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Showa TAC 2015 KX450f

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Can anyone give me some pointers on where to start with these forks. I've tried the three configurations the manual recommends. Still feel like the bike was unstable. Almost feels like it's blowing through the first part of the stroke. Going right into the mid stroke. When you add air to the inner chamber, it feels stiffer, but the initial part of the stroke still feels soft. I was hoping the manual would give a break down of what the three chambers do and which one to adjust when encountering different  symptoms. But it doesn't.  I do know a little. The inner chamber is compared to the main spring. Changing the psi will either go stiffer or softer in spring rate. But how much psi changes 1 spring rate, I don't know. The lower chamber or balance chamber is like your negative spring or anti spring. The more pressure the lower the fork sits. It seems to effect turning and some of the small bumps.  What does the outer chamber do. And what kind of increments do I want to make Air pressure adjustments in?

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let some air out of the lower(balance) chamber. That should help stiffen up the first part of the stroke i think.

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Maybe go up in pressure on the inner and also increase the Balance pressure as well to soften the initial.  The outers from what it sounds like just control the bottoming portion.  Oil heights will prob dictate more of a result being there is only 7psi of pressure on the Kawi and Suzi forks and just ambient pressure suggested on the Honda forks.  Crazy on the ranges that they give you on the pressures.  I am getting ahold of a set of the Showa TAC forks for the hondas this weekend.  Going to test them out on my 450.  Being similar to the Kawi forks I will let you know what I find out work good in stock form.  

 

If anyone knows what stock pressures are for the Honda Forks please feel free to share as I am starting from scratch as I dont have a manual.  I think 175 for the outer and maybe 130 for the Balance will be good start. 

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I would start removing air in balance chamber before I added air to main if the only part that felt soft was initial stroke.  At the end of the day however - you have to realize that it's just a spring - and if the valving is too soft for you - will still require valving.

I would make 20 psi changes on inner chamber and same with lower tac chamber.  This equates to about 10 percent...anything worth doing to get a solid idea what direction you need - should be 10 percent.

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I found a couple settings that I really like. Took me a few tries to get the spring (air) set right. Now I'm messing with the compression/rebound.  I ended up running 167 in the inner, 167 in the lower, 0 in the outer. compression went from stock which is 5 out to 14 out, and rebound went from stock 13 to 9/10.  The bike feels much better than stock did on my local tracks. I know track prep and soil type will make a big difference. The only thing I need to figure out is how to eliminate bottoming on steep quick landings, without losing my small bump compliance. I'll test adding a couple psi to the outer, vs a few turns in on the compression vs 3-4 psi in the inner chamber to see which helps out the most, without hindering anything else. It's so close to feeling great.

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Outer chamber pressure will increase initial stiffness much more than inner chamber pressure.  Much more area the outer air pressure is acting on.
 

You didn't state where you had started at in the first post.

 

 

 

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I'm trying to keep the outer chamber as low on pressure as I can. That way if I get a seal leak it won't effect my riding so much.

My starting point for the suspension was the three stock configurations that the manual gives. I won't list them all. I can't really remember them without the book in front of me. But the last one, what They refer to as their hard setting has the inner chamber at 145 psi, outer at 7.25 I think, and the lower at 145 psi. The compresion at 5 clicks out and the rebound at 12 or 13 clicks out. I can't recall right now. I really like my current setting though. I'll probably go in 2 clicks on compression. and it should be really close to perfect for me, for that one track. I might even try raising the inner and lower chambers up to 175 psi, which I think is what the rmz450 is running stock.

 

Does anyone know if the kawi and suzuki forks both being showa triple air chamber forks, are the same internally. Now I'm not asking about the left fork. I"m pretty sure the compression/rebound valving is different. I"m just talking about the right fork with the air chambers. The suzuki test riders are running the air pressures above what the kawis owner manual lists as the top of the operating range for psi. For example. kawi says not to run the inner chamber above 188.9 psi. and comes stock around 131 psi. Now the rmz450 comes stock at 175 psi and many riders are raising that up to about 200 psi. I wouldn't mind trying a stiffer air pressue but don't want to mess something up in the process.

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They are not the same from what I read as one has the external chamber and the other doesn't , that may account for the pressure difference

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Sorry I am talking crf 250 15 model , got confused lol

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Kawirider37, I downloaded an owners manual just to have on my laptop and noticed they changed pressures from the printed one we received. The hard setting says 165 inner, with the rest the same. When I looked again the metric pressures are correct, but they misprinted the psi in the printed manual.

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Kawirider37, I downloaded an owners manual just to have on my laptop and noticed they changed pressures from the printed one we received. The hard setting says 165 inner, with the rest the same. When I looked again the metric pressures are correct, but they misprinted the psi in the printed manual.

HAHA. I knew 145 was too soft. Well at least now I know I was going in the right direction.  Are the pressure ranges still correct. i.e., inner chamber should not exceed 188.9 psi, etc.? Where can I download one from?

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Mog hasn't the crf got adjustable neg presure. Surly it's still 3 chamber

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The Suzuki and Kawi fork appear to be identical. I doubt running the pressure that high will do any harm but you will have to be the test pilot. Both Suzuki and Honda spec 0 psi as their standard outer chamber air pressure. You can also add oil to the outer chamber to stiffen the fork up at the end of the travel.  FYI, the Honda balance chamber is inside the fork and you fill it from underneath the the fork leg.

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Since the Honda has the airchamber on the left side, there is no space for an external reservoir like on the other fork type.

Seems like that Honda liked the fork better with the spring on the left side for some reason...

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They said it equalised forces or something like that

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I picked up my 2015 CRF250R last week and yes the balance chamber is in the bottom of the left fork leg. As a Supercross racer with in house suspension tuning and testing this will be extremely convenient for re-valving the forks during testing because we will never have to deal with removing the front brake caliber assembly. I am extremely excited to get to testing and will certainly provide feedback. On the injured list for 6 more days :(

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