Rear Brake Pad Drag - Normal? W/ Video

[Oldschool1]

JfHEATH, thanks for the excellent info and another level of depth to consider.

Discussing with Igofar I will remove the element of uncertainty with the EBS pads that are notorious for issues, and ordered a new SMC, as that is suspect as well but not confirmed ( if does act like it is not bleeding off the pressure after front brake is release completely, by manual test).

Larry was kind enough to put a "buy list" together to ensure I got all the needed odds and ends..... thank you Larry (again!).

Its about 2 weeks for parts to arrive so this thread may go into hibernation for a while......

Next steps:
1. HONDA pads replace EBC pads, then test.
2. SMC. replacement - then test.

If that doesnt get it, the only thing I can think after this would be new piston seals and dust seals.

(P.S. I did have a Nighthawk 650 that I bought after it had sat for 10 yrs, at that time it was 22 yrs old, brakes locked up after one squeeze of brakes while pushing into the garage. Problem was the seals still sealed but "crud" had accumulated underneath the seal causing excess squeeze on the piston. HYDRAULICALLY you could push them out with the pedal but they were stuck in that position - it took everything you had to get the bike to move on flat
pavement while pushing - remembering clearly!

I changed the seals and it was night and day different. The old seals/dust rings were square cross section rubber that had lost all of the elasticity (22 YRS OLD at that time). When I put the new seals in the pistons extended easily and retracted probably a good 0,010" after release of lever ( going from memory, but visually it was very apparent) and i dont recall any noise from contact of pads with the disc while toting the wheels! Just wondering if anyone has changed these seales out on a early ST and the observations and results?)

 

[Igofar]

I have found hard/stiff seals from bikes that have sat a long time to cause similar issues, as well as similar issues from folks who use spray can brake cleaner(s) causing the seals to swell and stick.
Then again, its what I find behind the pistons that scare me
This came off a bike that was flowing clear brake fluid while flushing/bleeding brakes.
You never know what lurks beneath the surface till you dive in

 

[Larry Fine]

You never know what lurks beneath the surface till you dive in

The Shadow knows.

 

[Catmandu2]

Then again, its what I find behind the pistons that scare me

what worries me is, what happens when this gunk migrates to the fine valving in the smc,, the proportional valve,, m/c's,,, etc. Guess that is the reason for the frequent flushing. This gunk forms as the result of age and heat exposure,,, me thinks,,, cheers,, CAt'

 

[jfheath]

I am surprised that gunk was lurking behind only the centre piston. Of the three on the STs, I had always imagined the rear caliper forward piston to be the most likely culprit - it never gets any flow of fresh fluid unless you deliberately flush out the old with new fluid, by see-sawing the pistons. The problem is that the inlet port and the bleed valve are both on the rearmost piston, leaving the forward piston out of the flow.

@Catmandu2 - Age is certainly an issue, but for brake fluid, 2 years is aged enough. Anything more I'd be wanting to 'dive in'. Actually I wouldn't want to. I hate brake fluid. Nasty stuff. But needs must.

Does the fluid decay like that with heat ? The pistons are in direct contact with one of the hottest bits of metal on the bike. I'm asking because I don't know. I sort of assumed that the fluid was capable of coping with normal high operating temperatures.

What is it that modern cars use in their brake systems ? They don't seem to require brake fluid flushing and replacement. I never touch the car for maintenance - I don't have the space or equipment.

 

[Oldschool1]

Still waiting on parts; i.e. no updates for a while. Slow shipping, best case is this weekend .

 

[Chris09]

brake fluid is hygroscopic, [I guess] and I know you know this; it has an affinity for moisture, hence recommendations [as you have also espoused] to just get rid of it all after a couple years; I just bought a twenty year old bike well kept, [yeah, right] with orange brake and clutch fluid; I guess we all look like we just fell off turnip trucks; does anything ever change,

 

[Chris09]

dealer serviced, complete with [worthless] reciepts

 

[Oldschool1]

Ok! Well parts "FINALLY" arrived and this weekend I made some good "pro-gress".

FIRST - I swapped the EBC pads for the new Honda pads to rule out the pads causing the drag - no bueno - still exactly the same front and rear wheel.

