Is it possible to increase front suspension "trail" or caster angle?

[tcrooks]

In addition to having two degrees in automotive techchnology and experence as an application enginner for a division of GM, I taught brakes and suspension and front end alignment at three colleges. I know what caster angle is and Have learned the treatment of same in motorcycles re;terminologies rake and trail.

Bottom line: Increased caster angle adds directional stability and wheel centering characteristics coming out of turns; particularly important at speed. I think the stock ST1300 has too little caster or too little "trail" (99mm). This is highly subjective based on how I want to drive.

The ST1100 and BMW R 1200 RT, both share greater caster angles i.e., heading toward 28 degrees (BMW trail - 118mm). I'm probably barking up the wrong tree with this group and this position, but; has anyone heard of a means to modify (increase) caster or trail on the ST1300?

 

[sennister]

Not that I have ever seen.

They made the change in the 1300 to make it a little quicker to turn. Having both bikes I can tell the difference and what it translates to is the 1300 being more fun in the twisties and the 1100 more stable on the slab. Neither bike is bad at the area the other is better, just a difference.

 

[nhdiesel]

Keep in mind that the handling characteristics use a combination of the rake & trail, along with overall wheelbase, swingarm angle, and rear suspension design. Its tough to compare two bikes just by the front forks; and before changing the front, the rear also has to be considered.

There really is no adjustability to the front, unlike with cars. The angle is set by the steering head, which is a welded part of the frame. Custom bike builders cut this off and change the angle to build choppers, but its a lot of work, especially if you are only after a small adjustment.

If it was something that might become popular, such as maybe for a motorcycle with poor handling by design, and a 1 or 2 degree change could fix it, and be able to sell lots of kits, then it could be possible to use steering head bearings with the same I.D. but smaller O.D., and fabricate an offset sleeve to relocate the outer races. There would have to be more to the spacer though, as a simple sleeve would then leave the bearings misaligned with each other, so they would have to be tilted as well. Not impossible to do, but a lot of work for just one bike- especially when the result is unknown.

This is coming froma master tech with a degree in automotive technology, and 10+ years as a precision machinist in the tool room of a major bearing company. Fun combination to have when it comes to fabbing up custom parts.

 

[tcrooks]

I like the bike. At 80 on the fwy I would prefer more directional stability. It's such a damn nice bike and I read about other suspension mod.s and just wondered if the groups intelligencia had already addressed the issue.

 

[tcrooks]

Agreed nhdiesel. When I looked at that massive frame and welded steering head I held little help for adjustment. I'd heard these bikes were initially introduced in Europe; developed to run the Autobahn, this peaked my interest in the ST. I was interested in long runs and higher speeds. I know the sports bikes tend to have less caster and I understand the attraction. Though I think Honda misunderstood its target market. Just thought I'd throw it out there.

 

[nhdiesel]

You can also look to suspension modifications. The very soft ST suspension has been known to cause some odd handling traits at times. Even simple changes like new fork and shock springs can help, but the real changes come when the forks and shock are revalved. You might even look at your shock preload adjuster- with age they lose fluid. The preload adjuster on these bikes works like a hydraulic ram- when they lose fluid, the knob will show that its cranked up, but it won't be. Its pretty simple to drain and refill the fluid. I noticed a big improvement when I did mine last year, and I think it was due by the end of the season. It will be one of the first maintenance items on my list once I get into the new shop (hopefully next week).

The nice thing about the ST is that its in the middle between SPORT and TOURING. They can be tweaked toward either side of that. I put mine more toward TOURING, but it was still a blast on the Dragon last year (see my profile photo at left

As for stability...with a week's worth of camping gear piled on the back I still cruised at just about 100 mph with one hand, while using the other to take photos. There aren't many bikes I would dare to do that with.

Jim

 

[ST1100Y]

...has anyone heard of a means to modify (increase) caster or trail on the ST1300?

