P****ures caused by brake blocks???

[dand_uk]

Hello all,

I was happily cycling to work this morning, taking the main roads thru soton, on my road bike with 23 x 700 tyres. I was approaching a traffic light at the bottom of a slight hill and pressed the front brake pretty hard and was dismayed to hear a hiss from my tyre. There was a fair bit of grit and dirt on the tyre but no visible damage. 10 minutes later I had replaced the tube and was off down the next hill. Once again I was braking for a red light quite hard using the front brake and I heard the same hiss - the second tube was deflating!

Now I checked my brake blocks and they are very worn, with a sharpish unworn bit on the top of one of the blocks - would this cause a p****ure? I can't see how the block would touch the sidewall... Anyone else had this happen?

Interesting way to begin the January commute, hopefully I get home ok as I have no more tubes!

 

[fossyant]

I would check your tyres, as you could have worn a hole in the side wall if the pads aren't aligned correctly.

 

[HelenD123]

I would check your tyres, as you could have worn a hole in the side wall if the pads aren't aligned correctly.

+1 I wore a patch away on my front tyre because I hadn't adjusted the brake pads . The LBS told me to get a new tyre as I risked a blow out.

 

[summerdays]

Now I checked my brake blocks and they are very worn, with a sharpish unworn bit on the top of one of the blocks - would this cause a p****ure? I can't see how the block would touch the sidewall... Anyone else had this happen?

Interesting way to begin the January commute, hopefully I get home ok as I have no more tubes!

Have you checked the angle the brake blocks hit the rim and if they are firmly bolted on ... if its a bit loose then the force of braking could rotate the block slightly (or on some kids bikes with naff brakes arms I've seen it happen).

 

[mgarl10024]

Hi dand_uk,

I'm a relative newbie so I may be miles out, but I'm sure I remember reading that consistent braking can overheat rims and cause flats. I'd be amazed given the ambient temperature, but I wonder if your worn blocks are causing really excessive heat - especially if you are applying them firmly downhill.

As I say, probably miles out, but didn't hurt to throw it out there!

MG

 

[martint235]

Hi dand_uk,

I'm a relative newbie so I may be miles out, but I'm sure I remember reading that consistent braking can overheat rims and cause flats. I'd be amazed given the ambient temperature, but I wonder if your worn blocks are causing really excessive heat - especially if you are applying them firmly downhill.

As I say, probably miles out, but didn't hurt to throw it out there!

MG

It can happen but you really need to be braking hard, think on the way down a French col at high speed type braking. I doubt braking for lights, even with worn blocks would generate that kind of heat.

 

[fossyant]

Never blown a tyre through heat - you'll need something like Alpe D'Huez.......and even then it's unlikely.

I've have a mate who had to stop on the Alpe to let his rims cool as the heat was melting his tub glue (he had tubular tyres on)...

 

[mickle]

It's not about heat, it's simply that the brake-block has worn through the tyre. It can be caused by a number of different factors -

* Inadequate torque on the brake-block mounting bolt. Brake-block moves out of alignment, rubs on tyre, pop.
* Excessive wear - as the block wears down an unworn section creeps over the edge of the rim until it contacts the tyre. Pop.
* Replacing the wheel on the piss. Brake block crawls under rim - rubs on tyre - pop.
* or any combination of the above

- but the punchline is the same - your tyre is dead and fit only for the bin.

 

[gbb]

Assuming there is NO damage to the rims of the tyre, i'd take the wheel off, remove the tyre and carefully inspect the inside, looking and feeling for holes caused by glass etc (when this happens, you inflate the tube and it may hold for a while, then the pressure causes the innertube to force its way out of the hole...bingo) It may help to hold the tyre bead with your thunbs and use your fingers to 'invert' the tyre so you can get a good look at the inside of the tyre.
A good time to look for debris jammed in the tyre as well. You may have just got away with something still in there, then its just worked its way back into the new innertube.

 

[ttcycle]

If there is a sharp edge on your brake block, sounds like they should have been replaced a long while back. The worn blocks may have then over time rubbed away at the tyre wall- I'm with mickle on this one, sounds as if you need go get a new set of tyres and brake blocks.worth keeping an eye on how worn they are. If there's a good amount of soft brake pad left on your blocks then it's an alignment issue but it still may be the case that your tyres are toast.

 

[gbb]

Ops made no mention of visible tyre damage, he's actually said he can see no damage. Assuming he's right and closely inspected the sidewalls...i dont see the need for new tyres on that basis.
IF there's a split in the running surface of the tyre that he's not seen or found yet...then a new tyre would be wise.
The strange thing is deflating as he's braking ? Co-incidence ? Is it worth checking the rims of the wheel itself...looking for splitting or cracking of the rim. Could a sharp piece of a split rim be causing this ? Under braking, the rim could (and probably would) deform...worth checking, even though its moderately unlikely.

 

[gbb]

Hello all,

I was happily cycling to work this morning, taking the main roads thru soton, on my road bike with 23 x 700 tyres. I was approaching a traffic light at the bottom of a slight hill and pressed the front brake pretty hard and was dismayed to hear a hiss from my tyre. There was a fair bit of grit and dirt on the tyre but no visible damage. 10 minutes later I had replaced the tube and was off down the next hill. Once again I was braking for a red light quite hard using the front brake and I heard the same hiss - the second tube was deflating!

Now I checked my brake blocks and they are very worn, with a sharpish unworn bit on the top of one of the blocks - would this cause a p****ure? I can't see how the block would touch the sidewall... Anyone else had this happen?

Interesting way to begin the January commute, hopefully I get home ok as I have no more tubes!

Funny innit, you read a post and dont see it all.
The 'sharpish' unworn bit on the pad. Do you mean sharp (as a sharp object) or just unworn compared with the rest of the pad... You say you cant see how it would touch the sidewall...have you applied the brakes hard and looked ? Can it touch the sidewall...worse still force the sidewall in. That may allow the innertube to 'escape' where the tyres deformed under braking.
Even so....you still make no mention of tyre damage, i'd expect the tyre itself to be damaged if the pad could touch the tyre.
Real real close inspection of everything is whats needed.
Check the following..
Inner surfaces of the tyre for slits or thorns that may be still there from the first deflation.
Sidewalls of the tyres for damage from the blocks.
Bead of the tyre, make sure the bead is not showing through the rubber. (metal strands perhaps)
The wheel rim itself for splits or cracks.
Make sure your rim tape is seated properly and no debris or spoke nipples showing.

 

[MontyVeda]

did you keep the punctured inner tubes and suss out where the hole is? I had a problem with innertubes going at the valve welds and after numerous replacements, I decided to stop buying tubes from Wilko and I've not had a puncture since

 

[Tynan]

if the tyre is badly worn, the act of braking might be subjecting a thin area of the tyre to more strain than it can deal with

I ran a tyre that thin once, a hard stop literally wore away the last of the carcass on the running line

 

[dand_uk]

Hi everyone thanks for your input. I checked out the damage on Tuesday night and it looks like the first p****ure was caused by something sharp p*ncturing the outer tyre as there was a small hole in it. I could not see any significant damage on the sidewall. The tube is repairable.

The second tube is a mess, has about three holes in it, some near the valve! It looks like either the tube was dodgy or I made a mess of it replacing it!

Anyhoo I changed the brake pads and the outer tyre since I had not changed it for about a year including an End to End ride.

I think the fact that I was braking hard at the time was probably just a coincidence, or the extra weight pressing on the front wheel could have done it.