Any tips on avoiding pinch flats?

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Any tips on avoiding pinch flats?

Postby boss » Wed Jan 16, 2013 1:43 pm

Hi all,

I am currently running a set of Aksium wheels with Conti GP4000s tyres. The Conti's are maybe 2000km old and according to the wear indicators, still have a bit of life left in them.

Over the last two weeks I've had a couple of pinch flats - similar kind of situation both times. Riding along, check over my shoulder, hit a bit of debris, TWANG, followed by a flat.

The first time it was my bad - I was in a world of my own. I should have been more alert as the area was covered in debris. Luckily the tube came down fairly slowly (slow enough for me to realise I had a flat), pull over, swear a bit, fix the flat and ride on.

The second time was a bit hairier. I was riding down a mild descent but I was really giving it to it. The road was pretty much free of any visible debris. Travelling in the high 40's / low 50's with a fairly high cadence, I checked my shoulder for cars, heard a TWANG, and got a major wobble going. The wobble was actually so bad that I actually thought I'd lost the front tyre. Managed to keep it together and slow down.

Both times I was running around 100-105psi in the rear, and both times the tube had been installed for a little bit so it wasn't an installation error issue. Debris hit tyre = pinch flat.

Now I'm just looking for a bit of advice - are there any tips or tricks to avoiding pinches? I was always told that the more pressure the better to avoid pinches, but that was in a different discipline of riding bikes...
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by BNA » Wed Jan 16, 2013 1:53 pm

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Re: Any tips on avoiding pinch flats?

Postby wombatK » Wed Jan 16, 2013 1:53 pm

boss wrote:Both times I was running around 100-105psi in the rear, and both times the tube had been installed for a little bit so it wasn't an installation error issue. Debris hit tyre = pinch flat.

Did you find the classic "snake bite" puncture pattern on the tube ? If so, you haven't said anything about you weight, but if you're under (say) 80 kg, you could probably afford to up the pressure to 115 to 120 psi. Except on really hot days where you might be braking a fair bit.
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Re: Any tips on avoiding pinch flats?

Postby boss » Wed Jan 16, 2013 1:58 pm

It didn't snake bite but I'm sure that at least the second instance was a pinch. 90% sure on the first, but I didn't inspect it that closely.

The second was lined up with the bead, no damage to the rim, rim bed, or tape.

I'm 65-70kg. Not sure exactly but I think I'm on the lower end of that right now.
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Re: Any tips on avoiding pinch flats?

Postby boss » Wed Jan 16, 2013 2:00 pm

Also, is there any benefit in moving from 23mm tyres to 25mm tyres?

I'm not going to go out and prematurely ditch my current 23mm GP4000s, but I've been tempted to go 25mm's next time around, if they are less susceptible to pinching I reckon they will be the go.
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Re: Any tips on avoiding pinch flats?

Postby HappyHumber » Wed Jan 16, 2013 2:04 pm

pinch flats by definition aren't caused by debris.... usually under inflation, or hamfisted installation* esp. where a lever has pinched a point in the tube.

+1 to WombatK's "snakebite" description as the strongest tell-tale of a pinch.

Other than the patterns you've described of hitting debris - have you noticed anything else - like relative position of the hole on the tube to the tyre? Have you thoroughly inspected the tyre for remaining glass/metal splinters? They can cause multiple punctures if left.

Old sages recommend mounting the tyre logo aligned with the valve & hole in the rim so you can relate a "12 O'clock" position to any found puncture in a tube to a "time" on the tyre to zero in on when looking.

* Yes, I'm still occasionally guilty of this. Though, gratefully less and less. :oops:
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Re: Any tips on avoiding pinch flats?

Postby boss » Wed Jan 16, 2013 2:19 pm

HappyHumber wrote:pinch flats by definition aren't caused by debris.... usually under inflation, or hamfisted installation* esp. where a lever has pinched a point in the tube.

+1 to WombatK's "snakebite" description as the strongest tell-tale of a pinch.

Other than the patterns you've described of hitting debris - have you noticed anything else - like relative position of the hole on the tube to the tyre? Have you thoroughly inspected the tyre for remaining glass/metal splinters? They can cause multiple punctures if left.

Old sages recommend mounting the tyre logo aligned with the valve & hole in the rim so you can relate a "12 O'clock" position to any found puncture in a tube to a "time" on the tyre to zero in on when looking.

* Yes, I'm still occasionally guilty of this. Though, gratefully less and less. :oops:


Pinches aren't only caused by hamfisted install (although I don't disagree that you can pinch when installing), they can also be caused by bottoming out or anything else that can cause the bead to position itself on top of the tube.

