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See them on various forks and I believe they help relieve pressure build up.
How would I know if need to release pressure?
When done, what does it release - air or fluid?
Once done, does anything then need topped up?
Why does this need doing?
I love technology, but I also like to understand it a bit and I'm definitely thick on these things.
Yes, pressing them equalises the pressure within the lowers. In theory, air might be released when pressing.
In practise, mine (Lyrics) never seem to do anything. Quite different on the KTM enduro bikes (motorcycles) where the rapid cycling of 300mm+ of travel does build some pressure inside.
I think you could get the same effect by inserting a small and lubricated cable tie through the fork's seals.
In the case of a riding buddy they provide a perfect route in for water and dirt ingress. He didn't realise that the eyelets of his mudguard were an integral part of sealing them. When one split a little bit, it allowed a load of crap in - enough to permanently damage the stanchions.
To me they seem an unnecessary weakening of a fork's defences again filth getting in.
So would there be any issues with just semi-regularly giving them a push?
If air does escape, does it then need topped back up?
no, just press them when you want to
Its so they can be at atmospheric pressure, in theory if you go to the top of an Alp then the air in your lowers (not the air spring) will be higher than the atmosphere around you and the valves let them equalise
He didn't realise that the eyelets of his mudguard were an integral part of sealing them.
Did someone else fit the mudguards for him? When you put them on, you remove a washer that’s quite obviously part of the seal. Anyway, looks like he’s far from alone, newer Fox forks now have separate eq valves and mudguard mounts to avoid this. Well, apart from the 38 that so obviously needs updating to get all the improvements (or fixes if you like) the other forks have received.
I thought i wouldn’t need instructions to fit a mudguard, but I’m glad I scanned the qr code and had a look, so I knew which washers to remove and which not! it was quite clear on the instructions 😉
Did someone else fit the mudguards for him?
No, the eyelet split somehow (might have been crash damage) and the less than perfect seal did what less than perfect seals do on a UK mountain bike.
Marketing BS.
Whenever I go anywhere high I never remember to press the things anyway 🤔
Marketing BS.
Yep. Will go the same way as buttercups on RD pushrod ends (allow a tiny bit of waggle that speeds up wear on air spring seals) and dimpled stanchions (will just allow more crap into lowers over time).
Fork manufacturers are slipping into electric toothbrush / hand razor territory with their current need to 'innovate' to apparently keep moving forward and justify new lines and prices.
My wife’s forks have them. Back home in Devon they’ve never made a difference, but they worked out in the Alps this summer.
What did they do to make a difference? Or...how was the fork behaving/feeling to make you push the buttons? And how quick was the fix? A second or 10 seconds of pushing?
Use mine before every ride, but then I also do fork and tyre pressure too so my bike feels the same every ride. All the release buttons do is stop too much pressure building up in the lowers which can lead to an added progression feel and hard to use all the travel. A tip for using them is don’t press with the pad of your thumb, use your nail instead so you don’t cover the hole up
Marketing BS.
If no air comes out when you press them you will think this and you don't need them.
If air comes out when you do you will see why they are there...
Think about how air in the lowers will alter the end stroke of the fork and stop you using all the travel. It acts as an extra unwanted air spring.
Forks tend to ingest air into the lowers via the seals even at the same altitude.
Newer Zebs you need to use a hex key to bleed them. It's still less hassle than sticking a zip tie down the seal to perform the same operation.
Ok, slightly wiser...if the lowers get this air build up, once it is released, does the rider need to top the fork air pressure up? So if they are riding and fork is 'inflated' to 92psi, if they press the release buttons and air escapes, will they now be riding less than 92psi and need to put air back in the fork?
I think my thickness on this is not really understanding where the air is coming from...if inside the fork, how does the leg without the air chamber get it? That suggests the air chamber isn't linked to this - have I just answered my own question?
Good grief, I really am being thick about this!
Yes you've kind of answered your own question.
The air spring it totally seperate to the lowers.
Not talking down to you but maybe try doing a simple lower leg service to understand how the air spring is a totally sealed seperate system to what's going on in the lower legs.
Once you start working on this stuff it'll give you a better understanding and for me at least it's far better to visualise how stuff works when you get your hand on it and it's far easy to understand.
I've generally steered well away from servicing the fork and shocks due to a fear of reassembling incorrectly, but your suggestion sounds like a good idea.
I've got them on my fork and never used them but I've seen them on plenty others and wondered what they did.
Currently on holiday and this has been annoying me in my sleep!
