Lakeside Raceway Brekkie and laps - Saturday August 4 2018

[Tobes_WIR35]

Not saying you're wrong, but I am a bit surprised because that is the opposite of what I've read pretty much everywhere, and from my father in law who has been in motorsport for 30 years (owned & ran a V8 supercar team). My understanding being that by dropping slightly below cold road pressure, the heat induced will raise the track pressure back to a few psi above cold road pressure. For example I run 280kpa on the road as per the tyre placard, but will drop back to 260kpa for track days (cold pressures). I haven't measured them (maybe I should) but in theory the hot pressure should then be around 300ish ... unless my engineering degree was a waste of money that's the theory side at least 😂

[prh1973]

Some people like to corner hard as soon as they go out on track. This is why we say bump up the pressures so they don't roll the bead off the rim. With good high performance tyres if you are sensible and wait for the tyre to pressure up before going hard you can run with a few psi lower starting cold pressure. This way they wont over pressure and less likely to start losing grip from too high a pressure when hot later in the session. This is my experience.

[Tobes_WIR35]

Some people like to corner hard as soon as they go out on track. This is why we say bump up the pressures so they don't roll the bead off the rim. With good high performance tyres if you are sensible and wait for the tyre to pressure up before going hard you can run with a few psi lower starting cold pressure. This way they wont over pressure and less likely to start losing grip from too high a pressure when hot later in the session. This is my experience.

Yes, totally agree and this has been my experience too. I probably should have been a bit more thorough in my initial post.

[Mattlock]

Yes, totally agree and this has been my experience too. I probably should have been a bit more thorough in my initial post.

And is consistent with F1 teams running their cold pressures low and having to wait for the grip to come back as the tyre heats up.



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[Machine]

You guys have the theory right, but it’s all moot when dealing with street tyres. A racing tyre has optimum grip at a narrow window of hot psi. A street tyre when hot will have the same grip throughout a wide band of psi. I think it’s far more important to ensure the tyre has enough pressure to hold the sidewall up, as it will outweigh any perceived drop in mechanical grip from “overheating” the face of the tread.

Having said that, if you really wanted to be pro on a clockwise circuit, you’d start with your front left having the least cold pressure and your right rear having the most. Front right and left rear start about the same. That will ensure your hot pressures end up even.

Now, having said THAT, look up videos where they’ve strapped gopros under the car to get a close-up of the deformation that occurs in a tyre under load. It’ll make you think twice about dropping your pressures on street tyres!

[Mattlock]

Absolutely!

I did a defensive driving course a number of years ago now and a street tyre on low pressures was very scary.

I run my all of my cars at the ‘fully loaded occupant and luggage’ pressures all the time. And then add ~3psi to that for the track. That put my R’s tyres at 48psi (against a max inflation of 50).



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[Machine]

Cool. I like what I’m reading.
Remember, though, that the max inflation of 50 printed on a tyre is actually max cold psi, not hot. Just to add more confusion and mystery to the topic.

[Mattlock]

Cool. I like what I’m reading.
Remember, though, that the max inflation of 50 printed on a tyre is actually max cold psi, not hot. Just to add more confusion and mystery to the topic.

Yep. Fully aware of that. Just keeping things within tolerances; prior to last week, it was always my daily drive doing these sessions.

As of last week, I now have a weekend car as well!




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[HPRS230]

I've noticed over 43psi and the tyres are **** for any meaningful grip.

I've got a aftermarket TPMS with live pressures with 0.3 psi resolution. Can get cheap eBay valve cap TPMS that are about 1.5psi resolution, had that before this new system.


As one said, I'll be lowering a few psi and left front will be 2 lower again. You just need to build that heat/pressure back up on the out lap.

Looking forward to seeing you all there sat too. Been a while since I've been out

Skoda RS230

[Tobes_WIR35]

Oh yeah, good point. Will definitely do that. Thanks Szechuan. Am I pronouncing that correctly?
I’ve also stopped eating until Saturday, so that should help too.

Surviving on a liquid diet of Mother?