Tyre pressure relief valves

[jeff666]

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 ?

[jeff666]

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.

[jeff666]

@ 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.

[jeff666]

BertBert said:

At the risk of repeating myself
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.

[jeff666]

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.

[jeff666]

carl_w said:

I'm not speaking from experience (I do sprints) but knowing the difference between hot and cold would you not be better off under-pressurizing them cold so they reach your targeted pressure when hot? After all, cold only lasts for the first few corners and 60 mins is a long race.

I think they are aiming for 30 psi hot, to get that I think the starting pressure would be too low.

I agree we are not talking F1 here, but it does make a fair difference to the handling of the car, so I am told anyway.

[jeff666]

BertBert said:

yes the issue can be that the cold pressure takes too long to get up to temp so you lose out early on. Or you end up running over-pressure later. That's where running nitrogen could help. I've not experienced how you use it, so no idea how you purge the air out.
Bert

I have been given the name of a tyre co near me, apparently they will get all the old air out 1st before the re-fill, I may get them to do my track day car 1st to see the results.

Must be some sort of vacuum jobbie, I will give them a bell tomorrow, I have a day booked at Coombe next Monday so weather permitting might be a good test.

PS. Track car is running slicks.