Tyre pressure

[Wheezybiker]

How critical are tyre pressures

Checked mine yesterday when cold and they were 3psi down on what I set them at 36 front 42 rear which is reccomended on the bike for riders over 90kg
I always use the same tyre gauge (digital)
Bike had felt a little bit squirrelly which was why I checked them

[Confusion]

[jaffa90]

Also the roads are slippy this time of year.

[MCN]

[Fizzer Thou]

There is an interesting article in the latest 'Practical Sportsbike' magazine about tyres that is worth reading.

I overinflate my tyres the previous night before a rideout so that it is easier to adjust the pressures immediately before setting off.

I have found that barometric pressure also affects the air inside tyres as well as the ambient temperature.
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Just talk bikes.What else is there?

Always have a 'Plan B'

[MCN]

Barometric will be redundant if you set pressure for current atmospheric.

I would not consider the effect really. Unless I rode the bike from sea level to 10,000ft.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[jaffa90]

[Polarbear]

It's quite amazing how much tyre pressures change with temperature.

My Trophy has a digital readout of the tyre pressures and from cold, after riding a while they can easily change 3 psi but if it wasn't for the readout I can't say I would notice a difference.

I therefore doubt you would notice a few psi drop unless you were really caning it. I bet it's more winter road surface than tyres making you bike 'squirrelly'.
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[Wheezybiker]

Thanks for the replies
Feel more reassured now

[Ste]

[MCN]

[Sister Sledge]

[JackButler]

I was in the garage of a top flight WSBK/BSB rider on a test day. He was new to the team & everybody was poking & prodding around trying to find a way to make the bike work for him.

He came in & asked for the front pressure to be increased by 2psi.

After just 1 lap he parked in the garage & threw what can only be described as a tantrum.

The team never put that 2psi in, they sent him back out with exactly the same pressures.

The point is that a top flight rider will be able to tell the difference. Sadly, the rest of us can't.
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[Easy-X]

[RhynoCZ]

[Skudd]

My tyre pressure read out when I move off cold is 0.2 Bar less than when the tyre is warmed up in this weather.
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[JackButler]

[RhynoCZ]

[Kawasaki Jimbo]

I reckon I get an inkling on the road when about 6psi down on the front, which is 1/6 of standard. On a smooth, dry track I might do better, I suppose.

[Ste]

[Fizzer Thou]

I found this was an interesting article to read....

https://www.oponeo.co.uk/blog/motorbike-tyres-temperature-and-grip

Although barometric pressure was not mentioned,I have found that when this pressure has changed overnight,according to my barometer in the hallway at home,that it has affected the tyre pressure.This is why I adjust immediately before a rideout and especially if I am out on my sportbike.

A good example of how temperature and other extremes can affect how the tyres feel,a few years ago I was on a rideout with friends down to the coast.On the way home the bike was responding well to feedback and I felt that it was handling really well.Later on that same day,but later in the afternoon,we all met up once again down at the pub,which was a ride of about 10 miles or so.Without having done anything to the bike,it felt completely different,in a way that was difficult to comprehend.I put it down to the ambient temperature having changed a fair amount from the ride home earlier and the ride later in the day.

I read somewhere that race bikes,typically Moto GP bikes,do not use air but nitrogen gas to inflate the tyres,because it keeps the temperature more stable.I have the article somewhere from a magazine but could find no information on-line.

As for differences in tyre pressures on the road,I tried using 35psi in the front tyre on my R1 and during a particularly spirited ride I felt that the front was squirming a bit under heavy braking in not one place but in several places where I needed to brake particularly heavily.The next time that I rode out I set the front tyre back to 36psi and that feeling was no longer evident.
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Just talk bikes.What else is there?

Always have a 'Plan B'

[MCN]

Nitrogen doesn't expand/contract as much as air due to the lack of water and oxygen when heated/cooled.

But is not immune from Boyles Law.

It is advisable to fill heavy plant tyres with n2 to prevent explosions and flying heavy bits if the tire ignites. (The rim can spin inside the bead, generating enough heat to ignite the fumes created. Oxygen in the air fill will support combustion. N2 won't support combustion.)
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[Nobby the Bastard]

[stinkwheel]

Most decent racers I know will happily haul about on the most horriffically fucked, worn, squared, feathered and/or pointed tyres on their road bikes. You seen the state of a set of race tyres at the end of a meeting?

They generally run them way softer than manufacturers spec too for the increased grip. Actually to the point where I find them hard to ride on because they are squirming about and have to be dragged kicking and screaming into and out of corners.
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