Completely bamboozled with chronic tube failure

[Alien27]

I have a new set of Fuji track wheels that seem to be causing failure in my tubes. I get one ride in (30km fixed commute) then in the morning when I go into the garage and one wheel is usually flat. It's gone flat a few times on the ride but mostly overnight.

The failure is either side of the valve stem on the rim side of the tube. Dimples form midway between the stem and the first spoke holes in the rim and get worse until failure. I have tried different batches of the same tube brand and different brands of tube all with the same result. I have tried different rim tape, one cloth and the original ones on the wheels which was plasticky. I have gone through about 10-15 tubes and am at a loss as to what is causing the failure.

Any one got any ideas?

[Alien27]

The rim is smooth under the rim tape and the rim tape is smooth as well.

It's a track wheel set (Fuji PGC Aero 46 wheel-set) on a fixed gear bike I use for commuting.

[Alien27]

[familyguy]

Your rim tape doesn't look wide enough. Try a wider tape, or try doubling it. I reckon it might be forcing its way between the tape and the spoke hole edge under pressure.

Jim

[Mulger bill]

Oh, I dunno Jim, the warts don't look close enough to the spoke holes for that to be it. I'm wondering if both warts form simultaneously or not...

Shaun

[HappyHumber]

I'm with Jim actually.

I've had a couple of similar spates of flats with very similar little 'cysts' evident either side of the valve seam, and eventual little pinch type cuts on the inside edge of the tube.

The first time it happened to me it drove me nuts swapping things around trying to eliminate the cause. Once I replaced the rim tape inthe first instance the the issue disappeard. The second time around, I was a bit more wary early on about the tape. It was on some Open Pros which I was having some truing issues with on a relatively new wheel build. Checking how much thread I had through the nipples, I had actually stripped off and reused the same cloth rim tape and thats when the series of flats began. Fixed when I stopped being a tight ar5e and replaced the tape with new stuff.

I think the bumps probably appear closer to the valve stem on the tube becuase they're not under pressure and stretched as they would be fully inflated.

[brawlo]

Having a look and a think, I reckon Jim is wrong for a start. The tube is made to be the same length as the rim circumference and therefore doesn't stretch to meet up with the spoke holes. The cysts/holes are right beside the ring of rubber around the valve. I wonder if the lack of flexibility/give due to the extra rubber is a reason. I also wonder if the lack of flexibility means that the tube is trying to expand back in under itself under where extra rubber is.

Do you powder up your tubes to allow easy movement inside the tyre as you're inflating the tube? If not, give it a try and see if it helps.

[familyguy]

You're right, the bumps are the edge of the valve stem seat within the tube. I had one batch of long stem valves fail like this, but it's never happened with short ones. I do still think the rim tape is too narrow and may assist. It shouldn't be coming off the edge of the rim this far:


In continuing 'asking the stupid questions': does your tyre size match the tube size?

Jim

[HappyHumber]

Doesn't stretch!?

Haven't you ever inflated a tube off a rim & outside of a tyre? It's the bead of the tyre that normally constrains the inside circumference of a tube to the rim.

Maybe it's because I'm one these dying breed of people who still uses patches & repairs tubes. Before rolling up a fixed tube and putting it back in my toolbag or jersey pocket I always lightly inflate it free of the rest of the wheel and hang it on a wall hook overnight to test the soundness of my repair. Their inflated circumference, even though not a rigid circle, is greater than a rim.

Not that I have done it (yet) myself, but I'm also told it's perfectly fine to use decent 700c (622mm ISO Eff. Rim Diam.) tubes into old, 27 1/4" rims (630mm ERD) wheels and tyres.

[Alien27]

I don't think it is the spoke holes as the dimples are a long way off them. You can even see there the spoke hole depression has made a mark on the tyre a good bit away from the failure points which are just off the edge of the bit of tube that is reinforced near the stem.

I don't think the tube inside the tyre will stretch away from the valve side that much. especially as the thicker reinforced bit of the tube would have to It's happening with every tube on both wheels. Different brand tubes and different batches of the same brand.

I did notice with these rims that the walls are quite thick, maybe the tubes are a little squished in there? But the rims themselves are the same outside width as all my other wheels (23mm rims) and I use the same tubes (700x18-25c).

[Alien27]

Brawlo what you say makes sense, i had a look tonight again and measured the inside width of the rims. They are 13mm, which is 1-2mm narrower than the other wheel sets I have. They are also a good bit deeper with a channel in the middle of the bottom of the rim (hard to explain but see pic below. The reinforced section of the tube will be pushed down into this channel making the already narrower rim even narrower for the reinforced bit of the tube.



