2 punctures simultaneously, just unlucky or another explanation??

joker77 · 10-12-2009 12:07am #1

Hi there,

I'm looking for an explanation as to what happened this evening, or if this has happened to anyone else here is there something I'm doing wrong… The long and short of it is I got 2 punctures at the same time, here’s the full series of events – it’s a bit of a long read so fair play if you finish it!

I got a new Planet X Ultegra a couple of months ago and have been out on in less than 10 times so far, not as much as I would have liked to due being away and being sick. The longest spin I’ve done is 50km, all told I’d say I’ve done about 300, thereabouts.

So before heading out this evening I checked the tyre pressure, had been out on Monday evening so pumped them back up to 110. Now one thing I noticed here was that there wasn’t a whole lot of the valve to work with – I’ve a Specialized foot pump and that was flush to the rim when it was locked. When I pumped up one, think it was the back, the pressure went to say 110 but started dropping straight away. I thought it was because the valve wasn’t fully locked on, but I reckoned there was nearly 110 there so I removed it and closed the valve. Last time I'll be taking a chance like that...

I headed off hoping to get a decent spin in, up the Dundrum bypass and then was heading across the Sandyford Industrial Estate. The road got a little bad, and I went through what looked like was a puddle but turned out to be a pothole. Was a fairly rough hit, and something came off the bike. I thought it was the front light, but when I went back it turned out to be the mini pump I have attached at the bottle cage. Put it back on and noticed the back was flat. Fairly p*ssed off, I went over to a bus shelter to change the tube. It was then I noticed the front was flat as well – couldn’t believe it. I only had the 1 spare tube with me, luckily I hadn't gone too far so walked the bike the 4km home.

So – 2 punctures simultaneously – what the F*CK!

I searched for any problems with the rims / tyres but couldn’t find any. Both punctures were identical – 2 small slits in each tube, both going lengthways right next to each other. This makes me think there were caused by the holes in the rim for the spokes rather than anything else – maybe a combination of possibly too much pressure and a sharp edge on the pothole. The wheels are Planet X model B, 20/24.

That's the end of my tale. Anyone have any similar incidents, or any better idea as to what happened??

DirkVoodoo · 10-12-2009 12:15am

joker77 wrote: »

The road got a little bad, and I went through what looked like was a puddle but turned out to be a pothole. Was a fairly rough hit, and something came off the bike.

Sounds like that was all it was. I've seen a few monster potholes recently, as in the kind that would throw you clear off the bike. The recent weather has really played havoc.

2 small slits normally indicated a "snake bite" pinch flat, when the tube pinches the rim. Sounds odd seeing as your tyres were fully pressurized, but like you say you hit the pothole fairly hard.

Wouldn't worry about it, chances are it won't happen again. 2 tubes.

EDIT: Similar tales? In my most smug posting voice, I can't remember my last puncture commuting, I think it was a year ago. I got a flat before a saturday spin during the summer, that was my last one. The valve was coming away from the tube. Before that, I think it was march. I'm pretty sure I have had 2 punctures in 2009. Cue the double puncture tomorrow.

blorg · 10-12-2009 12:21am

They are pinch flats, you got both of them by going over the pothole. The impact of the pothole pinches the the tube against the rim, puncturing it. Also known as "snakebites" due to their appearance (always two slits like you describe.)

Possibly you were underinflated but it is not impossible to pinch flat even if correctly inflated, it just makes it less likely. Give the wheel enough of a bang and you will still do it. Certainly not overinflation anyway.

joker77 · 10-12-2009 12:23am

DirkVoodoo wrote: »

EDIT: Similar tales? In my most smug posting voice, I can't remember my last puncture commuting, I think it was a year ago. I got a flat before a saturday spin during the summer, that was my last one. The valve was coming away from the tube. Before that, I think it was march. I'm pretty sure I have had 2 punctures in 2009. Cue the double puncture tomorrow.

Have been lucky as well the last while - prob 1 puncture in the last year, maybe 2, commuting on 700x23.
This bike has 700x24 Conti Grand Prix, I reckoned I'd be safe for ages!
'Snake bite' - I like the analogy - I was looking how to describe it and that sums it up!

EDIT:
Cheers for both of you for the replies - puts my mind at rest. I think I need a new pump - with those rims there isn't a lot of clearance to lock onto the valve

BostonB · 10-12-2009 12:30am

Last puncture I got, was when I hit a pothole. I reckon some glass was in the tread, from road debris previously and when I hit the pothole it punched the glass through the tyre.

LastGasp · 10-12-2009 12:36am

joker77 wrote: »

with those rims there isn't a lot of clearance to lock onto the valve

If that's an issue you should get the tubes with the long valves. They come in various lengths like 50mm and 70mm for deep rims. It doesnt make any difference if they're a bit longer than strictly necessary.

Thinkingaboutit · 10-12-2009 12:41am

I got some from the actual rim cracking, wasn't a great bike though.

blorg · 10-12-2009 12:51am

BostonB wrote: »

Last puncture I got, was when I hit a pothole. I reckon some glass was in the tread, from road debris previously and when I hit the pothole it punched the glass through the tyre.

Not impossible, but unlikely. You can trivially puncture from hitting a pothole hard with no foreign object necessary. While for it to be a bit of glass you would have to hit it in just the right place.

Last time I did it was touring in Sicily, it has happened to me front and back frequently enough.

@joker77- I have the same rims and know what you mean about there not being a lot of valve showing (it's the same with anything with a slightly deep section) but there should be enough to pump it up OK, you shouldn't need to get longer valves. Bear in mind that as you pump the valve will come out a bit more so you can get a bit of a better grip on it as you go.

petethedrummer · 10-12-2009 1:51am

This brings me back to my first post on here, it was about snake bite punctures.

Anyways be careful going through puddles, there can be anything hidden under the water; potholes, glass, drains etc... I once hit a pot hole covered by water that was so deep it jerked both my hands off the handlebars, thankfully they landed back safely.

joker77 · 10-12-2009 11:49am

Cheers lads for the replies.

I guess the lessons to be learned are to:

make sure the valve is fully locked on the pump
also make sure the tyre pressure is right before any decent spin
take 2 spare tubes with me just in case
try my best to avoid any potholes / puddles while out there!

2 punctures simultaneously, just unlucky or another explanation??

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