Car magazine tyre test results??

[redwon]

I had Owen fit a set of Bridgestone Turanza's 2 months ago to my Legacy GT
and he told me the same thing - set the
presures at 40 - 44psi.When driving home from his shop the car felt like I
was driving on marbles- no feeling
in the steering and wandering all over the place which it hadn't done with
the worn Grid 2's.
Next morning I checked the presures cold that he had set - LF 44,RF 40,LR
39,RR 42,
I reset them all to 37 I had been using and the car totally different -
steering felt great ,no wandering
and on a trip to Whakatane with the car loaded with dive gear it handled
great with a quiet ride.
The 44 psi Owen talks about is the maximum allowable presure for the tyre.My
advice is to experiment
and go with what feels right to you.
Cheers

Steve Easdon
Production Planning
Amcor Cartons Australasia
12-14 Lockhart Place
Mt Wellington
Auckland NZ
Ph: 64 09 9793833

[zorruno]

David Moughtin wrote:

Owen at Performance Tyres fit a new set of Grid 3s to my car on
Saturday (185/60/14). He does appear to be very knowledgeable on the
subject of tyres, and his recommendation is that they be set at 40psi
when cold - they increase to around 44psi after normal driving.

He also suggested that I have the wheels aligned, not to the car
manufacturer's specifications, but to the requirements of the tyre.
What are your thoughts about that idea.

David Moughtin

Owen says that to me too, I disagree with him and get him to set them a
little lower at around 36 cold. I settled years ago on running my
bridgestones around that pressure (which some people still think is
high) but it suits me for my 205/45 16" which I've always had.

Alignment is also personal preference, but it is cheaper to see the
benefits & disadvantages of changing tyre pressures rather than
alignment settings every week (unless you own alignment kit...or shares
in Pedders).

I'd start with a tried and tested setting for alignment from another
enthusiast with similar driving needs (e.g. every day driver/track only
or whatever - even if they don't have the same tyre size/brand) and if
it feels less controllable or chews up tyres tweak the settings
slightly. It also obviously depends on how often you want to replace
your tyres, as wear is a big factor with agressive alignment settings.

cheers
zorruno

[jeff]

IIRC, the autocross method is to check tyre temps in the middle and both inside/outside edges, and adjust pressure/alignment/driving-style until temps are even. Rather than using a zillion-dollar tyre pyrometer for this, I just use my hand to get in the ballpark (usly 32-36 psi) , so to speak

Owen also reckons that low profile tyres made his rx7 accelerate faster, I think most 1/4-mile racers use very high profile tyres instead... he probably put on smaller and/or stickier tyres, methinks.

Nice guy tho!


David Moughtin <Davidm@Snackmate.com> wrote:
Owen at Performance Tyres fit a new set of Grid 3s to my car on Saturday (185/60/14).
He does appear to be very knowledgeable on the subject of tyres, and his recommendation is that they be set at 40psi when cold - they increase to around 44psi after normal driving.

This seems a much higher pressure than I have heard discussed before. The ride is not too harsh - Owen was also able to tell me that from the state of the Kelly tyres that he took off, my driving does not excite the car anyway, although aren't Kellys supposed to be caressed and cherished? - but what do I know.

I would be interested to hear comments on running at this high pressure.

He also suggested that I have the wheels aligned, not to the car manufacturer's specifications, but to the requirements of the tyre. What are your thoughts about that idea.

Thanks

Regards

David Moughtin

[poison]

My two cents...

I did an advanced driving course at bay Park years ago and
they had us up all the tyre pressures to about 36-40 PSI.
The reasoning explained in this case was that many car roll
overs occured when the tyre starts to roll under the wheel
and the rim digs in causing the car to roll (assuming you
didn't end up in a ditch first).

From personal experience on this course I tried 30, 36 and

40 round the cones on a wet track. The 30 to 36 was an
improvement but I spun out with 40PSI, the 40 was the most
fun for sliding (this seemed to be the purpose of the
training) but didn't give me any confidence on the road.

At high pressures such as 40PSI on everyday roads, you're at
the tyres limits, and I'd assume raising the risk of a
blowout on a pot hole or something. I had a right rear blow
out on the desert road at some speed (I'll plead the 5th on
the actual figure) and it was not nice at all. At least my
motor mouth hitch hiker shut the **** up for the rest of the
trip.

Moderation 36 PSI

Gazza

"PO1SON"
[...]

[Colin]

And my two cents...

Tyres have changed considerably in the last few years. I can remember
going to compete at Manfeild with road tyres of the 185.60.13.variety
and using 45 psi cold. This was mainly to try and induce some side
wall stiffness into the tyre to keep as much of the surface as
possible touching the tarmac and to reduce rollover. Modern high
performance road tyres used on the track can be treated very
differently. I have used various sizes and types and suggest that a
temperature (pressure) used brilliantly on the road is seldom
effective on the track. This is also true the other way.
Road temperatures are far lower than those generated on the track.
This often means that a Lower pressure is used to generate more heat
to get the tyre into its 'best' range. Low pressure = tyre works
harder=generates more heat=increases pressure.

I agree with zorruno that changing pressures (temperature) is an easy
and very effective mod. Particularly if the car is mainly used on the
road with just a little track work. ( could look at other tyre/wheel
combinations)

I also use 205.45.16 on the road. The small profile means that I do
not need to use high pressures to retain sidewall stiffness and to
keep the tyre squareish. They are also modern high performance tyre
and have very good even heat dispersion qualities and are made of
excellent compounds for traction.
As a compromise for the variety of surfaces we have in NZ (seems to
change inch by inch) I use 30 -32 cold depending on loading. To use
these tyres on the track I would raise them at least 4-6 psi cold and
check them immediately at the end of the session. Looking for a 4-6
psi increase when hot. More than that - increase pressure 2 psi. Less
than that - lower pressure 2psi. It is aok for all four tyres to have
different pressures. ( this is a general guide)
Depending on the track and the weight of the car as well as your style
will induce more or less work on each corner, thereby generating more
or less heat and effecting the pressures differently.
For example at Manfield with road tyres it would be quite normal to
have cold pressures in the right rear tyre lower than those in the
left front. Of course modifying the suspension is all about getting
the best from all of the tyres and so dispersing the loads as evenly
at possible. After all it doesn't matter how much horsepower you have
or how many 'name' parts you are using if you can't make the most of
the small dark interface with the asphalt.

As a point of interest, A friend of mine generated enough heat in his
Dunlop targa tyres that when stopped with one side in a culvert the
remaining two tyres on the tarmac melted the bitumen so badly that
the tow truck could not pull the car out 4 hours later until the road
had been chipped off the tyres. They had sunk through the bitumen to
the rock below. The tyres were working perfectly and showed no signs
of overheating. I think the exuberance in Russels right foot may have
contributed.

Of course this could all be rubbish!
I'm hopeful though that some of it makes sense.

A good pressure gauge and a notebook.

Better get of my box... Cheers

Colin


Certified Vehicle Security Ltd
Tel : (04) 389 2096
Fax : (04) 389 8700
Cell : 021 782 748

[Lou Girardin]

The whole idea of low profile tyres is to reduce sidewall distortion. High
tyre pressures date from the days of 80 - 100% aspect ratios and poor
suspension systems. Neither of which apply to the MX. Anyone who reccomends
this should be ignored and/or not dealt with, stupidity should not be
encouraged.

[Jeff]

While I wouldn't put 40+psi in my tyres either, tyre pressure does have a
major and noticeable effect - you can't just dismiss it altogether! Unless
you're using those new-fangled semi-solid run-flat tyres