapore and told me it was no biggy and as the other guys are saying, you can have them removed without it being a big deal for day to day driving. I've kept them on, am used to it by now!
 

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One advantage of the scraping is that it is an 'early warning' that you are reaching the clearance limit of the undertray.

I ignored it and took the front undertray off so Mclaren relieved me of £600 or so for its replacement plus the two front rubber bits and the two plastic ones ahead of the rear wheels.

So my take is to enjoy the noise and take heed of it!
 

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One advantage of the scraping is that it is an 'early warning' that you are reaching the clearance limit of the undertray.

I ignored it and took the front undertray off so Mclaren relieved me of £600 or so for its replacement plus the two front rubber bits and the two plastic ones ahead of the rear wheels.

So my take is to enjoy the noise and take heed of it!
Sorry to hear about your negative experience roundincircles, its loss in a sense for you yet a gain for any of us that are reading about it. Much appreciated and admittedly that is way this forum comes in handy. Cheers.....??
 

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Is it the small bend plastic thingy that scrapes?
 

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Is it the small bend plastic thingy that scrapes?
Just for clarity, the front ones are made of a flexible rubber like material and thus can be deflected. The rear ones are hard plastic and will shatter if grounded........my car is on a second pair of rears and third pair of fronts.

No real problem as they are relatively inexpensive.

ps solid rubber can not be compressed, only displaced. Hence the old Chinese proverb, If a Mclaren MP4-12C is grounded it displaces the content of your wallet with empty smiles.
 

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We got some impressive speed bumps over here and I never heard them scrape. She does sit quit high and wanted to drop her but... Still don't know how. I never tried an underground parking either and not so sure I'd want to do that.
 

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Discussion Starter #11
Is it the small bend plastic thingy that scrapes?
Yes, as can be seen from the the picture above, the plastic piece is mounted on the carbon chassis and located trailing the front wheels and axle. This part may scrape when the car and suspension dips whenever the car negotiates over a high but narrow hump.:(

There is another similar piece located at the rear but does not pose a problem because it is located inline with the rear axle.

The feeling between this plastic scrape is somewhat different from the 'rubber bumper' fore of the front wheels that can be normally experience whilst entering a raised ramp or under extremely hard braking in Normal mode.

I can accept the rubber rub but not the plastic scrape.:(
 

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Yes, as can be seen from the the picture above, the plastic piece is mounted on the carbon chassis and located trailing the front wheels and axle. This part may scrape when the car and suspension dips whenever the car negotiates over a high but narrow hump.:(

There is another similar piece located at the rear but does not pose a problem because it is located inline with the rear axle.

The feeling between this plastic scrape is somewhat different from the 'rubber bumper' fore of the front wheels that can be normally experience whilst entering a raised ramp or under extremely hard braking in Normal mode.

I can accept the rubber rub but not the plastic scrape.:(
The other thing I actually noticed is that whilst not entirely paying as much attention as I should have one day, I went over a carpark speed bump a bit quicker than I meant to and hey presto, no scraping noise.... I think I go over the bumps so damn slow that it kinda produces a 'beaching effect' which then causes the scape.

Certainly McLaren here when I did my first drive were encouraging me to take speed bumps fairly briskly although certainly not advocating anyone just point and shoot........! :D
 

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Not sure that Mclarens technical name for them is "plastic thingy"...but i could be wrong...

Both are there to move air around in the right way and so prevent lift at the front which in turn increase down force.
 

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Discussion Starter #14
The other thing I actually noticed is that whilst not entirely paying as much attention as I should have one day, I went over a carpark speed bump a bit quicker than I meant to and hey presto, no scraping noise.... I think I go over the bumps so damn slow that it kinda produces a 'beaching effect' which then causes the scape.

Certainly McLaren here when I did my first drive were encouraging me to take speed bumps fairly briskly although certainly not advocating anyone just point and shoot........! :D
I agree with you that 'flying' over the humps may clear the 'plastic thingy' altogether.:p... but it is not so realistic to do that all the time when there are pedestrians and traffic around us. It's the beaching effect scrapes that causes discomfort sensation going up my spine.:(
 

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It's all about the shape of the speed hump, suspension settings, additional weight within the vehicle and how fast you are travelling ..... If it's a narrow but tall hump, you have the suspension in it's normal setting, have a hefty passenger in the vehicle and are going at more than just a snail's pace then you'll have a problem. The car will still be travelling downwards on it's suspension as you travel forwards after the front wheels have gone over the hump and hence the air deflectors BEHIND the front wheels will catch the top of the speed hump. In fact, if you get it really wrong you will smash them to bits (I have experience of this). Sport or track setting for the suspension helps (as has been stated) as the downward travel isn't as great. If I have a passenger in the car and encounter such a hump (the humps here are designed to slow down modified Nissan Patrols so can be quite extreme) then I hold the car on the brakes as the front wheels pass over the hump and slow it all right down .... scraping problem solved.

The faster approach does work for the wider speed humps.
 

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Getting over speed bumps is almost becomming a science. Fortunately or unfortunately my hearing is not too well so experience less problems than others perhaps.
 

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Discussion Starter #17
As can be seen from the picture posted below, I had my trusty specialist from the local dealership removed the air deflector plastic thingy from the chassis and trimmed off about 25mm off the height from the rear trailing edge ... only the rear 60% half section (as indicated by the white marker spot in the picture) is causing the 'beaching' and scrapes over high and narrow speed humps.

I experimented the mod by driving over the usual trouble humps at the same approach speed and I never felt the sensation of plastic 'crashing' over the humps henceforth.:cool: I was nonetheless delighted.:p

It is a simple mod after some thought that resolves the problem but hopefully still retain some attributes of deflecting air trailing behind and around the front wheels whilst serving its intended aerodynamic purposes.;)

I hope this suggestion can save our forum members some costs towards the repeated replacements. :D
 

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Two bad the factory can't figure these things out; we'll probably see this in about 18 months, at the paralyzed snail's pace that they rectify problems.:p
 
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