Dragging brake caliper

[wfooshee]

If the fork tubes were free to move independantly of each other then brakes on one side would have an effect, like your dozer tracks. But the front end is a single rigid assembly, from the triple tree down to the axle, so any force applied internally to that assembly affects the entire assembly. You could have the brake 6 feet off to the side, and nothing on the other side except something to balance the weight, and the brake would not steer the fork.

The left fork hitting something is not the same as the brake operating against the left fork. Hitting something brings an external influence into the bike's management.

 

[JR'SFJR]

For what it's worth, before washing the bike getting ready for Daytona, I took a few mins. to pulled one front caliper, blocked the pads, strapped the caliper to the fork and take it for a short ride around the neighborhood at 40 mph max. Didn't even think about pulling. Granted, it not 80 mph on the slab with a rotor that's ready to melt.

Good troubleshooting advice so far. I have replaced many brake hoses on vehicles that only let fluid flow one way. I don't see how it can be the master cylinder, since it is common to both front calipers.

 

[wfooshee]

^^^^^ Not to mention having that big ol' ABS unit in between the master cylinder and the calipers.

 

[John d]

I'm no expert, but could it be that the hydraulic pressure is not being relieved by the ABS control system, in effect creating a check valve?

 

[xc1974]

If the fork tubes were free to move independantly of each other then brakes on one side would have an effect, like your dozer tracks. But the front end is a single rigid assembly, from the triple tree down to the axle, so any force applied internally to that assembly affects the entire assembly. You could have the brake 6 feet off to the side, and nothing on the other side except something to balance the weight, and the brake would not steer the fork.

The left fork hitting something is not the same as the brake operating against the left fork. Hitting something brings an external influence into the bike's management.

If the fork tubes are a single rigid assembly with no movement then why do guys put fork braces on? Because the tubes flex...

Not trying to poke holes in your theory, you've been very helpful to my brother, and I agree with your single brake theory. I tried telling him that before he posted here. Just tryin to make sure we think this out completely. Plus i like to argue.

 

[Auburn]

Had an issue similar to this on a Suzuki GSXR750. I had replaced the brake lever with a new one. The lever looked identical, but it was actually slightly engaged to the master cylinder and was not allowing the brake to fully release. The slight pressure on the front brake which caused everything to heat up and after a few miles the brake fuild would build up more pressure causing the front wheel to really feel like it was dragging bad. Only this did affect both front discs together.

I am wondering if your rear brake lever is not disengaging fully and causing the issue similar to what I desdcribed above. There are many posts about the rear brake lever not releasing fully due to dirt and grim building up at the pivot point.

The reasoning is the rear brake only activates one piston on one caliper in the front. Or maybe you are inadvertently dragging the rear brake with your foot and not realizing it?

EDIT: the cause on the Gixxer was the front brake lever where it engaged the master cyclinder sooner and did not release like it should. The fix was to file the lever slightly so it fully released. It only took a couple of passes with the file to clean it up.

 

[incoherent]

I'm no expert, but could it be that the hydraulic pressure is not being relieved by the ABS control system, in effect creating a check valve?

That would be my guess if I ruled out a faulty hose. Is there a way to test the bleed-off pressure in an abs module?

 

[Vmaxrider]

Just a thought... Is the wheel installed correctly? I seem to recall if the spacers are swapped then one caliper will not work correctly. I could be way off though.

 

[wfooshee]

AuburnFJR, the linked piston is on the right side, it's his left caliper that sticks and drags. Rear would have nothing to do with it.

xc1974, I just knew somebody would do that!!! But that flex comes from outside the fork assembly, by interaction with the road surface. Wrong frame of reference.

Stand beside a ladder and push it sideways. Pretty easy to move it. Now stand on the ladder and try to push it sideways. I don't mean swinging your weight around and hanging off of it, I mean try to push it sideways while standing on it. You will never move it. Try to twist it by pushing forward on one leg. It won't twist. But stand on the ground and push one leg, it'll twist pretty easily.