As mentioned above, the debris was sizable enough to cause a loud twanging which I suspect was movement of the tyre bead. Similar sound to a massive rubber band snapping.

And again, as mentioned above, the hole on the second occasion was on the side of the tube.
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Re: Any tips on avoiding pinch flats?

Postby il padrone » Wed Jan 16, 2013 2:27 pm

100-105 psi, 65-70kgs? You shouldn't have enormous risk of pinch flats with this. My old roadie runs 20mm tyres at 105psi and I weigh just 60kg. Of course if you hit something big enough you will puncture. You need to watch the road surface (but of course you do).

I've ridden my 20mm tyres on significant stretches of rough gravel roads without any pinches. Pinch flats are normally caused by inadequate tyre pressure and/or hitting a road bump or debris.

Remedy for pinch flats:
1. Pump tyres to pressure

2. Observe the road ahead

3. Stay out of the junk-zone (ride wider on the road)

:wink:
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Re: Any tips on avoiding pinch flats?

Postby boss » Wed Jan 16, 2013 2:34 pm

il padrone wrote:100-105 psi, 65-70kgs? You shouldn't have enormous risk of pinch flats with this. My old roadie runs 20mm tyres at 105psi and I weigh just 60kg. Of course if you hit something big enough you will puncture. You need to watch the road surface (but of course you do).

I've ridden my 20mm tyres on significant stretches of rough gravel roads without any pinches. Pinch flats are normally caused by inadequate tyre pressure and/or hitting a road bump or debris.

Remedy for pinch flats:
1. Pump tyres to pressure

2. Observe the road ahead

3. Stay out of the junk-zone (ride wider on the road)

:wink:


Cheers.

I'm pretty good at 1) and 3), but I think I'll just need to be a bit more cautious of road conditions.

The second time that I pinched, the road isn't the nicest piece of pavement (Waterfall Gulley Rd in Adelaide, for anyone playing along at home). I don't know if it was debris or the road surface, I'll be a bit more cautious there in future.
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Re: Any tips on avoiding pinch flats?

Postby RonK » Wed Jan 16, 2013 2:58 pm

You would have to hit a pothole or some other sharp edge to get a pinch flat at those tyre pressures, so there would be more than a mere twang. And this kind of impact would usually cause a snake bite.

More likely the tyre has glass, stone chip or wire embedded in the tread.
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Re: Any tips on avoiding pinch flats?

Postby boss » Wed Jan 16, 2013 3:01 pm

RonK wrote:You would have to hit a pothole or some other sharp edge to get a pinch flat at those tyre pressures, so there would be more than a mere twang. And this kind of impact would usually cause a snake bite.

More likely the tyre has glass, stone chip or wire embedded in the tread.


I'll take the tyre off tonight and check it out. But I checked it pretty thoroughly on both occasions with no luck. I should add that while I'm relatively green on the subject of road bikes, I've changed my fair share of tubes over the years. Fixed many a flat.

FWIW I wouldn't call it a mere twang. I'd call it an effing loud twang.
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Re: Any tips on avoiding pinch flats?

Postby sogood » Wed Jan 16, 2013 3:30 pm

1. Suitable tyre pressure.
2. Avoid raised obstacles/pot holes.
3. Slow down on crossing obstacles.
4. Learn to bunny hop and unweighing.

Pinch flats no more!
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Re: Any tips on avoiding pinch flats?

Postby il padrone » Wed Jan 16, 2013 5:15 pm

RonK wrote:You would have to hit a pothole or some other sharp edge to get a pinch flat at those tyre pressures, so there would be more than a mere twang. And this kind of impact would usually cause a snake bite.

More likely the tyre has glass, stone chip or wire embedded in the tread.

My wife had a puncture the other week (first one ever in any of our Vittoria Randonneur Cross tyres). I was amazed and disappointed - checked the tube and fond a large hole - tube would barely stay up long enough to trace it - and there looked to be just one hole. But there was absolutely nothing in the tyre :? On questioning Marg about the incident she did say she had hit a 'stick' just before the tyre went flat, Must have been a BIG one as these tyres are 47mm. Anyhow on checking the hole more closely it did seem to be two penetrations very close together ie. a very tight pinch.

After changing the tube the tyre stayed up and is still fine. Re. the 47mm tyre, I think she must have had the tyre pressure down low. If I don't check her tyres nobody will :roll:

The Vittoria Rando Crosses still remain the tyre with zero penetration punctures in my book 8)
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Re: Any tips on avoiding pinch flats?

