I've destroyed two latex tubes by inadvertently and slightly pushing the valve into the rim. Also Vittoria, so no nut is possible. It can tricky when working in a small opening of a disc valve cut-out.

In the past, there might have been 40, 50 or 60 psi in the tube before I attempted to top it off. With that psi, I was unable to keep the valve from sinking into the hole when I pushed the crack pipe and chuck onto the valve. There was no room to allow my fingers to hold the valve between the crack pipe and rim. The valve would slip down a mm or two without me knowing it. I would inflate and...hisssss.

I no longer have any problem. I now completely deflate the tire/tube whenever I inflate that disc setup. Fully deflating allows me to apply some counter pressure on the tire side of the valve assembly (outside diameter of the wheel/tire) with a finger as I seat the crack pipe and chuck on the valve. That counter pressure ensures I am not pushing the valve down through the hole at all. I make sure to hold the chuck and valve (keeping the valve fully seated) for the first two or three pumps. After that, the air pressure seems to hold the valve against the rim strip during remaining pumps.

Yeah exactly right. You have to actually pull on the valve stem for that first couple pumps so the valve seats. I know it's a bit difficult if your pump head doesn't squeeze down on the valve stem (in which case you can just pull gently on the pump head) but it's important that you do it. Otherwise there's a pretty high failure risk. Once the tire has some pressure in it the valve will stay seated by itself.

 


I had a “blowout” this morning with my latex tube. I was about 10 miles into the ride on smooth pavement when “BAM”. No puncture on new 5000. I use liberal amount of talcum powder. Very strange!

What's with the smooth circle around tear? Are you using veloplugs?

He had the tube twisted, that is a spoke hole and he needs better rim tape.

To be honest I regard all this as poor design on the manufacturers part and because of the legend of latex, people accept it, all you need is a special skill to make it work, or some trick additional step on installation and it's our fault if we fail to comprehend that. Sorry, not in my world. One too many race day morning failures (two), comes under the fool me once motto.

I don't think I do anything that special, and the only problem I've had that would be installation related were a couple distortion failures around the valve. Once I figured that out, zero. Probably around 60k miles on the road? It isn't "hard" but latex is less forgiving of bad technique.

Correct me if I'm wrong, but are you and rruff talking about installation or about regular inflation?

If this is related to installation, then I first installed the tube in question in March. The flat happened early October. If this installation technique is prone to cause damage, shouldn't it have been damaged more like March?

It's starting to seem like rruff is talking about doing this when inflating from scratch alone. You seem to think we need to do it every time we inflate the tire.

I'm also unclear how this is supposed to help the presta valve seat in the pump. I'm not clear why this would be a problem with latex but not with butyl. And if this technique is particularly important, how come Josh Poertner doesn't mention it in his Youtube vids? This is the first I've heard it mentioned.

• You only need to seat the valve when the tube drops to close to zero pressure -- so either when you install a new tire, or when an old tire sits for a while and the pressure drops to close to zero.
• As for when the tube will fail, usually it will be in the first day or two (often right away) but not always. Sometimes it takes a while and can even take months (if the gap inside is small).
• This is not necessary with butyl: (i) butyl is more slippery so it will usually slide in and seat itself, (ii) butyl is stiffer so it will not bubble out into the gap and fail
• IDK those vids so can't say why Josh doesn't cover it. Anyone who has worked a lot with latex should know this.

It's to seat the valve against the inside of the rim, not the pump.

If there is a gap between the valve area of the tube and the inner surface of the rim when you first inflate, the latex tube will stretch around the black rubber reinforcement and fill the gap. It'll fold under that black rubber part, and be pinned against the rim. Basically it takes less air pressure to make that happen than it does to push the valve tight to the rim. So you need to get the valve tight to the rim to start with.

The tube can live in that condition for quite awhile, but it will be weak in that spot.

Another failure this morning re-inflating a 23mm GP5000 with a Vittoria latex tube, with the "new" style small round grommet at the valve stem base.

I'm sure those who have said it's due to the valve stem being depressed are correct, but when you're still working on your first cup of coffee, and your floor pumps have Silca heads, it's just too easy to screw up. I NEVER had this problem with the "old" style, large oval grommet, valve stem support.

IMHO, not a "Real world" product! Challenge latex tubes from now on.