Inflation pressures with modern tires - different from manual's specs?

[Guest]

I was reading a while back and came across some apparent controversy about what pressures to run on our tires. The idea that struck me as odd was that supposedly modern tires need higher pressures than older tires.
Is there anything legitimate to that idea?

[sharpy]

3.25x19 and 130/80 x16?
ill be using 33-34 front and 35-37 rear one up. ad 2psi for passenger or highway

[GS ace]

I usually adhere to what is on the sidewall of the tire.

[Gorminrider]

I'm not the goto expert, but I have this tip from the forum:
The old rule of thumb for tire inflation still applies:

"There should be a 10% increase in pressure from cold to hot."

Adjust your tire pressure when cold to an easy number, like 30 psi. Go for a ride. Make it at least 50 miles or so to get the tires nice and warm. Check the pressure, it should be 33 psi. If it is more, the tires flexed too much, warmed the air and increased the pressure. If it is less, the tires did not flex enough to warm the air, so they are over-inflated. Adjust the pressure by the difference to that +10% number. In other words, if your hot pressure was 35 psi, you need to add 2 psi, making your cold pressure 32 psi. Of course, you need to do another ride to warm the tires again, but that's OK. If you regularly carry a passenger, you need to repeat the process with the passenger to determine your 2-up pressures, too.

[1980GS1000E]

I usually adhere to what is on the sidewall of the tire.

That is a maximum and not the recommended.

[Griffin]

That is a maximum and not the recommended.

That's actually the maximum recommended pressure with maximum load. The 10% rule is what most informed people use, and seems to works pretty well.

I and most of the "old timers" here have been using it for the past ten or so years, with reportedly good results all around.

[eil]

To answer the original question, the reason for the difference (and thus the controversy) is that tires are made differently now than they were in the olden days. Better processes, better materials, better tread patterns, and so on.

I'm not an expert but the 10% rule seems to be the consensus among those who know their stuff. The exact numbers vary by bike weight, rider weight, cargo being carried, whether there's a passenger, riding style, ambient temperature, and other factors. Takes some experimentation to find.

[jabcb]

Avon have a good recommended tire guide that also shows recommended pressure.
For their tire on a GS650G they recommend 29psi front & 36psi rear.
http://www.avon-tyres.co.uk/motorbike/gs-650-g

Their recommendations for a tire also depend on the bike.
They, for example, recommend the same front tire on a T500 & GT750, but recommend 29psi on the T500 & 33 psi on the GT750.

Shame the other manufacturers don't do the same.

[WilliamGLX81]

Cool, very helpful responses. I forgot about the 10% idea, which I heard quite a while ago.

[Steve]

Start with pressure at a number that will be easy to work with, and go from there.

30 psi will not hurt anything and will be a good starting point.

.

[tkent02]

Try it at different pressures and see how it rides, how it squirms, slips, and slides.
Then slow back down you crazy ass.