I’ve always used proper Stan’s tape before, except for a pair of Alex CX rims which worked OK with three layers of electrical tape.
I’ve just had a go at sealing some Weinmann CX rims with four layers and it’s leaking from round the valve, presumably because the air is getting past the tape.
I popped the tyre partly off and could see air bubbles around the valve on the inside. I take it the air had forced its way past the tape and pressurised the hollow rim and was then escaping again any way it could.
So, how many layers of tape for a CX tyre at ~70psi, or should I just give up and buy the proper stuff ?

I’ve found the problem.
The tyres went up OK at first, then one went down overnight.
Blew them both up again, then both went down overnight.
Took the tyre off and found this.

Bit out of focus, but you can just about see the tape all bunched up in the middle, leaving the spoke holes partly uncovered.

So…
It’s a 19mm rim.
Stan’s and Gorilla tape don’t go that narrow.
What’s the best tape to use ?
That’s Screwfix electrical tape on there. Is there a stickier option ?

I would also like to hear about other options apart from Stan’s, I’ve run out of Stan’s and need a cheap / good alternative for a couple of new rims.. (WTB I23’s)

Cut a roll of gorilla tape?

Gorilla tape can be cut to width if you buy the standard wide rolls – as here: http://www.pinkbike.com/news/Tech-Tuesday-Gorilla-Tape-Tubeless-Conversion.html

I was planning on doing this before I noticed that my rims are exactly the right width for the narrower Gorilla Tape “To-go”.

I applied full width Goriila tape to my 717’s, pressing down firmly all round, then using a flat blade scalpel I was able to poke the blade into the bead recess on one side of the rim, and hold the handle of the scalpel down flat against the other side of the rim.
Then I was able to run the blade colmpletely around the rim without it budging as it was neatly held in place by the bead recess.

Worked a treat, no leaks, tyre went up and stayed up first time.

Thanks timb34, that a useful guide.
The only thing I’d do differently is a bit of trial and error on the width.
Where he just cuts the tape to the same outer width of the rim, you might find that say, 1mm wider or narrower works better.

Looks like a detour via Screwfix on today’s commute then.

Slimjim78, yes that’s another way, cutting the tape after you’ve stuck it on, rather than before.
I’d be a bit worried about the point of the knife scoring the rim though, possibly leading to longitudinal cracks, especially on a CX rim at much higher pressures than an MTB.

I use 3 layers of electrical tape.

Make sure it is stretched quite tight when putting it on.

Make sure that the rim is clean and dry (use meths).

Rub over the tape once it is on to firm up the adhesion.

Ah yes, that’s the other thing – the pinkbike guide suggests pulling the tape tight when going round, then smoothing down into the recess afterwards.

This video from ENVE (who supply Gorilla Tape as their preferred tubeless tape for their $$$ carbon rims!) suggests pressing down in the middle as you go:
[video]http://www.youtube.com/watch?v=sU1q1omGyP8[/video]

I did the front as pinkbike and the back as ENVE – the tape seemed to go on better using the ENVE method, so I’d go with that.

I’ve just been using superstars rim tape, 25mm wide on both i23 and some DT Swiss 445(?) (19mm) rims.

No issues. Thought about using electrical but thought it could end up a faff if it didn’t work out never mind wasting the spaff.

Is electrical tape really waterproof? Surely it’s going to fail if dunked enough?

Duct tape is fine just cut to size