Swiss DT rr 440 tubeless problem

term1te

I've just finished building a rear wheel with an asymmetric Swiss DT rr 440 rim on a Hope Mono hub. I've used the Swiss DT tubeless tape and valve, however, I can't get the pressure above 70psi without the air suddenly escaping around the valve. The tyre seals to the rim no problem. I've taken the tyre back off, cleaned the interface between the valve and the rim/tape, but still the same problem. I don't want to tighten the valve with a tool in case I need to remove it out on the road, but it is as tight as I can make it by hand. The little rubber grommet that comes with the valve is on the outside, between the tightening nut and the rim, as per the instructions.

The only thing I can think of is that the off set valve hole in the asymmetric rim is preventing a good seal? I know others are using tubeless tyres on this rim, so what am I doing wrong?

cycleclinic

you need to tighten the valve collar. You should not being putting a tube in on the road, you use tyre worms and good tyres that dont puncture easily. You can bash the valve out with a stone anyway.

Dont be timid with tubeless.

term1te

The valve collar is as tight as I can make it. I've wiggled and pulled the valve as much as I can to gain extra thread for the collar, so I don't think I can get it much tighter. My concern isn't about removing the valve, but undoing the collar out on the road, if I tighten it with some pliers. I have another set of wheels I run tubeless, and have had no problem with them, although they are using Stan's notube valves which are a different shape. I may swap the valves over to see if it is the valve or the rim that is the problem.

ugo.santalucia

Fill with sealant... Those rims need sealant to work

term1te

Tried that. 70psi and sealant sprays out around the valve hole.

I've just found that the Swiss DT valves come in road or MTB form. I don't remember specifying which I wanted, I got it about 6 months ago, but have only just got around to using it. I'm guessing they would only have two if they different, perhaps designed for the different circumference wheels or different profile rims? Unfortunately it came in a small clear Ziploc bag with no reference, so I could have an MTB valve, which could be the problem? Does anyone know if there is a way of discriminating between the road and MTB version?

ugo.santalucia

The base is rectangular and slots in the rim channel

6wheels

Put an O ring at the base of the valve, should conform to the shape of the rim easier.

svetty

If sealant is pissing out around the valve hole the collar isn't tightened enough. I always give mine a slight tweak with pliers and they seal fine - assuming the inner rubber bung is correctly orientated in the rim bed.

lostboysaint

If all else fails, switch to the E Thirteen tubeless valve. Completely brilliant as it has a variety of rubber seals that work BOTH sides of the rim.

cycleclinic

with the DT Valves the O ring is almost essential. MTB valves and road valves are the same except for the length.

The problem is you valve or how its fitted.

you might also have too big a hole in the tape for the valve. A slight nick is all it takes and sealant will piss out under pressure.

term1te

Sorry to bring this one up again, but I've had another go, with exactly the same problem. I've fitted a different valve, with a tapered or cone shaped bung, no luck with or without the sealant. I've replaced the rim tape (Swiss DT, correct width according to their website) and tried with both the Swiss DT valve and the new one, again, same problem, gets up to ca. 70 psi, then just starts leaking air around the valve hole, drops to ca. 50 psi and happily stays there. I've tightened the collar with pliers, no difference. Because of the off-set rim, the rubber grommet doesn't cover the whole valve hole, one side is too close to the sidewall. I can't see that that should make much difference, as if the air can get passed the rim tape and valve bung, then it would come out thorough spoke holes if not the valve hole. The only thing I can think of is that the offset rim prevents the valve collar binding to the rim all the way around, which enables it to move slightly one way. Maybe above ca. 70 psi the valve moves slightly and releases the air pressure? I guess this would be the same problem with the E Thirteen valves too.

I've successfully built up wheels with Stan's no tube rims, and run tubeless with not problem, so hopefully I'm not making a complete error here, but it is beginning to drive me mad, so any further suggestions gratefully received. I'd also be interested to know if anyone has successfully used a Swiss DT RR440 offset rim with tubeless tyres.

dj58

IIRC drlodge is running these wheels with tubeless tyres on his Rourke.

ugo.santalucia

DJ58 wrote:

IIRC drlodge is running these wheels with tubeless tyres on his Rourke.

At the time I did fit his tyres... they aren't the easiest tubeless rims to live with, but they sealed OK with sealant. Hard to say what the OP problem is. Maybe the tyre is too big for the rim? I found these are OK for 23 mm tyres, but they might be too narrow for bigger tubeless

term1te

I'm actually using some Schwalbe Ironman tubeless tyres, 22 mm, so they are not too wide and seal to the rim no problem. Searching the net I came across someone on a different forum with the same problem. He found that the issue was the off set spoke holes in the rim. To facilitate the off set half the spoke holes are much closser to the rim wall than the others. With less of the tape on the wall side of these spoke holes it would appear that he air can get under the tape and round the rim, releasing through the valve hole. He ended up re taping with the tape going half way up the rim wall which placed the off set spoke holes in the centre of the tape. I'll have a go at that, although I'd be a little concerned that it would interfeer with the seating of the tyre.

6wheels

Using some Gorilla tape ( cut with scissors for couple of inches along its length then tear it) to the size you want. Use O ring , as mentioned before , and for belt and braces you could assemble with window silicone sealant around the valve/rim interface leaving it to dry before inflating.