@DickBarton think how a bike pump works, when you pull out the plunger, air enters the barrel past a one way seal. If the valve end is blocked the pump you act like a spring. Forks have oil seals that aren’t air tight, to help reduce initial stiction. After your fork compresses it extends and tiny amounts of air can get sucked from outside past these seals and get stuck at the bottom. These can build up acting like an additional air spring at the bottom of travel. These buttons let this out. Can be a non issue in the UK where elevation changes while riding are small but more useful if your riding in areas of large elevation change.
Makes sense, thanks...also very relevant as I'm just had a similar issue refilling insulin. Your description isn't far off what I was seeing.
Given I'm not a hard rider, I suspect there will be next to no air in mine, but I'll give them a push anyway. Or I will when I get to my bike.
Thanks for the suggestions and explanations. I'm slightly less thick now.
Slight hijack,
Does anyone know where you can get replacement cover caps for these air valve. Specifically for RS pikes. I have lost one and am struggling finding new ones.
Sram/RS are pretty good at listing part nos. if they do spares for such things… find your fork
tried the part number from Sram. That was the easy bit . Finding someone who supplies them is the sticking point, unless my Google skills have left me.
I get this question asked a lot! And there's much confusion and duff info online about these.
Their purpose is to release air pressure build up in the bottom section of the hollow lower leg which can occur when riding at very high altitudes. This pressure build up happens due to the atmospheric air pressure dropping as you reach higher altitudes (in the same way that if you've been in a ski resort and looked at bags of crisps you'll notice they're all ballooned up and look like they're about to pop!)
This air imbalance means that the fork has now gained an unwanted build up of pressure in the lowers, but it's only a tiny amount, perhaps a couple of PSI. By pressing the release valve you can remove this unwanted pressure build up.
It's not really a feature that is required for most of the UK riding as you'll rarely be anywhere high enough to encounter this issue.
Now, here's a more common scenario though - If you press these valves and regularly hear air releasing on the left side valve, then this is telling you that your fork is actually leaking from the seal head at the base of the stanchion and letting air leak from the air chamber into the lower leg. This means you need to get your fork serviced. The same rule applies if you slide a zip tie under the wiper seal and hear a hiss of air, again this is a sign that that your seal head seal is worn.
To clarify, it's not normal to constantly hear air escaping from the lowers when pressing these release valves. It means there's an issue that needs resolving (again, assuming you're in the UK and not at 1000m each time you're pressing them!)
dimpled stanchions (will just allow more crap into lowers over time).
Slight diversion, but all the stuff about these has been with dimples below the lower leg seals, so that's not an issue. 🙂 You're not going to see Fox releasing a 40 that looks like it's had a baby with a golf ball.
If you press these valves and regularly hear air releasing on the left side valve, then this is telling you that your fork is actually leaking from the seal head at the base of the stanchion and letting air leak from the air chamber into the lower leg. This means you need to get your fork serviced.
So where do you think the air comes from in my damper side fork leg.😉
This pressure build up happens due to the atmospheric air pressure dropping as you reach higher altitudes (in the same way that if you've been in a ski resort and looked at bags of crisps you'll notice they're all ballooned up and look like they're about to pop!)
This air imbalance means that the fork has now gained an unwanted build up of pressure in the lowers, but it's only a tiny amount, perhaps a couple of PSI. By pressing the release valve you can remove this unwanted pressure build up.
Even having gone up to 3000m this summer and pressed the buttons there was no audible or feel that any air had come out ro rebalance them
Marketing BS.
Yep. Will go the same way as buttercups on RD pushrod ends (allow a tiny bit of waggle that speeds up wear on air spring seals) and dimpled stanchions (will just allow more crap into lowers over time).
It blows my mind how many people saw those dimples and thought they were going to be on the visible part of the stanchion.
Did I see a pic the other day showing that new forks (Pikes?) are being designed with the release buttons at the top? Next to the adjuster dials?
Yeah, so they don't get sued by Fox apparently, there is a pinkbike article about it although it says Fox sued in 2023...
https://www.pinkbike.com/news/sram-rockshox-bleed-valve-crown-patent.html
Blimey... complicated this patent stuff innit.
Did I see a pic the other day showing that new forks (Pikes?) are being designed with the release buttons at the top? Next to the adjuster dials?
Like the Fox Podium. It's not the position of the valves that fall foul of the Fox patents, it's the "push to release". That's why others are using "turn to release" and "pull to release" instead. Both probably easier to use correctly as it happens, but use more parts.