Stupid tyre question

[mfc1876]

Not sure to be honest mate. I've been using the air machine at the local petrol station as I don't have a high pressure pump yet but I've got my eye on one. I don't have to unscrew the hose off the valve using the machine as you have to hold it in place and just pull it straight off when it's done so that can't account for my loss of pressure.

You'd have to use a pressure gauge to check your tyre pressure after you've unscrewed from the valve to see what sort of pressure you're losing when unscrewing from the valve. I wouldn't have thought it would be too much though?

 

[Tim Hall]

I did think it might be the track pump, as when I inflate the tyre to 120psi and take the pump off I do usually get a little hiss until the head of the pump is completely off the valve (I usually whip it off quick) nothing major but but could be deflating the tyre by the small amount im loosing?

The hiss is more likely to be the air in the connector hose (which as got to be at tyre pressure) escaping, rather than the air escaping from the tube.

 

[boydj]

It's not unusual for tyres to lose (note the spelling, please) 15 - 20 psi in a week or so, especially with high pressure road tyres.

 

[SWSteve]

No I don't know why either?! I'm an ex tyre fitter (albeit commercial stuff) so I know that all tyres lose a bit of pressure over time but not that much in less than a week. I just wasn't sure if this was normal on small bike tyres. I've checked for slow punctures and that the tube hasn't been nipped etc but all looks fine. I use schrader valves.

Don't forget there is a lot less air in a bike tyre, so even a little loss each day would make a big difference over a week

 

[mfc1876]

Don't forget there is a lot less air in a bike tyre, so even a little loss each day would make a big difference over a week

I suppose that's very true. I'm used to HGV tyres.

 

[Pikey]

I suppose that's very true. I'm used to HGV tyres.

They must slow you down a bit going up hills...