Rear Brake Pad Drag - Normal? W/ Video

Oldschool1

Joined
Oct 19, 2009
Messages
196
Location
Nor Cal
Bike
2005 ST1300A
I really wish there was a local ST community nearby for comparisons - tough to know what is normal!

If you could take a look at the video - it would be great to know what you think about the level of drag.

One specific question I have is: should the pistons retract perhaps 0.010" or something small to eliminate drag on the rotor? Or maybe the brake caliper should have some wiggle to after the brakes are release (pistons retracted)?


Thx,

Paul

---------------------------------------------
Evaluates rear disc drag: first for the condition of the center piston in the rear caliper with only the center piston extended to the brake pads and then 2) the additional drag after.the outer rear caliper pistons have been applied after manual compression of the SMC and then relaxing the SMC.

Service performed prior to this:
1. Brake fluid flush by PO. no date if correct sequence was followed on the bleed.
2. Current owner removed caliper cleaned pins, smir of silicone grease on sliding pins (all mint condition) on reassembly.
3. Pads installed in correct position for all clip detents (holds inner pad against inner caliper half)
4. Pistons pushed out to max pad wear equivalent and cleaned with brake fluid ( shoe shine method). Pistons collapsed back into caliper - probably built pressure in SMC).
5. SMC pressure bled at rear caliper outer bleed screw while squeezing pistons- no air introduced.
6. No data to be confident there is not air in the system- I didn't do the bleed!

This 2005 ST1300 is new to me.

I originally paid attention to the rear wheel brake drag after removing the rear wheel to ensure splines were Moly 60 serviced, and questioned if the pads dragging noise after reassembly was - hmmm "normal"?????

Brake pads are original @ 19500 miles. After 100 miles of around town riding (post rear wheel RR) certainly there is brake dust on the rear wheel rim ( finger wipe).
 
I had noticeable brake drag, detectable both with rolling resistance and rotor heat. I replaced the smc,,, pads,,, lots of proper bleeding. All those things needed to be done,,, but after that work,, I still had the drag. Something was preventing the pistons from relaxing off the rotors far enough. Then,,, I polished all the pistons,,, in the bike. It made a big improvement,, and now I do a polish on every pad change. It worked for me,,, the method is described in prior posts,, cheers, CAt'
 
Call Larry.

Just a comment on your first post. It isn't normally possible to activate only the rear centre piston on the ST1300.

The often quoted reason for rear wheel brake drag is the blockage of the tiny compensation port in the SMC - either by crud in the hole itself, or because the SMC piston is blocked from returning fully, and therefore failing to move back behind the tiny port. Either that or mechanical issues at the rear caliper and bracket.

But you said that after operating the rear centre piston there was some drag and after operating the SMC there was more. (The SMC operates just the two outer pistons). But in the garage, the rear pedal operates all three pistons in the rear caliper, so what you observed should not have been the case.

Explanation : In the garage, the fluid pressure from the rear brake pedal is also transferred through the forward lines to the front centre pistons, and through the SMC (passing from behind the SMC primary seal - which yields easily to pressure from behind - to the rear outer pistons. This is why you can bleed the outer pistons using the brake pedal. You felt additional drag at the rear outer pistons when using the SMC after using the brake pedal to operate the rear centre piston. But it should have operated all 3 pistons. ​

This might suggest that there is air in the line from the rear pedal going forward - preventing pressure reaching the rear outer pistons (which wouldn't cause drag).

OR. ... it might suggest a blockage in the line between the master cylinder and the front left centre piston / SMC - which could cause drag because that is the line through which excess fluid pressure escapes to the rear master cylinder. This latter scenario could be easily eliminated by bleeding the front left centre piston using brake pedal pressure.

That is easy to investigate and eliminate or sort out. After that it is down to Larry, SMC and rear caliper issues.
 
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I've checked the free running on front & back wheels and they both make a similar noise to yours.
They aren't actually gripping the discs so I wouldn't be overly concerned.
Probably better to check by going for a short ride and try coasting to a stop then see if any of the discs are hot...
 
