ST rear suspension sag

[Blake Sobiloff <sobiloff@xxxxxxxxxxxxxx>]

Hi all,
	As I threatened earlier this weekend, I found a willing accomplice to 
help me set the sag on the rear of my ST. The process and results were 
quite the eye opener, and left me with a few questions.

Background: I weigh 165 lbs (sans clothing), but 186 lbs in full gear. I 
did all the suspension measurements in full gear and with my saddlebags 
loaded with my typical junk: a laptop computer and some papers in the 
left bag, an extra helmet in the right bag. The gas tank was about 1/3 
full. (Yes, it probably should have been 1/2 full.) As setup from the 
dealer, the preload was 13 turns out -- not the 12 as specified in the 
Owners Handbook.

I reviewed my notes from Freddie Spencer's school regarding suspension 
setup, and I also read the RaceTech setup information at 
<http://www.triumphnet.com/st/acc/racetech/setup.htm>. Freddie 
recommends between 3/4ths and one inch of sag at the rear, while 
RaceTech recommends 30 to 35 mm (1.17" to 1.365"). Both sources 
recommended the following formula:

      Static Sag = L1 - ( (L2 + L3) / 2 )

where:

      L1 is the unloaded suspension extension (tire off the ground),
      L2 is the loaded suspension extension after compression,
      L3 is the loaded suspension extension after extension.

I decided that one inch of rear sag would be a good place to start, as a 
compromise between the two recommendations.

I already knew that 13 turns was way too soft. As Erik Miner had pointed 
out to me several months ago, the head shake I experienced when WOT in 
lower gears was likely a symptom of not enough rear pre-load. Remember 
that I have RaceTech'd my front forks, so they're stiffer than stock. 
The imbalance between the front and rear is likely the cause of the head 
shaking. So, I started with Triumph's recommended eight turns for a 
firmer ride and worked from there. Here are the results, with the 
measurements taken from the top of the seat lock cylinder down to the 
top of the rear hub:

8 TURNS:
	L1: 14 12/16"
	L2: 13 4/16"
	L3: 13 4/16"
	SS: 1.5"

7 TURNS:
	L1: 14 12/16"
	L2: 13 4/16"
	L3" 13 5/16"
	SS: 1.46875"

4 TURNS:
	L1: 14 12/16"
	L2: 13 7/16"
	L3: 13 7/16"
	SS: 1.3125"

0 TURNS:
	L1: 14 12/16"
	L2: 13 8/16"
	L3: 13 9/16"
	SS: 1.21875"

Is this typical of what others have found? I'd heard that the stock 
shock was supposed to be pretty good and that the range of adjustment 
covered most loading scenarios. I'd hardly call my loading extreme -- 
I'm not even trying to set up the suspension for two-up traveling -- yet 
I couldn't get the sag to where I wanted it. Are my sag recommendations 
extreme?

At least it was nice to see that the rear shock didn't show much stiction.

I took a quick spin in between the rain showers to see what the new 
settings felt like. Although the conditions wouldn't allow any WOT runs, 
even the half (OK, OK, 3/4) throttle runs felt much better. I felt very 
little squat on acceleration, and there was no perceptible head shake, 
either.

I'll try this pre-load for a few weeks and see how it feels, but it 
looks like I need to get a heavier rear spring. If this was the max 
loading I ever planned I might be content, but I hope to take a 
girlfriend for some weekend escapes on the back. In that case, I'll need 
some more adjustment room.

- -- 
Blake "Dawgbert" Sobiloff <sobiloff@xxxxxxxxxxxxxx>
Burlingame, CA, USA


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