FORK WORKS: JGRMX SHOWA TAC AIR-TO-SPRING CONVERSION KIT
It is no secret that the Showa SFF air TAC forks on the 2015–2017 Suzuki RM-Z450s are the worst forks on the market. They are harsh from the beginning to the end of the stroke—if you can even get there. Top Supercross riders like them for their resistance to bottoming on hard hits; if they can’t bottom them, chances are you can’t, either. While these are generally the same forks that we have grown to like on the 2017 Kawasaki KX450F, the KX engineers use different valving, forks stanchions and internals; along with lower oil heights than on the RM-Z450. Both, however, with their three chambers (inner, outer and balance), TAC forks, are over-engineered for the average joe.
It is amazing that all of this new air technology can’t compete with the old-school technology of Yamaha’s Kayaba SSS forks. This fork blows every air fork, save for the WP AER air fork, out of the water. We aren’t suggesting that you need to buy a Yamaha fork for your Suzuki RM-Z450, but you might consider the JGRMX hybrid TAC conversion kit.
JGR’s hybrid fork throws the complexity of the TAC air fork out the window. The conversion kit basically makes the SFF TAC fork into a Showa SFF single-spring fork (with the addition of an inner air chamber to give you the initial feel of a spring, not air). That’s right, just one air chamber, not three different air chambers. Plus, the solo air chamber is optional in that you don’t have to put air in it. If you do choose to run air in the single chamber, it would only be a very low 15 to 25 psi. The air pressure gives the fork the freedom to run a lower spring rate and increase bottoming resistance. In theory, the hybrid air/spring fork offers a plusher ride at the top of the stroke and gives just enough bottoming resistance to absorb hard hits. The goal is to combine the best traits of coil springs with the best features of air pressure.
IN THEORY, THE HYBRID AIR/SPRING FORK OFFERS A PLUSHER RIDE AT THE TOP OF THE STROKE AND GIVES JUST ENOUGH BOTTOMING RESISTANCE TO ABSORB HARD HITS.
You might be wondering, what happened to the other two air chambers? The outer chamber is still there, but all that’s required is to bleed off excess air-pressure build-up just as with any normal spring fork. As for the external balance chamber unit at the bottom of the fork, it is totally blocked off.
The best thing about the JGRMX Hybrid TAC conversion kit is that if you are mechanically inclined, you can order it from JGR (www.jgrmxstore.com) and install it yourself for $680 (spring included). You will need Showa’s special tool to unscrew the bolt at the bottom of the air fork to get the TAC cartridge out. The damping leg remains untouched. However, if you want to spend a little extra dough to get the forks and shock re-valved while having the hybrid TAC conversion kit installed, the total for the whole kit and caboodle is $1340. If you only want the forks converted and re-valved, the price is $920. The best thing is that if you don’t like your suspension setting, send it back and they will adjust it to your liking for free! Contact them at www.jgrstore.com
We tested this kit on a Suzuki RM-Z450 Showa SFF TAC fork, but the conversion kit is also available to turn a WP AER air fork or Honda CRF250 TAC fork into a coil-spring fork.