Rear Brake Pad Drag - Normal? W/ Video

[jfheath]

What is your explanation for why this works ?

I was referring back to the previous question - why does holding the brake lever in over night make the brakes feel firmer.
The bubbles will migrate upwards anyway - unless they are attached to the sides or joints.

 

[Oldschool1]

Working through the list update(ing) below occording to each.

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.

I'm absolutely sure there is no mix up of pads the correct front and rear in the right position. It's good to clarify/ rule out - THX.

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.

Update - all is good here. JH I read your article early on and have subscribed to thes methods.

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.

All is Good here

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

Did this with multiple bounces per your method, the left fork stays flush with the end of the axle shaft. Tightened up the pinch collars on left tube. Made no difference in drag. Clearance

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

Checked this and also removed front wheel and reinstalled. The from allinment appears perfect - able to insert the axel through both forks super easy - just goes right through. Same with going through the wheel can push it through and it's seats st the flush depth in the left fork through hole. With no pads in I can spin the wheel a good 10 revs easy. Bearings are butter smooth.

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

Distance collar verified correct.

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

VERIFIED PER ABOVE.

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.

No mixes

7 Check your pad pins are smooth and clean.

Really good condition, smooth surface, very 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.
Pushing the calipers in by hand to the point of no pad contact and then applying the hand brake (front) only caused the condition in the video. I don't see an increase in drag after applying the rear brake (center piston). The right caliper contributes more than the left caliper, to drag.

Will update this reply soon more to come.

Well I'm pretty sure the rest of the checklist wrt clips, pad install is good. When I put this together there was extreme focus on that from your article alerts.

One thing to note is I can't get a feeler gauge of 0.12mm in between the pads and the disc or the the pad and caliper mating surface, well there isn't much of any gap so list retraction must be minimal.

 

[Andrew Shadow]

Air should rise to the top ......

That was Al's point above. The rear brake hose rises from its attachment point on the swing arm up to its connection point on the rear caliper, so any air in that section will rise to the top, which in this section of the hydraulic circuit is up in to the caliper.

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....

I suspect that the difference in elevation between the lowest point in the brake hydraulic system and the highest point is not enough to impart any such effect, at least not a measurable one.

 

[Andrew Shadow]

Obviously we have no scuba divers on the forum

Do tell. I am not one but would be interested in the principle.

 

[jfheath]

One thing to note is I can't get a feeler gauge of 0.12 2mm in between the pads and the disc and the pad interface to the caliper mating surface is really tight, not sure I could get a feeler gauge in a gap ( tight to the caliper wall).

Ah - I should have described that a little more clearly. Sorry about that.

I see you have eliminated the front centre pistons from the problem - because the problem only occurs on the front calipers when the front lever is applied

If you have got to the stage of deciding that the pistons are not releasing, then to get a 'feel' for which pistons are not releasing, you need to push the pistons in a little bit. Put in the card/paper/feeler gauge between the piston and the back of the brake pad and then pull the brake lever so that the insert is trapped. Let go of the lever. The insert should pull out relatively easily - maybe after a couple of revolutions of the wheel.

But if it is happening on both wheels then maybe there is something else going on. Have you had the brake lever off - maybe there is som muck inside the alloy cup that pushes the master cyclinder push rod - preventing the piston from returning properly and inhibiting the release of fluid.


Nb - this is the lever for the pre-2008 models. The later models do not have this cup.

I think that this is an unlikely long shot, but worth mentioning.

 

[X811]

Hi, newbie here but looking for help On my 2005 St1300 With 55k miles on it.

Been through my brakes multiple Times, cleaned everything, new seals, new SMC seal and piston kit. All pistons move freely and easily by hand yet as I start the bleeding sequence the rear wheel starts locking up. The more I bleed it the more it starts to lock up to the point where it is almost solid. The front wheel however spins freely and pressure feels really good at the lever.

I wouldn’t mind so much but I’ve decades of experience, built and raced a multitude of bikes at varying levels but with this I’m now going round in circles so seeking that specialist knowledge that comes from others suffering similar headaches And exposure to the solutions.

jfheath i noticed that you’re UK based and appear to be a font of knowledge, i can‘t see how to PM you but would really like to talk this through and try to identify a, something I’ve done wrong or b, that i need to bite the bullet and spend £560 on a new proportional control valve

My apologies for hijacking this thread, although i take comfort that this issue is well documented.

thanks

chris

 

[Kevcules]

Hi, newbie here but looking for help On my 2005 St1300 With 55k miles on it.

Been through my brakes multiple Times, cleaned everything, new seals, new SMC seal and piston kit. All pistons move freely and easily by hand yet as I start the bleeding sequence the rear wheel starts locking up. The more I bleed it the more it starts to lock up to the point where it is almost solid. The front wheel however spins freely and pressure feels really good at the lever.

I wouldn’t mind so much but I’ve decades of experience, built and raced a multitude of bikes at varying levels but with this I’m now going round in circles so seeking that specialist knowledge that comes from others suffering similar headaches And exposure to the solutions.

jfheath i noticed that you’re UK based and appear to be a font of knowledge, i can‘t see how to PM you but would really like to talk this through and try to identify a, something I’ve done wrong or b, that i need to bite the bullet and spend £560 on a new proportional control valve

My apologies for hijacking this thread, although i take comfort that this issue is well documented.

thanks

chris

As you have noticed, these braking systems are not very forgiving. The complex design works well when it works , but needs a lot of TLC, OFTEN. What's happening to you has happened to many, especially when the fluid hasn't been changed at least every other year. The SMC usually can't be rebuilt and needs to be replaced.
A quick test for it is to lay down on the left side of the bike (bike on center stand) and kick to spin the rear tire, then press up on the SMC. (part of the front left caliper) The tire should stop right away , then release the SMC and the tire should spin freely. If your tire is still locked by the rear caliper, release/push back the pistons and try the SMC test again. If that works well, you may have issues with the rear caliper. Check where the caliper locking bolt goes through the caliper. If it's scored, like a rifle barrel, it needs to be replaced. Check where your pads line up on their guides. Your pads might be crooked.
There is a strict bleeding sequence also. Check the articles section above for detailed "how to's"
John and others will hopefully reply soon and have plenty of knowledge to get you back on the road.
Good luck...

