[Healeys] Speaking of tire Pressure

Chris Dimmock austin.healey at gmail.com
Wed Dec 16 06:06:14 MST 2009


The correct tyre pressure for your car is easy to calculate. And it's  
fun....
Assuming radials, start with 34 lbs all round. Cold. At night. When  
you haven't driven the car for 12 hours or more.

Next morning, on a warm day (that's almost any day in Australia!! -  
you Americans/ Brits may need to wait a few months...), find your  
favourite stretch of road, and drive vigorously. Then drive to a  
nearby old style shopping centre carpark/ school carpark (on a  
weekend) and do a few figure 8s at a reasonable speed (without being a  
complete hoon.....)

Jump out and measure your tyre pressure when your Tyres are the  
hotest  You are looking for a 3- 4 lb increase, and a max hot tyre  
pressure on road radials of around 38- 40. If they are say 40 at the  
front, and say 38 at the rear, write it down and go home.

Next day (12 hrs cold) make the fronts say 36 (from 34 cold, 40 hot)  
and rears  can stay the same (34 cold, 38 hot)

Best part - do it all again! Enjoy your Healey!! See what the pressure  
is after you've done it all again, and as long as you see a 3- 4 lb  
increase, with Tyres at full max temp, you have the right tyre  
pressure for your car....

If you started at e.g. 30, you'd possibly still end at 40 or maybe  
more. You need more air to start with...

You can get all carried away with tyre pyrometers. And spend a day at  
a track. Ive done all that. The results generally aren't much  
different, the pyrometer just tells you more, e.g. heat across the  
face of the tyre which e.g. helps with e.g. Camber adjustment and  
contact patch stuff. Which isn't easy to adjust.

But for most of you guys, just looking for some guidance on road  
radials, this method is pretty damn close.

And yes, the manual is talking about bias ply tyres. Not modern radials.

If this is all to compIex,  start at 36 front and 34 rear on the road.  
Higher pressure in the end which slides first. But I've never owned an  
oversteering Healey.... Unless I want it to...

And yes, tyres. Not tires. Read the manual. Guage isn't that relevant,  
it's the increase/ cold/ hot pressure relativity you need to focus on.

;-)

Chris
www.myaustinhealey.com

On 16/12/2009, at 10:51 PM, "Mark LaPierre" <lapierrem at sbcglobal.net>  
wrote:

> I have 3 pressure gauges that give me 3 different figures.   Which  
> one is
> correct?


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