How To Adjust Air Volume Spacers In MTB Forks Mountain Bike Maintenance


Global Mountain Bike Network


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- Most suspension forks available today are for a range of adjustments to get enough feeling just the way you want and the most obvious options out there tend to be air sprung. As well as adjusting the air spring in the fork to suit your body weight, you can adjust compression rebound damping, but also the air volume. Air volume adjustment takes care of the initial break away force under small bumps and how the fork ramps up through bigger hits. So, with the Rockshox Yari and the Fox 34, we're gonna demonstrate how to change the air volume of your fork. (GMBN jingle) What are volume spacers? Volume spacers like these are small plastic spacers that instal into the air chamber of the fork. Now, what they do is decrease the size of the air chamber, basically by increasing and decreasing the air volume. By doing that, you make the fork feel more progressive. Before air spacers like these, you used to do this by adjusting the oil heights. Had the same effect, bit more fiddly to adjust and a lot messier. Thankfully, fitting air volume spacers is very easy. (jazzy music) Why do you need to adjust the air volume in your forks? Okay, so, when you've got your sag set up correctly, you wanna monitor how much travel you're using on your fork on a regular basis, and also, in some of demanding conditions, and then you wanna ask yourself a few questions. Do you use all that travel and how often? Do your forks feel too firm and uncomfortable? Do they dive too much in cornering or under braking? So, the riding characteristics of a fork with no volume spacers in will feel slightly more linear to one with spacers in. Air itself, when it's in a confined space, is naturally progressive. It means it ramps up the more you compress it. However, certain forks with different lengths of travel and that can feel quite linear and the effect of that is you'll feel quite firm at the beginning of travel, the initial break away force to make the fork move, and you might end up blowing through that travel too much. While some riders like that, it might not suit the riding style that you have. If you like riding hard terrain, jumping, dropping, stuff like that, you want the fork to ramp up more towards the end of travel. By installing volume spacers into the fork, you're making the fork ramp up and firm up towards the end of travel and you're also making the fork feel different through the rest of the travel. It's possible to make the fork sit up more in the mid-stroke so the fork will feel more controlled under braking or into turns and, also, the initial break away force is gonna feel slightly less. So, the floor feels super grippy and really comfortable. So, we're gonna do your air volume spacer adjustment on a Rockshox fork. First, this is a Yari, so we need to do that or the relevant spacers you put inside. A 24 mm socket to undo the top of the fork, shock pump and some suspension grease. Okay, so, a step before you can do this with the fork on the bike-- I'm just doing this with my steerer tube clamped to the work stand, just to show you. So, first thing's first is remove your air cap on the top of the fork and attach a shock pump to it, so you can note down the air pressure that's in your fork. This will make it easier when setting the fork back up again at the end. It's to get you out on the trail quicker. So, I'm just gonna attach the shock pump to the fork, take note of the pressure that's in there, and just let the air out. (air hissing) That is done. I'm just gonna check that it's all out just by depressing the valve itself. (air hissing) Okay, that's fully deflated. Now, using the 24 mm socket, make sure it's a decent socket, nice sharp edge because you don't wanna damage the top of the fork here. You just wanna undo this on the top. (tool ratcheting) Again, take your time. You don't want the tool to slip. This is an aluminium top cap. Okay, now it's ready to remove and that is your air top cap. Now, the Rockshox system is very simple. All you need to do is simply screw in the required amount of spacers that you want into the top. They've got plastic thread on them, so you don't wanna over tighten them. If you feel you need to nip it up tighter, there's an eight mm allen key socket on the inside there, so you can just stack them up as you like. I'm gonna put three into this Rockshox Yari fork. Have to bear in mind that in certain forks, you can only fit a certain amount of spacers. For example, the 200 mm travel boxer you can fit 4 spacers, whereas you're gonna fit six in a 29 inch, 120 mm fork. So, just check the chart on the Rockshox website for that. Now, just before you instal them, get into the fork. Just wanna put a little bit of grease just on the O ring around the top. And then, instal it back into the fork again. Just make sure that sits in straight. (tool ratcheting) And, that's how simple it is. And noting the air pressure that you released from the fork to start with, just connect the shock pump and reinflate. So, there you go. It's that simple to instal bottomless tokens air volume spacers into a Rockshox fork. Of course, I put three into this particular fork and that's the way I like this fork set up. It's down to you. Experiment a bit, try a single spacer, try two or three. You gotta figure out what feels right for you. (jazzy music) Okay, now we're gonna look at the same process, but with a Fox 34. So, it's very similar and they also use plastic spacers inside. And instead of having a 24 mm socket on the top, it's a 26. Equally as important with a Fox is to make sure you've got a good quality socket that won't round off the top of your fork. First up with a Fox is to remove the air cap, same as a Rockshox. And then you just wanna attach your shock pump, take note of the pressure that's in there for later on, and then just deflate the fork. You might find that you can't get all the air out with the shock pump. You might need to sort of depress the valve afterwards. (air hissing) If you do that, just be careful. (air hissing) Now, using the socket, carefully remove the top cap of the fork. Again, make sure it's a quality socket and make sure that it connects properly at the top. You do not wanna round the top of this off. (clanging) As you can see on this fork, it's actually got two spacers inside already. Gonna add an extra one to that. The Rockshox units screw together. The Fox ones just simply clip together. (clicks) Just like that and there's just the case of applying a little bit of grease just to the O ring, just like we did with the Rockshox offering. And then, reinstall. Carefully line up the threads, screw the top cap back into place, and tighten with your socket. Now, simply reinflate just to the desired pressure and you're good to go and hit the trails. (air pumping softly) Okay, so that was using a Fox 34 as an example for installing air volume spacers. Nice and simple. The same with the Rockshox. Hit the trails, experiment, see what it feels like with one, two, three. Find your sweet spot and then let it rip. Hopefully, that's been an informative video for you and you'll be inspired to do exactly the same at home. If you wanna know a bit more about this stuff, so click up here if you wanna see fork lower leg service, really good practical video. Works on the Fox and on the Rockshox option. And if you wanna see some tubeless setup mistakes, click down here. 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