Mazda ND1, but question is open. its more about MOT and requirements…
I have an eye on getting a rear spoiler for my ND. but i am not a big fan of big (read as: tall) spoilers which look universal and stuck onto the back. i prefer a design which looks like it could have been OEM.
that said, i also want a functioning spoiler if i get one. its not for show, it needs to be adding downforce. hence, my sway towards the Verus as it has published data.
So to the question at hand:
I have eyes on a few different spoilers, 3 examples below.
Problem is, they dont have a relocation for the 3rd brake light (* one does, but in this example im looking at the design where its not moved).
is this an MOT failure? because the 3rd brake light location could be obscured to a following motorist by the spoiler itself?
followup question…
if the answer is Yes its a fail (or a likely fail), then would a suitable option be to wire in a new 3rd (4th) brake light further back. such as the red LED strip option?
such as this? (in this pic its wired to the rear lights, but could easily be wired to the brake lights instead)
reason for the ask - is that typically its the underside of a spoiler that performs the work. by putting a brake light mount i would probably be greatly diminishing the performance valve of the spoiler. so, trying to avoid.
I believe the answer to be no, lack of visibility of the high level/3rd brake light wouldn’t constitute an MoT failure.
This is covered under Section 4.3 of the MoT testing manual. It states that it isn’t a mandatory item, but that it should be tested for operation if one is present. There is nothing I can find that lists any testing requirement for the high level/3rd brake light to be visible. Again, I believe that to be because it isn’t mandatory to have one fitted, so no further testing stipulations are made.
“Additional stop lamps, over and above the obligatory requirements, must be tested.”
Hope this helps. Again, this is from my own reading and understanding of the requirements, so always up for debate and/or challenge!
I would say that testing them means that the tester has to see them from the rear of the car. In the case of the black car the 3rd brake light would be seen, the red car not so much.
However the real question is how well low boot spoilers are going to work and I would say not much. Which is why the Verus is the height it is to be in the airstream to work effectively.
You are correct over the led strip light if its being obscured then you might depending on the test get a fail moving 3 brake light might be a factor … which I thought of doing with mine however I in the end installed some led lights into the spoiler its self on my build mines only cosmetic anyway so but you still have to make it Compliant and insurable …thing to do is ask at the local testing station …
thats the bit i was trying to find (and, doesnt seem to exist)…
i mean, its ‘‘common sense’’ that if your brake light isnt visible, then that a fail. but based on what measurable criteria? does the tester put his eyeline at car-height 10meters behind the car? does he turn the garage lights off to see if illumination is clearly seen in the dark?
etc.
if theres no specific criteria, then it cant be a pass or fail. ?
As said above, if there was a visibility criteria I would expect this be outlined in Section 4.3 of the MOT testing manual. But there is no such stipulation regarding visibility, that I can find.
just what I was told at two MOT testing stations in rugby it seemed to be if its fitted by the manufacture and is still on then it must be working and visible …not my way of looking at this anyway thats why I lowered my small wing so the third light could be seen and also added some leds on the tail of the wing just belt and braces the insurance was the hard part the amount of extra coin they wanted was eye watering …say that the 5 is pretty low most cars Ride higher than the 5 so the 3 light should be easy visible I think its the MOT tester on the day …
so if your at this level my 3rd blight is not visible how ever sit behind the car in my vw Polo you can easy see it …who knows I think its pot luck …!
Made the hole wing its two part hollow less then 3lbs in total bonded together then carbon fibre hydo dipped the mounting struts are hollow aluminium the wiring for the lights runs through them
No spoiler will give useful downforce. A wing will, if it’s at least 18" above the boot and preferably 10" behind the car with very strong mountings through the boot. The one in the pic with the grey car goes some way towards that.
Remember you’ll need a front splitter to balance the rear downforce to avoid building a big understeery thing. Possibly bonnet vents as well as they reduce front end lift as well as helping get more air through the cooling system.
And that if you add any useful downforce you’ll need to look at spring rates and strengthening suspension mounts. And suitable tyres.
And then, if you’re (presumably on track) going quickly enough to create downforce, you’ll need to re-learn your braking technique as the more you slow the car approaching a corner the more you’ll have to slow it again because you’ve lost the downforce.
Many years ago I was told exactly the same philosophy by a friend who was into sprinting at places like Santa Pod. He was actually a biker running a supercharged Triumph, but moved in all the right circles to pick up specialised knowledge, almost to the point of being OCD.
He was commenting on the spoiler-like thickening with a hint of up-tilt in the centre on the “boot lip” below the sloping back window of my old FE Victor estate’s tailgate, as designed by Vauxhall.
He pointed out it was inspired by the Kammback and reduced drag factor by cleaning up how the air left the slope and met the vertical rear of the car.
Compared with the normal pictures I’ve seen of cars claimed to have Kammback the FE Estate flow-break-point was very subtle and almost non existent, but GM were using the idea on other cars of the 1970s.
I don’t know if he was correct, but driving in the wet on the motorway one could see two well defined spray vortices in the mirror and no random turbulence. Was this good or bad?
I can’t find a good pic to show this detail, but (apart from those horrible little wheels and tyres) the car looked almost exactly like this one I found on the web.
