Just spent part of the weekend attempting to find out why my '05 was riding so poorly. I began to notice this problem after installing a fork brace which I purchased in an attempt to eliminate what I felt was extremely jiggly fork action in bumpy turns. Here's what I found:
FORK BRACE-- Out of the box, the brace installed with a slight "snap" but the forks seemed to move OK, if a little "scratchy". Big mistake.
If you have installed, or intend to install a fork brace, FIRST, pop the fork caps (very easy on the ST13 after laying the handle bars on a well-padded tank) remove the spacers and springs and operate the front end by hand, noting carefully the action. Should be buttery smooth and silent. Next, install the brace and try the fork action again. If changed, the brace is causing a problem. The design of the brace I purchased squeezes the sliders fore and aft, which is OK, but the side-to-side fit was NOT perfect, and it needs to be. Using a length of PVC pipe and sandpaper, I removed a few thousandths for about 3/4 inch on either side of the bore split. The bolt holes are large enough to allow the brace to seat perfectly and now fork action is smooth, with or without the brace installed.
SPRINGS--I wanted to find out at what point the tight coils on the factory springs go solid in normal riding. Using a stout length of threaded rod, nuts, washers and some handy barbell weights, I verified that k= 50 lb./in. (the same rate as ST1100 Progressive Springs at their firmest, BTW) and found that the tight coils go solid at 3 3/4" of compression. With stock preload of about 3/4" and fork sag of about 1 1/4" with rider (me), this leaves 1 3/4" of fork travel before the coils go solid and an additional inch or so before the fork itself bottoms. Note: There is surprisingly little fork compression from rider weight, as the rear suspension bears most of the load.
OIL--I decided to try for a boulevard ride as a baseline, so I lowered the fork oil level 50 cc's per side, then exchanged a pint of 10W for 5 W in each leg.
BOTTOM LINE--I have concluded that Honda engineers got it about right with the stock setup. Even with mostly 5W oil, I find that there is still sufficient fork damping, but small motion in front is reduced enough to be almost unnoticeable. With my 165 lb. riding weight, there is no bottoming on my favorite test vee-dip at speed, though under half-full braking the fork will bottom (as evidenced by zip-tie movement) however there was no "thud" of any kind that I could detect. I'm going to ride it this way for awhile. For heavier riders or hard riding, changes to oil level and preload would be first on my list, but for normal and sporty riding, heavier fork oil seems only to stiffen the ride, as would heavier springs. I've come to believe that softer in front is a Good Thing. (not so for the rear suspension, of course) Finally, I have no idea whether the fork brace is of any value. More riding needed, like to WeSTOC, where any and all are welcome to test ride this bike.
Tim Shevlin Anaheim, CA #1183
FORK BRACE-- Out of the box, the brace installed with a slight "snap" but the forks seemed to move OK, if a little "scratchy". Big mistake.
If you have installed, or intend to install a fork brace, FIRST, pop the fork caps (very easy on the ST13 after laying the handle bars on a well-padded tank) remove the spacers and springs and operate the front end by hand, noting carefully the action. Should be buttery smooth and silent. Next, install the brace and try the fork action again. If changed, the brace is causing a problem. The design of the brace I purchased squeezes the sliders fore and aft, which is OK, but the side-to-side fit was NOT perfect, and it needs to be. Using a length of PVC pipe and sandpaper, I removed a few thousandths for about 3/4 inch on either side of the bore split. The bolt holes are large enough to allow the brace to seat perfectly and now fork action is smooth, with or without the brace installed.
SPRINGS--I wanted to find out at what point the tight coils on the factory springs go solid in normal riding. Using a stout length of threaded rod, nuts, washers and some handy barbell weights, I verified that k= 50 lb./in. (the same rate as ST1100 Progressive Springs at their firmest, BTW) and found that the tight coils go solid at 3 3/4" of compression. With stock preload of about 3/4" and fork sag of about 1 1/4" with rider (me), this leaves 1 3/4" of fork travel before the coils go solid and an additional inch or so before the fork itself bottoms. Note: There is surprisingly little fork compression from rider weight, as the rear suspension bears most of the load.
OIL--I decided to try for a boulevard ride as a baseline, so I lowered the fork oil level 50 cc's per side, then exchanged a pint of 10W for 5 W in each leg.
BOTTOM LINE--I have concluded that Honda engineers got it about right with the stock setup. Even with mostly 5W oil, I find that there is still sufficient fork damping, but small motion in front is reduced enough to be almost unnoticeable. With my 165 lb. riding weight, there is no bottoming on my favorite test vee-dip at speed, though under half-full braking the fork will bottom (as evidenced by zip-tie movement) however there was no "thud" of any kind that I could detect. I'm going to ride it this way for awhile. For heavier riders or hard riding, changes to oil level and preload would be first on my list, but for normal and sporty riding, heavier fork oil seems only to stiffen the ride, as would heavier springs. I've come to believe that softer in front is a Good Thing. (not so for the rear suspension, of course) Finally, I have no idea whether the fork brace is of any value. More riding needed, like to WeSTOC, where any and all are welcome to test ride this bike.
Tim Shevlin Anaheim, CA #1183