Proper Tire Pressure

So the manual for my 1980 XJ650G has the tire pressures for different loads (26/28psi for my usual girth), then at the bottom it has the pressure for "high speed riding" (32/36psi). What constitutes high speed riding?

 

I'm not sure but apparently when there's more pressure there's less load on the tires resulting in a high speed, whereas low pressure gives you more grip on the road while the speed suffers a little.

 

Bigger loads or higher speeds result in more heat buildup. Excess heat can cause tire failure (Remember the Ford explorer with Firestone tires? Ford was recommending very low inflation pressures. When people didn't keep on top of the inflation, or loaded them heavily, or drove at high speeds on hot days [or often all of the above] the tires were prone to fail. Firestone took the rap on that one).

Higher pressures reduce the flex of the tire and reduce heat buildup, offsetting some of the effects of heavier loads or higher speeds.

Higher pressure will also reduce your contact patch - not good.

Not sure what Yamaha means by "high speed", my shop manual doesn't define it. I don't think I would worry about it unless I was going to run for extended periods above 85mph.

 

the Haynes book for my bmw says high speed inflation is for above 112mph with a passenger
must be a brave passenger

 

i run 30/32. works well for me....

 

I run 28 psi front and 40 psi rear.