Tech Tips: Air Fork Setup 16

Since the Motocross industry has been moving towards air forks, there's been a bit a of a learning curve for the general public in regards of how to adjust and take care of these new damping units. In particular, Showa's SFF TAC fork take a bit more attention when it comes to adjustments, due to the three air chambers they feature. To help take a bit of the confusion out of the TAC fork, we've got a few Tech Tips to make your life a bit easier.

For any other motorcycle parts, accessories, or gear needs, you can find them at Chaparral-Racing.com.

Transcribed version:

"Hey, this is Michael Lindsay from Vital MX, we're here at Chaparral Motorsports today and we're gonna give you a few quick tips on how to setup the Showa TAC air forks. So we've got a 2015 KX450 here which is one of the three bikes you can currently get with the Showa TAC air fork. To give you a little short rundown of what the fork is, it is a separate function air fork. You got valving on one side and you got your air cartridge on the other. The spring side on the TAC fork is supported by air. It has three chambers. It's got its outer pressure which is held between the outer tube and the inner cartridge, your inner pressure which is located inside the cartridge, and then your third chamber which some will people call, TAC, negative, or balance pressure, which is located down below on the lug. Basically to give you a short idea of why there are three chambers, an air fork without a negative pressure would start out extremely soft and ramp up too quickly. If you were to see it on the chart, it would be too abrupt. The negative pressure actually balances out and creates more of a linear effect to the fork. So it's really important to try to get the pressure's balanced correctly. So today we're just gonna go through a few of the dos and don'ts on setting up the TAC forks.

So starting at the top of the fork, we have two air valves up here. These fill your inner and your outer chamber. To remind you which one is which, you simply follow the little lines here. There's not an explanation, but what Showa has done, is left you a line that goes to an inner circle, that stands for inner chamber. Your line that goes to this little encompassing C, is your outer chamber. Your outer chamber is a much lower pressure, anywhere from zero to even maybe 20 at the most. And your second one over here is your inner chamber which is a much higher air pressure. It could be anywhere from 130 to 200. Starting off with how to actually set your pressures...a big rule is make sure the bike is on a stand, the front tire is not touching the ground, the front suspension is not compressed. This will change the numbers, so you wanna use a real stand not a triangle, not sitting [SP] on the bike. The other thing is you always wanna start with the inner pressure. The order in which you set the pressures in will actually change, so you always wanna start up top on the inner chamber. So in my case, I have a number I use on my inner chamber of 168. So we're gonna use a, you know, a high quality air pump here to get an exact number and set it. Another key when you're setting the pressure, is you definitely wanna do this at the track before you ride. Elevation and temperature makes a difference, so you don't wanna set this at home and expect to show up at the track and have it be correct.

Moving on from the inner chamber, we're now gonna move over to our outer chamber. Now that we're setting our outer pressure, there are some suspension guides that'll recommend no pressure in the outer chamber. Some recommend a decent amount. Personally, I've been running a little bit higher, around 10. For me, the outer pressure adds a little bit more of a speed sensitivity to the fork. You just really wanna...you wanna experiment with these forks but not over-experiment with them. You just wanna look for a basic feel and try to remember that you have compression and rebounded adjusters on the other side. This is basically your spring rate and you don't spend your entire time changing your spring rate. Now another interesting thing to remember is this fork isn't directional by any means. Their valves [SP] are usually facing forward, but depending upon your handle bar position, if it's easier, you can always turn the fork to the side and have the air valves face whichever direction works best for you. The last pressure we're gonna set is the TAC or negative pressure. On the KXF or the Suzuki, you're gonna find it mounted to the back of the lug. While on the Honda, it's gonna be mounted down below internally. Part of the reason for the term "negative" is because the pressure is fighting the inner chamber pressure. It actually does the opposite of what you think it would when it comes to air pressure adjustments. If you add pressure, it's gonna make the fork softer in a way, while taking away pressure will actually stiffen the fork. So as I said though, this is the last pressure we need to set in order to get the forks correctly set up. 

So this chamber's pretty interesting to set up. If you set it at the same number that you have your inner chamber, you can move them quite drastically and you'll get a pretty similar feel. Even if you go up ten PSI, if you move both this chamber and the inner together, it'll only be a minor change. Now say if you're to set your TAC five pounds lower or higher than your inner, you're gonna notice a much more massive difference in how the fork reacts. It's kinda hard. I've ran into people that like, you know, different versions, whether they like more, or less, or even. Personally, I run a little bit more to get the fork to soften up initially and settle a bit. But this is definitely something. It's hard to tell people what to try because this also depends a lot on what end of the bike you steer with is really gonna change how you're gonna probably adjust this. Being that the TAC chamber has a lot less volume than the other two chambers while still being quite high pressure, you'll see a lot more oil bleed off on this fork. Now with the Suzuki or the Kawi, this isn't a big deal, but we're gonna show you something here in a second on the Honda because the oil bleed off can actually be a problem on that model.

So now with the Honda 250F with us, the reason being is the Showa fork on this bike has a TAC chamber internally. It's inside the lug on the brake caliper side. The reason this is a big deal is when you go to take your air valve gauge off of the TAC chamber, as we mentioned earlier, this chamber does like to spray just a real light film of oil where this one points down towards the rotor, it can get on the rotor if you don't have a good brake disc cover on it or if you choose not to run one, you wanna have a rag or a piece of cardboard in there. It's not enough that you would notice it, but it's just a light enough spray, it'll get on the rotor and it'll cause it to slip on the pads for a couple laps until it wears itself off. So now that we've shown you the proper order in which to set up the forks, one key thing to remember, if you're gonna make changes throughout the day or if you're gonna double-check your pressures if the temperature has risen, you wanna let the fork cool down a little after you've ridden. During action, it definitely heats up which will raise the pressures and give you an inaccurate idea of where you're at. So these forks can perform well, you just definitely need to be a little bit of a student of suspension and just take your time to work with them and try new things. Keep checking back for more tech tips from vitalmx.com."

Credit: Joe Carlino
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