Supplier info:
TRAXXION DYNAMICS, INC.
261 Rope Mill Pkwy, Ste. 3
Woodstock, GA 30188
http://www.traxxion.com
Phone: 770-592-3823
Email: info@traxxion.com
Cost breakdown:
AK-20 kit $999.95
Installation $150
OEM Fork seals $24.95
OEM Fork bushings $14.95 each
Kuryakyn Fork Brace $219.95
Total Cost $1,424.75
Traxxion Dynamics is based in Georgia and has a good reputation in the racing community for making premier suspension components. They have their own CNC milling equipment and can design and manufacture their own components on site. Their AK-20 kit is widely known in the motorcycling communities to be among the very best damping cartridge available. Traxxion makes suspension components for many varieties of racing, touring, and street bikes.
The Traxxion fork upgrade consists of three major changes to the forks. The first change consists of stiffer fork springs. The Honda OEM fork springs in the GL1800 are extremely weak and results in the front end bottoming out on larger bumps. Traxxion’s answer is to install stiffer straight rate fork springs.
The second major change Traxxion applies, is to install their new 20mm AK-20 Axxion damper cartridges kits in both fork legs. Due to the anti-dive valve arrangement in the GL1800, the left fork leg is designed as an old technology damper rod fork leg and the right fork leg is designed to use a newer style damper cartridge. This is actually a rather strange arrangement, and will result in unequal damping forces in each fork leg. The Traxxion modification puts upgraded damping cartridges in both fork legs designed to match the spring rate of the Traxxion fork springs. This also allows the damping forces to be equally split between the two fork legs.
AK-20 Cartridges
Here is an inside look at the valving in the AK-20 cartridge
The third major change is that Traxxion totally disables the anti-dive valve in the left fork leg. This valve has been shown to be problematic in many GL1800’s when it sticks. When braking, the anti-dive valve hydraulically locks the left fork tube so that it can not compress. While this does reduce fork dive under braking, it also effectively stops all front suspension travel when the brakes are applied, so if you hit a bump while braking, the suspension can not absorb it. Since Traxxion installs a damper cartridge in the right fork leg, this effectively disables the anti-dive function altogether. The left fork tube is also permanently altered to accommodate the new damper cartridge.
One additional item that Traxxion recommends with their upgrade, is the Kuryakyn fork brace. This brace is a five piece design fork brace that bolts onto the front forks of the bike to reduce fork flex.
Installation:
I elected to remove the forks from my bike myself and ship them to Traxxion for the retrofit. Another option would be to visit Traxxion or one of their dealers and let them do the removal and replacement, but it was just more convenient for me to remove them and ship them in. The removal and installation of the forks was fairly straightforward, I just had to jack and support the bike, remove the front wheel and front fender, brake calipers and associated fender and hose supports, and loosen the pinch clamps on the triple trees and slide out the fork tubes. The forks were then separately boxed, and then reboxed in one larger box and shipped to Traxxion’s facility in Georgia. Traxxion installed the new springs, damper cartridges, and replaced the fork seals and bushings in both forks with OEM Honda parts before reassembling. Per Traxxion’s instructions, I raised the fork legs 10mm in the triple tree mounts to accommodate for the reduction in sag so the front end geometry was the same as before. It is important to note that after the upgrade, the forks can still be serviced by any Honda dealership or qualified service person since they still use the stock Honda seals and bushings.
Forks Removed from bike for shipment to Georgia Forks returned from Traxxion with Kuryakyn fork brace
Results:
Testing consisted of riding the bike over a series of 2x2’s and on several rough roads, as well as on a high speed test track both before and after the changes to the forks both with and without the fork brace installed.
It can be hard to quantify suspension changes into measurable results that are not just subjective feelings based on what the bike used to ride like without expensive and cumbersome test equipment, which I don’t own. I will do my best to try to convey in real terms what differences the Traxxion fork upgrade provides, but again, some of this will be strictly based on my “seat of the pants” feel.
The first thing that you will notice, and can be measured, is the difference in sag of the front end when the bike is off the centerstand with rider seated. I measured the “before” sag to be 2.1 inches (54mm) with Progressive Springs installed, and it is about 3 inches or 78mm with OEM springs. After the Traxxion upgrade, the sag was only about 1.6 inches (41mm). This is obviously a result of the stiffer fork spring rate used by Traxxion. This decrease in sag directly translates to more suspension travel, which not only provides more cushion between you and road when you hit a large bump, but also allows the wheel to stay in better contact with the pavement and prevents the front suspension from “bottoming out”.
The next thing I measured was fork stiction both before and after the fork upgrade. Since new seals and bushings were installed, I expected some increase in stiction just from the new rubber seals but that will go away as they break in. Before stiction measured a very low 1mm and after sticktion was measured at about 2mm. Again, all this really indicated is that the new fork seals were tighter than my old worn ones.
