Tyre pressure relief valves

Tyre pressure relief valves

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Discussion

jeff666

Original Poster:

2,314 posts

190 months

Thursday 17th April 2014
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Asking for a mate, has anybody used these, the Long Acre tire life ones ? they are supposed to keep the pressure at the PSI you select.

Any views ?

PhillipM

6,515 posts

188 months

Thursday 17th April 2014
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Every time you hit a bump, you'll lose some air...

simes43

196 posts

232 months

Thursday 17th April 2014
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nitrogen.

tristancliffe

357 posts

212 months

Friday 18th April 2014
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How will nitrogen help?

thunderbelmont

2,982 posts

223 months

Friday 18th April 2014
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You need OFN (Oxygen Free Nitrogen)(used by Aircon engineers to check for leaks in systems)

Because it's pretty well pure, it's more stable as tyre temp increases, this tyre pressures remain much more constant. It won't be totally stable as there will be impurities once in the tyre.


BertBert

18,955 posts

210 months

Saturday 19th April 2014
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It's the water in air that's actually a problem.

jeff666

Original Poster:

2,314 posts

190 months

Sunday 20th April 2014
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thunderbelmont said:
You need OFN (Oxygen Free Nitrogen)(used by Aircon engineers to check for leaks in systems)

Because it's pretty well pure, it's more stable as tyre temp increases, this tyre pressures remain much more constant. It won't be totally stable as there will be impurities once in the tyre.
My track day car has Nitrogen in the tyres, still has temp rises, I am guessing this is because it is not 100 percent pure, must still have some oxygen in them.

I suppose unless you have a system that can suck all the old air out you will still have issues.

So, no thoughts on these valves then ? and thanks for the replies so far.

BertBert

18,955 posts

210 months

Sunday 20th April 2014
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Presuming you mean "pressure" rises...

That's always going to happen according to Gay-Lussac's gas law http://en.wikipedia.org/wiki/Gas_laws

What you don't want to happen is when there is moisture present, the pressure rise is not linear with temp.

No idea on the valves in question though. Just feels a bit nasty, drilling more holes in the wheels and having a way for the gas to escape.

Bert

Silent1

19,761 posts

234 months

Sunday 20th April 2014
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jeff666 said:
thunderbelmont said:
You need OFN (Oxygen Free Nitrogen)(used by Aircon engineers to check for leaks in systems)

Because it's pretty well pure, it's more stable as tyre temp increases, this tyre pressures remain much more constant. It won't be totally stable as there will be impurities once in the tyre.
My track day car has Nitrogen in the tyres, still has temp rises, I am guessing this is because it is not 100 percent pure, must still have some oxygen in them.

I suppose unless you have a system that can suck all the old air out you will still have issues.

So, no thoughts on these valves then ? and thanks for the replies so far.
It's the moisture in the air not the gas that causes most of the pressure increase.

jeff666

Original Poster:

2,314 posts

190 months

Sunday 20th April 2014
quotequote all
@ Bert, I don't think you drill any holes in the wheels, they are a replacement type valve that releases air when the desired pressure is reached, (I think). I have only seen them for sale in the USA .

Interesting to hear that the moisture in the air causes the pressures to rise, I am guessing the Nitrogen is much more stable ?

Jeff.


BertBert

18,955 posts

210 months

Sunday 20th April 2014
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jeff666 said:
@ Bert, I don't think you drill any holes in the wheels, they are a replacement type valve that releases air when the desired pressure is reached, (I think). I have only seen them for sale in the USA .

Interesting to hear that the moisture in the air causes the pressures to rise, I am guessing the Nitrogen is much more stable ?

Jeff.

At the risk of repeating myself rolleyes
The pressure rises with heat. That's physics. If you have water present, you get much more pressure rise and it's not linear.
If you look up the valves they are separate and require separate holes.


jeff666

Original Poster:

2,314 posts

190 months

Sunday 20th April 2014
quotequote all
BertBert said:
At the risk of repeating myself rolleyes
The pressure rises with heat. That's physics. If you have water present, you get much more pressure rise and it's not linear.
If you look up the valves they are separate and require separate holes.
No need for the rollies, I have only read one review on them, no mention of drilling extra holes, not much info on them at all, hence the question posted on here.

