Rapidly deflating tyres but no puncture

tangled_metal · July 2014

My hybrid bike got a flat tyre which went flat in less than 2 minutes after hitting a small bump. Got home and tried pumping the tyre up again to 85PSI and tested the valve with water, no bubbling so guessing it's OK. The tyre has not lost any pressure since pumped up 2 days ago. Tyre is OK, the whole bike is 10 months old and has only been ridden for 400 miles. Kept inside a brick shed or weekdays in partial sun (on one tyre for a couple of hours a day) on weekdays only so very little UV light I reckon. Means unlikely to be old or UV degraded rubber.

I commute on this bike so need confidence it'll get me to work in the morning. Not knowing what went wrong does not give me confidence. It seems OK now, but is it? Can I trust it after 2 days of staying inflated without pressure loss? I don't want to have to replace inner tube in the morning commute as being late is not an option with work.

Help! Please! Advice needed.

ElectronShepherd · July 2014

My two guesses would be:

1) The valve came slightly unscrewed, and was then screwed up again as part of pumping the tyre up

or

2) You've picked up a sharp thorn which caused the deflation, but when you pumped the tyre up, the inner tube effectively sealed itself around the thorn again. The spines from blackthorn and hawthorn are particularly smooth and then inner tube can form a seal around them. I once did 10 miles on a mountain bike with a small bit of blackthorn sticking out of the tyre. Made it home just fine, pulled the thorn out, assuming that it was simply stuck in the knobbly tread, and hadn't made it as far as the inner tube, and the tyre promptly went flat in about 10 seconds.

tangled_metal · July 2014

Someone else suggested the thorn idea. Thought it a bit too unlikely. It went flat, I pushed bike home and then when pumping up the tyre I manage to get the thorn back into the puncture hole and it all to seal up nice and tight. Possible and guess but a rare chance happening I think.

Well I'm risking the ride in but taking a spare tube and puncture kit. Will check to see if there is a thorn in the tyre first.

Thanks for your help.

Matthewfalle · July 2014

Why don't you just change the tube now, checking for thorns, etc and save potential early morning hassle?

rolf_f · July 2014

These things sometimes happen. I was riding in a group the other week. Something got thrown up from another bike and clattered through mine. A few moments later the tyre was flat. When I got the offending tube home and pumped it up, it was absolutely fine. Nothing wrong with valve or tube. If the tube holds air for a few days then it is probably fine.

PS if being late for work is not an option, you need to leave home earlier. Even if you run super heavy ultra puncture resistant tyres, they can still puncture, chains can break and gears can jam. Taking a spare tube and puncture repair kit should be a given though neither of the above will help if you don't take a pump with you as well!

Incidentally, UV might degrade the tyre but it isn't going to have much effect on the inner tube!

macleod113 · July 2014

Matthewfalle wrote:

Why don't you just change the tube now, checking for thorns, etc and save potential early morning hassle?

Exactly what I was thinking. change it when you have 10 minutes as its not nice to have to do it half way to work on the side of the road.

tangled_metal · July 2014

Yes, I know I should change it and I have a few spare inner tubes around to do it. it's ok though now, I have put it down to one of those strange things that happen. The inner tube is ok, nothing is sticking in the tyre or has gone through. Unfortunately i have been too busy these last few days to sort it out, with only a few spare moments away from the bike to post on here. Plan to check the tyre out properly tonight. Taking the inner tube out and the tyre off the wheel to get a proper look and feel inside to see if anything could have gone through to the tube.

Appreciate the replies. I was hoping someone on here had the same thing happen and knew the reason. Until I get the time to look at it properly I won't get any clue to the answer. I have a feeling there isn't any thorn or other sharp fragment because we were on a cycle/footpath that was in a bit of a trench between houses. Surprisingly it is clear of debris even though there are trees either side. A nice path really apart from the annoying chicane gates to stop motorbikes getting through. It was while riding away from one of these that i think the trigger for the deflation happened. Up until then there was no sign of any loss in pressure. I checked and there was no debris there at all. There was a little bit of broken glass to one side of the path earlier on but that was easily avoided.

I really don't like the tyres though. That cracking round the rim might not be a big issue but I don't like it. Might consider replacing. What are good tyre options? Currently got 38s on (700 wheel). it is a hybrid with suspension. What would you recommend for commuting, leisure riding and the odd tour (with child trailer)? I'm thinking a thinner tyre 32 or 28 if it will fit on the rims but would they be awful if I ever did a bit of off road (other than gravelly towpath and forest tracks that is)? People sometimes take touring bikes on slightly off road and I reckon they are 25 to 35 tyres. Would getting a bit thinner tyres make any impact on the road ride? Is it not worth it and the sacrifice of off road makes it a bad idea???

Any input on possible tyre upgrades? Brands, models, recommended tyre width, etc.??

holiver · July 2014

I did a ride last year where I hit a big crease in the road which seemed to burp a lot of air from my rear tyre. Had to do another 20km on low pressure before I could pump it up again and do the final 40km. It was fine for a long time after too before I replaced the tube with a lighter one.

Rapidly deflating tyres but no puncture

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