Postby Mulger bill » Wed Jan 16, 2013 10:31 pm

sogood wrote:1. Suitable tyre pressure.
2. Avoid raised obstacles/pot holes.
3. Slow down on crossing obstacles.
4. Learn to bunny hop and unweighing.
Pinch flats no more!


All of the above, with emphasis on the blue bit. Learn to flow over what you can't avoid. Of course, sometimes it's impossible for various reasons :oops:
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Re: Any tips on avoiding pinch flats?

Postby boss » Thu Jan 17, 2013 8:47 am

As a BMX rider by trade (well, sort of) I'm reasonably acquainted with old mate bunny hop. On the BMX I can hop over things about 1m high, not so high on the roadie though!
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Re: Any tips on avoiding pinch flats?

Postby sogood » Thu Jan 17, 2013 10:33 am

boss wrote:As a BMX rider by trade (well, sort of) I'm reasonably acquainted with old mate bunny hop. On the BMX I can hop over things about 1m high, not so high on the roadie though!

On the roadie 30km/h, an obstacle 1m high will bring somewhat more than just a pinch flat to the OP. :mrgreen:
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Re: Any tips on avoiding pinch flats?

Postby il padrone » Thu Jan 17, 2013 10:43 am

.
Last edited by il padrone on Thu Jan 17, 2013 11:40 am, edited 1 time in total.
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Re: Any tips on avoiding pinch flats?

Postby RonK » Thu Jan 17, 2013 11:35 am

il padrone wrote:
sogood wrote:On the roadie 30km/h, an obstacle 1m high will bring somewhat more than just a pinch flat to the OP. :mrgreen:

Just ask Martin Ashton :wink: :D

Another lycra lout riding stupidly.

If they think they have to ride over rocks and along cliffs it's no wonder ordinary people are put off from cycling. :lol:
Last edited by RonK on Thu Jan 17, 2013 4:21 pm, edited 1 time in total.
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Re: Any tips on avoiding pinch flats?

Postby sogood » Thu Jan 17, 2013 11:49 am

RonK wrote:Another lycra lout riding stupidly.

A bit harsh isn't it? :roll:
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Re: Any tips on avoiding pinch flats?

Postby find_bruce » Thu Jan 17, 2013 12:47 pm

sogood wrote:
RonK wrote:Another lycra lout riding stupidly.

A bit harsh isn't it? :roll:

Having seen RonK's comments in various lycra threads I suspect he is being sarcastic
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Re: Any tips on avoiding pinch flats?

Postby RonK » Thu Jan 17, 2013 1:40 pm

find_bruce wrote:
sogood wrote:
RonK wrote:Another lycra lout riding stupidly.

A bit harsh isn't it? :roll:

Having seen RonK's comments in various lycra threads I suspect he is being sarcastic

:roll: :lol: :lol: :lol:

Dunno how to do a smiley on my phone...
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Re: Any tips on avoiding pinch flats?

Postby sogood » Thu Jan 17, 2013 3:53 pm

RonK wrote:Dunno how to do a smiley on my phone...

Get an iPhone! :mrgreen:
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Re: Any tips on avoiding pinch flats?

Postby Metor » Thu Jan 17, 2013 9:57 pm

Conti 4000s are great tires but soft. So regularly check your tires for little stones, etc which start digging in the tires. If you do that it will save you some flats.
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Re: Any tips on avoiding pinch flats?

Postby sogood » Fri Jan 18, 2013 12:20 am

Metor wrote:Conti 4000s are great tires but soft. So regularly check your tires for little stones, etc which start digging in the tires. If you do that it will save you some flats.

Not relevant for pinch flats.
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Re: Any tips on avoiding pinch flats?

Postby boss » Sun Jan 20, 2013 11:41 am

I think I may have discovered my issue.

Turns out the aksiums I had were badly worn - past the wear indicators and concave. They came with my bike (2nd hand) - I know how many k's the bike did, but no idea on the rims as they weren't standard fitment. They were gone though...

Luckily I had a set of DA c24's ready to go.

But I have a feeling that the weakened walls may have contributed to the tendency to pinch flat.

But I could be wrong. Who knows. Good excuse to get off my butt and swap my wheels out.
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Re: Any tips on avoiding pinch flats?

Postby Metor » Sun Jan 20, 2013 1:19 pm

sogood wrote:
Metor wrote:Conti 4000s are great tires but soft. So regularly check your tires for little stones, etc which start digging in the tires. If you do that it will save you some flats.

Not relevant for pinch flats.

True, didn't saw "pinch" sorry for that.
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