It takes a volume of air to seat a tubeless. Even if you lube the tire it takes a volume of air to get it to pop onto the seat. Cannot deliver that volume with my floor pump. At the shop they remove the core to the presta and have this conversion tube they put over the open stem with a compressor on the other end.
It depends on what type of tubeless standard you are using.
UST rims are designed to be able to be inflated with a floor pump. The rim profile has an inner channel. The tyre bead should be placed in this as per the picture when you begin inflating the tyre. When it reaches a high enough pressure it pops into place and you can continue to seat it easily with the pump. You can also add sealant before inflating with USTs.
- Tubeless Ready
Tubeless Ready have a shallower rim bed that require far less volume to inflate with a floor or CO2 cartridge. This is trickier with a floor pump and people often remove the valve core to allow a higher volume of air in. Once the tyre is suited you can also to remove the core to add sealant.
- Ghetto Setups
If you are using any other tyre/ rim combination it's really just luck if you're going to get a tyre to seat with floor pump, compressed air or ever at all.
If you don't have a compressor, you can use a CO2 cartridge (or two or three) inflator to quickly give that burst of air/CO2 that you need to seat the tubeless. It's very difficult with a floor pump.
Source: Wikimedia commons
I use a tubeless inflator.
My skills and track pump will not seat a large volume tyre, just can't get enough air thru, I've managed 23/25mm road tyres, but nothing bigger.
My inflator is a Bontrager Flashcharger, but there are lots of similar products on the market these days.
They all work in a similar manner, charging up a cylinder of air and releasing it in one go by pulling a lever or turning a valve.
I find it better than a compressor as it's cheaper, portable, doesn't need power, replaces my track pump and has never failed to seat a tyre.
Need to have a compressor. Remove the core then just press a schrader fill up end on the stem. I have had to take a couple to the shop and this worked for me today.
This is more a problem on older tires where I break the seal to add sealant. I am gong to buy an injector so I can add sealant without breaking the seal.