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I have a old mountain bike (10 years old) and for most of it's life it's sat in the shed (being ridden lightly maybe once or twice a year), only recently have I tried riding it regularly for the first time since ownership.

I have a really strange problem with the bike tyre pressures, sometimes whilst it has been in the shed they have gone completely flat and just sat there like that for over a year. When I finally get round to riding it, I pump them up and they are good to go, however, sometimes after pumping them up they go completely flat the next day. Other times, when I pump them up they hold pressure for months on end (if not years) without going flat.

What I found really strange is yesterday I thought my front tyre pressure was slightly low so thought I'd pump both tyres up nice and high as I'm mostly using the bike on the road now. Pumped them both up, put the bike back in the shed. Today, I go for a bike ride and the back tyre is perfect, solid, the front one is completely out of air. So pumped it up again and went for a ride, half way on my journey it went completely flat again and so had to ride back on the flat.

Now I've taken apart the front tyre and pumped up just the inner tube, it's holding pressure fine for now, will do the water bucket test tomorrow, but there are currently no signs of leaks.

Does anyone have any idea why my front tyre can hold pressure for months on end and then after being pumped up it immediately goes flat very quickly sometimes (the back has done the same in the past).

Since I'm riding the bike more often, I really need to sort this as I am travelling further and further and it really sucks to come back on a flat.

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    Sounds like its a valve problem. I would just put in new tubes.
    – mattnz
    Jun 21, 2020 at 22:52
  • One thing my father showed me for Schrader valves (well, couple things actually) - before you pump your tire up, put the end of the pump near the valve and pump it, to blow out any dust etc from the valve (especially if you don't have dust caps on the valves) and #2, after you're done blowing your tire up, lick a reasonable amount of spit onto your finger and rub it over the top of the valve hole to make an unbroken skin of water.. and wait. If the valve leaks you'll see the membrane blow out into a bubble. If you leave that valve as is it'll be flat in no time. Use a core tool and clean it
    – Caius Jard
    Jun 22, 2020 at 16:16

1 Answer 1

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Sounds like the butyl rubber inner tubes have perished a little, and you have either a very slow leak, or a valve that lets the air out slowly.

Just buy three new tubes from an online supplier - they'll cost about $5 each. Two to fit, and one to carry as the spare. You should also have two/three plastic tyre levers, a working pump, and whatever tools are needed to get a wheel off the bike.

The old tubes can be used to hold plants to stakes in the garden, or as a chainstay protector, or sliced up into rubber bands.

Also, I'd suggest having a close look at the tyre's surface, and decide if they're getting a bit old. Rubber is attacked by ozone, UV, and heat, so if your bike was stored in a shed/garage then they can slowly deteriorate. If you're doing strictly road riding then its a good chance to change to more efficient tyres too, compared to MTB knobblies.

Finally, check your brake pads. Rim brakes have rubber blocks which can harden with age, so your brake performance can suffer. Disk brake pads are not rubber so don't deteriorate in the same way.

These are all consumable items, so don't get put off by some costs.

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  • The levers might not be necessary; in many cases it's not a great idea to give a beginner levers to change a tire, because they only go and lever the tyre on, nipping the tube and puncturing it in the process. Bicycle tires can usually be changed with hands alone
    – Caius Jard
    Jun 22, 2020 at 16:05
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    @CaiusJard got to learn how to do it at some point. And better to have levers and not need them than the opposite. There's a lot of variables, so trying to keep advice general.
    – Criggie ♦
    Jun 22, 2020 at 21:12
  • So I have an update, I tested the tyre and it had a small hole puncture in it, not sure if this was caused by me when riding it back or taking the tyre apart without levers, but I patched it and rode it for 10 miles and seems good for now. Trouble is with my tyre, it seems quite hard to find a tube that fits. Currently, I have KENDA 26 x 2.125/2.35 tubes and I think the tyre is 2.35 - anyone know where I can buy a good MTB tube in that size?
    – KillerKode
    Jun 23, 2020 at 8:22
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    Ok, so as an update, I've had 3 more punctures since, can't explain what is causing them as the tyre itself seems fine and there are no debries that I can see inside the tyre that would cause the puncture. The rim tape rubber is in there as well, so the only real explanation I have is the age and the fact the rubber has deterioated. Have ordered another tube now so will see if it punctures again or solves the problem.
    – KillerKode
    Jul 21, 2020 at 19:32
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    Long story short, I replaced the inner tube with continental ones and guess what, they don't puncture anymore. I've done nearly 100 more miles than when the old ones would puncture. So you are right, the rubber just seems too old and puncturing in random places. This was the front tyre, now the back tyre has punctured for the first time in two places, not going to bother with a patch, just going to replace that 10 year old tube with another continental one.
    – KillerKode
    Aug 10, 2020 at 21:05

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