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Discussion Starter #1
My father has a relatively new Triumph Thunderbird LT with about 7500 miles on it. He recently noticed that the front brake leaver goes nearly to the grip. It used to be further out. First thought was pads were worn, but when we took them out they had .015 wear, basically non. The brakes still work good, but you can pump them up and the leaver compresses the brakes further out. But there's no fade or bleed, there's no fluid leakage anywhere and the fluid level is the same.

Not sure what's going on here. Normally I'd associate the brake leaver or peddle going further with pad wear, but there's next to no wear.

Thanks
 

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Brakes is something you shouldn't monkey with. My first thought since you say relative new is take it back to the selling dealer. But if you are still going to go the shade tree mechanic direction I'd start looking for a leak. Air getting in versus brake fluid leaking out but you should see leaking fluid at some point. But this is something I wouldn't second guess if it was me.
 

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Discussion Starter #4
Thanks, first thought was break wear, but that's a non issue.

I should also state my father was an auto mechanic for years, and I was an aircraft mechanic. Neither of us are trained motorcycle mechanics though. I have rebuilt brakes before on an older bike, and various autos. That's why this is bugging me, there's no rhyme or reason for the lever moving in, unless maybe it somehow got bent. The brake system is a simple hydraulic piston system, it's not rocket science.

First, it's not my bike and I don't ride it, so it may be that he's imagining the extra lever travel. I know my bike and where the brakes engage and if there was a change I'd know it, not so much on this bike.

Also, there's no adjustment on the lever, if anything you'd get more free play, not less.

Thing is, there's no sign of a leak anywhere, and the fluid levels are unchanged.

The only thing I can think of is that about 4 months ago he dropped it on it's side, wet grass and soft ground. It did throw the antilock system off for a bit, but that reset after a while. I'd thought maybe it'd gotten air in the line, but that should have migrated back up in the months since.

Thanks, brakes are something I take very seriously, just want to be sure.
 

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You may well have it right here, levers bend very easily when you drop a bike, I had to change one on my stepdaughters bike, she was riding it with a bent lever until we noticed it. Maybe you can get a look at a good lever on the same kind of bike and see if it's bent?

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That's why this is bugging me, there's no rhyme or reason for the lever moving in, unless maybe it somehow got bent.

The only thing I can think of is that about 4 months ago he dropped it on it's side, wet grass and soft ground.
 

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Discussion Starter #7
It's a 2014, purchased Dec. 2014, fluid has not been flushed yet.

I don't believe the lever got bent, it's got highway bars and it was a very gentile lay down, and I can't see where it's bent. It could be however and it wouldn't take much. I'll take another look at it this afternoon. Might ride up to a competing dealer and look at there TB's for comparison.

Basically my father is telling me that it used to catch about 2" or more from the grip, now it's about 1/2" from the grip. By catch I mean you feel the pistons grip the rotors, not brakes start to work. If you were moving you'd likely lock up or have the antilock engaged.
 

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Air introduced will tend to stop at the banjo fitting - the outlet fitting of the master cylinder. Normal use will not, normally, pull it back into the MC. If you can, tilt the bars to the banjo is lower than the MC (or move the reservoir). Then, very slowly (count of 10 to 20) squeeze the lever until it stops, count to 10 again, then let it snap back. Keep repeating until lever movement is at a minimum. Sometimes, you have to work the lever a bit to expel the bubbles from the MC before continuing. If you want to see if bubbles are coming out, make sure to cover everything, so the fluid that will splash out doesn't damage paint or polished metal.
 

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It doesn't take much to make the brakes spongy. There is very little fluid movement in motorcycle brakes. Even a couple of tiny bubbles can do it.
 

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Discussion Starter #11
That's the thing, there not spongy at all, just the length of throw on the lever has increased. If I didn't know better I'd say the brakes were worn completely out, but they don't show but .015 wear.
 

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That's the thing, there not spongy at all, just the length of throw on the lever has increased. If I didn't know better I'd say the brakes were worn completely out, but they don't show but .015 wear.
You said you can pump them up, reducing the movement; that means, air in the system.

