Why does my crash helmet try to lift of my head at about 140mph. and also how can i stop it.( on the track of corse)
Do the strap up!
get one that fits you sounds like its too big for you
I,d say if its actually lifting that much then its too big.
cheers
andy
I would guess it is an offence under the road traffic act to play with your helmet at such speed.
Or,are you just telling us you have travelled at such speed and have no idea of aerodynamics
Its a good fit and the strap is done up tight.
quote:
Originally posted by madteg
Its a good fit and the strap is done up tight.
Buy a windscreen
Is it a motorbike helmet, or a car helmet... I read somewhere that it can make a difference.
Particularly (apparently) if it's a 'sports' bike helmet as it's designed for airflow passing over your noggin whilst it's
buried low-down by the tank!
On the face of it, it makes some sense, but could equally be a pile of poo...
Get a Car racing helmet that has aerodynamics on it, bike helmets always tend to lift up as car purpose helmets don't. As bike helmets are designed for you to be facing more downwards.
That would cut the top speed by acting as an air brake and thus solve the problem.
Paul
quote:
Originally posted by mangogrooveworkshop
Buy a windscreen
assuming it's a bike helmet, Buy a car helmet 
Huge difference to how they work with wind at speed in a kitcar, speaking from experience.
looks like i have to get a new helmet then. Thanks guys.
I get this too, although in my case the helmet goes "light" before 140mph.
I've always put it down to the fast air over the top of the helmet being at lower pressure (standard sort of wing effect).
Single seater helmets often have a sort of "bill" that I guess is designed to counteract this effect. They can also have spoilers and
stuff.
I guess the bit at the bottom serves some aerodynamic purpose.
Solution is to drive slower, or maybe put a DIY spoiler on the top of your helmet (although be careful with glues on these things).
Personally I quite like the effect.
Matt
Will be the bike helmet in a car! At 140mph im assuming you are talking about the back straight at Bedford?
I have a car helmet V2 pro with the lip round the bottom for down-force to keep your head on lol but also half doors and mine was fine! wasn't
as fast as you though i hit the rev limiter at 137mph
I wore a bike helmet once in my car - to SVA and back. At anything above 70mph, it was like someone trying to pull me out of the car by my head - I just wear goggles now, which is fine up to max speed
If your helmet pulls it's too big, nothing to do with it being a sports bike helmet or any other bike helmet. Full face helmets for sit up bikes and crotch rockets are exactly the same and if they are too big they will lift whatever you drive, car, sports bike or cruiser even if you strangle yourself with the strap.
quote:
Originally posted by Peteff
If your helmet pulls it's too big, nothing to do with it being a sports bike helmet or any other bike helmet. Full face helmets for sit up bikes and crotch rockets are exactly the same and if they are too big they will lift whatever you drive, car, sports bike or cruiser even if you strangle yourself with the strap.
Yeah I got this as well although not since I fitted an aeroscreen. The aeroscreen is just high enough to stop air hitting my neck and then presumably
pushing up inside the helmet. Now the airflow hits at about eye-level and the buffeting is much reduced and the helmet no longer lifts. Do you have an
aeroscreen of any kind?
You know you should have made the title of this thread, "Helmet suction at high speed". You would have had loads more people reading it...
http://www.soloracer.com/zeroninez9akr.html
http://www.soloracer.com/zamprz31.html
I've got the second one. Most comfortable thing you'll ever put on your head. And LIGHT.
I agree with Mark on tight helmets.
I have Big Head, and found it difficult to get a helmet that was large enough just to get on, let alone be loose!
Its all in the aero dynamics.
Try a fly screen first! It makes a lot of difference, and a bit of plastic temporarity fitted to the car (LOADS of Gaffa Tape?) for a test will cost
you nowt. Decent helment doesnt come cheap. It will at least help you to decide if its a helmet aerodynamics job or not.
Final parting shot... Try a couple of Bungee cords from your Helmet to the underside of the seat. That will stop your helmet rising at high speeds
Its a Lo-Cost solution as well.
If you look in the Demon Tweeks car parts catalog you will find aerodynamic parts forcrash helmets
Make a splitter out of plywood and glue it to the top of your helmet. That should help the airflow! Something A3 sized would be fine!!!
i have the same problem even have to tape visor shut , tried various helmets , have aroscreen , the wind just seems to hit in wrong place , the faster you go the more you have to tilt your head down ,if i get i cured i will let you all know
This tHE sole reason I fitted the fly screen to my car
It started lifting at around 70
Fit a windscreen and more power!
on a bike there are several helmet types, head down and head level.
i have in the past given a helmet away as it was a level head hat and no use on a sportsbike, as i rode the bike i could only look through the upper
1/3rd 1/4 of the visor, i'd suggest a well fitting Arai as these tend to be a head down hat and should limit the upper lift.
only problem, arai hats are expensive and don't fit everyones head and nose shape.
best of luck
Regards
Ewan
quote:
Originally posted by BigLee
Make a splitter out of plywood and glue it to the top of your helmet. That should help the airflow! Something A3 sized would be fine!!!
As people have said, the helmet is lifting because the top surface of it is acting like an aeroplane wing. Shielding yourself from the wind with a
larger screen is one way of fixing it. Another is to fit a spoiler to the back of the helmet at the top to 'square-off' the otherwise round
shape. Race car helmets are often squared at the back like this, but it's harder to do for bike helmets because of the variations in posture and
because you're not supposed to have anything on the lid that can catch and snap your neck if you're rolling across the ground in an
accident. Nice.
The type of spoiler looks like this:
not sure its all down to a bike helmet, im more likely to think its a badly fitting lid, I raced bikes, then went on to 250 superkarts where your
head is always being pulled off and never had any helmet lift issues wearing various motorbike arai's over the years and we were in a real non
bike position with our heads no probs including averaging over 117mph at Thruxton and pushing 160 mph down the back straight with no windscreen etc,
just got neck ache 
if its a crap lid they can feel tight when you are stationary but add a 100mph and its a bit different. just my 10 cents )