I purchased my ST3 in the summer of 2005. After riding my ST3 for 5-6 months, it was painfully apparent the something needed to be done with the suspension. However, the best solution was not immediately clear. This [long] report outlines the twists and turns in a sega along the way towards perfecting the front suspension of my ST3.
One of the first things one realizes after riding a stock ST3 (my first road bike), is that the suspension is very plush. While I suppose this arrangement is nice at first; after I began to learn to be more confident and began enjoying faster and faster rides through twisty mountain terrain this became a annoying liability to my continued learning progress and enjoyment on the bike.
Although I had a good working knowledge of racing suspension on 4 wheeled vehicles, my knowledge of the subject as it related to road bikes was nill. I began reading the racing motorcycle forums, the "Independent Bike Suspension Forum", and many of the leading suspension vendor sites. I read and re-read motorcycle suspension setup articles to get a grasp of what was available, how to set it up properly, and also to try and separate the BS from the truly knowledgable and informed suggestions.
The conclusions I came too for my needs may not be the ones you would necessarily come to, and I'm sure there are 10 people lined up to defend their choice in suspension vendors, etc.
It was abundantly clear that the spring rate would need to be increased. The change to .95kg front springs was almost universally suggested (depending on your weight of course - I'm about 185lbs). After that, everyone seemed to have a differing opinion.
There are quite a wide variety of options in terms of valving, shim stack arrangements, complete cartridges, etc, being promoted by a wide variety of vendors promising to provide you the "ultimate ride"
Stock ST3 Forks
The stock forks on the ST3 only provide for pre-load adjustment. There are no external adjustments for compression or rebound, and they are very undersprung. I was reluctant to invest in new fork internals and ultimately still end up with non adjustable forks.
What Fits What? - Monster/748/749/998/999
Over at the Ducati Monster List forum, there are quite a few threads detailing superbike fork swaps onto Monsters. This seemed like a reasonable and direct approach if it could be applied to my ST3. This would achieve the goal of adjustable forks, and even if the internals would need to be replaced, it seemed a better overall investment.
It turns out that Ducati (in it's infinite wisdom), decided that forks on some models needed to be different lengths. They also specified that different bottom and top diameters be used (54/53/50mm). They even decided that brake caliper spacing and offsets should be different as well as fender mounting brackets on model to model and year to year, just to keep us on our toes....
The Tear Down
While still trying to figure out the ideal fork solution, I went ahead and dismantled the front end of the ST3. After taking off the side fairings, front fairing, windscreen, mirrors, etc, I could finally get to the lower triple clamp bolts. I secured the bike by using two "redundant" tie straps through the front of the frame to some rafters above. This allowed the removal of the front wheel, forks, and steering stem. Stock forks are below:
While it was in this state, I installed new tapered steering bearings. I also installed an insanely loud air horn. Damn that's loud.
The poor bike - it looked so naked, all tied up and hanging in the air...
After navigating this maze of options, it turns out that the commonly available 748 and 998 models are the correct length and have the right front fender mounting arrangement. The problem is that while the stock ST3 forks are 50mm through the top triple clamp and 54mm through the bottom triple, the 748/998 forks are 53mm both top and bottom.
Usually this fork swap issue is easily solved by using a 1.5mm shim in the bottom triple, and by boring out the top triple & risers by 3mm. But nothing is ever that simple is it?
Ebay to the rescue
I was finally able to find some 998 forks on ebay and purchased them. The lower sliders had the Ti-Nitride coating, and they had been modified by suspension tuner G.M.D.
Keep in mind that the stock forks are 50mm top, and 54mm bottom. The newly purchased 998 forks are 53mm top and bottom.
I had just purchased some Cycle Cat risers for my ST3, which have a 50mm bore for the stock forks. The wall thickness is only ~0.150", which doesn't safely allow enough extra material to be bored out for my comfort to fit the 53mm 998 forks.
So here I had new forks and new risers which just wouldn't fit each other. What to do?
I had heard good things about GP Suspension, and after much research, decided to go with their custom fork valving, shim stack, etc. From everything I could learn, this setup was in a different league than your generic "Gold Valve" drop-in
I talked with Dave there, and asked him to see if there was anyway he could get the stock ST3 fork upper tubes mated up with the 998 bottom fork sliders, retaining all of the external adjustability.
This would let me use the stock ST3 upper and lower triple clamps without modification, use the Cycle Cat risers, and retain all of the external adjustability of the 998 forks.
I took the stock and the 998 forks down to his shop and he said he'd give it a try. I crossed my fingers.
"Hey, it's GP Suspension and your forks on done."
Really, that was fast! Did you get it all to fit?
"Yep. You have our custom fork valve kit with all new internals, new springs, seals, fluid, etc. You're good to go."
998 sliders matched to ST3 upper tubes with GP Suspension internals below:
This was very good news, as the inve$tment was climbing and I feared starting over.
Putting it back together
Good thing I took some pictures...
GP SUSPENSION 998/ST3 FORKS
On the Road
This is a different motorcycle. It is so stable on braking it is amazing. I've set the sag and I initially had to soften up the compression a bit, but the improved road feel gives an immediate confidence boost.
I'm still getting used to the sensation of feeling so much more of the road surface, and my reaction skills need improvement. Almost all of my experience so far has been spent reacting to the stock suspension, and now that I can feel what is really happening, the bike feels like's it's going much faster than it really is through the corners. Seat time will remedy this.
Of everything I've done so far, the upgraded front forks have made biggest difference, and now this really is a different motorcycle. A huge improvement.
Now I fully understand the many suggestions to not even bother with engine performance until you've addressed suspension. Never was a statement more true.