Two flats in one week: wrong sizing or low quality inner tubes?

[katonda]

Hi all,

TLDR; scroll to bottom.

Last week I got a flat tire which appeared weird to me because it seemed to happen overnight after having ridden on my bike for a relatively long trip (25km) the previous day without any problems. The flattening was also a slow process and I had trouble finding the initially finding the leak. It didn't seem like it was a puncture since there was no obvious hole and the leak was on the inner part of the tube (facing closer to the wheel). I patched it nonetheless and didn't think about it much more.

Fast forward to this week: got a flat in the other tire 15km from home on a public holiday. No bike shops were open and the supermarkets I visited didn't have bike repair kits (from now on I will always have one on me). Had to take the train home. The leak was in a similar spot as the last time. This piqued my curiosity since now it wasn't just a fluke, but a pattern. So naturally, I did a bit more investigating. It's a 650B setup and if you're curious about the bike itself, you can find more information HERE.

FYI, the tubes are only 5 months old and I estimate I've driven on them max 250km. I replaced the rim tape, tires and tubes at the same time. I did clean up some of the rust and grime inside the wheel, but I didn't spend a long time on this since the wheels and bike are quite old.

Cracking inner tubes at two spots (only visible when bent):


Inner rim width 20mm:


I think these are decent tires from a reputable brand (but what do I know?):


Rubber flakes on inside of tires (not sure if normal):


Rear wheel fixed last week and inflated for reference (will likely fail again soon):


It seems that the inner tubes are cracking where the tire meets the wheel, but due to the stretching of the inner tube once pumped up, I can't say precisely where or why this is happening. Therefore, before I buy new tubes, I wanted to check with you to see if it might be an error in part sizes that will lead to similar issues even with better inner tubes. Before originally buying them, I did spend considerable time to properly match the sizes using charts online.

The chart:



Here are the specs of the parts:

AMIGO Inner tube 26 x 1 1/2 x 1 5/8 (44-584) FV 48 mm


Ritchey Pro Snap On Rim Tape 27.5", black (Width 20mm)


Panaracer Pasela Clincher tire 27.5x1.75", black/skinwall (wheel size 42-584 | 27,5x1,75")


So, is the inner tube to blame? Do I need wider rim tape to cover more of the wheel? Is the wheel itself not good with this type of tire? What do you think?

Thanks in advance!

 

[SkipdiverJohn]

Protruding spoke thread or a small piece of abrasive material such as sharp sand trapped inside the tyre which rubs the tube until it leaks. I've had several inexplicable slow deflations over the years and my response is always to thoroughly clean out the tyre and wheel voids by wiping them multiple times with a clean rag. I sometimes will use a couple of wraps of electrical insulating tape under the rim tape on old wheels where the surface is getting rough. Being meticulous not to allow dirt into the inside of the tyre generally minimises these sort of incidents. Also don't ever allow your tyres to get flat in storage with it stood on it's wheels, so the tyres break their seal on the rim. That can allow gritty suff to get inside, which you really don't want.

 

[katonda]

Protruding spoke thread or a small piece of abrasive material such as sharp sand trapped inside the tyre which rubs the tube until it leaks. I've had several inexplicable slow deflations over the years and my response is always to thoroughly clean out the tyre and wheel voids by wiping them multiple times with a clean rag. I sometimes will use a couple of wraps of electrical insulating tape under the rim tape on old wheels where the surface is getting rough. Being meticulous not to allow dirt into the inside of the tyre generally minimises these sort of incidents. Also don't ever allow your tyres to get flat in storage with it stood on it's wheels, so the tyres break their seal on the rim. That can allow gritty suff to get inside, which you really don't want.

Thanks for the quick reply, @SkipdiverJohn. I don't think a single spoke or abrasive part is the issue since the cracking is evident on both sides of the inner tube, for the entire length of the tube. It's not just one spot. I highlighted the issue here:



I also don't think the light rust is an issue. What could be a problem is the edge of the rim tape which protrudes a bit and may cut, but the damage looks like it's a fracture due to mechanical stress, not abrasion or cutting. This is why my hunch is that it might be caused by excessive stress on the inner tube being exerted where the tire (skinwall) meets the metal. There isn't much material there to disperse the load. This is just a moderately educated guess though.

