Author Topic: Mystery punctures  (Read 2424 times)

rogerzilla

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Mystery punctures
« on: 18 October, 2020, 08:34:31 pm »
Ever since I fitted 25mm tyres to one of my bikes, it has suffered punctures in the rear tyre with depressing frequency.  They are always on the valve side of the tube,  almost on the central seam.  They are not in the same place every time.  It takes 15-30 miles to happen.  Rim tape has been changed and there is nothing poking through it.  The tubes have been both Specialized and Vittoria.

Front wheel has the same rim, rim tape and tyre and is trouble-free.  The rear wheel has gone literally thousands of miles between punctures in previous years.

Any ideas?
Hard work sometimes pays off in the end, but laziness ALWAYS pays off NOW.

Pedal Castro

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Re: Mystery punctures
« Reply #1 on: 18 October, 2020, 08:36:33 pm »
Faulty batch of tubes?

rogerzilla

  • When n+1 gets out of hand
Re: Mystery punctures
« Reply #2 on: 18 October, 2020, 08:46:21 pm »
Faulty batch of tubes?
Unlikely.  Two different makers.
Hard work sometimes pays off in the end, but laziness ALWAYS pays off NOW.

Re: Mystery punctures
« Reply #3 on: 18 October, 2020, 09:05:44 pm »
pressures, loads and driving torque  are all higher in rear wheels and this makes the tube intolerant of even slight faults with the rim tape.  A series of unexplained punctures on the rim side of the tube is the usual result.

A very common fault is that the rim tape is slightly too narrow and the tube can 'see' the edges of the rim tape when the tyre is inflated. Some rims tapes have sharp enough edges that they can chafe through a tube.  Or the rim tape moves when the tyre is inflated, so that the rim drillings can nibble at the tube.

Other possibilities include that the tube is getting pinched between the tyre and rim during installation.

A further (and rare) one is that the tyre is a loose enough fit on the rim shoulders that it is well clear of the rim shoulders when the tyre is inflated, such that the tube can extrude into the gap and burst. This looks a lot like the tube has been pinched during installation (even though you might have checked for that), and appears to defy all logic until the penny finally drops. IME this fault is not likely to happen unless the tyres are a really slack fit.

hth

cheers

Davef

Re: Mystery punctures
« Reply #4 on: 18 October, 2020, 09:26:34 pm »
Did you perhaps forget a wedding anniversary? It can have mysterious consequences.

Re: Mystery punctures
« Reply #5 on: 18 October, 2020, 09:39:14 pm »
I’d personally start by adding 2 or 3 layers of electrical tape over the base tape- wide enough to cover the full width of the bed of the rim.
I guess you’ve checked for any over-long spokes just brushing the rim tape until you pump the tube up. I only ask because I had a series of punctures caused by just that, with little sign once tube was deflated and changed.

robgul

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Re: Mystery punctures
« Reply #6 on: 19 October, 2020, 08:01:23 am »
I’d personally start by adding 2 or 3 layers of electrical tape over the base tape- wide enough to cover the full width of the bed of the rim.
I guess you’ve checked for any over-long spokes just brushing the rim tape until you pump the tube up. I only ask because I had a series of punctures caused by just that, with little sign once tube was deflated and changed.

Same suggestion with extra but use masking/painters tape over the proper rim tape - it's softer on the edges - and make it wide enough to reach the inside of the rim wall.

Re: Mystery punctures
« Reply #7 on: 19 October, 2020, 09:34:33 am »
Anything on the inner bead edge of the tyre that might rub/wear/poke??

Re: Mystery punctures
« Reply #8 on: 19 October, 2020, 04:24:20 pm »
May be tiny cracks in the rim tape, which are difficult to spot when the tyre and tube are off but which get forced open by the pressure of the tube when inflated - wide enough for the crack edges to gradually cut into the tube.  More likely in solid/plastic-type tapes than cloth/woven ones I'd have thought.

Re: Mystery punctures
« Reply #9 on: 19 October, 2020, 10:33:23 pm »
May be tiny cracks in the rim tape, which are difficult to spot when the tyre and tube are off but which get forced open by the pressure of the tube when inflated
I've had that.
It put me off plastic rim strips (i.e non-fabric) for a long time.

Jaded

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Re: Mystery punctures
« Reply #10 on: 19 October, 2020, 11:31:55 pm »
Pops tiny model of roger on his bike into the bin. With the pins.
It is simpler than it looks.

zigzag

  • unfuckwithable
Re: Mystery punctures
« Reply #11 on: 19 October, 2020, 11:51:11 pm »
i'd re-tape them with two layers of tubeless tape, first making sure there are no burrs or anything sharp on the rim.

