Triple tree question

[Ivan]

What is the purpose of the large flange bolt that goes through the top triple tree through the steering axle? Mine vibrated loos the other day while going down I35 at about 80. It was a bit daunting thinking about the forks and wheel coming off at that speed.

I got to looking at it though and there are a couple jam nuts below it, so I am assuming nothing too spectacular would happen if the bolt fell out, but I may be wrong?

[randy]

You've got three pinch bolts, one there in the center and one at the top of each fork tube. If you lost (or loosened) all three, the handlebars will lift right off. Scary at speed, eh?

[CatatonicBug]

This one?



The fische calls it a "Fitting Bolt", and the 2 nuts are "Fitting Nuts". It looks lt me like they are allignment items to keep the center of the steering axle and the steering head bearings alligned. Just a guess though, based on the picture.

[Ivan]

So the bolt is redundant?

Scary? You can say that again.

The pinch bolts are all tight. I double checked them.

[fredintoon]

What is the purpose of the large flange bolt that goes through the top triple tree through the steering axle? Mine vibrated loos the other day while going down I35 at about 80. It was a bit daunting thinking about the forks and wheel coming off at that speed.

I got to looking at it though and there are a couple jam nuts below it, so I am assuming nothing too spectacular would happen if the bolt fell out, but I may be wrong?

Hi Ivan,
if you are not jerking the list's chain but really want to know, the jam nuts below the top tree keep the head races in adjustment while the flanged bolt holds the top tree on.
But, lucky you, that's not all that holds the top tree on.
There's pinch bolts onto the fork tubes and another one that grips the steering stem.
They all gotta come loose before pulling up on the bars lifts the top tree off the steering.
But if that top fastener did work loose perhaps it's torque wrench time for the entire front end?

[crazy steve]

All that stuff is there to keep the forks aligned/rigid (as well as the reasons Randy gave!). It was interesting to note that the FJ forks that Phil and I have swapped to don't have the steering stem pinch bolt, only the nut on the end of the stem. I added a pinch bolt to mine...

'78E original owner

[Ivan]

No, Fred not jerking any chains.

I did check everything for tightness after that bolt came loose. I wondered about the bolt, since I have seen other bikes without it and just the jam nuts on top of the triple tree. Cant remember which ones though, possibly a CB750? Which lead me to ask if its redundant. I have never had a triple tree apart yet.

This all leads me to another question. Does the top and bottom triplr tree need aligned if they are taken apart? I am going to be checking on the steering head bearings on the other bike, since it seems to have a "detent" forming in the center of travel.

Well, the phraseology of my last post was meant to be humorous. It was funny to me, that's what counts right?

[fredintoon]

- - - the FJ forks that Phil and I have swapped to don't have the steering stem pinch bolt, only the nut on the end of the stem. I added a pinch bolt to mine...

Hi Steve,
how did you do that? I have to assume that as the FJ top tree don't have a pinchbolt it wouldn't have the formed lugs to machine the pinchbolt hole through either?

[fredintoon]

- - - This all leads me to another question. Does the top and bottom triple tree need aligned if they are taken apart? I am going to be checking on the steering head bearings on the other bike, since it seems to have a "detent" forming in the center of travel. - - -

Hi Ivan,
the fork tubes automatically align them.
When you reassemble the steering head you'll see that the top tree has no part in the bearing adjustment so you can assemble the entire forks without it if you like.
The ability to remove the top tree without disturbing the rest of the forks is handy if you forgot to put on every last one of those fiddly chrome things and rubber rings that keep the headlight ears from rattling.
What I did was to leave the top tree fasteners loose until the front wheel and lower tree were bolted solid then do them up last.

[crazy steve]

...This all leads me to another question. Does the top and bottom triple tree need aligned if they are taken apart?..

