5

I just got new schrader valve tubes that have the rim fitting nut on them.

Since this question has not been asked on here before, what is the proper tension that the nut should meet the rim? My understanding is that the nut prevents the tube from slipping in the rim and being damaged over time.

My questions are:

  1. Do you tighten the nut before inflation, or after inflation?
  2. After inflation should the nut be finger snug or tightened with a wrench?
  • Welcome to Bicycles @Shawn. If you must have it, then finger tight. I've a) never kept them, b) never seen one on a schrader valve, and c) never seen on that didn't have finger knurls. There's not much room for a spanner anyway! – andy256 May 26 '16 at 2:30
  • 3
    @andy256 - I'm surprised you didn't point out rule #60. – Batman May 26 '16 at 2:39
  • 1
    @Batman D'oh! I must be losing my touch! – andy256 May 26 '16 at 2:46
  • 1
    With my Prestas I tighten the nut barely finger-tight before inflation, then tighten again after inflating, as tight as I can with my fingers. You don't want it so tight you won't be able to remove it if you have to do a roadside repair (without a pair of pliers), but you want it to stay on and not rattle. – Daniel R Hicks May 26 '16 at 11:10
7

You don't need the nut, really (and its rather abnormal on Schrader valve tube) -- a lot of people just throw it away.

The point of the nut is so that the tube's stem doesn't go into the rim when you're trying to inflate the tube and the stem doesn't move around when you're trying to pump the tire. Note that the tube can only go significantly into the rim if the stem is very short relative to the rim or the tube has very low pressure -- you won't see its effects when topping up your tires.

If you're using a Presta valve in a Schrader valve rim, they sell specific grommets for a few cents to use to keep the Presta valve secure, though some people install the nut on the inside of the rim to act as the grommet.

If you want to use the nut, inflate and lightly tighten it down after inflation with your fingers (there are some other schools of thought on how to use them, but this is probably the simplest). Don't over tighten it or you'll damage the tube.

  • 1
    I tend to buy continental tubes (nothing special, just what the shop has in stock) and they're fully threaded with a nut (on Schraders). I also fitted a Specialised tube recently which had one (again, just what the shop had by default). Either they're becoming more common, or they're more common in the UK. They're quite handy when dealing with flats using a less-than ideal pump especially on stiff/knobbly/studded tyres.where pushing from the back to get the nozzle on isn't trivial. – Chris H May 26 '16 at 8:52
  • Some tubes like Mavic's have valves with rubberised unthreaded stems. – Carel May 26 '16 at 10:10
3

I think an overly tightened nut can cause a leak at the point where the metal valve stem is fixed to the rubber tube. I've had this happen a couple of times and now I leave it very loose. As someone commented, the nut is useful in keeping the valve stem accessible and from damaging the tube when inflating an empty tube, particularly with a CO2 inflator; which for some designs require a considerable pressure applied to the valve stem.

  • Quite correct - thank you for your contribution. Do please have a browse of our tour to see how Stack Exchange works. Welcome. – Criggie Jul 10 '17 at 1:38
2

I loosely tighten before inflation- just to stop the valve from disappearing whilst inflating it. After inflation, it needs to be finger tight- else it will rattle on the rim. This is probably the number one reason why most people don't use them- the slightest looseness here will be very noisy (especially to deeper section wheels).

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.