Traxxion Dynamic Rear Shock replacement for the GL1800

TRAXXION DYNAMICS, INC.
261 Rope Mill Pkwy, Ste. 3
Woodstock, GA 30188
Phone: 770-592-3823
Email: info@traxxion.com

http://www.traxxion.com/

One of the problems that many folks have had with the GL1800 suspension is that the rear end of the bike is sprung too softly, especially when you get the bike fully loaded with a passenger on back or increase your speed. The result is that the bike sags too much when loaded and compromises your ground clearance and can even allow the suspension to bottom out on larger bumps when loaded heavily. Very few aftermarket alternatives have been available, mainly due to the design of the electro-hydraulic preload actuator that is installed on the shock, as this further complicates the design of a replacement shock. Traxxion is one of the premier motorcycle suspension experts, and they set about solving this problem by utilizing the existing shock for the GL1800 and rebuilding it with a stiffer spring and better damping. Unlike other add on springs that only change the spring, Traxxion also re-valves the shock so it can properly dampen the increased forces of the new spring rate. The front end of the GL1800 is not much better as it is also sprung too softly, and Traxxion also does a fork rebuild for this bike, but this review will concentrate on the rear shock rebuild.

Designing a shock for any vehicle is always a series of compromises. Too soft a spring and the ride is mushy, and too stiff a spring and the ride will be too harsh. Too much rebound damping can cause the wheel to skip and the suspension to "pack in" and too little and the suspension will feel like a pogo stick that never stops. If you get too much compression damping then the ride will feel real harsh over smaller bumps and if you don't have enough compression dampening then the ride will again become too bouncy. Now throw into the mix that there are both high and low speed damping circuits, and you will start to see just how complicated getting a shock set up correctly becomes. There are equations that the designer can use to set up the initial parameters, but even so, the whole process is a bit of a black art.

The shock on the GL1800 also has an electro-hydraulic actuator on it to adjust the pre-load applied to the spring, which allows you to adjust rear sag and hence ride height. The range of travel that this adjuster has is 11mm. The slave cylinder on the actuator fits over the body of the shock cartridge, so this further limits design changes to the shock as the diameter of the cartridge that you can use is fixed since this slave cylinder has to fit over the shock.

Here you can see the new valve added to the top of the shock
Traxxion's approach to the GL1800 shock is to change the spring to a higher rate, and reuse the existing cartridge after dissembling and modifying it internally to increase the damping. This allows the stock pre-load actuator to still work as before. Basically, they drill a hole in the top of the shock to relieve the nitrogen charge, and then rebuild the shock with modified internals for the valves and piston and then refill it with fresh oil and recharge it with nitrogen. A schrader valve is screwed into the hole that was drilled in the shock so that it can be recharged, and a benefit of this is that now the shock can be rebuilt and recharged multiple times instead of throwing it away when it wears out. However, one down side is this new valve is positioned in a way that it blocks removal of the preload adjuster or spring.


Spring rate and pre-load are the first things that need to be chosen to build and set up a shock, as all other factors will rely on it. The Traxxion rear shock uses a higher spring rate than the stock Honda spring (which is around 900 lbs/ft), though I can't say exactly what spring rate Traxxion is using. This increase in spring rate means that the shock will be able to better handle loads and larger bumps than the stock shock does and it will not bottom out as easily. However, this increased spring rate means that the rebound damping has to be increased to keep the spring under control. The damping rate is increased by the improved piston and internals that Traxxion adds and/or changes in the shock. Again, I can't specifically say exactly what is changed internally or how, but the end result is that the shock provides better rebound and compression damping than the OEM shock does.

COSTS

Traxxion charges $399 to rebuild and modify a rear shock and this price includes a complete service to the electo-hydralic adjuster to properly bleed it of air. Many GL1800 shocks do not begin to actually move the slave portion of the actuator right away due to air that has gotten into the system. By purging the air, and making sure the actuator is properly filled with oil, they are able to regain this lost movement in the lower range of pre-load numbers. Turn around time from when I sent them my old shock and adjuster to when I got the rebuilt one back, was about one weeks time, including shipping.

INSTALLATION

Removing and replacing the shock on the GL1800 can be quite a chore. It is not really difficult, but it is time consuming. You first have to remove the left and right fairing pockets and instrument panel cover, and then the seat and top shelter. Once you have all that off, you have to remove the gas tank, and then the right saddlebag has to be moved out of the way. Only then can you access the shock and pre-load adjuster to remove and replace the shock. I should also mention that when you do this, you should take this opportunity to tighten all the hose clamps under that gas tank, and check that the G1 ground connector is tight. This is also an excellent time to change the air filter and adjust the lag out of the cruise control.

