The left shock has an adjustment wheel. However, the right shock has been removed from the assembly. It's basically just a strut inside a spring to create a mono-shock type rear suspension. 1) It seems a it was a cheap way to take a dual-shock swingarm and give it a dial preload adjuster in essence, making it a mono-shock set-up but with the second shock body/spring (or strut) to continue to hold the dual-shock architecture. 2)
Article by spacetiger of the XLFORUM:3)
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Although I didn't really push the bike (I did scrape a few times), the suspension is near bottoming out 6) | On the front I have a zip tie on each fork tube. On the right fork tube there is a strip of black electrical tape just above the zip tie. The bottom edge of the tape denotes the max travel possible of the fork lower. So, I can get off and see how much of the suspension travel is left by eyeballing the distance between the zip tie and the bottom edge of the electrical tape. I reset the white zip tie every ride so I can see what is the max use every ride. 7) | I use the rubber bumper to track the rear but for the sportster, it is hard to get in there every ride and dig out the stopper so I've added a 0.5“ ID nylon washer to the shock shaft after I've pushed the stopper all the way down. The nylon washer is easy to move and stays in place like the zip tie in front. I carry a Popsicle stick with some measurements on it to measure the front or rear and to push the washer back up on the shock. 8) |
With summaries and charts 9)
Test results18) → | Right Shock Capacity19) → | Left Rear shock, the workhorse of the rear suspension20) → |
Left Shock disassembled21) → | Left Spring testing: I just load a 45lb weight, then measure spring length; then repeat the process. Pic shows five 45 lb plates compressing the spring enough to exceed the working range of the shock.22) → | Left Spring test results23) → |
Left Spring test result Implications24) → | Here, you can see the left and right are 2 different springs25) → | Determining the Combined Spring Rate (Magenta line); to get the combined spring rate, you can add them and get the Magenta line. This is the total rear spring rate with no preload dialed in. You can see the max weight it can carry before bottoming out is 439 lbs.26) → |
This is the total rear spring rate with no and ALL preload dialed in. You can see the max weight both springs can carry before bottoming out is 577 lbs.27) → | Now, I can measure the gap between the rubber bumper on the left shock to see how far away it is from the shock body when I was checking rear sag. Knowing this distance + having calibrated the rear springs, I can determine the sag weight load through the spring.28) → | I am certain I will need a stronger spring. The oem setup has a small working range (1.06“) and low total capacity (577 lbs). Here is the test results of a different spring from a 1986 Honda VF700C [Showa] shock. It checks out at 97.3 lbs/in.29) → |
This a pic of 3 different springs; the 2014 XL1200T oem setup, 2003 XL1200R, and the 1986 VF700C spring. The VF700C spring would be mounted on the XL1200R shock and add considerable more top end performance over both the XL springs. This pic shows the comparison with no extra preload dialed in.30) → | This is a another comparison with max preload. Still a great top end performance gain + the spring rate is very close to the OEM 2014 rate.31) ✔ |
Left rear side of the bike; you can see the working range of the shock using the movement of the rubber bumper. As I use the jack to move the swingarm, I measure the remaining gap, then go to measure how much the axle moved33) → | This is the side where I measure the axle height34) → | Eventually, I get near the top; then find I have a small clearance issue with the front saddlebag mounting point.35) → |
I take the last measurement and see the same clearance issue. It doesn't look to be a big issue to fix - if I stay with these bags36) → | I mapped out the shock and rear suspension relationship. The shock operates over a 2.63” range, and the axle moves over a 3.26“ range. Knowing this relationship helps me set the sag strategy37) → | I will base the sag on 25% of the axle movement range; which translates to on 18% of the shock range. That means with a 2.63” working range, I will commit 0.48“, or about 0.5” using the rubber bumper to make that set. But setting the sag is NOT enough to set up the suspension because you can get a weak spring to make the sag measurement38) → |
The left shock is the workhorse so I will only concentrate on it. It has a 1.25” working range 48) → | No Right shock 49) → | Fully compressed 50) → |
I put the right shock to verify the shortest working range of the 2 shocks. They compress at the same time with the working range at 1.25“ 51) → | The oem test results show the same relationship as the XL1200S shock. 52) → | By holding the test setup the same, I can estimate how much the rear will be sitting up; ~1.75” taller in the rear. I am going to need longer fork tubes. I will have to figure that out once I move to the front. 53) → |
The oem riding envelope is small. I knew that going in, but it is still surprising to see how small. There is only really 0.92“ of shock travel to ride in, that is small. You better have your springs sorted out or you will be riding a “hardtail” 54) → | A comparison of riding envelopes; the larger one will give me flexibility to tune the suspension for my needs as I have some room to work with 55) ✔ |