The tip with the electric tape is worth trying! I was initially thinking of placing it over the rim tape to help with the edge. Why do you place it underneath?

 

[13 rider]

If you line the tubes up valve to valve is the hole in the same place . If it is line the valve up with the valve hole on the wheel and that's the area to check . Does look like something on the rim/ spokes

 

[Sharky]

Panracer Pasala are good tyres. Had one on my tandem trike for over 20 years and still OK, although not ridden more than once or twice a year.

One possible cause to eliminate is the re-fitting and making sure that you haven't nipped the inner between the tyre and the rim.
- don't use tyre levers to re-fit
- after inflating the tyres about 50% - let them down again, then go round both sides of the tyre and rim pushing the tyre in and making sure that the inner is fully inside the tyre and not caught. Then re-inflate to normal pressure.

Third time lucky

 

[alicat]

Two flats in different wheels in a week isn't a pattern. Just treat it as good puncture-repairing practice.

 

[jay clock]

+1 for wrapping elec tape over the rim tape

 

[biggs682]

Two flats in different wheels in a week isn't a pattern. Just treat it as good puncture-repairing practice.

It's a pain for sure

 

[ilcaccillo]

I was riding 700x23c slick tires and was constantly having flats.
Changed the tyre for a 28C with an extra puncture protection layer and also changed the inner tubes for self healing ones.

Have been riding in the last 2 weeks and no flats for now. hope that helps

 

[boydj]

Did you find the cause of the original flat and remove it from the tyre? Sometimes a tiny flint can stay in the tyre and be hard to find other than by turning the tyre inside out and knowing where, relative to the valve the puncture occurred.

 

[voyager]

We have used electrical tape in place of rim tape more than once , about 5 layers seem to work , sounds like the tubes were under inflated .

 

[katonda]

We have used electrical tape in place of rim tape more than once , about 5 layers seem to work , sounds like the tubes were under inflated .

I've ordered some 35mm rim tape to cover the open spots and new tubes. I may add a layer or two of electric tape if it looks like it will help. Hopefully that does the trick.

It could be that the tires were under pressured. I once had an inner tube tear through the wall of my tire and explode while I was riding. Ever since then I've been a bit wary of excessive pressure. I will try to add a bit more, but I thought that with larger (42mm) tires, a little less pressure is better.

 

[voyager]

Under inflated tyres mean the tubes are well massaged over bumps etc and if they were older stock could start to deteriorate at a faster rate.
Hitting a bump could have squashed the tube between the rim and tyre and split it ,( l had that a few days ago) yes I knew it was under inflated but wanted to get home.

 

[SkipdiverJohn]

The tip with the electric tape is worth trying! I was initially thinking of placing it over the rim tape to help with the edge. Why do you place it underneath?

I generally put insulating tape under the rim tape because it's sticky and I don't want the tape sticking to the tube if any of the glue seeps out. I'm probably being overly pedantic though in this respect. A lot of my wheels are old (as are the bikes!) so there is sometimes some roughness or the passage of time has caused the spoke nipples to deform the rim tape into bobbles. Unless the rim tape is really bad, or has broken where it's weak at the valve hole, I tend to re-use them but adding two wraps of electrical tape (which is FOC at work!) is a belt & braces measure.
If you use electrical tape wider than the rim tape over the top, it will cover any suspect sharp edges, but you have to be very careful when fitting the tyre not to dislodge the tape along it's edge and ruck it up. The trick to minimising non-penetration punctures is basically keep everything the tube comes into contact with as clean as possible, hand mount the tyre without using levers, and check and double check the tube is completely inside the tyre and not creeping out under the edge of the bead before inflation. Considering how old and ratty a lot of my stuff is, I do not have much trouble with mystery flats with no obvious cause..

 

[katonda]

The new tubes and rim tape arrived today. The extra wide rim tape covers more than the entire rim and it took a while to install without any folds. The way the tubes are installed now there is no touching with anything that isn't tire or rim tape and the rim tape is entirely within the tire.



I also inflated the tires to a much higher pressure than before. I'm about to go on a 60km ride from Amsterdam to the coast and back, so hopefully they hold up!

Thanks to all for your input.

Edit: On another note, while I have your attention. The rims of this bike have indentations which look good, but aren't great as braking surfaces. Is there a special type of brake pad I should be using? When I got the bike, the previous brake pads we're worn down.