Chronic Rear Flat

[Graphxbiz]

I have a Mavic 717 rear rim, properly taped with a Velox Rim strip. I am running a Michelin Comp S Lite tire and a generic brand tube. My problem is that no matter what type of tube I use the tire goes completely flat in about 48 hours. I have run my fingers inside the tire casing and have felt nothing. I have checked the inside of the rim for obstructions but found nothing, not even around the valve hole. I have used 3 different tubes so far with the same result. Upon removing the flatted tube I would pump as much air as possible to see where the leak might be but was baffled to find NO obvious areas where air could be escaping. Anyone out there know what could be going on?

 

[lumpy]

I would guess the tire is pinching the tube. Pump up the tube and hold it under water and follow the bubbles to see where the hole is. I bet it's on the side.

I had it once where I had to change the tire to solve the problem.

good luck!

 

[EoinC]

...no matter what type of tube I use the tire goes completely flat in about 48 hours...Upon removing the flatted tube I would pump as much air as possible to see where the leak might be but was baffled to find NO obvious areas where air could be escaping.

The tube goes flat when it's in the tyre, but you can't find a puncture once you have the tube out? Check the tube with air in it using water with some dishwashing liquid in it (shows the bubbles much better). May be a valve problem.

 

[tfstrum]

You could try the tire and tube on the front to see if you have a chronic front flat. rules out the rim. Sounds like a bad valve or there's a small hole near the valve stem.

 

[cydewaze]

I had this once and also could not find anything suspect in the tire. Finally I replaced the tire with a new one and the problem disappeared, so I assumed it was debris in the tire that only "appeared" when loaded under rider weight.

 

[neil0502]

Do you use the lock nuts for the Presta valves? If so, you may want to stop. Lots of people tighten them a little too tightly--especially if you tighten them before inflating the tire.

If this happens, you can tear the tube right by the valve.

Stop using the nuts and see what happens.

I'll wait right here

 

[el Ingles]

I would guess the tire is pinching the tube. Pump up the tube and hold it under water and follow the bubbles to see where the hole is. I bet it's on the side.

I had it once where I had to change the tire to solve the problem.

good luck!

double check the rim tape and try checking the hole in the rim that the valve goes through - sometimes theres a sharp edge left by the machining .

 

[mountainbikemad]

have you tried using thorn proof tubes which are much thicker

 

[mountainbikemad]

have you tried using "thorn proof" tubes. they are much thicker and stronger

 

[limerickman]

All of the above is what you need to check.

Make sure the tube isn't being pinched.

The rim tape - is it even all way around the rim ? It isn't uneven anywhere on the rim, is it ? If it is this could be pinching your inner tube.

There are no perforations of the rim tape from the spoke poking through (where the spoke and rim, meet) the rim tape ? If there is a perforation, this could be
what is puncturing your tube also.

 

[Bill Wellborn]

I have a Mavic 717 rear rim, properly taped with a Velox Rim strip. I am running a Michelin Comp S Lite tire and a generic brand tube. My problem is that no matter what type of tube I use the tire goes completely flat in about 48 hours. I have run my fingers inside the tire casing and have felt nothing. I have checked the inside of the rim for obstructions but found nothing, not even around the valve hole. I have used 3 different tubes so far with the same result. Upon removing the flatted tube I would pump as much air as possible to see where the leak might be but was baffled to find NO obvious areas where air could be escaping. Anyone out there know what could be going on?

I had a similar problem and noted finally that my rim tape didn't quite cover one spoke hole very well on my Bontrager Fairlane asymetric rear wheel. I reapplied my rim tape and no more problems.

 

[WP33]

Pretty simple idea, too, is to get yourself a long, thin ballon, like the clowns at kids' parties make animals out of, and inflate it, then drag it around the rim and/or inside the tire. You'll know in a hurry if something's catching your tube...

 

[Graphxbiz]

Just an update:
I changed to a wider rim strip and new heavy duty tube. It's been over 48 hours and the tire is just as firm as when I first put air in it! Thanks for all your suggestions!

roman

 

[tyler_derden]

Immerse the inflated tube into a bucket of water. Follow the bubbles to the leak.
Besides checking the tire casing, check along the rim. There may be a sharp edge or point on the rim strip or a burr from a spoke hole that is poking through the tube.


edit... this is weird. When I first looked at this post, I saw only the original post. As soon as I posted a response, there were 10 other responses. nevermind...
TD