BMW R1200RT/R1250RT Forum

Out of nowhere, the front tire is losing air steadily out of a newish front tire with a couple of thousand miles. I have just finished immersing the tire in water after having overfilled it and can detect no air bubbles. There are a few minor dents in the rim to which I paid particular attention, and no bubbles anywhere nor anywhere on the wheel body (in case there was a hairline crack), and no bubbles anywhere. Same result for the air valve and the tire itself, and no sign of nails, etc. I don't remember having hit any teeth, rattling potholes prior to the beginning of this problem.

Typically, after overfilling the tire slightly, the tire is within spec pressure for about two days, but occasionally it will drop off drastically after one day. I'm beginning to wonder if, particularly regarding the rim deformations, I may lose more air if I had written over particularly rough roads, which may distort the tire/rim interface, causing more leakage.

I was really hoping that dunking the tire would identify the problem, but I guess no news is bad news in this case. Any ideas?

When the new tyre was fitted, was the inside of the wheel rim where the tyre bead seals checked to be clean and in good order.

Just a thought, perhaps when the wheel/tyre is checked off the motorcycle, without any load on, it's ok.

However, under load, there may be the smallest of movement between the tyre & wheel rim to cause a loss of pressure.

Had a similar issue with a 90 degree valve stem on a Goldwing. I would check pressure prior to a ride only to find I'd lost significant pressure on the next check. Checked for leaks with soapy water and found none. Re pressurized that tire, let it sit overnight, and then checked it the next day. No pressure loss! Turns out the pressure loss was at the valve stem but only when actually riding as the centrifugal force acing on the valve stem caused it to deflect slightly and expose a crack in the rubber seal.Replaced it with an all metal 90 degree and all was well.

When I changed the tyres last time, I had to use a wire brush to the inner lip to get rid of the crud. Before I did this the tyres would slowly lose 10-15 psi over 2 weeks

Could be a slow leak in the valve stem itself, even if you didn't see bubbles. Sometimes those little things are sneaky. Worth getting a new valve stem put in, cheap fix, and it's a common culprit.

My experience is that unless requested, tyre fitters don't change the front wheel valve core. With the dust cap fitted, any minor leakage may not be detectable.