Tyres losing pressure

[abo]

I pump the tubes inside my Double Fighters up to 65psi, the top of the range they give on the sidewalls.

If I say, go for a ride and then park the bike up for the night, the next day I go to ride it, the tyres are noticably flatter when I sit on the saddle, and checking the pressure I find they are down to the low 40's.

The pressure always goes down to about the same, regardless of how long the bike is left for. When I got back from my hols and checked the pressures they were 44psi IIRC, after two weeks of standing unused.

I suspect that this could be a valve thing. The tubes have schrader valves; should I expect them to be able to hold 65psi for more than a few hours?

FWIW I'm happy to sort my pressures out properly before 'going for a ride' but could do without having to faff about before popping down to the shops if you see what I mean.

 

[on the road]

It might be worth putting them in a bowl of water to see if there's any air bubbles.

 

[tyred]

The valve would be the most likely culprit ime. As a first step, find something like a window box and fill it with water and place the wheel in it with the valve under the water and look for bubbles coming from the valve. Some Fairy liquid or similar might make it easier to spot the bubbles. If not the valve, remove the tube and put it under water and check for leaks.

 

[Mad at urage]

[QUOTE 1536495"]
Just watch you don't drop the wheel out of the window.
[/quote]
If you've pumped it to max, it should just bounce right back to you surely?

 

[spence]

A few things:

- Whenever you remove a pump/gauge and re attach it you will see a drop in pressure, air lost from the head and refilling the chamber.

- Why are you putting 65psi in anyway?

- If you doubt the tube just stick a new one in.

- What is with people on this site always pumping tyres up to “the max on the side wall”?

 

[abo]

A few things:

- Whenever you remove a pump/gauge and re attach it you will see a drop in pressure, air lost from the head and refilling the chamber.

True, and accounted for. Plipping the pressure gauge on and off the valve drops my tyre pressure by 0.5psi when I take a reading

- Why are you putting 65psi in anyway?

To lower my rolling resistance?

- If you doubt the tube just stick a new one in.

True, they're not exactly expensive. Just wondered if it were a problem with the tube or my expectations...

- What is with people on this site always pumping tyres up to “the max on the side wall”?

See point 2

 

[fossyant]

The only down side to using Latex tubes is they go flat in a week - so as mine are on the best bike, it's not used during the week, so you never really know if you picked up a puncture on the last ride.

 

[abo]

[QUOTE 1536495"]
Just watch you don't drop the wheel out of the window.
[/quote]

 

[mickle]

It's one of only two things: Porous tubes or leaky valves. (or possibly both...) Get to Halford's and buy a valve key and a pack of valves, they are a useful thing to have if you are running Schraders.

Or just buy a pair of decent tubes..

 

[spence]

by 0.5psi

Blimey! That's good, what gauge? The squeeze test or the rim not touching the ground is usually good enough.

To lower my rolling resistance?

I'd rather have the grip and traction, especially when breaking and cornering. If you want lower resistance change tyres for something slicker.

See point 2

That's a safety figure as a maximum (conservative usually) for the tyre construction/fitment on the rim. I'd expect the minimum drag for the tread on a surface to be at a lower point and affected more by the surface. I's not just you, almost every "what pressure" thread seems to revolve around the figures. Just use what you feel is appropriate for the surface/conditions - mud, rocks, roots etc., usually a lot lower than you think.

Anyway just my thoughts.

 

[mickle]

It's strange that tyre manufacturers print the max pressure onto their product. It's much more likely that the rim will fail first.

 

[byegad]

Schreaders will take 120psi and hold it for several days. My wife's Dahon Speed-Pro has narrow 120psi 406 tyres and they stay up well.

In my experience all tubes leak air, not via a hole or valve but through the rubber of the tube itself. At the moment one of my trikes loses 10lbs in one back tyre and 20lbs in the other over a fortnight, both from 70psi. This has been going on for months and is not due to a slow puncture or leaking valve. I know because I stripped the tube out and submerged it in a bowl of water. The tube that loses most was a cheap one I picked up from Halfords, the other is a Schwalbe.

 

[spence]

It's strange that tyre manufacturers print the max pressure onto their product. It's much more likely that the rim will fail first.

Interesting thought. Just checked one of mine; rim manufacturer says max pressure of 3.3bar (for tyre size), tyre manufacturer says 1.8-3.7bar (I usually go to about 2bar) so in this case tyre would exceed rim limit if pumped to its max.

 

[abo]

It's one of only two things: Porous tubes or leaky valves. (or possibly both...) Get to Halford's and buy a valve key and a pack of valves, they are a useful thing to have if you are running Schraders.

Or just buy a pair of decent tubes..

Hmm never thought of checking the valves are screwed in properly! doh

 

[abo]

Blimey! That's good, what gauge? The squeeze test or the rim not touching the ground is usually good enough.

Can't remember the make offhand (Laser-something?), it looks like a disc with a digital readout and a flexible connector to the valve, like an old-style hand pump. It has a little button to plip some air out, so you can get an accurate pressure. I acquired it a while back from when I did the car racing.

I'd rather have the grip and traction, especially when breaking and cornering. If you want lower resistance change tyres for something slicker.

I did consider getting some City Jets TBH, I bought Double Fighters as a compromise to stop me switching tyres all the time. Day-to-day I ride my MTB on roads and cycle tracks, but I like the fact I've got some off-road capability still, to go a bit more rural if the whim takes me. Then I only need to switch to my full MTB tyres if I know I'm going to be riding somewhere where I need their extra bite.

Plus I like the look of the Double Fighters