Re: Mystery punctures
« Reply #12 on: 20 October, 2020, 12:12:42 am »
I've had that.
It put me off plastic rim strips (i.e non-fabric) for a long time.

Happened to me in 1989.

Campagnolo brought out its Omega Strada Hardox v-section clincher rims.  These were non-eyeletted (unlike the standard box-section version Omega Strada Hardox), and the upper holes, above the spoke nipples, were rather wide. 

Due to the size of the holes, Velox cloth rim tape didn't have enough strength to resist being pushed through into a deep depression that would eventually lead to tubes puncturing there.  So I replaced the Velox with plastic tape (fairly thick - yellow Michelin I think) which was stiffer and wouldn't deform so much across the wide holes.  All was fine until the plastic tape developed fine cracks above the holes, which would then cut the tube.

I ended up using two layers - one of plastic to provide the resistance to deforming into the spoke holes, and then Velox on top of that to protect the tube from the cracked plastic below.  My Vittoria Oscar X (subsequently renamed Corsa CX) 'open tubular' tyres still went on very easily, despite two fairly thick layers.  All fine after that, and I still use those wheels to this day.

Paul

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Re: Mystery punctures
« Reply #13 on: 20 October, 2020, 08:32:11 am »
Make appropriate sacrifices to the fairies.
What's so funny about peace, love and understanding?

Re: Mystery punctures
« Reply #14 on: 20 October, 2020, 08:35:51 am »
when I first started using narrow HPs and Mavic Module E/E2 rims (or Rigida AL1320) the Michelin Yellow plastic rim tape was the only tape that was widely available that would work at all. However every single one I ever had cracked sooner or later. Later I had the choice of Velox rim tape too but I didn't use that for years, reckoning that

a) on a touring rim a roadside spoke replacement might require removal of  the rim tape, and it mightn't stick well enough afterwards to be any good for anything

b) on a training bike rim the inner eyelets would always rust, and the acidic rusty water would rot the fabric.

Given that I thought I'd 'solved' the problem with the Michelin tapes by simple expedient of adding a couple of layers of lasso tape (thicker than normal PVC insulation tape) on top of the Michelin tape, and the Michelin tapes were lighter too, I didn't bother using the Velox tape for a long time.   However, although both concerns about the velox tape were legitimate, the former is incredibly rare and the latter takes a very long time to occur;  rust staining seems to have to be severe and prolonged before the tape is likely to fail; it is a good deal more rot-proof than most other cloth rim tapes.

Eventually the reinforced Michelin tape strategy bit me in the arse;  I fitted some folding tyres to my touring bike and these were a much tighter fit than my usual fare. When these  tyres deflated (eg in storage) these tyre beads dragged at the (by now at least ten years old, brittle, and cantankerous) lasso tape, making longitudinal creases in it. These creases then cracked and the cracked edges then started slicing into the inner tube.  This resulted in what was probably 'my worst ever day for punctures' in which I only just managed to limp to my destination, having spent hours wrestling with tubes, patches, rim tapes etc.  Had I not had the remains of a roll of insulation tape in my saddlebag I would have been stuck.

Rim tapes seem to be a source of more problems than they should be; Velox tapes are pretty good (BTW at home I restick them using cheap spray adhesive, should they ever have to be disturbed)  but they are very slightly thicker than some plastic tapes, and this causes problems in some cases.  There are plenty of rims where the manufacturers clearly intended a narrow rim tape to be fitted, which sits only in the lower part of the rim well. However this is hardly ever perfectly reliable in double-walled rims; all too often the edge of the rim tape moves away from the drillings in the inner wall (or gets dragged into them) and punctures ensue.  A wider tape which goes over the rim shoulders too is always more reliable; it is trapped beneath the tyre beads and is less likely to move. However in some cases the added thickness of the rim tape is enough to make the tyres a tight fit.  Tubeless rim tape is sometimes thinner by enough to make a difference here. I don't know that any of it is any good if it has to be disturbed 'in the field' (eg in the event of spoke breakage near the nipple) though.

Anyway if Roger could say what rims, tape, and tyres (old and new) he is using it might be that someone has used a similar combination and can comment.  Arguably I got bitten in the bum by tyres that were tighter than normal; these caused a previously reliable rim tape to move around in a way that I hadn't anticipated.

cheers

Re: Mystery punctures
« Reply #15 on: 20 October, 2020, 10:36:11 am »
A further (and rare) one is that the tyre is a loose enough fit on the rim shoulders that it is well clear of the rim shoulders when the tyre is inflated, such that the tube can extrude into the gap and burst. This looks a lot like the tube has been pinched during installation (even though you might have checked for that), and appears to defy all logic until the penny finally drops. IME this fault is not likely to happen unless the tyres are a really slack fit.

