Dragging caliper assistance

[B.D.F.]

I assume you opened the bleeder on the caliper rather than the one at the handlebars? If so, there will always be a little pressure there because it is low in the system; if you left a lower bleeder open overnight the system would empty itself. To check the system for pressure, you will probably want to re-test by bleeding the system, riding the bike and then opening up the top most bleeder.

I want full credit for not making a funny about the spurt followed by a dribble..... 

Brian

Well, took a spin and when I got back and opened the bleed valve, I did have fluid coming out.  For the first split second it came out with just enough force to clear the top of the bleed valve by about 1/4 ish inch then slowed to a dribble.  I closed the valve, lifted the front wheel and gave it a spin, didn't notice any difference in resistance.  With out touching the brake lever I opened the valve again and allowed somehwere around a 1/4 teaspoon of fluid to escape then closed the valve again.  When I spun the front wheel it seemed like less resistance.  I know that is a pretty subjective test but those are the results I found for what it's worth.

[Tactical_Mik]

I didn't try at the master because the right caliper doesn't drag.  My thinking was that while gravity would have it's way, the initial overpressure would be obvious.  While I think that might have worked, given the slightly more exuberant start ending in my dribble,  I don't know if it really means anything.

[VirginiaJim]

I assume you opened the bleeder on the caliper rather than the one at the handlebars? If so, there will always be a little pressure there because it is low in the system; if you left a lower bleeder open overnight the system would empty itself. To check the system for pressure, you will probably want to re-test by bleeding the system, riding the bike and then opening up the top most bleeder.

I want full credit for not making a funny about the spurt followed by a dribble..... 

Brian

Credit noted....

[B.D.F.]

I agree- it would be really hard to tell what was going on by cracking the bleeder unless the fluid hit the ceiling.

I am also out of guesses. The only thing I can say is that it would be highly unusual for one side of a hydraulic circuit would pressurize and not release while the other side did. One of the advantages of hydraulics is that all pressures and (assuming the same area pistons) forces will always equal; that is why they can put pistons on both sides of the rotor and have the pads squeeze evenly. If there was any imbalance at all the pistons on one side would simply push the rotor as far as it could to the other side, including into the caliper.

Definition of hydraulics: Ancient Egyptian writing form found inside tombs.

Brian

I didn't try at the master because the right caliper doesn't drag.  My thinking was that while gravity would have it's way, the initial overpressure would be obvious.  While I think that might have worked, given the slightly more exuberant start ending in my dribble,  I don't know if it really means anything.

[VirginiaJim]

You could try cracking the bleeder on the other side and see if you get the same result I guess.

[Tactical_Mik]

I was thinking that maybe something in the crossover line might be messed up, acting kind of like a check valve but one that leaked.  I'm out of guesses myself.  I am tempted to get a cross over line headed my way, continue with a disassembly on my weekend, reassemble and wait for the line to come in.  However, I don't really like throwing parts at it until I stumble upon the issue.  I suppose I should probably take it apart and see if I can find anything and if not, schedule a shop visit.  It would appear that this issue has beaten me. 

[lather]

Actually, I think that was Lather...

No. Lather was the guy who put a pad in backwards.

[lather]

Loosen (slacken if your British) the axle nut and the left axle clamp bolts. Then spin the wheel and see if the brakes still drag on the left. Read the procedure for installing front wheel section 10-7.
I am thinking if the axle is not properly seated/installed the left fork could be in a bind and the caliper and rotor not perfectly parallel. Or some such. Maybe worth a try since it looks like we are out of other guesses.

[Tactical_Mik]

I'll give it a try when I get home from work today.  At least it will give me something new to try.

[VirginiaJim]

No. Lather was the guy who put a pad in backwards.

At least it was something to do with brakes...what took you so long to chime in?

[B.D.F.]

OK, one more thought- the caliper that is dragging is new, right? The other caliper is original. So perhaps there is some pressure in the whole system but the old caliper is sticky enough to resist piston movement at those low pressures but the new one does move the pistons and pads toward the rotors. That would at least explain how there could be a small amount of pressure in the whole hydraulic system. And all of that makes me suspect the master cylinder again.... or still.

I just don’t like the idea of a piece of debris making a check- valve in ½ of the system. It is hard enough to make a check valve that does not leak when you need one, never mind making one out of crud by mistake.

Brian

I was thinking that maybe something in the crossover line might be messed up, acting kind of like a check valve but one that leaked.  I'm out of guesses myself.  I am tempted to get a cross over line headed my way, continue with a disassembly on my weekend, reassemble and wait for the line to come in.  However, I don't really like throwing parts at it until I stumble upon the issue.  I suppose I should probably take it apart and see if I can find anything and if not, schedule a shop visit.  It would appear that this issue has beaten me. 