TESTING

The first thing I did was to measure the sag of the Traxxion Shock. This is with the TRAXXION shock and spring, and a 180lb rider (me) and full tank of gas.

Pre Load setting-----Static Sag-------------Loaded with Rider on board
0---------------------- 1-1/8 (28.5 mm)--------1 3/4 (44.5mm)
5---------------------- 1 (25.4)-----------1 1/2 (38.1)
10--------------------- 3/4 (19)-------------1 1/4 (31.75)
15--------------------- 5/8 (15.8 )----------1 1/8 (28.6)
20--------------------- 1/2 (12.7)-----------1 (25.4)
25--------------------- 1/8 (3.1)------------3/4 (19)

I have not measured the sag of the OEM shock to see how this compares, but I hope to do that in the future and I will update this review and put that data here when I get it.

After I got the shock reinstalled and the bike put back together, I took it on a couple trips to fully test the shock. I took the bike on some of the roughest roads in Texas and pushed it fairly hard to see how well it handled. This included several higher speed passes on sweeping turns that had bumps or pavement undulations in mid turn, as well on slower tighter turns to see how the ground clearance compared to the old shock. I also tested it through a variety of pre-load settings and measured the sag of the shock as well.

All in all, I have been extremely impressed with the shock. It handled everything I could throw at it. One of the most revealing test was riding a sweeping turn that had a large dip in the middle of the turn at a fairly fast speed. With the OEM shock on the bike, at any speed over about 70 mph, this turn would induce a po-go effect of the rear end that would start an oscillation of both the front and rear suspension and would throw me off my line in the corner. With the Traxxion shock installed, the rear wheel would absorb the shock, and return to normal with minimal fan fare, regardless of speed. As a result, the bike tracked my chosen line in the turn and the dip did not upset the bike much at all. I attribute this to the increase in rebound damping, as this type of turn is a real good way to see if you have enough rebound damping. Additionally, I tested the bike on some extremely rough roads to see how well it absorbed larger bumps and dips at both high and low speeds. At low speeds the shock does feel just a bit stiffer than the OEM shock but it still absorbs the bumps and dips nicely and feels compliant. The increased stiffness of the spring makes the bike a bit easier to ride quickly, as the suspension does not feel soft and vague when you increase your speed. It also holds the bike up better under load, and eliminates the possibility of being able to bottom out the shock. The new spring rate feels like it is better suited to the bike overall.

Another big advantage that this shock offers is increased ground clearance. You no longer have to run the pre-load adjuster up so high to make up for all the sag that the OEM shock has, and the result is that you can comfortably leave this shock set between 0-5 for solo riding and still have more ground clearance than the OEM shock did when set at 25. This means you won't be dragging pegs and hard parts on the bike quite so early in the tighter corners, and this gives you an extra safety margin and more usable lean angle. I did notice a very slight increase in ride height when sitting still which in turn effects how much of a purchase you get when putting your feet down at a full stop, but it did not really feel like it was a very significant change, and after about the first hour riding the bike around town, I no longer could even detect it.

CONCLUSION

For me, the true test of a good shock is how it handles when the speed increases, as higher speeds really tend to bring out the weaknesses in a poor suspension. After the first few hours on the bike, I noticed I was unconsciously riding faster than I normally do, as the bike just felt smoother than before, so I had lost some of my sense of speed as a result. This is probably the best compliment I can give of the shock, and it made the whole bike feel more confident and planted as the speed picked up. The increased spring rate feels just right for the loads of the bike and the suspension remains compliant, yet firmer at the same time. There is always a compromise to be reached between compliance of the spring and ride firmness, and from what I can tell; Traxxion hit the perfect balance of the two just right. The ride is not so rough that the suspension tops out or the bumps rattle your teeth, but not so soft that when you hit a large dip at higher speeds that the bike looses its composure. If you ride two-up and loaded, you will even like this shock more, as you no longer loose all your ground clearance when a passenger climbs on, and the bike seems better sprung for handling the load. For the amount of money this shock costs, I would have to say it is definitely worth it and is probably one of the best modifications I have done to my bike. It not only enhanced the ride and performance, but increased my safety margin as well by giving me more lean angle. I can confidently recommend this shock to anyone as I honestly donít see how you could be disappointed.