Thanks for taking the time to reply anyway.

anonymous-user

53 months

Sunday 20th April 2014
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jeff666 said:
BertBert said:
At the risk of repeating myself rolleyes
The pressure rises with heat. That's physics. If you have water present, you get much more pressure rise and it's not linear.
If you look up the valves they are separate and require separate holes.
No need for the rollies, I have only read one review on them, no mention of drilling extra holes, not much info on them at all, hence the question posted on here.

Thanks for taking the time to reply anyway.
BB's point was that Nitrogen, which will be dry, is little better than dry air (which is mainly nitrogen in any case), it's the moisture that you need to avoid, because it is the moisture that leads to erratic pressure rises as the temperature rises. The nitrogen will be little, if any, more stable than dry air.

BertBert

18,955 posts

210 months

Sunday 20th April 2014
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jeff666 said:
No need for the rollies
Sorry, just thought it in the realm of normal PH banter biggrin
Spent a minute or two googling to find out about them, hence the (slightly) superior knowledge. Hence as I say, no practical experience to add.
Bert

carl_w

9,154 posts

257 months

Sunday 20th April 2014
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BertBert said:
At the risk of repeating myself rolleyes
The pressure rises with heat. That's physics.
Yes but it's pV = nRT where T is the temperature in kelvins. I think over the operating temperature of a tyre the pressure increase of an ideal gas would be negligible, particularly considering that the tyre is flexible and hence the volume can change.

BertBert

18,955 posts

210 months

Monday 21st April 2014
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Yes indeed. How hot does a tyre get? Or more importantly how hot does the gas inside it get?
Bert

BertBert

18,955 posts

210 months

Monday 21st April 2014
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Good question Bert. The internet says that F1 slicks operate at 100 degrees C. So range from 293 K to 373K - still quite a lot of temp change for the pressure to rise with temp.
Bert

NJH

3,021 posts

208 months

Monday 21st April 2014
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BertBert said:
At the risk of repeating myself rolleyes
The pressure rises with heat. That's physics. If you have water present, you get much more pressure rise and it's not linear.
If you look up the valves they are separate and require separate holes.
This is where the myth comes in, the physics theory tells us the moisture content makes very little difference to the pressure rise. Water is only a few percent of our air for a start. The thermal conductivity of water vapour is actually lower than air! Another one of the myths. The one and only possible reason for drying the air is to get to a position where highly accurate and repeatable forecasts can be made on the tyres pressure whereas with atmospheric air one will likely not know how much water vapour is in it and hence can't make such highly accurate predictions.

Like many things in motor sport though this in the realms of 0.01s stuff that obsesses the F1 teams and should be considered a bit silly to even think about for club racing where the consideration of whether or not one took a dump in the morning and the effect it has on weight will be more of an impact. Worrying about moist air for most guys using pressure gauges that probably aren't even accurate to less than 1 psi is just plain silly.

How many guys on here calculate what their starting ideal tyre pressure for each tyre should be for each track in the UK and for every type of atmospheric condition to tenths of a psi? Nope thought.

Edited by NJH on Monday 21st April 14:11

BertBert

18,955 posts

210 months

Monday 21st April 2014
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It's quite an interesting topic and probably of more interest to those running slicks. I thought that it really didn't matter *all* that much, but we focussed on tyre pressures a lot last season and found it made a huge difference. It's actually quite hard to get right and a lot of Friday testing was about seeing how the tyres behaved with the circuit and the conditions (and then hoping that race day would be the same).

Bert

jeff666

Original Poster:

2,314 posts

190 months

Monday 21st April 2014
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I was asking for a club racer, (Team Trophy) so a 60 min race, when they come in for the mandatory pit stop (2 mins) we check the pressures and have to reduce them, both guys say the car felt better after the stop.

We start around 24psi cold, and they can be as high as 34 hot, both cars are on ordinary air, not Nitrogen, they are running the Khumos v70's from memory.

Just hoped that some body may have had some experience with these valves, the only review that I found on them rated them highly.

Again, thanks for the replies, much appreciated.

Jeff.