They should be, but the FM is silent on this for whatever reason, and the 'brake caliper alignment' procedure for the special goes against all conventional knowlege for fork alignment. I have seen procedures in other bike manuals, and it usually goes like this:

1. With the calipers, fender and/or fork brace removed, and all bolts loose (including the axle), first set the tubes at the correct height by measuring at the top tree, making sure both side are the same. Lightly snug the pinch bolts on the top tree if needed to keep the tubes in postion.

2. Now torque the lower tree pinch bolts. These are usually the 'larger' of the tube clamps, and will 'align' the tubes.

3. Now go back to the top tree, and if you tightened the pinch bolts, loosen them (to allow the tubes to move it needed), then torque them.

4. Torque the stem nut and stem pinch bolt.

5. Torque the axle bolt and axle clamps (in that order).

At this point, if you don't have any bent parts, everything should be aligned. If you disturbed the steering head bearings and need to set those via 'fall-away', you need to go back and loosen the lower tree pinch bolts, the stem bolt, and the stem pinch bolt. Adjust the bearings, then torque the lower tree bolts, then the stem bolts.

The order is what's important here, as this allows the various parts to 'move' into alignment. This will get the tubes to be as parallel as the factory machining will allow, hopefully eliminating any binding. You can now reinstall the fender and calipers. If you have a fork brace, it should install without having to force it into place or have any binding.

If you really want to be anal, do steps 1-4 and with the fork springs out and wheel off (but with the axle slipped into place), check the inside-to-inside distance at the axle with the forks fully extended and compressed; if everything is good, the measurement should be identical.

I do all of this, and it has made a difference on several bikes in terms of how smooth the front suspension worked. Now, if you have a special and have to pry one leg to align the caliper, you're losing a big part of the alignment. But even so, even on a special I'd do at least steps 1-4 as that will ensure you don't have any 'twist' in the trees. I'm not saying you have to do this, but this is a recommended procedure in some 'other' manuals and can make a difference.

Fred, as to the FJ top tree, there was enough 'meat' around the stem hole to allow me to drill a 5/16" hole for a pinch bolt. I 'split' the stem hole with a hacksaw (carefully!) and it now clamps to the stem. The 'before' pic...

[IMG][/IMG]

And the 'after'...

[IMG][/IMG]

The more rigid you can make the forks, the better the bike will track.

'78E original owner

[Ivan]

Ok, I am starting to fully visualize the whole system of the forks in my mind and what you all are saying is making sense to me now.

The special caliper alignment has never been much more than about .050" for me. Usually just tugging on the fork leg by hand gets it in position. Am I just lucky?

[Bigfoot]

I had mine come completely out and land in my lap soon after I got the midnight running. Hit hard enough in the family jewels to really wake me up too.

[DGXSER]

I have had the trees off several times on the special models. Never worked on a Standard yet. But of course fred hit it exactly correct.

The top tree is part fo aligning the front end. Basically, loosen all hte pinch bolts on the forks, the fender bolts, and the front axle as well as the pinch bolt and that stem bolt on the top tree. Align the wheel, and tighten back up from top to bottom IIRC.

[crazy steve]

Ok, I am starting to fully visualize the whole system of the forks in my mind and what you all are saying is making sense to me now.

The special caliper alignment has never been much more than about .050" for me. Usually just tugging on the fork leg by hand gets it in position. Am I just lucky?

The idea is to eliminate any possible binding that may introduce twist into the forks. Like I said, if nothing's bent, this method will do that. If you do have damaged parts, this will show them up.

As to the special alignment, I did notice that the XS forks are 'looser' than some of the newer forks I've done and that's probably how they get away with that. That may also be why the XS has somewhat less 'precise' handling (besides the wimpy 37mm forks) compared to some newer bikes.

I'll have to disagree with 'start at the top and work down' thing; the lower tree (particularly it seems on these) is a closer-tolerance hole compared to the top tree, so getting 'correct' alignment with the top is less likely...

'78E original owner

[bikerphil]

You can check your fork alignment with a piece of plate glass against the front of the stanchions. Any rocking back and forth indicates a misalignment.