2

I purchased a brand new bike from auction several months ago and although the tyres were pumped up a little they were not pumped up fully. I purchased a presta valve adapter for my old pump and I know that you have to turn the little nozzle on the presta valve to allow air to go in when pumping and then you close it afterwards. HOWEVER, when I start to pump it just does not inflate and stays flat, I cant figure out why. They were inflated when I purchased it and the bike was brand new without ever being used. I keep pumping but my tyres just stay flat. Strange one for me even though I last rode a bike about 15 years ago but surely things have not changed that much have they? Please help as with the lockdown I cant even go to a bike shop to show someone. I tried pumping them several times on different days with the same result - still flat. Remember they were inflates when I got it and its been kept in my garage nice and safe from harm. Thanks

  • 3
    Usually this is because the pump's chuck is not making a tight seal against the adapter, so the air leaks out as fast as you pump it in. There is also the possibility that you did not unscrew the little knob far enough, or you failed to press it in (a brief tap is all that's needed) after you unscrewed it, so that the air cannot get into the tire. And, not knowing your bike, there is a vague possibility that you have tubeless tires, and these can be a devil to fill if the tire beads are not "seated". – Daniel R Hicks Apr 8 at 17:23
  • To add to daniel's ideas, it might be a good idea to pop the tires off and check the tubes for punctures or other damage. If you find that there aren't tubes it would confirm that you do have a tubeless set up. – bradly Apr 8 at 17:48
  • 2
    I have found that I often need to press in the center rod to overcome any stickiness in the valve before I can inflate a Presta tube. – Adam Rice Apr 8 at 18:00
1

Some Presta valves can accept stem extensions and the upper valve body (containing the little nut you unwind to add air) can be unthread from the lower part to accept extension. Anyway, this sometimes comes unthreaded with the use of a presta to Schrader adapter and air is lost. Perhaps this is loose and air isn't getting into tire/tube but escaping here. There are tiny wrench flats on the upper valve body of many Presta stems. If present in your case, try snugging it up.
Another problem might be at the pump. Some hand pumps require a lever in the correct position to deliver air into the valve. Make sure you fully engage the valve and if the pump has a lever try both open and closed positions (here I mean lever up and lever down positions). Hand pumps that can switch from Schrader to Presta set-ups utilize the lever in opposite positions for filling depending on which system you're doing. The limited # of ones I've seen, the lever is placed "up" or 90 degrees to the pump body when in Presta mode. So with the lever down (parallel to pump body), you fully engage the open Presta valve and then lift the lever to the 90 degree position and begin pumping. A presta tube can be partially inflated with your mouth, should you choose, by pushing the unwound valve tip with your tongue whist you blow into it. You can check the valve integrity this way. I recommend a cold beer with that dish. My guess is your pump end is not engaged correctly or is faulty.

| improve this answer | |
  • AHHH i have just checked the inner tube and it does have a inner tube and is not tubeless. The Presta Valves on both tyres have come away from the tube!! no wonder the tube does not pump up. I guess i will have to try and put the valve back into the tube and secure it with some sort of rubber patch and glue or something, is that right? having last ridden a bike about 15 years ago im hoping its not too difficult, any suggestions on what to buy off ebay or other sites that will do the trick to secure it without the valve separating from the inner tube and it coming back out? Many thank. – Pradster Apr 9 at 10:53
  • @Pradster It is unlikely to be repairable. Buy new tubes and some more as spares. Check that the rim does not have any exceedingly sharp edges at the valve opening. – Vladimir F Apr 10 at 18:25
  • @Pradster Yes. New tubes are the only viable option in that case. Google or eBay search something like "bicycle tire, inner tubes, Presta valve, 26 inch" and you'll have a plethora of choices. – Jeff Apr 10 at 20:54

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.