2010 FXSTC brake questions

[TheOriginalEasyrider]

I hope this doesn't come off as abrasive but I've had mixed results when posting on various forums. There are a few VERY good Harley wrenches on here and I'm hoping one or more of them chime in. What I need is the feedback and advice of someone who knows a lot more about TC softtail brake systems than I do. If that's not you and you'd like to offer your opinions please so-state that in your preface. Also, I am not all that interested in red herring thoughts. What I'm encountering is most likely something fairly simple and in all likelihood someone with a deeper understanding of this stuff will quickly set me on the path to success.

The project was to look into what appears to be a dragging rear brake issue although the wheel does turn freely. There is just zero (less than .0008", which is the smallest feeler gauge I have) clearance between the pad and the rotor).

Flushed the brake fluid and installed a speed bleeder to make that chore easier moving forward.

See attached picture. As you can see, the brake pad is right up against the rotor even though the bike has been sitting for a couple of days. The brake pad(s) are not compressing the rotor... just up snug next to it. This is a two piston oem caliper.

When I removed the bleeder, zero brake fluid came out. This tells me that there is no "residual" pressure coming from the master cylinder or the brake line. That whole "residual pressure" opinion is a fairy tale I see posted often. There is no such thing as "residual pressure" in any properly operating Harley brake system that I am aware of. Red herring #1, right?

It also tells me that the supposed design of the piston seals is not "sucking" the pistons back in to the bore according to popular folklore. This design claim always struck me as sketchy and is probably red herring #2.

I'm not even sure this (pads snugged up to the rotor) is a problem per se. HD brakes are not the greatest and this two piston design was obviously done on the cheap. I'm only looking into this because this is my third set of pads in only 22k miles. I typically get twice that mileage on a set of pads. First two were OEM. Currently has EBC sintered pads installed. Some brake dust is evident but nothing compared to what I was getting with the oem pads. The idiots at the stealership claimed that the brakes were wearing out because I was braking incorrectly. Anything to avoid doing warranty repair on clearly defective or improperly installed parts right?

I also had an issue where the rear brake was pretty anemic. The brake fluid looked ok... a little brown but not concerningly so. Never been flushed. Just flushing the fluid gave me a MUCH firmer pedal. The rear brake does stop a LOT better now.

I'm sure the brake slider pin and clip has never been replaced although the service manual says to do this. Reasonably confident that the caliper pistons have never been cleaned which is what you get when you pay someone else to do the work for you.

Since the bike stops pretty well now and the pads won't need to be replaced until I'm probably long in the ground I will probably not be tearing into this for a while. But I would value knowledgeable opinions so I can start planning my next move. I probably have one more season left on the rear tire and when I have it changed I am going to put on a much better aftermarket rotor.

Fact-based opinions on what sort of rotor (floating or not) and best vendor/model/value would be welcome. I don't race this thing or brake hard so I just need a much better rotor, not the best rotor on the planet. There's no money tree growing out back right?
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MORE IMPORTANT AND NOW PRESSING ISSUE: So while I was in there I figured I might as well flush the front brake fluid too. Note to myself: never try to fix anything that isn't broken.

Removed the bleeder and was surprised that it drained every drop of brake fluid from the system! I suppose that's due to gravity but when I removed the rear bleeder not a drop came out.

Installed the speed bleeder and was never able to get any lever pressure. My bike supposedly takes the same bleeder part number in both calipers. After screwing with this for a half hour I re-installed the oem bleeder and had a VERY difficult time getting any pressure on the lever.

So any thoughts on why this was such a trial would be welcome. Yes, I kept the master cylinder full and didn't let any air in from the bleeder end. No, I didn't try to reverse bleed the line figuring that gravity might not be on my side again. No MyTvac in play although I have never needed one in the past.

A LOT of air burping up and out of the master cylinder with the bleeder closed just working the lever. After a LOT of work I finally got my brake back but nowhere near what it was prior to doing this "repair".

Here's where I am: Brake lever has 1 1/2" throw from disengaged to pads locking against the rotor. Used to be around half that much travel.

The brake is not "soft". I can hold the lever in tightly and it stays right there. There does not seem to be any air in the line.

Used to be you could see a significant gap between the pads and the rotor when sitting idle. Now there appears to be very little gap. This seems counter-intuitive to me. If anything, if the pads are right up against the rotor it should take less lever to fully lock the brake right?

As soon as I compress the brake lever the pad starts moving. Again this seems counter intuitive to me. If the pad is closer to the rotor than it was before and if the pad starts moving as soon as you actuate the lever why does it take almost the full throw of the lever to the grip to completely lock up the rotor?

My dimwit brain would assume this problem is being caused by brake pads that are worn down but they are fine. Like new, really. Plus, the front brake worked perfect prior to me monkeying with it.

So I'm feeling pretty stupid here and once again, I am clearly not a gifted mechanic otherwise I wouldn't need help with this pretty primitive design brake system. I'm hoping some really smart fellow will say "look dummy... you forgot to do x,y,z."

