Simultaneous inflation.deflation of tyres.

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Originally Posted by TB

All fair comments, but I didn't say "radical" (I don't think I did... nail me if I'm mistaken about that!) and I also listed cooling as a reason for ending up with different pressures when working on one tyre at a time.

Doing both tyres on an axle simultaneously with equalised pressure eliminates two sources of difference. That's the point of these kinds of things. Whether they're worthwhile overall is pretty much an individual decision – everybody weighs up the pros and cons according to their personal priorities.

I haven't decided to get one. It's just something I've been mulling over.

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Not if one tyre is in the sun and the other in the shade. The one in the sun will not cool down as fast as the one in the shade.

Also if you aren't on perfectly level ground, there will be slightly more load on one tyre anyway. However, the load on the tyre doesn't dramatically change the pressure.

Anyway even if there is a difference between tyres it's not going to be huge doing it the normal way. Just say its 2psi difference doing it tyre by tyre. Who cares? It will hardly make a difference off road. I think you are over complicating something that doesn't need it. Of course happy to be proven wrong [emoji14]

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Originally Posted by gusthedog

Not if one tyre is in the sun and the other in the shade. The one in the sun will not cool down as fast as the one in the shade.

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True. Not sure how big an effect that is though. It's also variable and somewhat controllable, so not something which you have to think about every time you air up.

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Also if you aren't on perfectly level ground, there will be slightly more load on one tyre anyway. However, the load on the tyre doesn't dramatically change the pressure.

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Pressure = force divided by area. You add weight (which because of gravity increases the force), you increase the pressure between the ground and the contact area of the tyre, which in turn increases the internal air pressure. The tyre, being elastic, will expand a bit, which allows it to squash down onto the ground a bit, increasing the area and so decreasing the pressure slightly. But being elastic is like being a spring – the more it's stretched the harder it resists. So the net result is that the extra weight does make tyre pressure increase up until the point where your rims are squished to the ground or the tyre pops.

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Anyway even if there is a difference between tyres it's not going to be huge doing it the normal way. Just say its 2psi difference doing it tyre by tyre. Who cares? It will hardly make a difference off road.

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Agreed. But I don't air up to go off road, I air up when I'm getting back onto the bitumen. At 110kph on the blacktop a couple of PSI is more noticeable.

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I think you are over complicating something that doesn't need it.

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Every real thing is complicated when you look closely. That just means it's interesting. Doesn't mean everybody needs to change the way they're dealing with their tyre pressures.

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Of course happy to be proven wrong [emoji14]

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I think we are in agreement that it's not a big deal. But I still wonder whether I might personally prefer doing my tyres with one of these things compared to what I'm doing now.

Gawd! Before reading this thread I never realised how complicated airing up/down was. Now I won't sleep tonight as I lay there trying to figure out if I've been doing it wrong all these past 25 years or so. :-)
AlanH.

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Originally Posted by ATH

Gawd! Before reading this thread I never realised how complicated airing up/down was. Now I won't sleep tonight as I lay there trying to figure out if I've been doing it wrong all these past 25 years or so. :-)
AlanH.

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There are no better places to over complicate something than Internet forums [emoji23]

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Originally Posted by ATH

Gawd! Before reading this thread I never realised how complicated airing up/down was. Now I won't sleep tonight as I lay there trying to figure out if I've been doing it wrong all these past 25 years or so. :-)
AlanH.

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Don't sweat it Mate as most of us older Farts don't know nuthin , Apparently [bigwhistle][biggrin]

30 psi in your tyre. Jack the car up. Still 30 psi in the tyre. The stance will have no effect.....

So, driving south down the Bruce highway, for example, in the morning your car will have more pressure on the left side, and in the afternoon, more on the right side? Should I stop at lunch time and adjust tyre pressures?

I think there are more variations in pressure readings of tyre gauges anyway so all this does is to equalise pressures a little bit more accurately side to side than you can generally achieve by reading a gauge. Most pressures we set for different terrain are those that work for us from experience.
I once had to return a well known make of gauge as it was more than 6 psi out. So, for me, chasing this marginal perceived difference side to side is irrelevant compared to all the other variable pressure factors?
Cheers, techron[smilebigeye]

One of my mates made up a similar device for airing up. Works a treat - but he has an onboard air sytem that is very quick.
I would think you would need a fairly good compressor with a fair cfm for it to be effective.

Does it save any time VS doing each wheel individually - maybe a bit?

How much difference would 10mm air hose VS 8mm VS 6mm would make in inflation times.
Only you can decide if it is worth it or not.

For deflating I have a cheap triggered air hose with a gauge attached - pull the trigger deflate - stop and check pressure on gauge.

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Originally Posted by jh972

30 psi in your tyre. Jack the car up. Still 30 psi in the tyre. The stance will have no effect.....

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Technically, I don't think that's correct. For practical purposes, on a given vehicle/wheel/tyre combo, the effect could be negligible. Neither of us should fret about it either way.