Bonneville America Forums Forums Technical Forums General Tech That "clunk"....rear caliper plate question

I hate thet clunk you get when opening the throttle from closed. I always thought it was in the cush drive, but after taking the wheel off many times i realize that sound is the plate the caliper is mounted on. It's held in place from turning with the wheel by a slot that fits over a ridge on the swingarm. But the ridge fits loosly in the slot and allows the plate to move backwars and forwards about an 1/8 to 1/4". Thats the sound i hear.

Looking at it it seems it should be shimed with rubber, but i don't see any way there could have been anyhing rubber attached to it because i can't see how it would stay on unless it were glued and i see no evidence of glue residue.

So my questions are, is there supposed to be rubber there that may have come off? Would it be ok to glue some rubber in there to keep it from cluncking or is there some reason it has to be like that?

There's no rubber bush from factory. No reason you can't put one in - take some pics and let us know how it goes.

daz you sure worry alot.

You would too if you had a problem you can't solve that's irritating enough to sell your bike.

(Warning: This Message Contains Friendly Harrassment and an Unprovoked Harley Bash)

Daz,
There sure is a lot you don't like about your bike! If you rode a Harley I would understand ,but this is triumph we're talking about!

Whats this all about? All i've posted about in the last week is based around a serious problem my bike has that i cannot suss out and these are the kinds of replies i get? Walk a mile in my shoes. Geez........

dude, relax. He's busting your chops. Geez.....

It isn't a serious problem. It is the nature of the beast. A piece of rubber or even some RTV may quiet it down, but it isn't hurting anything.

Just a guess, but I would imagine that slight amount of play may be to make assembly/alignment easier.

But that's just a guess. I have been told that other bikes have similar set-ups with similar amounts of play....

Hey Daz,
As stated earlier I was just busting your chops. You are always asking questions the rest of think of, but fail to ask. It was just a friendly jab. I had hoped the disclaimer made that clear. I hope you figure out the vibration problem.

I never noticed a clunk on takeoff. Seems like you would have to apply foot brake while backing to get slack in that assembly. If you do put rubber in there, It would have to have a rectangular hole or be thin enough not to throw caliper out of line.

Lonzo,

It won't trhow it out of line because the axl being tightened holds it in place from side to side. It moves back and fourth from front to back. Maybe yours is tighter. Could be a case of slop during manufacture when they weld the ridge on there. Rubber should work, but i was just wondering why it was so loose and if there's a reason. But i'm gonna try it eventuall. Right now i'm just too concerned with the problem i'm dealing with tho. And yes, i think it does happen after braking, but also after decel at times tho not as likely.

It may be that it was designed for a rubber bush but the beancounters canceled it. Also could be that they wanted to make good and sure that there was no chance it could fill with dust and bind.
Rather than stuff the slot with rubber, you would probably get better results laying a moderate coating of RTV on the sides of the slot, just enough to absorb the clunk without making the fit too tight.

With this being added to the vibration issue, I would start by looking at a new rear wheel bearing. This could be the cause of both problems. Mine doen's move at all. If it got tightened WAY too tight, which is rediculously hard to do, it could have warped the bearing a pubimeter and now it would be ever so slightly bent, causing the slop at the axle and the vibration.
Another vibration issue may be the swingarm itself. If you have ever had the swingarm axle out, you will notice that the two spacers are pretty sloppy. Jojje, the turbo Swede, made little metal shims to eliminate all the slop for his dragbike due to vibrations. You could probably cut some beer cans, or Coke cans if you don't drink, and place them inside the bushing guides on each side of the swingarm.

Pat,

The bearings seem fine, but they have no "bearing" (couldn't resist:))on the caliper plate. The axl goes thru it but the part i mentioned is what holds it in place. The bearing would have nothing to do with it. The bearings would of course be a possibility in the vibe issure tho, and i already posted that question. But i've since checked them out and they seem flawless. Smmoth as silk, no noise or friction, tight as possible with zero play either when testing with a finger or spinning the wheel on the bike or trying to push the wheel in all directions feeling for play. I may have to come back to them, but i have to eliminate everything first. I'll look into the swingarm once i'm completely out of ideas, but nothing really points to that as far as when this began and what i did before it all started.

I imagine the plate that holds the caliper is made that way because it has to be able to move back and forth as the wheel/rotor move back as the axle position is changed during chain adjustment.
I've never heard mine make a sound of any kind and I seriously doubt it has anything to do with your vibration.

Strange that it was fine, you took it apart and put it back together, and its not fine. Did rear wheel assembly go back in easily, or did you have to pry frame apart to get it back in? I remember a spacer that would only seat one way, wonder if it is backwards. I think it was between wheel and sprocket hub.

Yes, that one is between the sprocket hub and wheel and it can only go in one way so it's orrect. The other one is that top hat looking affair that goes on the brake sid and the rim of the hat goes against the caliper plate. It can go only one way too. So unless i'm missing some piece it's all together correctly. I looked at the exploded view in the manual a million times hoping to see something i did wrong but it all looks to be there and on correctly.

Chy.....yes, definatly. But it's the up/down movment that i'm talking about. If it were tight in the slot it could still move for chain adjustment but it then wouldn't make that sound. Someone said thiers doesn't do that plus no one else has confirmed the noise, so i'm assuming my slot is just wider. The lug is a welded part, so if the weld were not built up as much as others it would be sloppy. In fact, maybe thats why they make the lug smaller than the slot.........to compensate for the welding bead, and possibly mine has less of that.

Mine does it, but usually only once per ride, and only if I have to back the bike up for any reason. Then the first application of the rear brake turns the caliper mount forward and down and "clunk"....

This is rather embarassing, but i may be wrong about this whole thing. It does NOT move at all, and whether it can or not, i suppose you (grump) are right about it....backing up and applying the brakes seems to be the only way it could happen that i can see. So why did i post this then? Duh, i must have noticed it when i was spinning the wheel WITH THE AXL LOOSENED. And the axl pressure keeps it in place, and i don't see how it could move other than grumps suggestion. Yeah, go ahead and beat me now. But now i'm curious what that sound is. It can't be the cush drive because the rubber couldn't possibly make such a sound, or at least i can't imagine that.

It's a gremlin daz. Get yourself a ride-bell.
A shotgun and a good labrador will get rid of them also.

Can you reproduce this clunk with the motor off (rolling the bike or with the wheel off the ground)?

I don't think so. But now that i've removed the wheel a million times and understand what all is going on back there i think i can figure it out. But for now i'm so focused on this vibe problem it'll have to wait. Sprocket arrives today so at least i can eliminate that possibility.