Front End Instability: Easy, Effective Fix

[dduelin]

Raising the fork tubes in the triple clamps does what, boys and girls?

That's right! It effectively decreases the rake angle and decreases the trail. While both make the bike turn in quicker, the downside is a decrease in forward stability. Raising the rear by increasing preload has the same effect.

I noted in another post earlier today that I cured a case of wander by adjusting my preload lower on the fly going down the road yesterday.

To clarify, are you talking about the light steering "wander" or happy feet at fast highway speeds or the weave the ST1300 can exhibit at speeds in excess of 110 mph? Lowering preload if the bike is going to be ridden to top speeds is the opposite of what you want to do. Excess sag with standard damping settings leads to the rear suspension moving up and down in a less controlled or uncontrolled manner at very fast speeds. Speaking in generalities we increase suspension preload and damping when riding motorcycles very fast, we don't want the bike wallowing up and down on soft suspensions at very high speeds. By changing springs or adding spacers some ST1300s are running much less front sag than the bike comes with stock and reducing sag alters the frame geometry to slow down the steering so sliding the fork tubes up 5 mm or less doesn't even began to make up for the rake and trail changes the sag reduction made.

 

[Papa]

Made me go look,, mine are flush.

 

[STBEN]

The second photo shows what mine look like now. The top of the tube is flush with the top of the cap. I think the bike handles much better this way.

I don't know what you guys mean by "flush" but it sounds like we are talking about two different things. What I mean is the top of the fork and the top of the clamp are even (the same height off the ground).

So that brings us back to what I was originally saying. If your tubes look like the first picture, and you have happy feat, try lowering them.

It worked for me....

 

[STBEN]

Also, I'm talking about the happy feet issue. Lowering the fork tubes 1/8th inch from the stock position, so the tops of the caps are even with the top of the clamp, helps a lot with the happy feet issue. Lowering the rear spring preload also helps.

Raising the rear spring preload does help for high speed handling. I'm saying that raising the rear spring preload will also have the unwanted side affect of making the happy feet thing worse.

Lowering the front tire pressure is something you would also normally do, if the bike isn't fully loaded. But I think on this bike doing that also makes the happy feet thing worse.

So to sum up, lowering the fork tubes, raising the tire pressures, and lowering the rear preload should all help with the happy feet issue. If you want a stiffer suspension, start by getting new fork springs, then you can raise the rear all you want.

 

[sennister]

The second photo shows what mine look like now. The top of the tube is flush with the top of the cap. I think the bike handles much better this way.

I don't know what you guys mean by "flush" but it sounds like we are talking about two different things. What I mean is the top of the fork and the top of the clamp are even (the same height off the ground).

So that brings us back to what I was originally saying. If your tubes look like the first picture, and you have happy feat, try lowering them.

It worked for me....

Alright I think we are getting confused here when you say second photo and flush with the tube. So using Hound's photo and his photoshoped version of his photo

Photo #1: This would be tubes flush with the clamp

Photo #2: This would be caps flush with the clamp

I will look at mine again but I am pretty sure mine is like Photo #1. That is how I have always set up my bikes and how I mounted the forks on my 1100 just last night.

 

[STBEN]

I'm saying make the cap flush with the top of the clamp. I was taking the tube to include the metal cap. Mine look like photo 2: caps flush with top of clamp!!!

 

[Gene]

Sounds like a nice old fashioned round profile front tire might be a bigger help then a fork adjustment that is equal to a turn or so on the read preload , Track down a a style Pilot Road if you want slow steering and great hyway manners , I think tire profile is the issue round = stabile pointy gives happy feet but great back road manners you have to decide which one is more important .

 

[Jerry55]

My tubes (not caps) were about 1/8” above the bridge clamp. When I lowered then flush like photo 1, and the service manual illustration (page 15-32) and the decrease in “Happy Feet” was very noticeable. My preload was cranked up from day one, and I run 42lb front & rear.
Considering all the variables, it is hard for me to believe that an 1/8” increase in front end height makes any difference, but it does. I’m puzzled ??
Are the forks and front tire assy installed at the Dealer? This would explain the variation we are seeing.

 

[GlenT]

According to the ST1300 setup manual, the forks are preinstalled at the factory. The dealer installs the front wheel, fender and calipers on delivery.