Thought this post may be of some use for some - but Im no expert on these matters. The following is simply my experience and opinions from the following install.
Battled with the stock suspension on the ST for 40K. Hired a BMW RT1200 in NZ for 8 days 2 up loaded - worked out the ST had really shity suspension compared IMO. What to do? Never really happy with the stock set up.
Background. Im 120k my wife about 80k. I ride solo light - sometimes quick, but at times 2 up fully loaded. To make matters worse I pull a Classic Industries Mini Tourer from time to time. The way I see it- if you were 70K or there abouts, probably have no issues with the stock springs solo. Add some serious weight, I consider the stock arrangement woeful at best on reflection.
For our weight - the front is completely under sprung. Im / we are simply bouncing up and down on whats left of the spring travel but mostly siting on the 63mm air gap.
The rear seemed OK I thought with the preload fully adjusted up (2 up), but was again completely under sprung as it turns out. The amount of squat mid corner was not apparent until I changed it out with something different - more on that later.
After some research, I settled for the following arrangement:
Front - Race Tech gold valve arrangement front end. 1200 springs RH19 standard rebound valve and RH34 standard compression valve running 5wt motex oil with recommended 130mm air gap each leg.
http://www.shocktreatment.com.au/racetech.htmlRear - Nitron Race shock R3 fully adjustable shock length, hyd preload, hi/low speed compression adjust. 1350 ib spring (24kg). Provide to Nitron - riding weight, style, load details etc. Shock was built to my specs. Delivery was 8 weeks from USA.
http://www.nitronracingshocks.com/Nitron-R3-Honda-_p_644.htmlInstall: I fitted both front and rear at the same time along with pair road 3s.
Front - had to completely pull front dampers apart following instructions. No big deal here. Compression came pre assembled. I had to build the rebound shims leaving one shim off each leg so as to remain standard. Measured front sag unladen (30mm) laden (me) (35mm). Its very important to have at least a 12 - 13 mm static preload on each spring pre assembly. Spacers supplied. With out this steers a little nervous. 3 mm made a big difference.
Rear - was a little fiddly to fit through side access - but no biggy - just followed instructions, with hyd pre load swapped out for the OEM part and hi/lo compression canister fastened under rear seat. Measured rear sag unladen (10mm) laden (41mm). Adjusted the hyd preload (very small amount) to bring rear laden up to the fronts (35mm) to balance total bike sag solo as a start point.
Riding and dial in: - Initially was amazed at the difference. No external adjustment can be done to the front. Re the rear I needed to add a little more hyd preload which felt a lot better, then make a major reduction to the rear rebound rate (make it rebound faster). After the rebound was set I moved to the hi/lo compression, (hi/lo reference is to the speed of the shaft moving within the shock body). I did this by going from one extreme to the other; riding, then working from mid point until I was happy with the ride over various surfaces. Noted and marked.
Re 2 up. I required a lot more hyd pre load initially working it up and down until I felt it was right. I then increased the hi speed compression under the seat given the extra weight - played with a few positioned here as well until it was right. The lo speed adjustment(can be turned independently) was left at factory setting. By design it turns along with the hi speed adjustment by default. Lo speed adjustment appears to be a function of the hi speed value.
Summary:Totally impressed. The bike feels much lighter and stable to ride. The ride height feels higher - as it is. Far more ground clearance. Of note I thought the real issue was in the front. Turns out the rear has given me the greatest improvement by far overall. Before I could feel all the bumps in the front and the amount of rear squat particularly loaded mid corner was crazy as it turns out.
I can run through corners a lot faster now - and not meaning to - but just seems so stable and composed, holding a corner line so well. The bike squats evenly front to rear, 2 up its so much smoother (as reported), and in particular there is no further rear jacking down in the corner like the old shock. Its a totally different (new) bike now. Not cheap - but it was this or buy an RT1200. I took the cheaper option, and glad I did.
If I had to make any further adjustment - it would only be (maybe) put (1) extra rebound shim back into the front leg at the next fork service, as the front rebound may be just a tad lively; and thats marginal; - but thats it.
Hope this may assist others that think the suspension on the ST is a little ordinary. Its worth the spend if you have the coin.
Lyndon..