tyre pressures

[slow ginn]

I've had various opinions on tyre pressures when on track,anyone know the best settings for an m400?
Thanks

[joust]

I leave them at the standard COLD (i.e. very cold, after a night in the garage) - seems to do alright.

I know a few of the others have played around, one thing you can use is a IR thermometer to check the temps across the width of the tyre - hotter in the centre, let some air out, hot at the edges, put some air in.

J

[chillidog]

slow ginn said:

I've had various opinions on tyre pressures when on track,anyone know the best settings for an m400?
Thanks

Get them hot and set them to 20 F, 30 R.
--
Richard

[AMG Merc]

chillidog said:

slow ginn said:

I've had various opinions on tyre pressures when on track,anyone know the best settings for an m400?
Thanks

Get them hot and set them to 20 F, 30 R.
--
Richard

Isn't that the problem Richard - what's hot?

[JLSELAN]

AMG Merc said:

chillidog said:

slow ginn said:

I've had various opinions on tyre pressures when on track,anyone know the best settings for an m400?
Thanks

Get them hot and set them to 20 F, 30 R.
--
Richard

Isn't that the problem Richard - what's hot?

Exactly right, the only correct reference is COLD (unless you use F1 heating blankets ).

[paulcundy]

JLSELAN said:

AMG Merc said:

chillidog said:

slow ginn said:

I've had various opinions on tyre pressures when on track,anyone know the best settings for an m400?
Thanks

Get them hot and set them to 20 F, 30 R.
--
Richard

Isn't that the problem Richard - what's hot?

Exactly right, the only correct reference is COLD (unless you use F1 heating blankets ).

err no, what's cold?

today cold at 8am would be 15'c.
cold at 2pm will be 24'c.
cold at 8am on the 24th december will be? debate.

the correct pressure is the pressure that keeps the whole of the surface at the same temp. measure the surface temps with an IR gauge and adjust accordingly or Richards advice is a very good starting point. "Hot" means 5 spirited laps and the surface beginning to ripple.

[joust]

I'd concur, the best way is to use a IR temp guage and check the way the tyres are working.

Tyres can get 45-50C easily, with that much heat pressures are always going to be a guesstimate.

J

[AMG Merc]

What about the fact that Lee Noble (not name dropping!!!) said use same pressures hot and cold?

[paulcundy]

AMG Merc said:

What about the fact that Lee Noble (not name dropping!!!) said use same pressures hot and cold?

and how many championships did he win? :-)

[joust]

paulcundy said:

and how many championships did he win? :-)

One less than you lately , although I seem to remember he was quite handy 15 years ago...

J

[washy]

I used 20F 30R measured when hot. Obviously each tyre needs adjusting differently so I can't see how you could set them any other way than hot as soon as you come in off circuit.

[paulcundy]

washy said:

I used 20F 30R measured when hot. Obviously each tyre needs adjusting differently so I can't see how you could set them any other way than hot as soon as you come in off circuit.

and its amazing what a difference it can make. At Brands I was understeering like mad, dropped the fronts by 2psi and hey presto cut through the corners as sharp as a sharp thing.

[AMG Merc]

paulcundy said:

...and hey presto cut through the corners as sharp as a sharp thing.

Err, a knife "Doctor" Cundy!

[joust]

paulcundy said:

and its amazing what a difference it can make. At Brands I was understeering like mad, dropped the fronts by 2psi and hey presto cut through the corners as sharp as a sharp thing.

I'll tell you about Bruntingthorpe and a figure that began with a 3 at Bruntingthorpe when I next see you...

J

[chillidog]

AMG Merc said:

Isn't that the problem Richard - what's hot?

Hot is when the handling goes to rat poo.
Very hot is when you hit the tye wall and wished you'd come in earlier to check the tyre pressures.

--
Richard

[AMG Merc]

chillidog said:

AMG Merc said:

Isn't that the problem Richard - what's hot?

Hot is when the handling goes to rat poo.
Very hot is when you hit the tye wall and wished you'd come in earlier to check the tyre pressures.

--
Richard

You comedian Riccardo!

[JLSELAN]

paulcundy said:

JLSELAN said:

AMG Merc said:

chillidog said:

slow ginn said:

I've had various opinions on tyre pressures when on track,anyone know the best settings for an m400?
Thanks

Get them hot and set them to 20 F, 30 R.
--
Richard

Isn't that the problem Richard - what's hot?

Exactly right, the only correct reference is COLD (unless you use F1 heating blankets ).

err no, what's cold?

today cold at 8am would be 15'c.
cold at 2pm will be 24'c.
cold at 8am on the 24th december will be? debate.

the correct pressure is the pressure that keeps the whole of the surface at the same temp. measure the surface temps with an IR gauge and adjust accordingly or Richards advice is a very good starting point. "Hot" means 5 spirited laps and the surface beginning to ripple.

There are two important concepts in the earlier comment:
-You must have a stable reference pressure in order to understand how pressure changes affect behavior.
-A "cold pressure" is a pressure measured at thermal equilibrium while the tire is at a completely uniform temperature (e.g., after sitting several hours or more in the shade). The actual ambient temperature doesn't really matter that much, but a good reference often used by tire manufacturers is 15-25 degrees C. If the temperature is lower, expect slightly lower pressures, if higher then higher pressures can be associated with the "cold" reference.
Finally, IR temp measurements are an excellent way to sort things out, but they must be done quickly, in the hot pits and immediately after a hot lap--before cross-tread temp variations are obscured by a cool-down lap or by driving back to the paddock. In addition, always start making measurements at the most highly stressed corner of the car for any given circuit.