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

C50_profile_1424660203 ML512 10/8/2015 9:35 AM

Create New Tag

16 comments newest first

I have a better idea buy a spring conversion kit way more consistent and less to do.

×
Members who like this comment

ML512,
Great info from a reliable source. Question about the bike in your vid, what oversized bar clamps are those and will they fit stock triple clamps?

×
Members who like this comment

Awesome Video ML, and a great explanation on how it all work. Currently running a 15 RM-Z450 and it has taken some time to get my head around how they work and finally getting to a point where I am happy with them (though would take the old spring SFF off my 250 in a heart beat still)

Glad you talked about re-checking pressures after you first ride on each day you head out riding. I have noticed that the pressures always change after the first ride, but once they are re-set after the opening ride do not move for the remainder of the day.

One thing you did not mention (unless I missed it ) I have read that you should remove all the air from the balance chamber before staring with the inner / outer / balance, sequence of setting pressures. Just noticed Theycallmeebryan as posted the same.

Would like to hear your thoughts on that.

Once again great vid.

×
Members who like this comment

I've seen the recommendation, but I can tell you that none of Showa's race techs do that or tell us to do it. They just push how important it is to keep to the correct order.

×
Members who like this comment

I know this is a late reply, but I wanted to mention that the Showa SFF app specifically states to drain the balance chamber before setting air pressures and also the Kawasaki manual is consistent with this same requirement. I'm still trying to figure why this is so important because the chambers are separate so I would t think bleeding the balance chamber would be not be so critical but both Kawasaki and Showa seem to think it is. If you can provide an explanation I'd appreciate it!

×
Members who like this comment

So just leave what's in there as long as you go Inner, Outer, Balance? I've been emptying the balance and outer then filling them in order. I have arm pump by the time I'm done.

×
Members who like this comment

I ride moto and MTB and have used air exclusively on MTB for the last 10 years....that being said..THIS IS TOO COMPLICATED. Good thing I ride a KTM. I would change this back to spring first thing...waaaaaay too complicated.

×
Members who like this comment

Always amazed at the inaccuracies in which the so-called "insiders" communicate.

1.) A negative pressure balance chamber is NOT required as was suggested in this video. If you recall, the first generation SFF Air forks had only two chambers, an inner and an outer, without a balance or TAC chamber and they work well. In fact, they are easier to work with than TAC forks since you have one less chamber. and if you run zero psi in the outer, you are really only working with the inner chamber.

2.) Contrary to the comment made in the video about air pressures increasing inside the forks due to riding, this is a false statement. The only way pressures rise in these forks is from ambient temperature changes. You can check with the experts at Showa to clarify this statement. Thank me later.

×
Members who like this comment

The original A-kit Showa air forks have a negative coil spring instead of the negative air pressure chamber. Similar to how the PSF forks work (they have a negative spring internally).

There was never a production SFF Air fork on any bike before the TAC fork.

Also, I actually personally communicate with some of the Showa techs here in the US every week or two.

×
Members who like this comment

Mike did a great job of explaining, but my experiences are a bit different. Here are my tips:

-Always check/set your pressures ON LOCATION before each ride.
-When making adjustments or checking pressures, make sure the front wheel is off the ground.
-Any compression of the fork or any pressure from the balance chamber will effect the inner chamber reading.
-Forks do tend to raise a couple PSI in pressure as they heat up. Check when cold.
-The provided air pump has a check valve in it. When setting pressures, don't account for "air pressure loss" while removing the petcock. That air release sound is the pressure coming out of the hose in the pump, not the air fork.

-When making adjustments, follow these guidelines:
1. Completely remove the air from the balance chamber
2. Completely remove the air from the outer chamber
3. Adjust the air pressure in the inner chamber
4. Add air pressure to the outer chamber
5. Add air to the balance chamber

-When transporting the bike with the forks compressed, let all of the air out of the outer and balance chamber to help preserve the seals.
-If storing the bike overnight with the forks tied down, loosen the tie-downs and let the fork completely extend.

Hope that helps.

×
Members who like this comment

I understand the importance of filling the chambers in the specific order but if I have to add pressure to any one chamber, do I have to empty them all and start with 0 in each one (technically, I suppose I could just empty the outer and balance as the inner would be the first to fill)?

×
Members who like this comment

You do not need to empty them. They were already filled from the factory so all you are doing is checking pressures and setting to your desired setting. Some over-complicate this and it's really not as critical as some make you believe....

×
Members who like this comment