tire pressure

[Guest trispeed]

'years ago' is the key phrase here. It doesn't apply anymore.

Do not lower the pressure in the rain. You do not want a larger contact patch in that circumstance; you will hydroplane that much easier if you do so. You want a narrower, longer contact patch to cut through the standing water. This is one place where the old tall, skinny tires have a distinct advantage. They cut through standing water much more effectively. Oh well, we can't have it all.

[dlaing]

I have never hydroplaned and have ridden conditions where my car would be.

I am more fearful of oil and water or water coated metal.

Does the same apply for slick surfaces?

Why would I not just go with 50PSI or whatever the maximum is?

I thought the idea was for the tire to hug the road's irregular surface rather than just ride over the high points.

I feel like I get better traction in the rain at lower tire pressures.

Perhaps I have misled myself.

[belfastguzzi]

The wider/bigger your tyre contact area is, the greater will be the floating effect. If you were driving across a beach or a soft muddy field then you would benefit from lower pressure & a bigger/wider footprint. With a hard, stable surface (tarmac road) under rainwater, then you benefit from a smaller section tyre footprint for the same weight of machine, as you want to cut through the surface water as much as possible and float as little as possible. In the muddy field example, if the ground under the mud was hard stone, then you would probably benefit from a narrower tyre as it would cut through to the hard ground under the muck. Better to drive on the hard rather than floating/spinning on the surface mud.

 

I think you don't want to pump the tyre up as hard as possible because you still want a decent length of contact area. For a given contact area, I guess that if it is long/narrow there will be more rubber on dry road than if the section is wider/shorter.

 

Don't know how 'scientific' that is.