Pressure sensors torque question (stupid ones)

[er-minio]

After having the spokes of my wheels painstakingly re-tensioned and balanced by Slipperywheel of this parish (thanks again ) in March I did fit new eBay/Chinese pressure sensors to the two wheels, matched them to the bike, and they work flawlessly.

Only issue is that the valve stems seems to be slightly shorter. Now two (very stupid) questions:

There is torque setting for the valve stems/nut. I tried it, but since it insist on the rubber seal, I proceeded to destroy the seal as the torque wrench never clicked. Ordered new seals (5 quid on eBay) and re-fitted by hand, including the tightening/loosing/tightening again procedure.

Now, the rear wheel keeps the pressure, the valve is just long enough for me to attach my compressor to inflate the tyre. Just.
The front tyre doesn't keep the pressure (deflates within a day) and the valve stem is not long enough for the compressor to be attached and to inflate the tyre.
I think it might be just a couple of threads length short.

I left the bike since April, as I'm currently out of the country, but I'm back soon and want to sort this out to use it.

1. shall I ignore the torque specs for the valves?
2. I am guessing the leaky front tyre valve maybe just needs another couple of rotations, so the seal will seat/squish better and it will stick out enough for the compressor attachment to be able to attach properly?
3. am I missing something on how those valves could be torqued correctly?

thanks!

 

[Slipperyeel]

Hi er-minio

Sorry this one is still giving you trouble. The nuts on those aftermarket sensors are a little too long (meaning you can't get the air connector onto the valve stem!). Maybe they're for alloy wheels or maybe they're for cars?!

Shortening the nut is the only solution, so hopefully the verniers in the pic show you the OEM nut length.

For torque, I followed the book and have no leaks (so far!). The book says to first tighten fully to torque (I think 12Nm?) then back it off and then final torque again. I did use a little thread lock on the nut, not sure if you have? Though I see this as only stopping the nut loosening rather than sealing. Because of that seal being what it is, I think you could tighten it further without much worry, but obviously not so much more, maybe 1-1.5 turns after torque.

So in short, I think you'll need to shorten the nut length as per the pic. If the tyres are on, you may still be able to push the valve down and unseat the rubber seal - to give it another chance to seat.
*partly unscrew the nut, then push the valve in. Catch the valve with some pliers before removing the nut!

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[MWH]

They're known for being short. I broke my front one trying to get an airline on it. Replaced it and tried a 90 degree adapter on the airline but it wouldn't seal as not enough valve to go inside to seal. Ended up with the new type sensors and a manufactured 90 degree valve to go on the wheel so filling is now a lot easier!!

I didn't torque mine, just nipped it up by feel. I did put a little red rubber grease on the seal to prevent it catching and tearing. Been OK for a couple of years now.

 

[er-minio]

Sorry this one is still giving you trouble.

Haven't really had a chance to "fix" it, as I've been in Italy since a couple of weeks after we last met.
Should be back soon in the UK.

The nuts on those aftermarket sensors are a little too long

Aah ok. That might be the issue. I still have the other valves, I can switch.

The book says to first tighten fully to torque (I think 12Nm?) then back it off and then final torque again. I did use a little thread lock on the nut, not sure if you have?

Yep did this. Both times.
Thread lock too.
Just, first time, the wrench never clicked, over-torqued and it destroyed the seal.
Replace and did by hand. Maybe the leaky valve is not tight enough.

I'll check the nut when back. Tyres are on now, so makes it slightly trickier if I destroy the seal again. Oh well... something to do on a Sunday to relax.

 

[Slipperyeel]

They're known for being short. I broke my front one trying to get an airline on it. Replaced it and tried a 90 degree adapter on the airline but it wouldn't seal as not enough valve to go inside to seal. Ended up with the new type sensors and a manufactured 90 degree valve to go on the wheel so filling is now a lot easier!!

I didn't torque mine, just nipped it up by feel. I did put a little red rubber grease on the seal to prevent it catching and tearing. Been OK for a couple of years now.

The sensors you got, are these the ones with a trough hole, meaning you need a different type of valve (the sensor has no valve basically).
I've seen these and they looked like a better solution actually - valve and sensor separated.

If I'm describing the right kind of sensor, which valve stem did you use?

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[er-minio]

Mine are the old ones (banana shaped).

 

[MWH]

The sensors you got, are these the ones with a trough hole, meaning you need a different type of valve (the sensor has no valve basically).
I've seen these and they looked like a better solution actually - valve and sensor separated.

If I'm describing the right kind of sensor, which valve stem did you use?

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Schrader 5082m from memory, with the "newer" 3141m type sensor

 

[landmarkjohn]

Getting back to the OP I've been looking at sensors for car today and all the torque values are 6 Nm.

That's just a pinch, other more qualified engineers may have a better description.

 

[er-minio]

Testimony to what @Slipperyeel explained about the different length of the valve nuts:



BMW original left and Chinese on the right.


I'm back in London.
Found the bike with the rear tyre at the exact same pressure i left it 2 months ago (success!).

Front tyre completely deflated.
Reinflated and screwed in a bit more the nut, had some loss of pressure (minus .2 or .4 over a day) following this and using the bike Sunday and Monday.
Tightened it a bit more today at lunch and set the right pressure, right now it was almost at the same pressure. Almost. I'll check after tonight.

I have to MOT the bike on Saturday (at FWR). If it's not sorted by then, I'll admit defeat and ask them to have a look.

 

[botus]

cast wheel sensor

For vehicles with RDC and National version japan	X530A=Yes Y742A=No
05	RDC sensor		1			36317914365

spoked wheel sensors

RDC sensor		2			36317914365
	only in conjunction with
--	Nut	M8X1.0	2			36318359962

 

[The Other PaulG]

I did put a little red rubber grease on the seal to prevent it catching and tearing.

I would do that too.

 

[autogs]

So would I but tbh I'd definitely skip the locktight

 

[AberdeenAngus]

I fitted a new sensor and just reused the nut off the original one.

 

[Slipperyeel]

I fitted a new sensor and just reused the nut off the original one.

I did the same, at first. But after all that effort, I kinda wanted something looking a little smarter. Solved by facing off the replacement to length.

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[Slipperyeel]

So would I but tbh I'd definitely skip the locktight

I thought that, at first. But in the end I used it because I remembered that over a period of time, I found the little air leakage was cured by tightening that nut... So I figured, it will quietly loosen itself over time. The thread lock is not an issue to release/undo

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[er-minio]

Replaced at MOT.
Turns out I did pinch the little o-ring.