Double-up on Presta Lockrings?
 

So I got this really annoying flat on a new tube, I guess I cranked down too hard on the presta lockring, and squeezed the rubber so tight against the valve hole that I got an un-patchable pinch-flat right at the base of the valve.

So I was thinking, that little lockring is useful for trying to put a pump on the valve when it's totally flat, so the valve doesn't get all pushed in (although you could also hold the valve out by just pressing with your thumb through the tire).

What if I took a second lockring and screwed it all the way to the base of the valve _before_ putting the tube on, so it is inside the rim, and then another outside?

On the one hand, I would be able to lock the position of the stem without applying pressure to the tube; no worries pushing or pulling hard to get a pump on or off. And no worries about screwing the outer lockring too tight, it would only put (desirable) pressure on the other lockring.

But on the other hand, under 120psi, would the lockring between the tube and inner rim cause a flat because of continual micro-rubbing every time the wheel goes around?

I've considered doing that myself, but decided not to. Two possible issues.

1- it might increase the width at the base of the valve and cause seating problems on narrow rims.

2- it might hold the stem too high, and cause the tube to tear as it stretches around the ring and down to the rim next to it.

I'm disappointed in the way tube makers got rid of the base flange on valves to accommodate narrow rims, but gave too little thought to how weak the tube/valve joint is. I see more tubes torn at the valve than ever. For my own use, I now use a hole punch on a featheredge patch and add it as reinforcement on all the new tubes for my commuter.

Other than that, I suggest staying with only the one ring, but leaving it loose. It'll still work as a stop when you fit the pump, but is maybe (hopefully) less likely to cause a failure at the base of the valve.

Hey that's a good idea, I'll give that a try, thanks!

When I first saw the thread title, I was thinking you put two nuts on the outside and tightened them against each other like locknuts.

perhaps an O ring on the inside side of the rim..
But I have put one ring nut on the base of the stem , and another outside .
touring width rims..

Heck now that 48mm long PV stems are becoming commonplace..

I don't tighten the nut until the tire is fully inflated.

I never use the nuts.