Thanks in advance.

 

[TheOriginalEasyrider]

I did a lot of research on the front brake issue and came across a thread that talked about wrapping a zip tie around the brake lever and compressing it overnight. Fixed it! I now have a firm, light to the touch front brake again!

I know squat about hydraulics so I don't really understand how compressing the master cylinder forces air bubbles to the top when they can't find their way to the top over time due to the influence of gravity. Guess I need to find a hydraulics 101 course on the Internet.

I'm still interested in feedback on why the brake pads (now the front as well as the rear) don't retract more when the hydraulic brake pressure is released. I'm also puzzled why the front brake system immediately and completely drained the second I removed the bleeder valve. The bleeder is higher than the banjo bolt joint and the flow is upward in a U. This is basic sink drain technology. Wondering if I kept the master cylinder cover on when I removed the bleeder if that would have kept the brake fluid from gushing out. Again, hearing from someone who is a wizard with Harley brake systems would be a Godsend.

And just general feedback on Harley brake systems and useful upgrades in general. I do plan to slap on a much better rotor and will probably upgrade the brake lines thanks to a great suggestion by Dolt. The front brake is fine now and I mostly just use it to hold the bike when stopped on a grade. Advice on rotors (floating or not and best vendors) based on your actual experience is most welcome.

My OP is painfully long and detailed but I'd still be interested in feedback so that I can plan a strategy for upgrading the stopping power of this Harley as a winter project.

 

[herb King]

I will try to make my reply short and simple. The clearance between the pads and rotor is minimal, almost appear to be no clearance. This is normal and designed this way on all disc brakes to minimize the amount of fluid it takes to clamp the pads agains the rotor and minimizing lever travel. Most bikes do not have a residual check valve like cars have thus there is no "residual" pressure in the line or caliper unless there is a problem with the system. This also is the reason it is so hard to bleed all of the air out of the system as the fluid has the tendency to move back and forth without driving the air to the bleeder where it can be purged. Most people use a vacuum tool to purge the air from the system by hooking it to the bleeder and pulling vacuum until only fluid is seen. The strap on the front brake lever trick works because it lets the brake piston take a set against the caliper piston seals which also act as a kind of return spring by distorting as the piston moves out slightly pulling the piston back slightly when released. Most time brakes unless they are ABS are pretty simple.

 

[biscuit]

First up- all brake pads drag against their attendant disc. There are NO springs to retract them.And the pistons that push ‘em out aren’t connected to them.
NOT a heavy drag: but a drag nonetheless.
I’ve noticed not all bikes drag the same. Certainly, all my bikes are different.

They work( the brakes) by applying hydraulic pressure via pistons against the pads- thus forcing them hard onto the disc.
When you release the lever, the pistons retract and the pressure they applied against the pad(s) also releases and the pad sort of eases or slides back to its original position. Just rubbing against the disc.
The issues arise due to a couple of things. Firstly, if your brake pads are binding against the pins that hold them in place, then they won’t slide in and out as easily as they ought to. End result- binding. Clean the pins and LIGHTLY grease with copper grease. LIGHTLY.
Secondly, you need to remove the callipers from the forks and CLEAN the pistons that project out from the rubber boot or seal.
The pistons get covered in brake dust, road crud( dirt, salt, road grime etc)and this really affects the way they retract back into the calliper when the hydraulic pressure is released by the lever or brake pedal being released.

Do NOT squeeze them out too far as without the disc to stop them, they WILL just pop out. Wipe clean the rubber boots as well.
Thirdly, ensure that the area of the callipers where the actual brake pads fit onto is also clean. Wipe that flat area clean and also the ‘wings’ of the brake pads. Don’t grease- just wipe clean.

Also, OEM rubber brake lines expand under pressure. The older they are, the more expansion they have in them and they become weaker. Obviously, this expansion creates ‘applied pressure’ losses by the time the pistons are forced out to push pads against discs.
Fitting braided steel brake lines is a really good investment in braking performance.
I fitted braided lines to my Harley some time back; and my Sports bikes came with braided lines as standard.

That Zip Tie trick works wonders on a recalcitrant brake system. By squeezing the lever/pedal closed and holding it closed; you’re placing the entire system under pressure and HOLDING IT THERE.
This “squeezes” and pressurises the entire system and forces any trapped air to rise and exit the system into the air above your brake fluid level.( exactly the way that the “Bends” affect Humans with air in the bloodstream under pressure).
The air gap above your fluid is inconsequential- it’s NOT In the fluid itself. As you probably know, liquids are incompressible. Whatever force you apply at one end is transmitted through the fluid- with no loss of force-to the other end.
The problem arises when you have air trapped in your system- THAT air compresses and reduces any hydrostatic force that your lever applied. Doesn’t take much air to reduce the effectiveness.
Hence that squishy lever feel.