Tyre pressure dropping

I check my tyre pressure every time before I take the bike out of the garage [Once a week or so] and it always has a significant pressure drop,on both front and rear,about 4-5psi
I have checked the valves,sprayed them with soapy water to look for punctures and rim sealing and all is OK.
I have CORSA 111's fitted and never had this problem while I had Michelin 2CT's on the bike over the previous 3-4years.
Has anybody else had a similar problem,either when changing brands or in general
It has been suggested that when the rims cool after riding the rim seal might have a slight leak along with the rim and/or tyre being porous

Suggestions or cures[The tyres have only done 2K so I don't want to change them and not to keen on putting gunge in them]

my Strada's dropped about 2-3 psi over 2 weeks. But as long as you keep an eye on it shouldn't be a problem.

[yorkie_chris]

I had some race takeoff supercorsa pros and they lost air steadily, worse as they wore.

[embee]

I had some Contis which lost pressure, none of the other makes have, I put it down to porous carcasses.

bt21's lost a lot of air on my MT-03, even after refitment (check for punctures)

Check the tyres after a ride (once they've got cold again), and then the next weekend. Then you know if it's riding or sitting that causes the problem.

[Richie]

my wife loses all her pent up pressure and hot air when she opens her gob....

Yes Dear...

[timwilky]

My brother had terrible problems on his Mille. We couldn't find where the leak was.

In the end we decided to change the valve cores, turned out whoever had fitted them had put in cheap cores with not much of a spring. the slightest vibration was sufficient to permit a leak. New cores scrounged from a local tyre fitted and a month of head scratching, cured.

Changed core on my rear still leaked when riding,goo sorted it

Hi everyone,

Compressed air contains water vapor, especially if not dried correctly, and oxygen, both of which will, over time permeate through the tyre carcass and cause corrosion (Not so much on newer cast wheels, more so on spoked rims). Although tyre valves can be to blame on some occasions too. Since 'air' is a mixture of many components, the quantities of these are never exactly the same, variances with altitude etc.

Therefore alot of tyre fitting companys will use Nitrogen instead, which allows greater pressure retention, because Nitrogen molecules are larger than oxygen molecules,which make up about 21% of the air we breathe.

Nitrogen filling also helps reduce pressure variances with temperature changes.

Could be worth thinking about, it costs next to nothing...