1. Removed calipers (all 3) to replace seals (why not just do it all and be certain!).

- No gunk or traces of any fluid slime or not clean in any bore/piston.​

- Hydraulic Seals and dust seals all felt soft pliable, probably not detectable difference from the new seals (Honda of course)​

- Pistons (all 9) were all spectacular condition, two of the rear caliper had very minor stubborn deposits the scraped of with a credit card edge. Pistons literally looked new​

- No corrosion or crud buildup in seal grooves - I was expecting to find something here - no cigar! Scraped with credit card sharp edge - nothing.​

-One outer piston on the left front caliper before disassembly was definitely stiffer than the rest to push in by hand - still could.lush in with thumb but it was just stiffer - again no evidence of anything wrong after inspection - no significant buildup corrosion that could be felt on the piston or bore...... leaves one to wonder....?​

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2. SMC: this operated fine regarding piston, though after comparing to the new one - the motion is definitely not as smooth and easy to move the plunger.​

- No degrees or crud/gunk found at strainer screw.​

- Found some fluid boogers (the green-brown alien looking kind or regurgitated brustle sprouts!) in the port the return line fluid bolt screws into.​

-Cleaned out all oil bolts - just to make sure they are clean.​

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3. Bleaeder screws. Removed and put 3-4 wraps of teflon tape over these - perfect coverage of threads only. These feel nice and snug to prevent ingestion of air during bleeding ( THX John and Larry!).​

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4. Bleed breaks - now that it is all back together.​

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Wow - that is a long process and probably I could have done it in less than 3 repeats. IT took some serious time to get all the Air or what i was able to get out of the rear SMS circuit. ( I THINK IT WAS 3 HOURS OF BIKE BLEEDING JUDO) - well I'm pretty fast now!​

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I did get a good 10-15 degrees tilt on the SMS per manual during this.


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I did use a motion pro bleeder valve to prevent backflow.

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RESULTS​

FOOT PEDAL REAR MC: Well the rear pedal feels pretty stiff it's on squeeze down over night, no more visible bubbles coming through for any rear pedal or SMC pumping - entire circuit.​

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FRONT MC: this is still squishy definitely not as hard as it was before.​

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Couldn't get any more bubbles coming out. Pumped pretty fast ( I should say squeezing on the fluid pressure stroke) hoping fluid velocity would get a good stream of bubbles - certainly it pulled some out. It's on squeeze down over night - will so how it is in the morning. Thought maybe I would take it for a short ride tomorrow see if that dis-lodges a bubble (ok I'm reaching here). I did bang on the calipers and the brake linens with a screwdriver handle.....). Any tricks to bleeding the front SMS circuit?​

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OK NOW WHAT WAS THE GOAL OF THIS AGAIN? Oh yea it was that peske brake drag that started all this on the rear and front wheel!​

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Rear wheel - Ok well preliminary results.... the rear caliper drag seemed noticeably less than previous - that's good. Still can't pronounce it healthily u til I go for a ride tomorrow.​

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Front wheel - same seems noticeably better - it's not as free as with no brake pads - but significantly better than previous- a ride and temp test will tell the truth.​

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THAT'S IT FOR NOW - MORE TOMORROW!​

P.S. Ive really absorbed a lot of wisdom and knowledge from all my discussions with Larry. As I was doing this today what Larry said a few weeks back as he walked me through all this on the phone came into play - I knew what to do and how to do it. Your help really made a difference - Thanks Larry.​

AND thanks John Heath for your knowledge as well…… lots of great info, diagrams, tips, and help…. What would we do without this forum and your gracious help!​

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[jfheath]

Good write-up. Thank you for the feedback.

Pumping the brake lever faster when the bleed valve is open isn't going to help when there is air trapped in the line.
This is because the release of the lever sucks it back again to a certain extent. A non return bleed valve helps, but isn't foolproof. A better technique is to pump the lever hard and rapidly a few times with the bleed valve closed, hold the lever in on the last pump and open the bleed valve. The built up pressure will force the fluid out at the valve. Close the bleed valve before the fluid stops flowing out. Repeat.

If the lever feels squishy still, then there is still air in there. There are likely to be bubbles trapped at places where there is a joint. Tapping the joints helps to dislodge them. A commonly reported location, although I have never had it, is in the banjo bolt at the lever. You can bleed that by cracking open the bolt a tad and gently pump the lever. Turning the bar lock to lock also helps (make sure your reservoir is covered), and tap the joint to dislodge any bubbles. Retighten.

