Brakes slightly dragging

[Kev]

Hi people, just thought that l would put a general enquiry about the brakes slightly dragging on my '04. I've cleaned all the pads, pins, pistons as best l can without totally removing the pistons. I'm able to move the pistons in relatively easily by hand so assume these are not too bad. Bled the system a few times with and without a vacuum, until no obvious air showing. The wheels turn by hand but definitely slightly dragging. The SMC appears to operate ok, stopping the back wheel with slight plunger movement. Will check the calipers again this weekend to check that there is not too much grease on the slider pins. It's got to the point when l'm looking at stripping elements down and replacing seals, starting with the master cylinder. I'm only starting here as the cheapest kit and probably the easiest to bled, gotta start somewhere, after that thought the next logical step would be the front caliper piston seals. Not looking forward to that. If l go down this route, how best to prevent all fluid escaping, are the hose clamps any good or would cling film over the master cylinder before securing the covers down help create a vacuum.
Anyway just thought l would throw the question out there.

 

[dduelin]

Slight dragging is normal but what defines ‘normal’?

A good shove with your foot should get 1.75 to 3 turns out of rear wheel with bike up on center stand.

The brakes scrape a little and you are turning a pinion gear and drive shaft.

 

[ST-Traveler]

After a short ride if your disc is scalding hot then you have drag issue.

 

[dduelin]

John, if an ST1300 gets ridden regularly the owner should be able to assess how the rear brake is doing by the simple check of how free the rear wheel is to turn. A pre flight check so to speak. You check the bench mark each ride or every week or so and easily pick up on any change. That's what I did but I also did the services completely and on time and had a good feel for what to look for but any rider can use the simple wheel rotation check.

Of course for a bike that sits a long time between occasional use or a new-to-a-new owner bike that has set up a while a more detailed set of brake checks is in order.

 

[SMSW]

Never pulled the hoses off the calipers on my ST, but i have done that on cars that I've owned. Strategies for stopping the fluid from draining out of the hose/system have been to sharpen a wood dowel in a pencil sharpener, and push it into the open end of the hose (will leak a little but very slowly) and put plastic pads over both sides of a banjo fitting (less the bolt) and a very small C-clamp to squeeze these pads onto the banjo. No leaks but it frequently takes 3.25 hands to accomplish this. Last time I did it, I wished I had used a spring clamp AFTER I tightened down the C- clamp.

 

[Rob20111]

I use Sylglide on my slider pins, spring plates and any contact points that the pads slide on.
Go take it for a good ride with some hard braking, then see if it settles in and frees up a bit more.

 

[Catmandu2]

My "pre-flight test" is to look at the rear wheel,, as my bike warms up on it center stand (I always park it that way). I know the rear brake is not dragging,, because the engine vibrations (which are slight),, cause the rear wheel to spin slowly. For the longest time I had rear brake drag,,, with a hot disc,, and noticeable resistance when coasting. It was still there after my smc replacement,, and a million brake bleeds. But it finally cleared up when I polished my brake pistons. The method is listed in prior posts,,c/w pictures. Now my brakes discs run cool,, and the bike rolls freely. I polish the pistons without removing them from the calipers, at every pad change,,, Cheers,, CAt'

 

[mortenk]

Take it for a ride on roads where you don't need to use the brakes the last 5-10 miles. Make sure you cruise to a stop (e.g. uphill) without touching the brakes. Measure the temperature of your disks. If they are close to ambient temperature, you are good to go. If they are significantly warmer than ambient - you have a problem.