 

[Oldschool1]

Ah - I should have described that a little more clearly. Sorry about that.

I see you have eliminated the front centre pistons from the problem - because the problem only occurs on the front calipers when the front lever is applied

If you have got to the stage of deciding that the pistons are not releasing, then to get a 'feel' for which pistons are not releasing, you need to push the pistons in a little bit. Put in the card/paper/feeler gauge between the piston and the back of the brake pad and then pull the brake lever so that the insert is trapped. Let go of the lever. The insert should pull out relatively easily - maybe after a couple of revolutions of the wheel.

But if it is happening on both wheels then maybe there is something else going on. Have you had the brake lever off - maybe there is som muck inside the alloy cup that pushes the master cyclinder push rod - preventing the piston from returning properly and inhibiting the release of fluid.


Nb - this is the lever for the pre-2008 models. The later models do not have this cup.

I think that this is an unlikely long shot, but worth mentioning.

Thanks - good thought it was a worthy try. Checked it out and all is good. I now have the cleanest brake lever on all the STs!

One thing I did today is crack the bleeders on the right and left calipers. No real pressure just a few slow drops formed and I think this was gravity. No difference at all in break drag. This leads me to believe the pistons are not retracting the “normal amount”. Recall that I took them apart they were very clean but I replace all seals with new Honda seals. Still can this be the culprit. At this point it may make sense to take calipers off put a solid billet of aluminum in and squeeze down and see what small gap is there when released?

The other thought is should I push the pistons out and lube them with silicone grease and work them in out a few times…going to the extremes on what’s going on here. When I installed the pistons they were lubed with brake fluid…..but clearly something isn’t right.

With fender removed (allows a good spin) I get 1 revolution if both front and back brakes have been applied and 1.25 revolutions if only the front have been applied ( center pistons retracted).

Searching for light at the end of the tunnel!!!!

 

[jfheath]

Phoning @X811 on Monday morning Uk time.

@Oldschool1 - when you removed the piston seals, did you clean the grooves where they seat ? Brake fluid is the correct stuff to use for lubricating seals and pistons for re-assembly.

How does the wheel spin when the brakes are not involved - eg without pads in place. That would be a useful point of reference.

 

[Oldschool1]

Phoning @X811 on Monday morning Uk time.

@Oldschool1 - when you removed the piston seals, did you clean the grooves where they seat ? Brake fluid is the correct stuff to use for lubricating seals and pistons for re-assembly.

How does the wheel spin when the brakes are not involved - eg without pads in place. That would be a useful point of reference.

When i remomoved the orings I fully expected to find crud behind the orings and find rather stiff not pliable orings, but i found no crud and the prongs were pliable and the seal print slightly distorted from being in the extended (piston out) position (slight distortion). I cleaned them anyway - they were really clean no buildup or stain and washed with hot soap water a toothbrush and thoroughly dried with hair dryer (gentle heat).

I lubed the orings and piston with brake fluid on assembly. Maybe i didn't lube them enough?

Here is wheel spin w/o pads in, spins very nice - video:

 

[jfheath]

Brake fluid is lubed enough.

 

[Oldschool1]

Here are the clips from the Front. Both front and the back tabs look like this. It's not a perfect 90 degree bend ....maybe 75-80 degree. To me, I would think this is the factory condition.....but I've never seen new clips.

Is this a problem or do they need a slight adjustment to 90 degree?

Well I put it all back together. The tabs really don't come anywhere close to holding the pad away from the disc. They would easily allow the pad to float to the disc or away from the caliper mating surface about 1mm. So I'm not really sure that is the purpose of them...maybe it's to hold the pads in position for factory assembly...but there not going to do anything to prevent pad drag on the rotor that I can see ( I assembled it all with the caliper off so I could see with the pads tight against caliper wall where the tabs were in relation to the pads).

I did assemble the the caliper pads without the spring clip just on the right side and the drag was less - maybe got 1.5 wheel rotation vs 1 rotation with the spring clip in. So the spring clip is contributing to the pad to dragging on the rotor.

Piston retract test. I did put a uniform cross section aluminum bar in the caliper that allowed the pistons to extend out (from totally collapsed in the bores) about 3mm and then clamps down on the bar with the front brake lever only. After relaxing the Front brake lever, the bar is not clamped and can slide out of the caliper but clearance from piston retraction can only be a few thousands - pretty sure less than 0.005" or 0.12 2mm, no slop or wiggle clearance like the bar was going to fall out! If I compare this to other bikes I'd changed seals on, the retraction of the pistons was very noticeable visually (that would have been an 87 Nighthawk and maybe my prior ST1100 and brake drag was never an issue). I'm really wondering why the different design intent. I'd really like to know what the spec is on this. That could stop a lot of tail chasing possibly.

Went for a ride. After 2 miles no brakes, 60 F temperature out, the left rotor is slightly cool to touch and the right just barely slightly warm to touch. The back rotor was just barely warm to touch.

I really don't know if there is anything else that can be done - other than there is some suspicion about the spring clips effect??............maybe just ride it a few hundred miles and see if brake drag eases up?