Tyre losing it's pressure

Hi all,

About how much pressure should a bike tyre lose when standing for a day or two? The pressures were last done 10 days ago- I had 5 days of riding to work and went for a brief trip around Boxhill with my Bro yesterday. When checking, the front had dropped from 33 to 26 PSI. Granted that it's getting colder and that'll make a difference, but still seems to be a lot. The bike felt fine to steer through last week and only yesterday on the appaling conditions of the zig zag and top of Boxhill did I notice any problems- any pitting in the road seemed to be steering the bike for me...

Another reminder to check my pressures more often (like the off wasn't enough!), and I know it's sposed to be a daily check, but still seems like a large drop.

I guess it's gonna mean new tyre time, but cash being what it is, I simply can't afford to do it at the mo.

[fizzwheel]

IMHO it shouldnt loose that much over that period of time. My Gixer has been stood for a month without being ridden, it lost 2 -3 psi out of each tyre...

Give your tyre a good check you've probably got a screw or a stone stuck in it. If thats the case and the rest of the tyre is good tread depth and general condition wise you might be able to get it repaired, which will be less than a new tyre.

Personally I wouldnt be mucking about with it, I know your skint, but what price do you put on your own safety. Get it looked at before you ride the bike in anger again.

Just to check, did you use the same guage to do the checks?

Did you set the pressures when the bike had been parked out in the sun or had just been ridden?

And then checked them again in the garage after the bike had been left in there cold over night?

That would explain the difference but if the above scenario is not true then it is a bit suspect. Plus both tyres would have gone down and not just one...

Back in the summer one of the rear tyres on my car dropped 6psi which I thought was weird so I pumped it up and checked it again a few days later and it was fine. It didn't lose any again until November when it suddenly lost 15psi. At that point I inspected the tyre all the way around and found a screw which must have been letting air out occasionally.

You would see a nail though and any other type of puncture would consistently let air so if you check it in a couple of days you would have lost some. It is hard with bike tyres though as they are so much more sensitive to temperature.

It's not entirely unknown for tyre valve cores to come loose or leak otherwise. Take the dust cap off, put a bit of gob on your finger tip and smear it over the valve stem end. Does it bubble up? Yes? Try tightening it up. If that fails, replace it. If it doesn't leak, check your tyre for obvious damage or have it checked for a leak at a tyre place. Causes of slow punctures can be buggers to spot visually.

Cheers folks- will inspect for obvious faults then look into it from there.

It was a different guage- mechanic did it last time (when the reason for my off was spotted), this time I used a garage- rode it for 5 mins in the cold, slowly, so the tyres shouldn't have had time to warm up. I've heard garage guages are less accurate- I'm not sure of this though and the bike rode much better after sorting it.

20p for 2 minutes of air- it's not a lot compared to some garages (nearest to me is 50p!)- but it's JUST AIR!!!! I doubt the pump costs that much to run...

Originally Posted by thedonal

Cheers folks- will inspect for obvious faults then look into it from there.

It was a different guage- mechanic did it last time (when the reason for my off was spotted), this time I used a garage- rode it for 5 mins in the cold, slowly, so the tyres shouldn't have had time to warm up. I've heard garage gauges are less accurate- I'm not sure of this though and the bike rode much better after sorting it.

20p for 2 minutes of air- it's not a lot compared to some garages (nearest to me is 50p!)- but it's JUST AIR!!!! I doubt the pump costs that much to run...

Invest in a foot pump and a good electronic gauge. Set you back maybe £20? Here are some gauges. I have an Accutire though with a different brand name, though I use that on my car. I'm a bit more anal with my bikes and use an Oxford DigiGauge. This has a swivelling head that can easily get to a bike valve. It measures in 1/10ths of a PSI - Oooh, my tyres are down 0.3 PSI! where's the foot pump? It shows that pressures can go up as well as down. Ambient temperature and atmospheric pressure make the pressures vary.

Always use your own guage, it may not be 100% accurate but it will be better than a forecourt one. do the water test using water from a mist spray gun and with a drop of detergent in it. Do the valve then the tyre bead.

Best fo luck with it.

Over here, where winter temperatures are a bit more extreme, I've had instances where I put air in my car tyres only to have one go soft soon after. What happens is the valve stem doesn't always seat closed after you put air in and then the air leaks past the cheap little plastic dust cap. I replace them with steel caps that have a rubber seal in them. This happened to me again last week and the tyre hasn't lost any air since I changed the cap.
Oldie

you've either got something through the tyre - mine did the same thing, I had a 3cm piece of metal through my tyre - it only ket air out when the tyre got warm (on a run) took a serious investigation to spot it.

Other possibility if the tyre was fitted just before the problem started is corrosion on the rim - mate had that problem last year