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Bonnet lifting at high speed...help!

Posted: Mon Dec 07, 2009 7:07 pm
by matt9111
I took the 5 for a spin on the weekend and I've noticed that when I get above 130km/h the bonnet begins to lift at the front. When I'm doing around 200km/h there would be a gap of around 5-8cm at the front. Has anyone experienced this before? It's bothering me because I feel like the bonnet latch is going to let go and then who knows what will happen. I've been suggested bonnet pins, but I don't like the look of them so are there any other idea's?

I've wound down the rubber bonnet bushes to as low as they go, so the front of the bonnet is now sitting below the front bumper and it helped a little but still not enough for my liking.

Cheers

Matty

Bonnet lifting at high speed...help!

Posted: Mon Dec 07, 2009 7:56 pm
by Hammer
I hope you weren't doing those sort of speed on public roads :?

Bonnet lifting at high speed...help!

Posted: Mon Dec 07, 2009 9:04 pm
by matt9111
No way, never want to hurt anyone

Bonnet lifting at high speed...help!

Posted: Mon Dec 07, 2009 9:14 pm
by lowmiata
Um.. if your bonnets lifting 5 to 8cm you'e got more than a slight problem!

or did you mean 5-8mm?

if its 5-8mm the next question would be how are you measuring it :shock:

anyway some panel deformation/lifting may occur at that speed the amount of air going into the front of the car needs to ge somewhere and not all of it will go down!

if it bothers you that much you can put a secondary retraint on it just a bit of chain with a snap lock hook or something similar, the bonnet lock you have from factory is a well designed(tried and tested) and for it to fail mechanically would mean something has gone wrong in the manufacture of it or someone has pulled it apart maybe and it has not gone back together properly

that being said if you have wound the bumpers down you probably now have a gap and the bonnet will chatter in the latch (causing a sensation that the bonnet is moving)

simple result? look past the bonnet or slow down? :P

seriously I wouldn't worry about it if your doing 200kph (in a controlled environment of course) there is other more important things you need to be focused on!

Bonnet lifting at high speed...help!

Posted: Tue Dec 08, 2009 12:48 pm
by Juffa
Not sure on the NB, but on the NA you can move the main hood catch up or down to reduce any movement. I would lower the catch to where the hood is sitting in line with the bumper and then raise the rubber buses so that the hood is held down onto the bushes by the catch, while still be aligned with the bumper. I know that the hood is locked down tight if the only way I can close it is by dropping it from 4 feet. Also, check the metal hook thingy on the hood that is grabbed and held onto by the catch. These can wear if there is excess movement and allow even more movement.

J

Bonnet lifting at high speed...help!

Posted: Tue Dec 08, 2009 12:58 pm
by daffyflyer
good to make sure it stays down - the other MX5 at marulan last sunday had the bonnet flip up and bend itself over the windscreen :shock:

Had bonnet pins but no latch, looks like someone forgot to pin it


Dented the sh*t out of the bonnet, but was able to close after they punched it straight!

Bonnet lifting at high speed...help!

Posted: Tue Dec 08, 2009 1:14 pm
by rascal
matt9111 wrote: I've been suggested bonnet pins, but I don't like the look of them so are there any other idea's?


What about the flush mounted bonnet pins. (ala aerocatch) If colour matched to bonnet then they're not very noticeable at all..

Bonnet lifting at high speed...help!

Posted: Tue Dec 08, 2009 1:18 pm
by daffyflyer
Davex3 wrote:How are you managing to measure the gap and drive at the same time? :shock:

I think there is some serious macgyver sh*t going on here. :mrgreen:



Plastigauge?

A ruler on a stick?

A friend to climb out on the bonnet @ 200kph and measure? :P

Bonnet lifting at high speed...help!

Posted: Tue Dec 08, 2009 2:24 pm
by Mr_Q
daffyflyer wrote:A friend to climb out on the bonnet @ 200kph and measure? :P

Never do that! The bonnet is aluminium and could dent. :P

Bonnet lifting at high speed...help!

Posted: Tue Dec 08, 2009 2:31 pm
by Fatty
Mr_Q wrote:
daffyflyer wrote:A friend to climb out on the bonnet @ 200kph and measure? :P

Never do that! The bonnet is aluminium and could dent. :P


:lol: :lol: :lol:

Bonnet lifting at high speed...help!

Posted: Tue Dec 08, 2009 2:52 pm
by hks_kansei
Image

=

Image

Bonnet lifting at high speed...help!

Posted: Tue Dec 08, 2009 4:10 pm
by rascal
hks_kansei wrote:Image


An improvement on Chris Bangles designs..

Bonnet lifting at high speed...help!

Posted: Tue Dec 08, 2009 6:13 pm
by AJ
I'm just impressed that someone found a straight stretch of road that is long enough for an old NB to actually hit 200....................does it parallel the Nullabor or something??? :lol: :mrgreen:

Bonnet lifting at high speed...help!

Posted: Tue Dec 08, 2009 6:15 pm
by d-mag
rascal wrote:
hks_kansei wrote:Image


An improvement on Chris Mangles designs..


Fixed. :D

Bonnet lifting at high speed...help!

Posted: Tue Dec 08, 2009 8:06 pm
by matt9111
Lol, I measured it with a ruler on a stick! I guesstimated it, but i'm a land surveyor so my estimation of distances is pretty because that's what i'm paid for.


Now anyways, I don't have any race tape and Safeway and Coles have sold out so im buggered, basically, lol.

Can I get like a two latch setup?

Cheers

Matty