I got a new road bike with tubeless tires. I can't get the back tire to hold air. I got the front tire inflated but for some reason, as I am pumping the air all I hear is it coming out somewhere from the tire. I don't see a hole. It was shipped from another state and it came completely flat.
There could be many causes for a flat tubeless tyre, especially on first installation.
- Check the tyre is actually tubeless compatible
- Check the tyre beads are seated the whole way round
- Check the nut on the valve is tightened (finger tight)
- With the wheel off the bike, shake the wheel and listen for sealant.
If any of these conditions are not met, rectify the problem before trying again.
If they are all met, then you have a hole in the tyre - not at all unheard of in tubeless ready tyres which are designed for use with sealant.
To find the hole, get a helper to operate the pump for you, whilst you carefully inspect/listen to where the air is escaping. Whilst still pumping (to generate some air pressure), rotate the wheel so the hole is at the bottom. This will cause the sealant to pool in that area and plug the hole.
Tubeless tyres hold air only after being seated properly. That means the bead is at the shoulder of the rim's flange.
Many tyres have to be inflated and under pressure to seal the bead. One has to inflate them with more air per second going in through the valve then getting lost along the yet unseated bead.
For many MTB tyre-rim combinations a workshop compressor or tubeless charger (pump with air tank) is necessary.
Since you were able to seat the front tyre with your pump the following might be enough: Push each bead as far on the shoulder as possible. Then pump very vigorously until you hear the beads pop into their place. This can be very loud. Also, a little sealant spread on the shoulders might help to increase the initial seal just enough.
Larger volume tubeless tyres need a good blast of air to get them seated, a track pump often won't get it done, especially if you've had a few tries and have got tired.
A compressor will do the trick but they're not always available, consider a tubeless inflator like an Airshot or the Bontrager FlashCharger.
When my tubeless tyres won't mount it can often be down to the tubeless rim tape. Once it gets wrinkled or dirty with sealant the tyre can't slide up to the rim quick enough. Try cleaning the rim tape and inner rim walls. If this fails I generally replace the rim tape with new and it works first time.