There is some hearsay that a German (or Dutch?) workshop fabricated different triple clamps to alter rake and impact caster, trail and all other factors connected... but since the thing went mute, it obviously wasn't the solution...
Apparently its not that easy, too many other factors are involved and require consideration. In Europe the issue has been debated back and forth over years, many riders (probably the majority as generally only folks with 'complaints' will surface in forums...) seem to have not experienced symptoms, among those who have three factors seem to stand out: rider's weight, (rear) suspension setting, top case present... tire model/thread pattern/wear/inflation seem as well to play into this... many cases seem to have been 'cured' (or at least improved) by changing the rear shock adjustment to 'harder' (which does not seem logical, as such would 'raise' the rear, tilting the front even steeper...); some riders report to have 'fixed' their symptoms by installing aftermarket rear shocks, due which the rear probably also stands 'taller'. I personally started to consider some aerodynamic causes (one of Honda's modifications were perforated crash bar covers, obviously intended to relieve air pressure from the fairing...), but I can't tell if its only air buffeting, or if air pressure/drag is actually causing some flexing/warp of windscreen, front fairing or all of above together, causing resonance which is then transmitted into/inflicting steering head/front suspension and/or even the rear suspension. If appearing at all(!!), symptoms might show at speeds way over 180kph/110mph... I had a '02/'03 ST1300 at over 160kph/100mph (solo and with OEM TC installed) and found no serious issues (other's then the 1300 generally feels very 'light', yet almost 'skittish' to me as long time 1100 owner...). OTOH did those who experience instability at over 180kph/110mph report that it starts suddenly & violent, and if you fail instant countermeasures, it quickly grows into a serious tank-slapper on which a few were actually going down. But again: all of those cases seem to have the following in common: solo, top case installed, rear suspension setting/condition questionable...

 

[dduelin]

Small changes in rake and trail can be made in any bike by increasing ride height in the forks and decreasing ride height in the rear shock. Since the stock ST1300 does not have built in adjustments for height it must be attained by decreasing sag in the forks with stiffer springs and/or longer spacers and adjusting the rear preload to increase sag. Aftermarket modified rear shocks to lower the rear suspension are also available. Experience with many riders tells us the ST1300 has better high speed stability with lots of rear preload and/or stiffer rear springs so know that changes to rake from altering ride height with rear sag may affect handling adversely.

 

[ST1100Y]

Experience with many riders tells us the ST1300 has better high speed stability with lots of rear preload and/or stiffer rear springs so know that changes to rake from altering ride height with rear sag may affect handling adversely.

Also over here no instability cases were reported with pillion aboard, but that could as well simply be due the 'protein controlled' rev-limiter being present
OTOH have riders experimented: solo, no top case: no symptoms; solo, with top case: definite symptoms... which brings it back to aerodynamics...

 

[Throttlejockey]

Too bad they don't make offset triple clamps for the ST like they do dirtbikes.

My KTM actually has an offset steering stem you can remove and rotate 180 degrees to change the offset between 18mm and 20mm.

 

[sennister]

I like the bike. At 80 on the fwy I would prefer more directional stability. It's such a damn nice bike and I read about other suspension mod.s and just wondered if the groups intelligencia had already addressed the issue.

This is where I find the 1100 more planted. The trade off is in the corners. It isn't bad but not as quick to drop into the corners and takes more effort where the 1300 just falls into them without much thought.

Agreed nhdiesel. When I looked at that massive frame and welded steering head I held little help for adjustment. I'd heard these bikes were initially introduced in Europe; developed to run the Autobahn, this peaked my interest in the ST. I was interested in long runs and higher speeds. I know the sports bikes tend to have less caster and I understand the attraction. Though I think Honda misunderstood its target market. Just thought I'd throw it out there.

Yes it is my understanding that they were kind of introduced in Europe. It was really to go after the European market where BMW was strong. There was a demand for a smaller, more sporty Goldwing. Here the Goldwing is sold big, not so in Europe. I wouldn't say that is just because of speed. The Wing will run right with an ST at any speed that the ST will do on the Autobahn. Sure the Wing can corner but not like an ST. When they redesigning the ST for the 1300 release around 2000 (came out in 2002 Europe, 2003 US), there was a trend to put more sport in the sport touring segment. Look at bikes like the C14. You put more sport in a road bike by making the changes they made. More power and change geometry to make the bike quicker turning. There is a trade off though. More power came from a powerplant change which is higher compression and needs premium fuel, the geometry changes made the bike more work if you are slabbing it down the interstate. In time the instability goes away for most of us. I don't notice it much now on the 1300 until I jump on my 1100 for a ride. I still find myself grabbing the keys for the 1300 for lots of reasons though. The biggest is that it fits me much better. My knees bother me on the 1100.

I would say that in the Sport Touring Segment the main bikes that you see are going to be falling in a range. The Kawasaki, Yamaha are more on the sport side of the category and the ST and BMW are going to be more on the touring side.