Reynolds shadow on the right, Fuji set on the left

[A_P]

my thoughts....
The channel is quite narrow , the reinforced section around the valve isn't pliable enough to seat right down against the rim .
As you inflate the tyre, that section lifts up away from the rim leaving some of the softer tube either side not quite against the rim.
Time, pressure and heat stretches the tube and puncture results..
Taper some extra layers of rim tape either side of the valve hole.
Hope that makes sense.
AP

[Alien27]

Yes that makes sense A.P. I'll give it a go. Thanks everyone ill let you know how it goes.

[jules21]

the tube is failing precisely along the centre line - i doubt the edge of the rim tape has anything to do with it. making these statements over the web is unreliable though, as arguably is my judgment..

what pressure are you inflating them too?

[spirito]

what pressure are you inflating them too?

you might be onto something with this question

[Alien27]

95 front 105 rear

[spirito]

95 front 105 rear

Shouldn't be any issue there.

Have you used any other tubes other than the two pictured?

[Alien27]

Just those two brands but I'm using them on my roadie and on the other set of wheels for the fixed gear with no issues at all.

I built the narrow channel of the rims either side of the valve hole up tonight with 3 narrow strips of rim tape and then a wide strip over the top. It will be interesting to see how it goes.

[osrg]

Just those two brands but I'm using them on my roadie and on the other set of wheels for the fixed gear with no issues at all.

I built the narrow channel of the rims either side of the valve hole up tonight with 3 narrow strips of rim tape and then a wide strip over the top. It will be interesting to see how it goes.

It's your rim tape. Throw that Zefal shite in the bin and get a proper high pressure rim tape like the Reynolds stuff shown above. The Zefal tape cannot handle the pressure of the tube, it deforms, the tube deforms and hey presto.... a pinch flat.

I had the same issue with my wife's flat bar roadie when i converted it to a 23mm Gatorskin and 110psi... 5 flats in less than 48hrs.... changed the rim tape to a Shimano high pressure and none since. That was 4 months ago. The fabric rim tape was the issue.

[jules21]

It's your rim tape. Throw that Zefal shite in the bin and get a proper high pressure rim tape like the Reynolds stuff shown above. The Zefal tape cannot handle the pressure of the tube, it deforms, the tube deforms and hey presto.... a pinch flat.

hmmm.. the rim tape protects the tube from sharp edges protruding from the rim seat below. unless there are protrusions (e.g. spoke holes) aligning with where the tubes are failing, it's difficult to see how the rim tape is to blame. like many others, i've used fabric tape with no issues.

[RonK]

It's your rim tape. Throw that Zefal shite in the bin and get a proper high pressure rim tape like the Reynolds stuff shown above.

I agree - that is why there are dimples in the tube.

When inexplicable flats like this occur, the replacing the rim tape is one of the first actions I take. I've been caught out too many times in the past not to immediately suspect the tape.

[rkelsen]

it's difficult to see how the rim tape is to blame.

In this case, the tape is too narrow for that rim. It's probably moving sideways under pressure. Been there, done that. Fixed it by using tape which goes wall to wall.

[jules21]

In this case, the tape is too narrow for that rim. It's probably moving sideways under pressure. Been there, done that. Fixed it by using tape which goes wall to wall.

good tip, will remember that. but i do note in OP's case he tried different tape.

[RonK]

it's difficult to see how the rim tape is to blame.

In this case, the tape is too narrow for that rim. It's probably moving sideways under pressure. Been there, done that. Fixed it by using tape which goes wall to wall.

Quite right - in several of the pictures you can see that the cloth tape is barely covering the spoke hole, and will be pushed aside when under pressure.

I use and recommend Specialized Rim Strips.

[ironhanglider]

Brawlo what you say makes sense, i had a look tonight again and measured the inside width of the rims. They are 13mm, which is 1-2mm narrower than the other wheel sets I have. They are also a good bit deeper with a channel in the middle of the bottom of the rim (hard to explain but see pic below. The reinforced section of the tube will be pushed down into this channel making the already narrower rim even narrower for the reinforced bit of the tube.



Reynolds shadow on the right, Fuji set on the left

Stand by for an odd theory...

I wonder if the deep, narrow channel is preventing the reinforced bit of the tube from seating down into the bed of the rim. The other bits of the tube are more flexible and do so easily with no damage. If this theory is correct then there is a void underneath the reinforced bit and the nearest normal bit is right next to the reinforcing, which is where these blisters are forming.

As for a solution perhaps tubes with a more flexible reinforcing that can be brought down into the channel, possibly a latex tube.

Cheers,

Cameron