It is my understanding that the o-rings in the calipers are square for a reason. When the brake pedal or hand grip is activated, hydraulic pressure pushes the pistons out of the calipers and the square cross section ring is distorted slightly. When you let up on the brake, the o-ring pulls the piston back into the caliper a few thousandths and away from the disc. How many thous? I don't know. A quick check via google showed acceptable runout of 0.003 to 0.009" so any retraction of the pistons greater than that would provide clearance.

A guess would be normal movement of the brake parts will push the pads away from the discs once the pistons retract.
 
Thx for all the well thought out replies.

I did do the ride and touch brake calipers. The rear would be warmer than the front after coasting to a stop - probably 20 F difference - front rotors feel cool and back rotor warm on a 60F day.

Still because there is an added resistance after SMC - I would like to see that eliminated. I believe my ST1100 did not have this much brake drag.

I'm going to bleed the front left center piston to rule that out.

My guess is I'll be talking to Larry

- Paul
 
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I'm on call 14 this morning, I'll call you in a few minutes.
:WCP1:
 
Just for info, and probably to Larry's horror - my rear brake ALWAYS drags like yours after fitting new pads, and also when I back it out if the garage. By the time I've ridden it and applied the brakes a couple of times they are perfect. It's to do with a little settling in in the first case and fine surface rusting in the second. They are as free as anything when I put it away.
 
Oldschool1 said:
I really wish there was a local ST community nearby for comparisons - tough to know what is normal!

If you could take a look at the video - it would be great to know what you think about the level of drag.

One specific question I have is: should the pistons retract perhaps 0.010" or something small to eliminate drag on the rotor? Or maybe the brake caliper should have some wiggle to after the brakes are release (pistons retracted)?


Thx,

Paul

---------------------------------------------
Evaluates rear disc drag: first for the condition of the center piston in the rear caliper with only the center piston extended to the brake pads and then 2) the additional drag after.the outer rear caliper pistons have been applied after manual compression of the SMC and then relaxing the SMC.

Service performed prior to this:
1. Brake fluid flush by PO. no date if correct sequence was followed on the bleed.
2. Current owner removed caliper cleaned pins, smir of silicone grease on sliding pins (all mint condition) on reassembly.
3. Pads installed in correct position for all clip detents (holds inner pad against inner caliper half)
4. Pistons pushed out to max pad wear equivalent and cleaned with brake fluid ( shoe shine method). Pistons collapsed back into caliper - probably built pressure in SMC).
5. SMC pressure bled at rear caliper outer bleed screw while squeezing pistons- no air introduced.
6. No data to be confident there is not air in the system- I didn't do the bleed!

This 2005 ST1300 is new to me.

I originally paid attention to the rear wheel brake drag after removing the rear wheel to ensure splines were Moly 60 serviced, and questioned if the pads dragging noise after reassembly was - hmmm "normal"?????

Brake pads are original @ 19500 miles. After 100 miles of around town riding (post rear wheel RR) certainly there is brake dust on the rear wheel rim ( finger wipe).
Click to expand...
My 2005 always acted the same way.
New SMC, polished caliper pistons, new pads, did multiple bleeding chasing air in the brake lines, all of that didn't change anything.
After 70K I didn't notice any concerning wear on the rotors (front too) and they are not overheating.
I dislike it, but it's maybe more annoying than a real mechanical issue and troubleshooting the brake system on the ST is like ghost hunting.
I would check if the drag is the same after driving the bike, if it is increasing that could mean that there is some air in the brake lines.
Good luck!
 
Yes. And sorry - good progress on the weekend until the work week hit...... ahhh the day job always gets in the way!!

Well First, I have to say Larry has been an imense help at walking me through the process in every bit of detail imaginable. I've learned so much on the way, more than ever expected and well beyond the brakes. Thank you Larry - that is very kind of you!!!

Details:
1. NOT Honda pads installed in rear, I didn't realize this.
2. Verified SMC does activate rear outside pistons as expected.
2.5 Verified SMC has full range of motion by opening the (pcv) proportional control valve and finding piston moves through the full range smoothly and repeatably.
3. Jury is still out on if small hole in SMC is clogged/partially clogged, because it's hard to verify, other than probably disassembly. So the idea here is to flush this really good in step 3 potentially removing a problem particle (if one is semi blocking it).
3.1 Verified rear caliper install bracket is firmly planted and in OEM condition.