I don't like doing this because the washer is deformed to occupy all of the imperfections in the mating surfaces at the banjo bolt, So when I perform a complete refill, I fit new washers all round and don't tighten them to full torque. Then once I have fluid in, I can bleed the joint, and then fully torque them so that the new washer is squashed into shape.

when done, pump up the lever a few times and keep it held in overnight.

Tips on the SMS circuit. Do you mean the SMC circuit ? Not sure as you had been talking about the front brake lever, and you said that the pedal feels solid. But if you do mean the SMC circuit, there are two 'n' shaped loops of flexible hose between the front of the frame and the top of the fork legs - to allow for the movement of the steering. One is for the fluid from the braked pedal to the frint centre pistons. One is for the fluid from the SMC to the rear outer pistons. Both are air traps and need to be flexed when bleeding at the front centre piston and at the PCV bleed valve. Its difficult to tell which is which, so I flex both.

Read this if you haven't already, and watch the video of the behaviour of water and ink in a clear tube with loops and joints.

Article [13] - ST1300 Maintenance - Getting all the air out of the brake system | ST1300 Articles

A detailed look at the process of getting the air out of the Honda ST1300 brake lines. A sequence of diagrams of the brake circuits, colour coded to show which parts of the system are being accessed when each bleed valve is opened and explanations of where the trouble spots are. These are just...

www.st-owners.com

The new pads will drag lightly on the disk surface for a while until they are bedded in.

Read through 'avoiding the pitfalls' if you haven't already, before you go out on the road. See if there is anything that you have missed.

Article [13] - ST1300 - Brake Maintenance - Avoiding the Pitfalls | ST1300 Articles

A close hands-on look at the Honda ST1300 braking system. These are personal observations about the things that can go wrong, why they go wrong and what can be done to keep things working sweetly. Updated April 2020 and to address more recent observations, to include information about the SMC...

www.st-owners.com

 

[Oldschool1]

Getting back to this - I had some events that disrupted progress.

So I still for sure have more break drag on front than normal.

Since my last post I have verified the Front MC return port is not plugged and a jet of fluid flows through the small return hole with the clip on shield removed and the clip shield was installed correct orientation. And blade the Front brakes again , zero bubbles good and hard on squeezing front lever.

If I push on calipers to squeeze in piston both sides I can get probably 8 rotations of the wheel easily.

Applying only the Front brake handle (outer pistons) and then relaxing will take tomrotaion down to 3/4 rotaion.

Brake drag do to new bars still seating? I've been for 2 rides now probably 20 miles and activated front brakes through some good long stops ( progressively) I don't we any change in brake drag (I think this is beyond new pad seating).

Pad temp, not touching brakes at all on a 55F day for a two mile ride, both of the front discs are warmer than the rear disc and warm to touch - guessing about 105F by feel and the right disc. Prior to ever touching the Front brakes the Front were cool to touch - expected. The right is probably 5F warmer than the left (SMC side).

Here's a video. First is residual drag after returning and not touching brakes for last 2 miles, half way thru I push piston back in on right caliper and respond- noticeable better but not great.

Here's a video of wheel spin with both calipers manually squeezed to push piston back:

I could never have imagined this saga, really it's perplexing....beyond belief. Well try,try,try......try again!

 

[jfheath]

Front brake drag, new pads is 'normal' - ish. They scrape a bit - tsshhhh - more than when they are bedded in - ie the pad surface worn down to be parallel to the disc surface. But if the pads are catching then the catching disc will nudge them back into the calipers within s relatively short distance. If you come to a stop without touching the brakes for 2 miles then I would expect them to be free.

So its time to look at what else could be causing the problem.

Some suggestions - things to look at, because I cannot diagnose it from here !

1. The rear pads come with a hite heat shield sandiched between the bronze backing plate of the disc pads and the metal, anti-squeal, chromed plate. This is to prevent the heat from the brake disc getting to the pistons and transferring it to the fluid. The front brake pads don't have these - so if you have been tempted to fit old ones to the front pads - well, there isn't enough room for them, and new pads will drag. The front pads don't need a heat shield - they get plenty of cold are blasted straight onto them. The rears have the exhaust and the heat of the engine to contend with.

2. The pad springs - check out the 'Avoiding the pitfall' link I posted up above. Most of it talks about the rear caliper, but on your 2005, the front caliper is a very similar design to the rear. Check in particular, the orientation of the pad spring. The wider strip goes on the side of the pistons. Also check the tags on the narrow strip. They must not be bent and the pads should fit on the bracket side of the tags. When inserting the pad, push inner pad in last, part way. Then pull the claiper across so the the inner pad is squeezed between the disk and the inside are of the caliper. Then rotate the wheel so that the pad is guided in by the turning disc. That will ensure that the pad doesn't get on the wrong side of the little tag. Finally check that the tab end of the pad is properly seated in the retaining clip.

