Hi John,
You know the old 'give a man a fish......' story?
I don't know how to catch fish, but this may help you to set your tyre
pressures.
The general rule of thumb to find the ballpark for any given tyre on any
given car is that the tyre pressure should 'go up' from cold by about 4 or 5
pounds when the tyre is hot. So pick a nice sunny Saturday morning, rollout
the Healey, pick a cold tyre pressure, - say 28lbs in the rears and 30lbs in
the front- set the tyres to these numbers, take your pressure guage with
you, and go and drive your Healey on your favourite piece of road.
Preferably a non public road. After you've driven it in a spirted fashion
for about 20 minutes or so - jump out and check the tyre pressures by the
side of the road. Write down the cold and hot pressures. If the tyres went
up by 4 or 5 pounds - then thats probably perfect. If they all went up by
more than 4 or 5 pounds (eg lets say they went up by 7 lbs) - repeat the
exercise next Saturday morning but start at 2 lbs higher when cold (ie 30
rear, 32 front). If they didn't go up by 4 or 5 lbs (say they only went up
by 2 lbs) repeat the exercise next Saturday morning but start at 2 lbs lower
cold (eg 26lbs rear/ 28lbs front).
Get the idea?
That way - you get to sort out your tyres on your car - and have fun for the
next few Saturday mornings (in the name of serious research).... but just
don't do anything silly or dangerous.
: )
28R/ 30F would be as good as any number to start with - I tend to run my
A008Rs a little higher than that on the rack (around 38/39 hot); and the
Falkens lower than that on the road (about 26R 28F cold) to compensate for
the harder suspension. It becomes a compromise between comfort, chassis
longevity, and grip.
Once you get the temperatures right, you can much around with front to rear
pressure differences - depending on how the car handles, and how you want it
to handle - but generally I've found 2 lbs more in the front is a good rule
of thumb.
Generally, the higher the pressure, the better the grip - up to a point.
That point, on my A008s, is 40lbs hot - after that, the grip starts to
decrease again....
Hope that helps you to sort it out your tyre pressures.
Chris
www.myaustinhealey.com
----- Original Message -----
From: "John Snyder" <helyjohn@cablespeed.com>
To: <healeys@Autox.Team.Net>
Sent: Monday, December 27, 2004 8:07 AM
Subject: Tire Pressure
> Hello List,
>
> What is the collective wisdom out there on the best tire pressure to use
> in
> 185/70-SR15 Vredestein tires mounted on reproduction MiniLite wheels
> running
> w/ 23 psi pressure? The idea was that since these tires are wider than
> original and have a higher load rating, they should be run at a lower
> pressure
> than normal. My freshly restored BT7 MK2 has this set-up. It has what I
> would describe as a "bouncy" or "jiggly" ride on pavement that is less
> than
> smooth. The entire front suspension has urethane bushings, but this feel
> seems to come from the rear as much, or more, then the front. All four
> shocks
> have less than 1600 miles on them.
>
> This ride became more noticable to me when as an early Christmas present
> to
> myself I took back to back drives in the above car, my freshly restored
> BN7
> MK2 and my BT7 (MK1). Both those cars have 60 spoke wires and 165 tires.
>
> Any suggestions would be appreciated. TIA
>
> John Snyder
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