Depends on where the force comes from (frame of reference.) If the force comes from the ladder (or a brake caliper mounted to the fork) it can't move the ladder (or the fork.) If the force comes from off the ladder (or from off the bike, like dcarver's "hitting something,") then it moves the ladder (or the fork.)

 

[John d]

Earlier I mentioned that possibly the ABS control could be at fault, but that can't be if only the left front caliper is dragging, because the brake line is split at the lower triple tree and then goes down to both front calipers. If the control unit was faulty then both calipers would drag.

 

[xc1974]

wfooshe... :yahoo: laughs, thought i had ya there. Are you sme kind of physics geek or what?

 

[wfooshee]

No, just geek. :lol:

 

[Vmaxrider]

There was a guy on the FZ1 forum who had a very similar problem. It turned out that he had his front wheel on backwards. I know it would be pretty hard to do with the ABS ring and all, but given the circumstances I would check the simple stuff like wheel spacers first before diving into the ABS system. it seems unlikely that you would have two bad calipers and you already flushed the master cylinder.did the previous owner just install new tires or do any kind of maintenance to the front end when you bought the bike?

 

[Donal]

FWIW I had my front suspension rebuilt with a full RaceTech package. Immediately after (on the trip home) I noticed the bike had a (slight) tendency to pull to the left when I applied the front brake. The cure was simple - I just slacked off all the front suspension bolts, worked the front suspension a few times and tightened everything up using the correct torques and correct sequence - problem gone.

As for the dragging caliper it sounds like you are almost there. I would be strongly inclined to just replace the hydraulic line to that caliper. If that solves your problem then you are faced with a decision on what to do with the remaining hoses - replace or ..............?

Don

 

[cofz1]

I think I'm down to either the line goes to the caliper or the "T" above that. Plan is to check both this weekend.

I really appreciate all the help. Hopefully, this will be a fairly simple fix. (Of course I thought that a while ago.)

 

[Patriot]

recently, I lost my balls, ah, a front wheel bearing failed

just before when the bearing was loosening, the edge of the rotor would lightly contact an edge of the caliper causing a thump & vibration and the lever would go soft with a pump needed for the lever to harden to braking effectiveness. I thought it was a sticking piston not retracting, but it was bearing(s) with 150k+ miles badly needing replacing

 

[Constant Mesh]

Check everything carefully as you would if you were installing the front wheel after the mounting of a new tire.

Follow the wheel installation instructions on pages 4-22 and 4-23 of the 2006 Service Manual. If the wheel, axle, pinch bolts, etc. aren't installed properly you could possibly experience some alignment and tracking problems.

If braking with just one disk affected tracking, pressing the rear brake pedal would change your line since the pedal also applies a portion of the right front brake.

 

[Graham Downunder]

It sounds like a badly fitted front wheel causing missalignment of the one disc it only takes very little tocause a problem . Before you do anything check the tire has been fitted in the right direction !!!! you never know who has done what on the bike .

 

[J. Parrie]

Hmmm..

Imagine a case where the disc was 4 feet to the left of the tire.

Would not the force of braking on that disc cause deflection to the left front fork tube and thus direction?

Sure, the contact patches are in line, but energy is applied to left fork assembly, not right, causing an imbalance?

Or, put another way, if the left fork tube hits an immovable object (tree, rock, etc) would not the mass rotate around the deceleration causing course change?

(Please bear with me, I have a hard time understanding this physics stuff, but I love to ponder and bear total humility to facts!)

Applying your theory of something hitting the fork tube, the caliper is mounted behind the fork tube, and therefore would cause the bike to steer to the right if anything. I'm with wfooshee on this, something is bent or assembeled incorrectly. Have you removed the front wheel and checked the axle, bearings, etc? Possibly the spacer between the bearings was left out?

Are the forks in a bind? Have you loosened all the pich bolts on the triple clamps to let the forks relax if they were bound up?