NEXT STEPS
4. RIGHT NOW I'M going through the front calipers - to ensure they are in good health ( polish pistons, etc) in prep for bleeding.
5. After front caliper maintenance - will do 7 step bleed to be sure it's correct. Paying much attention to fluid flow in SMC.This will establish a baseline that all is in good health and no "air" in system.
6. Then assemble all back together and see the result to drag ( with existing aftermarket pads).
7. Then swap in the OEM Honda pads on rear and see if any impact from pads ( understanding that aftermarket pads may cause issues - I'd rather have the OEM anyway).

So it will probably take me to Saturday to complete this. Had to wait for a brake bleeder to make life easy...which just came.

Thanks all for te help on this and especially Larry for blessing me with more knowledge then I ever knew existed about these (truly amazing)

In the end if the drag hasn't changed and we know all is good with the brake system, this will still be an absolute success because without this much inspection on a new to you used bike you really can't be sure of condition on this critical system and ride with confidence. I hope everyone would devote their attention to do this when they obtain a new bike! Also it's important that people learn at least at this level about their bikes - no better way to learn!

P.S.

One thing I was thinking about is a standard to test to report wheel drag. So right now we all have our own spin method, some spin faster than others, and then we count rotations. This works for a general idea but it's a loose metrology. HOW MUCH drag is the norm, how much drag is definitely not acceptable.

Then there is the rear wheel drag without any brake drag - and this a function of oil drag viscosity bearings, etc. and influenced by the temperature.

What I will do to quantify a bit better with spin method is:

1. Squeeze calipers to seat piston to point of no pad contact then spin wheel - ( zero brake drag condition and most wheel rotation)
2. APPLY rear brake pedal - spin wheel
3. Hand activate SMC and ralease - spin wheel

At least this way we can see the contribution of brake drag relative to the wheel rotation drag caused by (everything other than brakes). This may be more telling and help us diagnose the condition of various bikes better.

Thoughts on this - ways to improve? (If we had a simple load scale to connect to the tire we could measure the load required to rotate the wheel at a given temperature with and w/o brake drag - still thinking on this one)
 
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Maybe just a small spring type scale to see how much force is required to initiate rotation after various brake activation sequences / manual rear wheel rotations. Be interesting to see if you could trend a problem or see how much variation occurs. From the first attempt last year when I performed the kick test I never achieved the range of rotation recommended so I've got some relaxed caliper / mechanical resistance. I have a sloped alley to my place and often I'll coast down and use only the foot brake then feel the temperature of the discs afterward.
 
Thank you @Oldschool1 . Excellent feedback.

There are all sorts of issues that could result in the wheel not spinning as much as you might hope. eg Inconsiderate bearing installation can result in drag. With pads fitted, you are never going to get the wheel to spin for longer than it will spin without them fitted.

You cannot really compare one person's rotation count with yours - although it is useful to have that information. There are too many variables. Just as an example, the viscosity of the oil in the final drive, or grease in the bearings - which will make a big difference to the number of revolutions. The viscosity will vary considerably with temperature. So here in Yorkshire, UK where 18C 64F is a promising Summer's day, behaviour could not expect to be compared with Australia, France, Spain, Southern USA.

The best tests are :
The one you carry out without brake pads compared to with brake pads fitted.
Also how it behaves when you check at the end of a ride coming to a stop without touching the brakes - then everything is clean, everything is warm and you have ridden so that the rotating disc has the opportunity to nudge the pistons away from it.

I've mentioned before that my rear brake will howl and squeal on some days when I back the bike out of the garage. It used to bother me, but it goes away often before I've wheeled it to the front of the house. It is largely due to the discs getting a light coating of rust since I put it away last - maybe it was wet, but it also happens as a result of condensation.

On the road, there are a few good indicators of serious or developing brake drag.

1. Level road, engine just keeping the bike at a steady speed. Pull in clutch lever. Bike should not immediately slow down. I do this every now and then when riding often if I feel that the bike is working hard - which it does into a headwind or if the road surface is rough tarmac or tar and chippings.
2. Ditto on slight downhill gradient. Bike may seem to speed up when clutch lever is pulled in if brakes are free.
3. Get brakes hot then ride without using brakes. Test temps a couple of minutes later. They should be cool again - or at least getting cooler.
 
