wbartram

Hi Guys

Could anybody make any suggestions please - I have changed my son's bike to a tubeless setup - He was getting flats all the time on the pump track.

The rear tire is working just fine - but the front one keeps going flat.

Thanks for any suggestions.

William

BikeLite

Assuming the tire fills and seats but has a leak, (copied from online)

1. Double check the rim tape seal. Re-tape, or add a second layer of rim tape. The telling sign of a rim tape leak is air escaping from the valve stem hole. A leak at the valve stem hole does not necessarily mean the problem is at the valve. It means that air is entering the rim cavity through a spoke hole (rim tape leak) and then escaping through the path of least resistance (the valve stem hole).
2. Add more sealant and ride. If the tire inflates and seats but small leaks around the tire bead keep it from staying inflated, try adding more sealant and take a short 15-20 minute ride to keep the sealant circulating to stop the leak.

alcjphil

Simply put, we don't know anything about your son's bike or the wheels it has. You mention having flats at a pump track. Is it a BMX bike? Something else? Are the wheels tubeless ready? Or not? Tubeless ready wheels can provide a very reliable seal. I just checked the tires on my gravel bike that have been sitting for about 3 weeks. They are down a few psi but are still very rideable. Higher pressure road tires lose pressure faster, but they also go down if you have inner tubes. What tire pressure are you running? Some tubeless tires run at very low pressure are prone to burping, but there is no way for us to know that. When your son was getting flats on the pump track while running inner tubes, were they possibly pinch flats? A bit more tire pressure could have solved that problem

icemilkcoffee 

Trying to tape up a TLR rim to make it air tight is not a trivial matter. Most of the time you end up with small leaks that can be plugged with the sealant. But sometimes the leak is too big for that. You'll just have to bite the bullet and retape it. The valve hole in particular, is a common place for leaks to start. There are three things you can do:
1. when you make the hole for the valve- make a small hole and push the valve stem through it gently. Don't let it rip.
2. you can also end the tape short of the valve hole. Such that the valve only contacts the aluminum rim, without any tape there
3. tubeless tape, like Stan's, tends to be very stiff and not stretchy at all. It's hard to make this tape follow the contour of the rim bed. Electrical tape is much stretchier and easier to press into the contours of the rim bed. But it's too stretchy to use on its own (tire pressure would push it into the nipple holes). You can, however, use it on top of the tubeless tape where you need to make an airtight seal. Or in a location where it's in no danger of being pushed into a nipple hole, like over the rim joint line.

FBinNY 

First of all a good answer would depend on knowing more. Among other things is how quickly it goes flat

Assuming a fairly slow leak, not from a glass puncture, it's a rim leak, either at the valve, spoke hole, or under the tire bead.

Since sealant tends to circulate unde the tread, rather than towards the rim, try pumping the tire and slowly turning the wheel while near horizontal. This will circulate sealant, hopefully helping it find and seal at the rim/bead area.

If no luck, then unmount the tire and examine the rim looking for any dings or burrs at the tire seat, and of course checking the tape, especially at the valve.

Canker

Use soapy water to find out where it is leaking. Then we can tell you how to fix it.

TerrenceM

As others have said step one is locating where there air is leaking from by rotating the wheel in a big, flat bucket or sink etc.. slowly and looking for bubbles of the leaking air..


Mystery slow leaks like this in my experience (assumption slow leak) has occurred in a few cases

1. Tape failure.. usually around valve... or if you replaced the tire, sometimes the tape might get pushed to one side... or nipple hole cuts tape possibly if you didn't double up the tape layers
   
2. Cut right in bead or sidewall.. REALLY hard hits can actually result in snake bite puncture in the tubeless tire itself.. since this usually occurs right in the bead if you put lower pressure sometime it will be able to seal, put in higher pressure and stops sealing.. also just from riding and the cut will open and close and leak air slowly
   
3. There is a hole that is only kinda sorta sealed and the tire will leak slowly over time.. this usually happens with older tires.. if your tire has wet spots on in where sealant is weeping out.. time to change the tire.. running out of rubber..
   

BUT.. step one.. find the leak.. or your just guessing 🤷🏾‍♂️

Polaris OBark

Clean the rim with isopropanol and apply 720° of tape. Put a tube in the tire, and seat the tire and tube with full inflation for 24 hours. Then carefully take the tube out, breaking only one bead off the rim if possible, and insert the tubeless valve. Inflate. If it holds air, add sealant, inflate to max pressure, swirl it around both horizontally and vertically, then have the kid ride the bike hard. Hopefully at that point it will do the right thing.