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[tml678]

Like engine oil on a dipstick, tyre pressures change quite a bit with temperature

The only time engine oil level on a dipstick changes with temperature is if the car hasn't been driven for quite a while and the oil is diluted with condensation etc. Then, the first time it is given a good run, the water and contaminants will evaporate, lowering the level a little.

The level will change with day to day driving however. Ie it takes about ten minutes or so after parking it up for the oil to run back into the sump, during which time the level will be a little lower on the dipstick. Nothing to do with temperature however.

 

[vc commodore]

Tyre pressures should be taken when the tyres are cold.....This is why it is best to use your own tyre pressure gauge.

At what stage do they blow up? Good question with no real answer.....You could have them pumped up to your desired pressure that you normally run, yet put way to much load on the tyres than what is recommended and they could blow out....

You could also put way too much air pressure in and have them blow....What that is one wouldn't want to find out, as an exploding tyre can kill you

 

[VS 5.0]

38 for 245/35/20

 

[mpower]

i generally try to aim for 38 too.

 

[Bigfella237]

The only time engine oil level on a dipstick changes with temperature is if the car hasn't been driven ~

Then why do manufacturers put this on dipsticks...

If what you say is true, then the "HOT" (or after running) range should be below the "COLD" (or sitting around) range?

 

[Ginger Beer]

Lets open up that can of worms, because I'm bored....

Depends on what I'm doing

Depends on tyres

Currently running RE003 245/45 17

Hwy is typically around 38-40psi cold

For spirited driving around the twisties 35-36psi cold

From there I sometimes adjust up or down a bit dependent on how the car is handling i.e. oversteer/understeer, sometimes....

Circuit work is dependent on the tyres/track/track temps

Typically each tyre would start at different pressures cold, then when hot, check temps across the face of the tyre and adjust from there.

IIRC, at Wakefield my old R33 with 255/40 17 RS3's started cold around:
RF 34
LF32
RR30
LR28

When hot after 2 laps they would all be around 36psi and have even temps across the face of the tyre.

Disclaimer: setting correct alignment settings is also done here.

What works well on the Hwy for tyre wear isn't good for spirited driving, and what works well for spirited driving will sacrifice tyre surface/straight line grip.

I'm currently working on my rear camber in my VX SS with a slush box, I'm more interested in Hwy and drags, thus I'm looking for as close to 0.0° camber I can get at the rear, both for tyre life and, to get as much tyre surface on the road when launching.

Currently with about -0.8° camber on the back, I'm sacrificing about 20mm of the 206mm that a 245/45 17 has as actual tread that hits the road.

That is alot of rubber "not" gripping up.

Sorry......for going way of topic....

 

[tml678]

Then why do manufacturers put this on dipsticks...

Because that's easier for people to understand than "engine running" and 'Engine stopped" (and easier to fit on the dipstick too).

When it's 'hot' (or in fact running at all), the oil is drawn up into the top end where it does it's thing and when it's 'cold' (ie turned off) it sinks back down. The terms on the stick mean nothing. Temperature doesn't play a part.

Edit - see below post..oil dipsticks have min/max, not hot/cold.

 

[tml678]

If what you say is true, then the "HOT" (or after running) range should be below the "COLD" (or sitting around) range?

That's a transmission fluid dipstick..oil isn't red..

 

[Bigfella237]

When it's 'hot' (or in fact running at all), the oil is drawn up into the top end where it does it's thing and when it's 'cold' (ie turned off) it sinks back down.

I think you'd better re-think your statement? If what you describe is true, then the "HOT" section on the dipstick should be below the "COLD" since you describe the sump filling back up when the engine hasn't been running for a while, I.E. "COLD".

 

[tml678]

I think you'd better re-think your statement? If what you describe is true, then the "HOT" section on the dipstick should be below the "COLD" since you describe the sump filling back up when the engine hasn't been running for a while, I.E. "COLD".

I think you'd better re-think your picture..as per my above post (#17), that's a transmission dipstick..