I agree with nhdiesel, look to suspension options first. The easiest is the preload adjuster. Last spring I looked at mine and refilled it with the notes from the article here. I went from 23 clicks before any resistance felt to 3. Now I can actually change the preload on the back where it did nothing before. Look at new springs on the rear shock and the front. There are lots of other suspension upgrades possible but those that have done them claim it is a night a day difference. I am looking at doing them as well one of these days. Might be a project for next winter. I want to do them at the same time and have been mainly waiting till I blow a fork seal. Not that I want it to happen but that would be when I would do it.

As I was reading what nhdiesel was thinking that a change to the triple clamp might work but it would be a PITA to try and figure out how much is enough and what is too much with a lot of expense in each shot at it.

 

[T_C]

Try a change to the rear tire. A little wider and flatter made the ST less prone to darting and more straight line stable at highway running. With a 205/50R17 on the back the bike just settles in and is ready for the long haul.

 

[LetErBuck]

Being a machinist for 30+ years and riding even longer....I agree with the fellows talking about optional triple clamps (like the MX boys).
I have actually gone as far as re-boring the sockets where the fork tubes go to a larger size and different angle to get the suspension EXACTLY the way I wanted it.
Keep in mind I then needed to go to a larger diameter fork tube.

 

[Throttlejockey]

I've seen guys make sleeves to fit into the triple clamps that were too big to fit the fork tubes. Probably be big $$$ to make a set of ST clamps. The offset stem is a great idea.

 

[W0QNX]

I'm probably barking up the wrong tree with this group and this position, but; has anyone heard of a means to modify (increase) caster or trail on the ST1300?

Yes. But I guess I'm not worthy. Let us know when you stoop down; to a lower level and can listen. Do you get my meaning or should I try and simplify it for you? With all your degrees and experience (spelled with an i) I'm surprised you'd even ask "this group".

 

[CarSalesman]

Small changes in rake and trail can be made in any bike by increasing ride height in the forks and decreasing ride height in the rear shock. Since the stock ST1300 does not have built in adjustments for height it must be attained by decreasing sag in the forks with stiffer springs and/or longer spacers and adjusting the rear preload to increase sag. Aftermarket modified rear shocks to lower the rear suspension are also available. Experience with many riders tells us the ST1300 has better high speed stability with lots of rear preload and/or stiffer rear springs so know that changes to rake from altering ride height with rear sag may affect handling adversely.

Dave, I agree with your comments but you can make significant changes in the character of the ST1300 buy adjusting the front ride height in the fork clamps. Personally I prefer a more lively turn in as most of my rides are on twisting. Dropping the clamps (tubes sticking up above the clamps) makes the turn in faster. Mine are about 5mm high. I never tried it but the opposite might be enough for the original poster in this thread. Of course there is a limit on how far you could put the tubes down into the clamps, but with what I have seen 5mm high, I expect that running the tubes 5mm low would make it more stable if that is desired.

Another thing for the original poster is that the stock front springs are very soft. If the suspension is too far compressed, that will change the geometry similar to a reduction in caster. Springs are easy to change. My Hyperpro springs were a drop in without even changing the preload. Very common upgrade.

 

[Rich R]

For what its worth, a set of springs goes a long way in settling the 1300 down. I used the hyperpro kit and flat out love the ride and the change in suspension geometry. I actually had to raise the forks in the clamps by 4mm to quicken up the steering.
While this may not be quite the answer you were looking for, I think it will be the most cost effective way to achieve the goal of straight line stability along with tire selection.
All the best,
Rich

 

[richpeabody]

Years ago I had a Can Am 350 that had concentric steering head bearings....trail could be adjusted with them...

 

[dduelin]

I have my fork clamps lowered about 5 mm to help regain geometry (quickness) lost when I set the sag at 36 mm with preload. At my weight of 155 the original sag was 47 mm and the OEM springs are fine by me after getting the sag right. The OP was seeking the opposite outcome though of slowing the steering response and I would not recommend dropping the fork tubes below flush with top clamp.

Yes, lots of people simply swap springs. I tried a more calculated approach and knew the sag I had and what I wanted. If the ST came with adjustable preload the first thing one would do is try more preload and see if static and rider sag targets could be reached. If not, a change in spring would be next. With my light weight I hit target with OEM springs.

 

[richpeabody]

Air in the forks would probably be the simplest, least expensive option. Simply install a Schroeder Valve in each and add a ir to pick the front up.
I plan to do this to my 1100 just to improve ride.