It might be time to finally use the stans rim tape I bought two years ago, buy some sealant and see how much of a mess I can make in the shed. I was going to cut some valves from old tubes, or am I making a mistake?

I’ve done both, can’t say I’ve noticed a difference. So long as the valves have a removable core you’ll be fine. Just leave a little of the inner tube around the valve.

For the sake of £9 i’ve bought a pair of proper ones each time.

So long as the valves have a removable core you’ll be fine

I was hoping to get away with unseating a bit of bead and putting sealant in that way, so not needing to remove the cores (or buy associated gadgets), but I suspect this will be the reason I end up buying valves and/or tools!

I’ve got DIY valves on my cross bike and they’ve been fine with 40-50 psi but if you get proper ones then get brass and not aluminium.

I was hoping to get away with unseating a bit of bead and putting sealant in that way, so not needing to remove the cores (or buy associated gadgets), but I suspect this will be the reason I end up buying valves and/or tools!

I’ve always done this and it’s been fine (well, the valves have never been the problem.

Only caveat is you need to leave a bigger flange of rubber on the valve, about 1p sized, otherwise I found they leaked (the cone of rubber on tubeless valves is a more elegant solution) , so it works much better with wider rims than it does narrow ones.

Removable core is more useful for maintenance although it is a much easier method of setting up too.

Following from TINAS above, the rim bed profile has quite an impact on this.  The conical ‘rubber bung’ on the end of most ‘proper’ tubeless valves is an idea solution for the average MTB rim, it interference fits itself into the valve drilling nicely providing a good seal.  Conversely, with flat shelf bottomed single skin rims (common for wider rims such as the 80mm common in Fat biking) the rubber bung can actually cause sealing problems and an old tube valve with a decent patch or rubber is a superior solution.  If you do go with cut valve and find it not sealing perfectly, you can always add an o ring under the valve nut.

I’ve always used valves cut from tubes when I’ve used rim tape – mostly I still use the ghetto split tube method though. I think it’s the most reliable.