Is the reservoir mostly level, or does it tilt down, with the banjo fitting high? If the latter, it is very easy to get air through the MC into the lines; all it takes is for the small intake holes that feed the MC to get into the air above the fluid.
 

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You said you can pump them up, reducing the movement; that means, air in the system.

Is the reservoir mostly level, or does it tilt down, with the banjo fitting high? If the latter, it is very easy to get air through the MC into the lines; all it takes is for the small intake holes that feed the MC to get into the air above the fluid.
Sounds like the stock/expected diagnosis, however, I've got what sounds like the same isssue on my Road King. Pumping the front brake brake lever, it goes back to its regular old self. It seems to be a common issue with the RK according to what I've seen on-line. I've had them bled - no difference. The only thing I can see is that the brake pads don't. Ride "tight" against the disk like they should, there appears to be some air space. Pumping the brake lever makes the pads sit where they should. Do it at the beginning of a ride and they're pretty much ok for the rest of the ride. No fluid leaks. No problems stopping. No sponginess in the lever. The only thing that happens is that the lever moves almost all the way back to the handgrip. This repeat every time the bike sits sits for several hours. Seems like the pistons withdraw too far back into the caliper when they sit for a while. It's been driving me nuts as to why.
 

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When the bike got dropped, the fluid level was such that when the brake handle was pulled while standing the bike up, it forced air from the reservoir into the brake line. Now all that needs to happen is to bleed the brake. The reservoir was not completely full to the top when the bike went down. Bleed the brake and ride.

Just guessing, but the bike was dropped on the right side?
 

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Discussion Starter #15
Bike was dropped on the right side, but that was 4+ months ago, issue just started a couple days ago. Also the banjo fitting is at the bottom of the master cylinder, little chance of air entering unless brakes are squeezed while the bike is nearly upside down. It could have happened 4 months ago, but doubtful.

After looking at a diagram of the master cylinder we decided to take the bike to the dealer. From the diagram it is our thought that the primary cup or piston seal is ruptured or split and the secondary seal, which is about an inch or so further back, is what is holding pressure to actuate the brake pistons. It may or may not be the case, but it looks like from the diagram what's happening. The bike is just over a year old with a two year warranty, so hopefully Triumph will take care of it. If not, it means at minimum a new piston and honing the master cylinder bore, more likely a new master cylinder.

On the Road Kind, does the brake calipers have a return spring? They should not be loosening up unless there is something to press them back like a return spring. The pads should not be tight to the rotor, but neither should they be flopping around.
 

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Sounds like the stock/expected diagnosis, however, I've got what sounds like the same isssue on my Road King. Pumping the front brake brake lever, it goes back to its regular old self. It seems to be a common issue with the RK according to what I've seen on-line. I've had them bled - no difference. The only thing I can see is that the brake pads don't. Ride "tight" against the disk like they should, there appears to be some air space. Pumping the brake lever makes the pads sit where they should. Do it at the beginning of a ride and they're pretty much ok for the rest of the ride. No fluid leaks. No problems stopping. No sponginess in the lever. The only thing that happens is that the lever moves almost all the way back to the handgrip. This repeat every time the bike sits sits for several hours. Seems like the pistons withdraw too far back into the caliper when they sit for a while. It's been driving me nuts as to why.
You have air in the system. You may also have a worn skirt or o-ring on your master cylinder.
 

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On the Road Kind, does the brake calipers have a return spring? They should not be loosening up unless there is something to press them back like a return spring. The pads should not be tight to the rotor, but neither should they be flopping around.
They use a quad seal which is square in cross section. As the piston moves forward the seal distends and keeps a slight pressure on the piston. When the pressure is released the seal returns to it's normal shape and pushes the piston back in the bore slightly. At rest there is usually a few thousands of an inch clearance between the pads and the rotor, but I've never measured it. The pads shouldn't be dragging on the rotor.
 

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Discussion Starter #18
That makes sense, most calipers, wether on cars, bikes or aircraft "float" the pads on the rotors, very little clearance and actually scrub slightly on the rotors. The square seal is acting like a small return spring.
 
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