The Never Ending Flat from Hell - Too Much Weight For 25cm Tyres?
 

I keep getting a flat in the rear (sometimes on inner sometimes on outer side tube). Ive inspected/dissasembled it rigourously but find nothing. I've replaced the rim tape, replaced the tubes several times, and have even bought a brand new tyre. and still i get flats. Ive even experimented with my tyre pressure, going from 120 PSI to 100 PSI... still flat....

Only thing I can think of now is maybe there is too much weight on that rear tyre? Is there a weight limit for narrower tyres? My tourer and grocery getter has 25's and after loading it up with groceries my bike can be as heavy as 230-250lbs (Im 6'1 ~185lbs).

I'm at my wits end here!

Are they pinch flats? (Check in the sink or bathtub. ;))

You might try a 28mm in the back.

I'm heavy and have not had that issue just because the tire is narrow. I have had it with certain tires, and I've had patches of bad luck. What are the roads like in your area?

What tire are you running?

ill have to check if it was a pinch flat or not. what would that mean if it was?

currently continental ultra sport II with continental tubes (which i have heard arent the best). but i previously had on new schwalbe tyres and tubes and they flat. and the rim tape is velox.

Not enough pressure to prevent the tube from bottoming out on the rim, or too narrow a tire for the pressure you prefer to run.

I'm 210 and run 23mm front and rear. Continental Gatorskins at 110psi.

I'm a relative lightweight at 160 and not a roadie, but have run 23s on my fixed with up to 58 lbs of groceries in a messenger on my back over Alaska roads and never had a problem.

This sure sounds like something going on with your wheel to me. Assuming you've checked your rim, tire, and rimstrip well, is it possible that your spokes are too long? Maybe a stripped nipple that is letting one spoke penetrate the rim strip and get your tube? I'm guessing here, but I just can't imagine the situation you are describing without some kind of mechanical something going wrong.

That doesn't sound like overload. Look for some problem with the wheel. Consider: Is it always at the same place around the wheel? Is it always the same position around the tube, meaning inside toward the hub or outside toward the rim? (You said sometimes inside, sometimes outside. Is that what you meant?) Check whether the rim strip has moved under the tube and exposed a spoke nipple. Check whether a nipple has a burr which penetrates the strip but isn't obvious. Check whether the sidewall of the rim has a burr. Finally, it could be your mounting technique that pinches the tube or gets it twisted up such that you don't always see the proper location of whatever is causing the problem.

Or it could be bad tubes. I believe I've a one or two lately.

I did not do well with those Conti tubes. My first impulse was something in the rim, like said above, but the OP said the location changes. That makes me wonder:

1. What are your roads like?
2. Maybe bad luck?
3. Mounting technique.

I know people think I'm crazy, but I flat less often with narrow tires. My theory is that there's less surface to pick up debris.

Add a pair of 'tire savers' onto your brake mount bolts.
They don't stop all sharp objects, but they sure help lessen the number of flats.

I'm 220 lbs, and use 25mm tires on all my bikes. I have had one flat in the last 5 years.

The question is the location of the the holes/pinches...are they consistant? Do you mount the tire with the label at the valve so you have a reference?

Heck I ran 19's back in the 90's (in the Tour of course) and I was 200 lbs. Michelin Hi-lite Super Comps.

My guess would be that you have pinched the tube under the tire when you install it. When you get the tire on, pinch in the sidewalls with thumb and a couple fingers all the way round the tire (getting the tire off the bead seat of the wheel). Then inflate the tire to about 30psi and deflate it. Then go around the sidewall again, removing the tire bead from the wheels bead hook. Then inflate it again.

Another thing is to use talc on you tube and just slightly inflate the tube (like what you can do with your lungs only) when mounting it initially. Leaving the tube completely flat when installing it is asking for it to get pinched somewhere. The bit of roundness combined with the talc should help keep it from pinching.

Also check that your wheel has no machining imperfections that would burst the tube under pressure. Good luck.

I think there are more than one cause contributing to the rash of flats you are experiencing:
For the flats on the 'outer side tube", I would subscribe to installation being the most likely suspect, with the tube potentially getting pinched between the bead and rim. @Chrome Molly 's method would help if that is the case. Given that you have rigorously inspected the rim and replaced the tape, I don't see a problem there.

I would not consider 100-120psi as under-inflated, so the likelihood of pinch flats is slim - unless you ride over RR tracks.

I think the remaining flats are likely caused by the occasional chard of metal or glass, and installing tire savers would help in that case.

Spokes protruding through the rim tape? It can happen.

Maybe you should try different tires.

Or maybe not.

zazenzach-

Lots of good suggestions from previous posters. Possibly re-think the rim tape. The plastic tapes will slip and expose the spoke ends and this slippage will vary after each repair leading to flats in various locations around the rim. Only the adhesive backed fiberglass reinforced cloth rim tapes like Velox hold against really high pressures, in my experience. As well, carefully inspect the tire casing itself. There may be a small glass sliver or, as in my case, a small piece of wire imbedded in the tire casing fabric which leads to repeated punctures and subsequent hair tearing. The only way I found it was by carefully running my thumb around the tire casing. Yes, it hurt but the wire was so small it was virtually invisible to visual inspection. Good luck!

RR tracks...or just generally ride heavy. That is staying seated and riding upright over every imperfection in the road.

Cloth rim tape.

25 cm!? Those are some wide tires ;)

I run the widest tires my frame will allow.

Have you inspected the inner walls of your rims for burrs? Like others have said, your tube could be trapped between the rim and tire.

I suffered a very major concussion in the month of February and spent a good part of the year getting over the consequences. In the early months of my recovery I was getting a relatively huge (in comparison to what had always been my experience over the past, i.e. one flat every few hundred miles) number of inexplicable flats. As my recovery progressed, I was able to see a marked reductions in these inexplicable flats, to the point where it has now been more than a thousand miles since the last one. I am convinced that it was my then deteriorated mental processing of road conditions which was sufficiently impacted to cause me to not be able to avoid road debris and higher risk flat situations. It might therefore be worthwhile to evaluate your level of cognizance at the time of the flats as it can impact the frequency thereof.

As regards the width of the tires, I have ridden 25 mm tires for thousands and thousands of miles on racing tandems carrying well over 300 lbs, and at times well over 400 lbs and they never suffered any worse issues with flats than wider tires, so I don't believe that is an issue.

Is the bike that's suffering through punctures a different bike from the "tourer and grocery getter"?

It's possible that a larger tire is needed or the weight needs to be redistributed about the bike.

Brad

Split the weight by using front panniers, the bike will handle better too.

And a wider tire like a 28 will make a huge difference.

+1 on the rim strip.