Snake bite punctures

[al3xsh]

Hi all,

After managing to avoid getting punctures for ages, I've had two in the last week. :'(

Both have been snake bite punctures - the first after hitting a big pothole, but today I don't remember hitting anything particularly noticable. I pump my tyres up pretty much before every ride to 100 psi which I thought would be enough. I'm about 70kg, and running conti gp 4000 s2s. Both have been on the rear.

Does anybody have any ideas to reduce the chances of this happening again?

As an annoying aside, when I went to change the tube today the new inner tube valve core kept unscrewing when I took the pump off! Not something I'd ever encountered before but required a walk to the nearest farmhouse to borrow some pliers to tighten the core up!

Cheers,

Alex

 

[raleighnut]

What width tyres ?

 

[al3xsh]

25s

 

[Cycleops]

Stay out of the grass.

 

[Tim Hall]

That sound a bit odd. I'm a well nourished individual (90kg) and I haven't had a snake bite puncture for ages and ages. I tend to run at about 90psi on 25mm tyres. Is your 100psi accurate? How big a thing did you hit?

 

[al3xsh]

That sound a bit odd. I'm a well nourished individual (90kg) and I haven't had a snake bite puncture for ages and ages. I tend to run at about 90psi on 25mm tyres. Is your 100psi accurate? How big a thing did you hit?

The first time the pothole was big enough to make me go "ouch"! The second time I didn't think I hit anything much - nothing memorable anyway.

I have no idea how accurate the pump gauge is - I've not got anything to compare it to! :-) 100 psi certainly feels pretty solid!

A

 

[ColinJ]

Does anybody have any ideas to reduce the chances of this happening again?

Avoid riding into potholes ...?

Seriously though - you can avoid most of them but sooner or later one will catch you out. I find riding down woodland descents on sunny days a problem. Wearing sunglasses reduces what you can see in the shaded bits, and scattered shadows make very effective camouflage for broken road surfaces. I hit a couple of holes at the weekend but got away with it.

You are using higher pressures than me and I weigh 20% more than you, so I don't think lack of pressure is the cause of the second puncture. Are you sure that you didn't damage the tube when fixing the first problem? Was the second puncture definitely a snakebite? (I.e. - did the tube have the classic double hole that looks like a snake has bitten it?)

When I first got back into cycling I punctured every day for a week until a more experienced cyclist pointed out that my tube replacement technique was damaging the tubes. (I was using tyre levers to put the tyres back on and was accidentally nipping the tube every time.)

 

[raleighnut]

Try another 10psi in the rear, 25s should be rated to about 120psi.

I'm running 25s on a couple of mine and at 100 ish rear and 90 front haven't had any problems and I'm hefty these days

 

[Heltor Chasca]

I helped a friend with a snakebite puncture on Saturday. She was descending a 20% hill

 

[al3xsh]

Thanks all for the advice.

Are you sure that you didn't damage the tube when fixing the first problem? Was the second puncture definitely a snakebite? (I.e. - did the tube have the classic double hole that looks like a snake has bitten it?)

Hard to be 100% sure regarding damaging the replacement tube, but I don't use tyre levers to replace the tyre - just thumbs. And I try to pump it up a bit, go round giving it a good squeeze, and then pump to full pressure (or as best as I can get with a hand pump!).

And they were both definitely snake bite punctures - two parallel slices in the tube.

I do try to avoid potholes - bit sometimes you don't see them til too late. Especially - as you say - shaded spots. :-)

@Heltor Chasca that's one thing that does freak me out a bit. Both of these happened at speed (30mph +) and I was fortunate that is was possible to stop reasonably easily.

A

 

[keithmac]

Take the tyre ofd and feel the wheel rim all the way round with your fingers, it's possible the first pot hole encounter has damage the rim (possible sharp point puncturing the new innertube?).

 

[al3xsh]

Take the tyre ofd and feel the wheel rim all the way round with your fingers, it's possible the first pot hole encounter has damage the rim (possible sharp point puncturing the new innertube?).

Thanks - I'll definitely have a look when I get a chance to take the wheel and tyre off the bike. I've had a look on the outside and can't see anything, but I'll definitely have a check of the inside later today or tomorrow.

Try another 10psi in the rear, 25s should be rated to about 120psi.

In the meantime I'm trying this!

Cheers,

A

 

[Tim Hall]

Try another 10psi in the rear, 25s should be rated to about 120psi.

I'm running 25s on a couple of mine and at 100 ish rear and 90 front haven't had any problems and I'm hefty these days

But for a 70kg rider that sounds like overkill and uncomfortable. @Ajax Bay normally pops up about now with his Useful Graph of tyre pressures.

 

[raleighnut]

But for a 70kg rider that sounds like overkill and uncomfortable. @Ajax Bay normally pops up about now with his Useful Graph of tyre pressures.

How else do you propose he cures the 'snakebite' punctures, only ride on smooth surfaces ?

 

[Ajax Bay]

After managing to avoid getting punctures for ages, I've had two in the last week . . . both snake bite punctures [on rear] . . . 100 psi . . . I'm about 70kg, and running conti gp 4000 s2s.
The first time the pothole was big enough to make me go "ouch"! The second time I didn't think I hit anything much
at speed (30mph +) and I was fortunate that is was possible to stop reasonably easily.

Is your 100psi accurate?

It'd be worth making an effort to verify the 100psi ie the accuracy of your track pump gauge. I believe this may have contributed to my 'off' (see below).

Avoid riding into potholes ...?

This is the secondary control measure for minimising the risk of snake bites, after having tyres at the 'right' pressure. Colin has pointed out that this is sometimes not easy, to which I'd add momentary lack of attention (eg distracted by cockpit devices, map or route notes).

Try another 10psi in the rear, 25s should be rated to about 120psi.

Given the OP already has his 25mm rear tyre at 100psi and he weighs 70kg, an extra 10psi will not significantly reduce the risk of snake bites. 100psi is already high (see attachment Tim flagged me for).
As an observation that chart suggests that front tyres (25/28mm) need 15psi less than the rear in.

I helped a friend with a snakebite puncture on Saturday. She was descending a 20% hill

My 'off' last year was a(n instaneous) puncture downhill (one chevron) at speed (slightly bending road) at 199km into a 300km audax. It did not end well: memory stops, endo, broken shoulder blade, ribs, punctured lung, unconscious for several (or more minutes), air and road ambulance discussing where and whether by road or air, intensive care - 2 days.
My posts describing/discussing the accident are here:
https://www.cyclechat.net/threads/t...challenge-chatzone.95264/page-84#post-4950192
https://www.cyclechat.net/threads/t...challenge-chatzone.95264/page-85#post-4952273
Happily, my bike was relatively unscathed. The inner tube had a major snakebite in it: 11mm on one side and 9mm on the other, which will have caused/allowed the near instantaneous deflation I remember. There is a significant dink in one side of the rim where the puncture was. And there is damage to the left hand rim edge for about a third of the circumference, consistent with the rim attempting to roll on the road surface before saying ‘enough’. There is damage to the tyre sidewall in this area too. Inspecting the hill a month later, the surface was fine (ie no potholes or the like), the light was fine and I was concentrating, on the drops, down that hill (with half a dozen others riders coming down behind me).
Full analysis post: https://www.cyclechat.net/threads/big-offs.224746/post-4987009
To add: I used a Joe Blow track pump to inflate my tyres (the night before). Subsequent checking suggests that the gauge on that pump reads about 10psi low (using a reliable tyre pressure gauge to calibrate it against) so it's possible that might be how my tube had less than the required pressure in. Or I might have lost pressure during the 199km of riding that day.