This was probably the warmest day I've ridden my 14 ultra.Rode aprox. 150 mls. and the bike just didn't feel right,felt a little unstable and wasn't sure footed in the corners.Since I had just checked my tire pressures,I decided I would see where they were at when I got home to rule that part out.Due to time I only checked the front tire but I found it had gained 5 psi and the tire was pretty warm.After the bike had sat for hrs the tire pressure was back to normal pressure.When I bought the bike both tires were aprox. 5 psi low on air from the dealer,but it handled and felt much better that way.I believe I'm going to go to a cold pressure of 4 psi lower to allow for warm tire gains and try that.I was surprised they are gaining that much pressure.The tires on our 14 bikes are supposed to be a little different tire than on previous models even though they look the same.

 

Cold Tire pressure for the front should be 36 psi.
Cold Tire pressure for the rear should be 40 psi.
I don't worry about the pressure build up from riding that is normal.
You didn't say what brand of tire your bike has, tires like Metzelers
need about 4 or 5 psi. more to get the maximum out of them.

 

That's why it's called COLD tire pressure. Check and add/subtract air only when the tires are cold. Pressure will increase when a tire is warm. You should never bleed air out of a warm tire.

 

I'm totally aware of what cold tire pressure is,I raced sprint cars with bleeders on the wheels to bleed off pressure build up,this aint my first rodeo.I still think gaining 5 psi on a 73 degree day is a little much.I bought this 14 last fall and in cooler temps the tires weren't doing this.I dropped the front to 34 psi cold and rode today,the bike felt a little better.If they are growing 5 psi on a 73 degree day I wonder what they are going to do on a 95 degree day in the heat of the summer with the roads good and hot? I'm running the oem dunlops by the way.

 

It's possible that the air the tires were initially filled with had a high moisture content. That will cause bigger fluctuations. One of the advantages of Nitrogen filling is that the gas source is usually dry.

 

Your right,nitrogen is a good way to go,alot of racers use it as it doesn't build pressure like regular air.Our new tires are supposed to be a little different design,we may have to keep a closer eye on them.

 

I've been running Tiregard TPMS since about 2009, on three different bikes: 1) 2007 Honda ST1300, 2) 2012 Honda Goldwing, and 3) 2014 HD Ultra Limited. I was initially shocked to see how much the tires gain in pressure and temperature - especially the rear tire. It is not uncommon to see the rear tire go up 10-12 psi, with temps into the 140-150° range. The ST1300 was shorn with Continentals, Michelin on the Goldwing and Dunlops on the Ultra. And I've seen the same phenomenon on all three bikes. I don't worry about it any longer. I just make sure my cold pressure is where it belongs at the beginning of the ride.

Steve

 

I've always been a bit skeptical of this claim, as "regular air" is itself composed of 78.09% nitrogen. But, I'm no chemist, nor do I play one on television....

Steve

 

Boyles gas law says if volume is constant (as inside a tire) and temperature goes up, pressure goes up. Does not matter what tire or what gas, they have to obey the laws of physics. If temperature is constant and we add volume ( adding air to your tires) pressure must go up.