This.  I too have had a series of mystery front wheel punctures. Four.  All while the bike is stood in the shed. All a 15mm split on the valve side in the same place.  The bike is a Halfords BSO* with channel section rims and really loose fitting tyres. First time I checked the spoke heads and carefully installed a new tube. Second time it happened before the bike had been ridden, replaced the rubber rim tape with a velox one and new tube.  Happened again, put an extra layer of velox on and it's happened again.  Brucey's explanation really resonates.  I'll try a different tyre before a different wheel.

*An experiment.  I wanted a hack bike, no emotional ties, short distances, that I could leave anywhere as long as I liked with no parking anxiety.  I thought I'd try a £100 hybrid to see if it was a viable proposition. It's a long story and the answer is very mixed.  This latest episode is part of that story but may be providing a conclusion.

Re: Mystery punctures
« Reply #16 on: 20 October, 2020, 08:17:42 pm »
it is a good deal more rot-proof than most other cloth rim tapes.

Velox's surprising resistance to rotting was well demonstrated to me over the last winter, which saw my main winter commuting wheelset suffering from water within the rims continuously for several months....to the extent that it could be heard sloshing around inside for the entire period.

My daily route to and from work included a lane with a 20-metre section permanently under 4-6 inches of water, due to a silted-up drain that the council declined to rectify, despite multiple requests and alerts as to the hazard it posed, excusing itself on the basis that all its contractors capable of undertaking the work were deployed elsewhere in the country dealing with the extensive flooding plaguing the nation.  Avoiding the lane added about 3 miles to the route each way which I was rarely in the mood for, or negotiating a deeply unpleasant main road, so I resigned the rims, tape, tubes etc to whatever unfolded.  Every day, twice a day, the wheels got another dose of rim-filling water, and I stopped caring after a while.

After over 3 months with water permanently and audibly present inside the rims, when lockdown hit I finally deemed it worthwhile to take the tyres off, empty the water and see what dire fate had befallen the poor rims and tape.

Interestingly, the stainless eyelets showed negligible corrosion, just some slight discolouration here and there but not really bad enough to call 'rust'; ditto the aluminium showed only slight corrosion.  As for the Velox tape - well, it smelt quite strongly, and had become rather dirty, but that was the only evidence of rotting, as it was still structurally very sound, with no significant decay.  I did change it though, to eradicate the smell.  It was in far better shape than I was expecting after being continuously wet for so long.


Re: Mystery punctures
« Reply #17 on: 20 October, 2020, 08:35:26 pm »
Go tubeless.

Re: Mystery punctures
« Reply #18 on: 20 October, 2020, 08:41:21 pm »
No

rogerzilla

  • When n+1 gets out of hand
Re: Mystery punctures
« Reply #19 on: 20 October, 2020, 08:52:07 pm »
Rigida Nova rims.  Specialized Rim Strip, which is reinforced plastic and IME very reliable, which is why I've sought it out for 20 years. Vittoria Zaffiro Slick folding.

The rim tape fills the rim very well - these are narrow rims.  The punctures are very close to the centre seam and niwhere near the tyre bead or the edge of the tape.
Hard work sometimes pays off in the end, but laziness ALWAYS pays off NOW.

Re: Mystery punctures
« Reply #20 on: 20 October, 2020, 09:25:21 pm »
have you checked the rim tape for cracks over the rim drillings?

Also are you using talc?

Does the rim tape sit in the bottom of the rim well by itself, or is it only pushed there by the tyre pressure?

What is the width of the tape exactly?

Are your rims like this?  The sketch of the rim cross-section is not accurate but the rim looks like it might be the same extrusion as was also called 'flyer' and 'racer' perhaps...?





IME tubes rarely sit exactly straight inside the cover, so splits that appear to be 'in the middle' can easily be at the sides of rim well in a narrow rim.

cheers

rogerzilla

  • When n+1 gets out of hand
Re: Mystery punctures
« Reply #21 on: 20 March, 2021, 12:26:21 pm »
I think it's solved.  I fitted Velox rim tape of the same 16mm width and it survived today's 32 miles.  I think the wider tyres do something that makes the tube impinge on the sharpish edge of plastic rim tape.  I don't like Velox as it retains moisture and oil (this has a SA rear hub which naturally seeps a bit) but I might be stuck with it.

I've never had an issue before with Spesh rim tape - it is usually the best option for high pressures and doesn't bulk up the rim well, so tyre fitting is easy.
Hard work sometimes pays off in the end, but laziness ALWAYS pays off NOW.