PSI? Under pressure etc.

[Ericthejet]

I have been riding bikes for 25 years and know a thing or two.
However as time marches on some aspects of bike ownership evolve.

Tires for one thing are a whole other animal and the choice available is incredible. So I got to thinking about tire pressures.

For a bike that only sees street use the rule of thumb is to go with the manufacture's specs? My bike has two sets of numbers depending on the weight of the rider etc.

If I buy new "super duper 5000's" or whatever, I believe the correct psi to use still would be what the manual states or has this changed as tires have evolved?

[RandyO]

the pressure on the sidewall is the pressure recommended for carrying the maximum load of the tire

its unlikely that your putting maximum load on the tire

the pressure recommended in your owners manual is for the oem stock tires that come on the bike

if your running different tires than oem..... go to the tire manufacturers website and look for any documention that recommends pressures, if they have somehting for your bike. then use that, if not, go by what is in the owners manual for oem tires

[sandman]

i go by the type of bike, the load on the bike and the road temperature and set my pressure accordingly.

i want heat in my tires, cold tires suck!

and yes i have a pyrometer on whatever bike i'm on (other than a dirtbike)

colder roads i run lower pressure, again it depends which bike and the tires that are on it.

[butcher bergs]

The tire manufacturer's recommendation is what I go by.

Afterall, they are the ones who designed the tire which contacts the road and therefore they are the ones who would know best what the operating pressure would be for their brand.

[scottieducati]

Maybe shed some light here thinking about weight and pressures, etc.

Tire pressure changes are a result of two things:

1) How much air is in the tire
2) Temperature of the air in the tire.

I think we can all understand how heat makes the air molecules move more rapidly, resulting in increased air pressure within a limited space.

Flexing in the tire carcass causes heat generation (this is why to heat your tires you should accellerate and brake with the bike upright versus "weaving" which does little to flex the tire carcass versus loading and unloading the tire while straight up and down). If you have more weight, you have more force on the tire under loading conditions and will therefore heat up the tire more quickly.

So theoretically, a heavier bike / rider combination will cause more flex in the carcass under loading and heat up any given tire more quickly than a lighter rider / bike combination. This likely will have little effect on street tires while street riding, however you can easily take the weight of you and your bike out of the equation....

Pirelli for example, recommends pressures for the Diablo Corsa III of 34 psi front, and 36 psi rear for street riding. Start with these as cold pressures, if you find after riding for an extended time at your typical pace that the pressures have drastically changed, you can drop them down. Most tire manufacturers have been shying away from "cold" pressures, however for street riding it is rare that anyone takes their tire pressures "hot" as most check tire pressures before their ride, not during it. I find it best to leave the house in the morning knowing my pressures are at least 34/36 (I currently have DCIIIs on my bike) and re-check them at the first gas stop. I'll typically drop them down to 34/36 if they have changed, and will know this pressure should remain relatively constant for the rest of the day. This way it gives the tires a chance to be flexed under normal riding and under my rider + bike weight, they will react similarly for the rest of your ride.

Being a pound or two over or below a recommended pressure will not drastically affect your grip levels, or tire life. But I personally like to start at the recommended setting, and then re-check once things are rolling. If you ride daily and don't fancy checking your pressures often, set them to the manufacturer's recommended settings on a mild day, and check periodically to ensure they are maintaining their pressure as often as you wish!

[Cerberus]

there's "proper inflation per loading" to consider, but i never took passengers, so that was fairly irrelevant to me.

i consistently ran about 32/32(cold) unless i was going to be on the highway for over an hour, in which case i would bump it a couple pounds per wheel to minimize overheating the tire from too much flexing.

this is just my opinion/experience.
curious to see what the tire pros will say

[RandyO]

I have always run high pressures, but solo, I weigh as much as many here are when 2up

with Azaros on my Sv, I ran 41r/37f my v-strom, I run everythng 42r/38f except in winter, I drop pressure a couplepsi for more flex, also run knobs, cause they flex more than a street tire