Upon doing some road testing and hard brake application it became immediately apparent that the stiffer fork springs are able to properly suspend the front end under braking even with the anti-dive valve disabled. One of my initial concerns with this system was that it defeated the anti-dive system, and I feared that front end dive might be excessive as a result. I was pleasantly surprised with how little the front end dives even under extreme braking, and I also noticed an immediate improvement in suspension feel during braking. Normally, when the anti-dive valve closes it hydraulically locks the left fork leg so that the front end can’t dive during braking. A side effect is when you hit a bump with the brakes applied, the front suspension can not give, so the bump is transmitted right through the handlebars. With the Traxxion upgrade the suspension can continue to absorb bumps and keep the front tire in better contact with the road during braking. This is an immediate and noticeable improvement and I like the way the bike handles better with the anti-dive disabled.
The next change is in both the compression and rebound damping of the fork legs that the new cartridges provide. The basic function of the damping cartridges is to slow the action of the fork springs, and thus dampen out any bouncing action of the front end during both fork compression, and extension (rebound). Getting the damping rates set properly to the spring rates is critical, as too much damping will make the suspension harsh and can cause it to “pack in” on repeated bumps, and not enough will make the suspension “pogo” up and down repeatedly after an impact. The changes to damping are a bit harder to quantify in real terms, so this will draw on my own subjective feelings for the change.
Damping in high speed sweepers has improved substantially, the bike no longer has a tendency to drift off its line in a corner and the front wheel feels more planted to the road when you encounter a bump in mid turn at speed. The pogo effect of the front end at higher speeds seems to be completely gone and the bike feels more stable at higher speeds in all circumstances. I believe the true test of any suspension system is how it performs at higher speeds, as this is where it will have to work the hardest, and the Traxxion fork upgrade does indeed provide a substantial improvement in all aspects of high speed handling. Low speed handing is also important, and making a suspension system that works well at both low and high speeds can be a challenge since you want it firmer at higher speeds, but more compliant at low speeds. At lower speeds and on rougher roads, I noticed right away that the new fork springs do indeed provide more travel and make it just about impossible to bottom out the front end. The damping rates of the new cartridges also seem to be dialed in real well to work with the new springs, and I found the bike felt much smoother both on smooth and rough roads and provided better response to steering inputs as well. An additional benefit of disabling the anti-dive valve is that the compression damping feels better and less road shock gets transmitted through the bars to the rider as a result on a bumpy road. Also gone are the worries of the anti-dive valve sticking closed, which has become a common problem on the GL1800 when the O rings in the anti-dive valve swell over time and cause it to stick.
A test track of 2x2 boards was set up and the bike ridden over multiple times both before and after the Traxxion upgrade. A noticeable improvement was felt in how much shock came through the handlebars after the Traxxion upgrade. The bike was also ridden on a high speed test circuit at very aggressive lean angles, and there was a slight improvement in ground clearance, as well as improved overall handling and response to steering inputs.
Kuryakyn Fork Brace:
The last phase of testing involved installing the Kuryakyn fork brace on the bike, and repeating the ride testing. This fork brace is different from other fork braces, as it is a true 5 piece design. What this means, is that the center section of the fork brace is independently mounted from the clamps which bolt to the fork legs. This design minimizes fork stiction that typically results from standard two or three piece design braces. It allows the center section to be installed last, which insures that the brace is not causing any binding of the fork leg movement. Other braces force the fork legs to conform to the dimension that the brace is milled to, and since there are tolerance differences from bike to bike, it may not always be a good fit, which will result in binding and stiction. Personally, I have never been a fan of fork braces for this reason. While I will recognize that they do improve handling, particularly at low speed, they price you pay is that the binding and stiction increase causes the forks to be less compliant. However, this new design that Kuryakyn uses on their brace really does a good job at eliminating the alignment problems, and the end result is a fork brace that even I don’t mind using on my own bike. It appears to have all the benefits of a fork brace without any of the drawbacks. Another point in favor of the Kuryakyn brace is that it is quite a bit lighter than most all the others, and the manufacture has made an effort to keep the overall weight of it low, (unlike some of the other products they make). Since this brace is attached to the lower portion of the fork legs, it will add to the un-sprung wheel weight, which you would like to minimize, so having it as light as possible is a good thing.
After installing the fork brace an immediate improvement in response to small steering inputs was felt at both low and high speed. The brace reduces independent fork flex, which can easily be seen on this bike by simply turning the handlebars back and forth rapidly. This reduction in flex means that the bike responds faster to counter-steering inputs at the handlebars. This results in a front end that feels more responsive and agile, especially at low speeds during parking lot maneuvers.
Conclusion:
Though the Traxxion fork upgrade is not cheap, I dare say that I think it is worth every penny it costs. The resulting handling improvement makes the GL1800 ride better in all aspects. It is smoother on the highway and transmits less road shock through the handlebars, is more responsive to steering inputs (especially with the fork brace add on), absorbs bumps better and does not bottom out, and provides more ground clearance in the corners. I was not able to find a single negative aspect to the change in handling and the bike rides and handles better at all speeds and in all conditions. Normally I am not a big advocate for fork braces, but this new Kuryakyn design deserves a look as well and really improves steering responsiveness.
Fred Harmon
Jan 14, 2007