3. The retaining clip for the rear pad has a ridge in it to fit the noth in the backing plate's tab. The front does not. If you have fitted the rear retaining clip to the front caliper braket, the pads cannot move. Its an easy mistake to make, and you wouldn't notice unless you know to look for it.

4. Check that your front wheel is installed properly. The left hand side caliper psoition relies on this for the brakes to function properly.

(2) Article [13] - ST1300 - Maintenance - Front & Rear Wheel Install and Front Axle Animation | ST1300 Articles | ST-Owners.com

Same article - check that the distance collars - one on each end of the axle - are correctly located and are the correct way round.

5. And someone will probably chime in with checking the fork alignment so that the axle pushes through the holes easily.

6. Just remembered. On a 2005, the rear pads backing plate is the same size as the fronts. But new, the rear pad friction material is thicker than that on the front. Make sure that you haven't mixed them. I don't think that there is enough room to fit new rears in the front, but one of each ? Maybe. I don't know. Worth mentioning though. Easy check rear pads have alittle rectangular notch at the tabe end - the end opposite the hole for the pad pin. Front pads do not.

7 Check your pad pins are smooth and clean.

8. Don't forget that the front brakes are also applied when the rear pedal is pressed. Which piston is not releasing ? The rear pedal applies the front centre pistons on both sides. The left one immediately, the right one when the pedal is pressed harder. Strips of paper slipped between pad and piston may help to identify.

 

[OldMcClelland]

Why do the overnight hold on the brake lever after bleeding? What does this accomplish?

 

[Kevcules]

Why do the overnight hold on the brake lever after bleeding? What does this accomplish?

I've wondered that also, because it does seem to work. My thought is that air bubbles, under constant pressure, will be forced to migrate "up"

 

[jfheath]

The air bubbles attach themselves to the sides of the brake lines. The surface tension of the liquid enables them to stick. Putting the fluid under pressure squeezes the air bubbles. Less surface area, therefore less surface tension. They are still air bubbles, but smaller and become detached from the sides and float up.

I've never seen this as an explanation anywhere, but it is the best I can come up with. It works for me.

It doesn't explain why the brakes are dragging though. That's a separate issue.

 

[Al st1100]

The air bubbles attach themselves to the sides of the brake lines. The surface tension of the liquid enables them to stick. Putting the fluid under pressure squeezes the air bubbles. Less surface area, therefore less surface tension. They are still air bubbles, but smaller and become detached from the sides and float up.

I've never seen this as an explanation anywhere, but it is the best I can come up with. It works for me.

It doesn't explain why the brakes are dragging though. That's a separate issue.

rear brake hose to caliper goes down from caliper to swingarm. So we think air bubbles go down first then up ? Doesn't make much sense.

 

[jfheath]

.... So we think air bubbles go down first then up ? Doesn't make much sense.

No, I don't think that ! - As I said, the bubbles float up. Some of the bubbles will reach the master cylinder where they will escape through the compensation port when the lever is released.

When you hold the lever back, you already have a pretty good 'feel' at the lever. You have already got rid of the trapped large bubbles. What is likely to remain are the tiny bubbles attached to the sides of the brake lines. I don't think that this action gets rid of all of those tiny bubbles. I think that it gets rid of some - which will definitely improve the feel. Other tiny bubbles will float up and get trapped together as a larger bubble at the highest point - which I suspect will be easier to flush out in the normal way.

I've read an explanation that is often repeated, that the pressure dissolves the air into the fluid. That doesn't make much sense to me. Air can be dissolved in fluids under pressure - think fizzy drinks. But as soon as you release the pressure, or you start to repeatedly apply the brakes it comes out of solution. ​

What is your explanation for why this works ?

 

[oude geit]

Air should rise to the top because the fluid pressure decreases with elevation.....so the fluid pressure at the lower point is greater than the fluid pressure in the highest point....

 

[Igofar]

Obviously we have no scuba divers on the forum

 

[Larry Fine]

Obviously we have no scuba divers on the forum

I happen to be a certified diver, but it's been years, and I would take a refresher course before diving again.

Are you referring to Boyle?