hydroplaning

[Lawrence C Leung]

Phil,

This post is one of the many reasons we'll miss you. Virtually no where
in the US would we even be able to talk about double decker busses!

Even still, we will all miss your personal anecdotes, and your tremendous
knowledge of Audi's. 

I'm glad you've found a better calling. As I've said before, do keep in
touch, NAC or not. We love hearing your stories.

LOL,

LL - NY

On Wed, 31 Jan 2001 19:08:55+0000 quk at isham-research.freeserve.co.uk
writes:
>>> that'd be a contact patch of 20 sq. in. at 40 psi.
>>> For 8" wide tires, the rectangular length of the patch would
>>> be 2.5".  Ok, sounds fine.  Now reduce the pressure to 10 psi.
>>> The expected length would now be 10".  Not likely.  But, ok,
>>> reduce the pressure to 5psi. I guarantee you won't see a 20"
>>> long contact patch!
>
>> the formula works until you are either riding on the rims or, 
>slightly
>> before that, the crumpled up sidewalls.
>
>Sidewall-floor contact comes much earlier than that.  Your 8" wide 
>tyre
>becomes a 10" wide tyre long before it's deflated to 10 psi.  At 5 
>psi
>it's on the rim.  Look at the pressures (around 60 psi) used in the
>emergency spare.
>
>>> The problem with the simple load x area assumption is that
>>> it implies that the tire doesn't exist.  The air is *not*
>>> supporting the car.  The *tire* is supporting the car, and
>>> the air is giving the tire it's shape.
>
>> the air is supporting the car.
>
>I've noticed they go down quite a lot if you take the air out of the
>tyres.  A trick used frequently where I used to live - to remove 
>stuck
>double-decker omnibuses from low railway bridges when the driver 
>forgot
>he wasn't driving a single-decker.
>
>(For the locals - the Barton Bus Company's '15' route to Sawley.  The
> single-deckers could go straight down the A453 Tamworth Road, the
> double-deckers had to take a diversion.  Except, every now and then,
> a driver would forget and they'd have to let the tyres down to get
> the bus back out.)
>
>--
> Phil Payne
> http://www.isham-research.freeserve.co.uk/quattro
> Phone +44 7785 302803   Fax: +44 7785 309674