[lather]

At least it was something to do with brakes...what took you so long to chime in?

I am still getting used to the new url.

[Tactical_Mik]

The check valve thing was more thinking out loud.  It's less than likely and I flush my brake system about every six months to keep corrosion down.  More often than needed but I am generally a stickler for the PMing.  Corps thing I suppose.  If all works out as planned, tomorrow or Saturday I will take the lines apart and give them a good flushing/inspection.  Might just take apart the right caliper as well just to see what I see.

It's entirely too hot and muggy for me to sweat in the garage resetting the wheel in the forks so that experiment will have to wait until tomorrow.  A little suspense for Lather's suggestion.   

[VirginiaJim]

Well, make sure your forks are parallel while you're at it.  I can't believe the new caliper needs to be looked at.  It's something external to that.  It has to be.

[Tactical_Mik]

Ok so it's not Saturday....

I checks wheel alignment and all is fine there.  Was going to take the brake lines apart but thought I would clean/hone rotors again first.  Got that done and decided while there I would check TIR.  I am at .022    I stopped and reassembled, called a shop and will get in tomorrow to have them confirm and order me some waranteed rotor(s).  Being that far out of spec may likely be my only issue.  Will find out after a couple of weeks when I get them replaced.  Here is a pic (not great) with gypsum on the rotor except for the "high" spot.  Not real easy to see but.....

[B.D.F.]

Wow, that would be visible to the naked eye. From some distance away.... 

Yep, that is probably your problem- the rotor is moving sideways far enough to bump into the pad on either side as it rotates.

Brian

Ok so it's not Saturday....

I checks wheel alignment and all is fine there.  Was going to take the brake lines apart but thought I would clean/hone rotors again first.  Got that done and decided while there I would check TIR.  I am at .022    I stopped and reassembled, called a shop and will get in tomorrow to have them confirm and order me some waranteed rotor(s).  Being that far out of spec may likely be my only issue.  Will find out after a couple of weeks when I get them replaced.  Here is a pic (not great) with gypsum on the rotor except for the "high" spot.  Not real easy to see but.....

[VirginiaJim]

I think I mentioned the rotor ploy a few posts back....let me check.....yes I did.     That would be great if that's it after all the OP has gone through.

[B.D.F.]

Yeah, and it was me who said a rotor cannot cause dragging brakes. That'll teach me to speak in absolutes. OK, how about a rotor running just a little straighter than a dog's hind leg cannot cause brake drag? Or, a rotor that a blind man straightened with a sledgehammer cannot cause dragging brakes?



Brian

I think I mentioned the rotor ploy a few posts back....let me check.....yes I did.     That would be great if that's it after all the OP has gone through.

[Tactical_Mik]

My TIR was (February) in spec at 0.007.  Since I have only put on about 2000 miles I never gave a thought to checking it again.  I could be wrong but I believe that the HUGE warp in the rotor is causing the pads to cavitate wildly.  But again, I could be wrong. 

In a few weeks, hopefully less, when I get a rotor or two on there I'll go back to make sure I don't have a pressure issue but I highly doubt it.  This should end my epic brake dragging saga.  Now I need to find something else wrong that I can misdiagnose. 

[Fretka]

A coupla things come to mind here, semi-floating rotor buttons tend to become non-floating pretty quickly! Causing the rotor to lock into a position that most likely ain't good. Thus your run-out.

Also calipers need to be positioned so the rotor runs through the caliper casting pretty close to the center of the casting. Otherwise you get a rotor that could be shaving the caliper at worst or just off-center so much that the pistons on one side are too far out of their bores (extended) while the other side is barely moving at all. Go look straight at the caliper from the front of the bike looking back and see if the rotor is shifted to one side or the other. Guarantee that just about all the bikes on this board will be off somewhat! This is a function of where the pinch/axle bolts are holding the bottom of the fork tubes, all it takes it one tip over or a wheel change where the mech did not bother to center the fork legs on the axle.

So.... lube the snot out of the carrier buttons and work them free with your hands, thus making them semi-floating again (very important).
Next... check that the rotor/wheel assy is centered in the caliper casting as above. This can be done by releasing the pressure in the hydraulic/brake system, loosening all the triple clamp bolts slightly as well as the axle and pinch bolts and re-tighten (using correct torque) everything so as to end up with a triple clamp > forks > axle > caliper/rotor alignment.

Fretka