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Update - on previous mentioned next steps that I completed this weekend.

NEXT STEPS
4. RIGHT NOW I'M going through the front calipers - to ensure they are in good health ( polish pistons, etc) in prep for bleeding.

Removed both left and right calipers, cleaned pistons they weren't bad at all to begin with, they we pushed in pretty far as they had EBS pads installed that are likely very close to new thickness! Calipers slid/floated nicely but I took the right side apart, really clean pins but cleaned and smeared with silicone grease (very sparingly) anyway. Clips all looked good and springs with detents in true form. Angle of SMS was probably 5 degrees rather than 15 degrees as this is every bit I could get with the steering locked full left and I was hesitant to swing that with front master open. Honda manual does specify 0-15 degrees, Just all I could get.

Reassembled right caliper to disc.

5. After front caliper maintenance - will do 7 step bleed to be sure it's correct. Paying much attention to fluid flow in SMC.This will establish a baseline that all is in good health and no "air" in system.

Bled system according to 7 step order and good writeup from JFHeath and tips from Larry. Not too much air came out at least by observstions. I didnt use a vacuum tool but did use a motion pro bleeder, can't imagine doing this w/o it! FLUID WAS all clear.

SMC/PVC#3: actuated SMC about 15 plunges alternating between foot pedal and SMC. If I tried to do SMC plunges back to back the SMC, chamber would not refill but if I used the pedal in between it backfilled.

Rear outer piston / SMS step 7: about 10 plunges with SMC alternating with foot pedal.

6. Then assemble all back together and see the result to drag ( with existing aftermarket pads).

PUT IT all back together, retorqued rear stopper bolt with axel loose to ensure correct order, and with rear brake applied by pedal when retorquing.

Applied brakes overnight and both pedal and front lever - were rock solid this morning.

7. Then swap in the OEM Honda pads on rear and see if any impact from pads ( understanding that aftermarket pads may cause issues - I'd rather have the OEM anyway).

I didn't do this yet because I'm getting too many variables to chase at one time, leads to guessing anomalies. Theory is I should be able to prove a correction and then replace with Honda pads.

RESULTs:
REAR: in garage results - definitely not imaginary was an improvement when applying brake pedal and SMC manually - MUCH QUIETER LIKE DRAG CONTACT WAS REDUCED - multiple repeats ( on center stand)

FRONT: Actually INCREASED in brake drag, very noticeable and caused by application of front brake lever. I'm baffled, was very careful of assembling pads relative to spring tilt (applied both to springs simutaleously - # of fingers challenged too John!), and attention to keep pad correct relative to spring detents. Clearly I impacted something and/or assembly didn't really achieve intent- and it is VERY difficult it inspect visually - with wheel in the way. OK THE PADS are not HONDA but I would not expect an increase in rotation drag. It appears each caliper contributes. The drag is actually grater than the rear (before the ride - discussed next). Total runout of each disc (front and rear) is 0.003" - actually that is amazing for that construction type on the front!

TEST Ride 2 miles: the goal of this was to see if the front pads would miraculously seat and remedie the added drag condition (I think I read something soon that).

Front discs were slightly warm - no brake applied ( confirms drag is higher because previous on a 40 degree day like today they would have been very cool or cold really). REAR disc was slightly warm, not hot but warmer than I expected

Both of these were on 5 or so ride and feel scenarios - trend is repeatable.

Return to garage, put bike on stand, REAR WHEEL HAS MORE DRAG AFTER THE RIDE THAN BEFORE AND MORE DRAG THAN BEFORE THIS WEKENDS WORK. So the ride increased the resistance compared to in garage pedal and manual application of SMC. It's repeatable that the SMC application does increase the drag after the SMC is released. My theory is the ride and and a good brake application of the front caused a higher hydraulic pressure via SMC, perhaps it will not release pressure? Or out piston don't retract from dust seals being stiff vs acting as a spring?

Ok time for a day of rest on this - the brain cells need to refresh and regroup!

Ok the highlight of the weekend is my new JIS screwdriver. Note - that is now a horizontal cantilever beam as it fits the screw like nothing else!

IMG_20221216_114802285.jpg
 
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Good result regarding the rear pads.