 

[Kev]

Thanks for the replies, it is definitely the front that drags, the back turns and spins fine and as mentioned operating the SMC stopped the rear wheel. I'm on the bike every day and cover around 16k miles a year. When l cleaned all the sliding pins, pistons etc everything was fine, l could easily push the pistons back in and when the caliper was back on the bike was able to slide them back and forth on the sliders, so no real problems up to then. I've bled the brakes as per Johns excellent guide, several times, it was for some reason when the brake lever was operated and built the pressure back up was when the drag came in. I tried spinning the front wheel and it would only turn about 3/4 of a turn. When pushing the bike and operating the front brake would stop the bike, release to a degree but definitely drag.
I have had to use the bike for work and fortunately with all the rain that we have had has kept the front discs cool and after a couple of hundred miles the brakes have freed up considerably. Therefore kinda assuming that its either the master cylinder or the caliper piston seals that was causing the issue. Haven't had a chance to check the caliper sliding pins for excessive grease that was mentioned in one of the earlier articles and to be honest as it appears to have sorted itself out probably will not bother at the moment.
Half of me wants to clean the pins and pistons again just to check if the issue comes back and probably will when l have a couple of days off work, but would really like to know why this happens. Finally, I've used red grease in the past, is pure silicon grease similar and is this ok for brakes?
As always thanks for the great help and advice.

 

[Ron_WI]

Hey John, what an excellent and timely post on the brake dragging problem! I ran into a similar issue while replacing my front pads a few days ago. The right front (right as when sitting on the bike) is dragging. The problem has been there a while as seen on the pads I removed.

Left Side - Even wear both sides


Right Side - The outside pad is totally consumed


I have your excellent article from 2014 on servicing the brakes. My bike has 108,000 miles. I’ve replaced the pads several times but had never previously greased the pins and rubber boots. Normally, I pull the calipers from the wheel, remove the pads, use brake cleaner to spray out dirt, dust and crud, and clean with an old toothbrush and a rag. The pistons still look shiny once cleaned but I’ve never lubed them with anything. With the new pads, the wheel only spins about ¾ turn by hand so there is still some drag.

After reviewing your 2014 article, I pulled the calipers from both sides and checked the pins and rubber boots. Both sides were dry so I lubed them with Sly-Glyde silicone grease. It seems I still have a drag so I’m thinking maybe I put too much grease on/in the rubber boot. Should you actually put a couple of small gobs in the boot or just apply some around the opening and on the pin?

Question for you. Can you explain step 1 in a little more detail?

Re the excess grease and air trap - If you have the pads out and push the calipers from the outside across to the disc and let go, the caliper should stay where it is. Ditto if you pull it back towards you and let go. If you have any air pressure, the caliper will move by itself when you let go. No need to take it apart - this is a good enough test.​

Does this mean with the calipers mounted to the fork with the pads out, pushing the calipers inwards towards the wheel and let go. Then pull the caliper back opposite from the wheel to see if the caliper stays in those positions? If the caliper moves by itself when let go, there is “air pressure”? Does that mean there is air in the lines which need to be bled?

I’ll be double-checking the springs and the tabs from step 5

Also, reference the photo on step 7 showing the axel and spacers. When you say viewed as if looking from the front of the bike do you mean as if sitting in front of the bike looking at it rather than what is normally referred to as left/right from the view as seated on the bike (which would switch left/right)?

Thanks!
Ron

 

[Ron_WI]

If you see this John, please disregard my question about the axel photo in step 7. I get it now.

 

[Ron_WI]

John, thank you for such a detailed explanation! I feel confidant now that I understand what I need to check when I pull the calipers again. When I did a few days ago, the slide pins and the rubber boots were in good condition. The pins were in nice shape and shined right up with a bit of brake cleaner on a rag although the pins and boots were quite dry and felt kind of stuck when I first tried to pull them apart. I had a devil of a time separating the left side bracket and caliper but eventually managed. I'll need to clean up the Sly-Glide I put in the boots as I'm sure it's too much. I want to have a good look at the springs and retaining clips to see if I may have damaged one of those. Then if necessary, I can double-check my front axle assembly.

I really appreciate your help! I'm often amazed by the collection of knowledge available on this forum.
Ron

 

[Kev]

Hi John; well what can l say apart from you're the man, big thumbs up. Such a well documented explanation of the brakes and those ever present pitfalls. A couple of the points l had on my radar to check but have a few days leave coming up so will play once again. i'll print this off as its easier to play on the bike and using this as a reference. These bikes are never ending with bits and pieces to play with. Had a leaky rad hose the other day and a puncture, it was a real love hate day. Many thanks once again.