I have an original Nimbus 24" MUni that I’ve been riding longer than I can remember. Recently though, I’ve been going through more and more tubes. Each one has been torn at the valve stem.
Online there is some general suggestions. Adjust air pressure, sand the rim, even glue the tube down… Has anyone found anything to work? I’m getting really frustrated as 24" tubes are uncommon and somewhat costly. As I could not find the tube that first came with my unicycle, I’ve been purchasing the Sunlite Thorn Resistant Schrader Valve Tube of size 24 x 1.90 - 2.35" / 35mm.
Rather than using a 24" tube in a MUni tire try a 26x2.25. I have been using normal weight MTB tubes in my 24 for years. I’ll admit that I havent really ridden the 24 for at least 2 years, but still the larger 26" tube seems to be a better fit in the 24x3 tire.
I had wondered about using a 26" tube in my Nimbus 24 muni. I’m on a 24x2.5 maxxis hookworm just now, would a 26x2.25 tube fit, and is there actually any advantage? Or would a 24x2.125" tube from a kids mtb work better or worse?
If you’re ripping the valve stem off, one of three things is happening:
The tube is being installed with the valve stem at an angle, so the tube is pulling on the valve stem. The valve stem should always be pointing straight out of the rim, and should not be under tension.
You’re pulling on the valve stem when you inflate it. If you’re using a hand pump that doesn’t have a filler tube, this is the most likely explanation. Look at using a good floor pump, or one of the Lezyne hand pumps that won’t stress the valve stem.
The valve stem hole in the rim is too big and/or has rough edges on the inside or outside. Use a round deburring file to get rid of any sharp edges, and possibly cover the hole with some kind of tape; I use cloth bike handlebar tape, or sometimes nylon strapping tape.
This can also happen to a properly installed valve stem with time due to friction between tube and tire. Use talcum powder when installing the tube to reduce this friction.