Front pad spring. The front calipers and pad springs are different for the pre 2008 models. I think you may have been reading the procedure for the 2008 and later models. I'll explain later.

For your 2005 model there is no such issue. I (still) always put my outer pad first, locate the tab end correctly in the chromed retainer clip ( no ridge in the front retainer clip, otherwise brakes will drag), press the pad pin end up against the spring and hold it in place with the partially inserted pad pin. Then put in the inside pad.

But the problem with the inside pad is that the spring is very narrow, and the pad MUST slide between the caliper body and those two tiny tags on the spring. Otherwise the brakes will drag. To make sure that this happens, I slide in the inner pad part way, then grab the caliper body and pull it towards me, outwards, so that the caliper is trapping the pad against the disc, then slide in the pad into the retainer clip at the far end, pull the caliper aagain to trap the pad, press the pad against the spring and push in the pad pin.

This makes absolutely sure that the inner pad is located behind those tags.

Then check that both pads are properly seated in the retainer clip. You can see the inside one through the spokes. At some point I will secure the pad pin, but usually leave it until later.

The other thing to check is that your front wheel is installed correctly. If it isn't then that will cause the brakes to drag. The quick check is the axle end should be flush with the hole in the fork leg. But the full proper check is worth carrying out, because it is possible to think you have secured it properly, but still have the wheel moving laterally on its axle.

Check this out, taking note of complete sequence, the final clearance gap check and the axle spacers position and orientation. There are 7 ways to get them wrong, one way to get them right, although some of those 8 possibilities you would be hard pressed to achieve, but .....)

Article [13] - ST1300 - Maintenance - Front & Rear Wheel Install and Front Axle Animation | ST1300 Articles

Animated sequence to show the correct procedure when installing the front wheel into the forks of a Honda ST1300. The right hand side of the bike is the side with the brake lever. Left is the clutch lever side. This is the convention used in the Honda manuals. The video and the photo below...
www.st-owners.com www.st-owners.com

Note that you should not be tempted to fit a white heat shield to the front pads. They will cause the brakes to drag.

The chrome anti-squeal plate should be clipped on to the backing plate. The rear pads should have the white heat shield between the chrome squeal plate and the metal side of the pad.

Check that your front and rear reservoirs are not over full.
-----------

The issue with fitting front pads on the 2008 and later models.

When fitting the outer pad first, the pad spring tends to 'rock'. Push the outer pad up to the roof, the inner side of the pad spring wil likely see-saw down a little bit. The natural position of the inner spring strip is just below the piston. It is possible for the spring to get dislodged and get trapped in the wrong position by the piston itself. This is not just theoretical, it happened to me.
To prevent this, I suggested pushing both pads to meet the spring at the same time. But it isn't easy.

A couple of years ago I had my front caliper out of the bike and I investigated further. I now use a different method.
The above scenario is most likely to happen when fitting brand new pads, or you have cleaned and pushed the pistons all the way into the caliper bore. If the pistons are moved out slightly, it is impossible for the pad spring to drop below the piston itself (which it will do naturally). Instead it rests on the piston. When the outer pad is put in place, the spring cannot then rock.

Alternatively the inner pad could be inserted first, but that presents the ' three hand required' scenario again.

Always remember to pump the brake pedal after fitting new front pads - in order to move out the front centre pistons.
​
 
Oldschool1 said:
Ok the highlight of the weekend is my new JIS screwdriver.
Click to expand...
Where did you purchase yours and does it have a smooth or serrated tip?

vessel_screwdriver_jawsfit-e1463983553194.jpg


This is what Vessel calls the JAWSFIT tip – something of a newer version of their JIS drivers. My first Vessels have smooth edges and are easily sufficient for some very tight screws. I've found the "new and improve" leaves teeth marks in even slightly tight screws.

This may be of 0 consideration to some users but I really like how the older (and non-Vessel) JIS drivers could remove and replace a tight screw with no indications it had be worked on. This is not the case in my experience with using Phillips drivers on JIS screws.

I didn't know way back when Honda provided tool kits that the included red-handle driver was JIS and not Phillips. Nor that the Vessel Impact Driver with 4 bits in the blue tin was JIS. Like I said the Vessel tip may make no nevermind to some. Just an FYI.
 
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