masi61

I have been using latex Presta tubes on my 2 clincher road bikes going on 3 seasons now to good effect.

Unfortunately my system of checking tire pressures before each ride has caused me to create unrepairable valve leaks on 2 different Vittoria latex tubes in this past year. You see I have been using a Lezyne digital tire gauge to check pressures before each ride. Latex is great, but as most of us already know - latex tubes loose enough air overnight to require topping up before every ride. I was having great fun daring to run a bit lower pressure both front and rear, exploring 70-80 psi front and 80-90 rear for my local chipseal and my 200# body weight.

You see, to get a decent reading from the Lezyne, the pressure gauge has to be pushed firmly onto the valve stem. Threaded stems that allow you to use the knurled nut against the rim would prevent the valve stem from pushing in. Unfortunately, from what I can tell all of the available brands of latex tubes use similar “smooth” brass or aluminum valve stems.

Does anyone one know anyone has ever made a little nylon or even wooden “stop” that fits over a Presta valve stem and has a side set screw to make it remain in place? If no such widget exists, it appears I will be prototyping said widget myself.

Anyone experience a similar issue where your own pumping or tire pressure technique irreparably ruins tubes?

Andrew R Stewart 

I assume your pump has no gage on it? Once inflated to what the pump's gage suggests is correct the valve should be able to be pushed on firmly without sliding into the rim.

But to answer the question, no I know of no valve stem clamp, I suspect no one else has needed one. certainly in 45+ years of shop wrenching I've not had a request for one.It would be fairly simple to make one. I would use metal, Al, for it as this would provide a more dimensionally stable clamp. The first way I think of is much like a frame building block but very small. A rectangle of Al with three holes. the middle hole is for the valve. The tow outer ones ate through the different long sides and are sized to be the tap pilot for a couple of pinch bolts. Saw the block in half so the valve hole is split. Tap with the pinch bolt's thread on one half, through those two outer holes, and clearance drill the other half's pinch bolt holes. Now you have a split collar with two pinch bolts that will secure this clamp onto the valve's stem. Andy

Andrew R Stewart 

I assume your pump has no gage on it? Once inflated to what the pump's gage suggests is correct the valve should be able to be pushed on firmly without sliding into the rim.

But to answer the question, no I know of no valve stem clamp, I suspect no one else has needed one. certainly in 45+ years of shop wrenching I've not had a request for one.It would be fairly simple to make one. I would use metal, Al, for it as this would provide a more dimensionally stable clamp. The first way I think of is much like a frame building block but very small. A rectangle of Al with three holes. the middle hole is for the valve. The tow outer ones ate through the different long sides and are sized to be the tap pilot for a couple of pinch bolts. Saw the block in half so the valve hole is split. Tap with the pinch bolt's thread on one half, through those two outer holes, and clearance drill the other half's pinch bolt holes. Now you have a split collar with two pinch bolts that will secure this clamp onto the valve's stem. Andy

dsbrantjr

Here's an item I designed for a different purpose (MCX RF connectors) which should work if you change the center hole diameter to suit your valve stems, like 0.230" or so: Make it whatever height suits you. It is easier to drill hex stock than round

Barry2 

Sounds like you are looking for a Set Screw Collar

Barry

70sSanO

A 6mm shaft split collar might work. Grainger has aluminum ones, but I imagine you can find them elsewhere.

John

JohnDThompson 

I just use a needle-nose vise-grip pliers to prevent the valve stem from sinking into the rim. You only need to secure the stem when the tube is dead-flat; once there's some pressure in the tube, it's less apt to sink into the rim.

masi61

The needle nose vice grip idea is a good one. I wouldn’t want to crush the valve though and also don’t want to score the metal. I may try some plastic tubing over the vice grip jaws then apply minimal clamping pressure.

But a couple of the 6mm locking collars may be more of the long term ticket to latex tube pressure gauge happiness though. Thanks for your help everybody!

JohnDThompson 

It doesn't have to be super-tight; just enough to prevent the stem from sinking into the rim.

Miele Man

A lot of my butyl tubes also have smooth stems. If the tube is low on air I just squeeze the tire together at the valve area and then slide the pump head onto the valve stem.

Cheers

masi61

I managed to purchase what I was looking for for about $5 each:



These weigh about 8g each.

I can shove my Lezyne digital tire gauge on the valve stem to get a reliable reading without excessive movement thus saving wear or premature failure of the latexinner tube.