front disc brake disengagment issue.

Hey everyone! back with another head scratcher,

so recently i noticed that at low speeds after applying the front brakes sometimes there is a grinding noise, very quiet hard to hear. I probably didnt notice before now, because my baby used to race at idle, due to cracked boots. Anyways so i figured out that atleast one of the front disc calipers is not fully releasing when i let go of the break lever, it does let off enough that it is no longer braking, but is still contacting the rotor.

So, my question is, where the hell would i start troubleshooting this problem? any suggestions are greatly appreciated, im new to all this but getting the hang of it.

thanks alot!
Brian

 

almmost forgot, '81 xj750 SECA

 

Disc brake pads should ALWAYS be in contact with the rotor. Otherwise you wouldn't get an instant brake response when you need it. They are not supposed to drag TOO much though. I would jack up the front end of the bike, and see how well the front end spins with no brake pressure. If it spins well, forget about it!

If it doesn't spin well, you may have one of your caliper "pins" sticking. You usually get uneven pad wear with this - like the pad is wearing at an angle to the back of the pad. I have seen this on many cars. If that is the case, take the calipers apart and grease with CALIPER GREASE the pins that the calipers are riding on, because one side is hanging when you brake.

 

Contact is normal, but as Rich said, too much is not good. Go really easy on the caliper grease, a thin film is all you need. Too much and it will find it's way onto your pads/rotors. Smear some on, wipe it off is all you need. Don't forget the pad guide shims (the pads contact the shims at the edges), a little there too. You may also have grit in the pads, pull them and check them out. If they are contaminated, replace them, the grit will score the rotors rather quickly. This grit is not uncommon when riding in the rain (another excuse for avoiding the wet). The water tends to help the crud stick around unlike when it is dry and the grit just falls back off the bike.

 

When I had this happed I noticed the brakes dragging when pushing the bike backwards. It was crud not allowing the caliper piston to retrieve all the way. I rebuilt y calipers but a good cleaning may take care of yours.

 

thanks for the advice, yes i noticed htat expecially when pushing it backwards, it squeeks. I will try a cleaning, and then apply some grease see if that does the trick. I'll let you guys know how it goes after i return from NY for the weekend.

 

I have the same front brake problem

I'm about to tackle this problem. My last step in giving my (new to me) 1985 XJ 700 Maxim a complete tuneup is... or at least I thought was... replace the front brake pads.

Following the owners manual, I removed the old brake pads, loosened the master cylander and then attempted to push the pistons back into place. I pushed them as far as they would budge and inserted the new brake pads. Pumped the brakes a few times and then spun the tire. Nothing. It wouldn't spin.

I removed the brake pads and took a closer look. The pistons on the right caliper will not fully retract. The ones on the left are almost flush. Upon closer inspection, there is "gunk" on the piston itself. Using an old sock I was able to remove the gunk that I could see, but still could not push the pistons back into place.

Made an appointment w/ a local independent bike shop to look at my brakes next week. This will give me time to mess w/ them this weekend and if I fail to get them working properly, at least my name is already on the schedule for being serviced next week.

I purchased a bleed kit from Sears for $32. I already have new pads. I'll stop by Schucks to pick up some brake cleaner and get to cleaning this weekend. I wish the manual was more specific on how to service the calipers. I realize there are only a few parts (that make up the caliper), but for a newbie, sometimes the simplest of repairs can be a daughnting task.

 

I would highly recommend you disassemble, clean and then flush and bleed the system big guy. Could be a bit of build up in the caliper. Plan on ordering a rebuild kit including the slider bolt bellows (not included in the factory "rebuild" kit) if your model has them. I had to spring about $150 for new pistons, seals, hardware, and new pads for the front on the 83 turbo.

 

I'm hoping (like most of us that encounter problems w/ our bikes) that it is a minor fix that revolves around cleaning and adding new brake fluid. I picked up some brake cleaner and a small tube of caliper grease. The front tire is off the bike (now with a new tire on it) so I'll tear into the brakes tomorrow. A friend of mine has an air compressor so I'll be able to use that to remove the stuck piston if worse comes to wear. I figure the worst that could happen is that next Thursday I'll be taking my local mechanic a box of cleaned front calipers which should save some time on labor. I plan on doing what I can for now. Thanks for all the responses.

 

samtidor, I didn't have any luck removing my pistons with compressed air, needs something more solid to remove them. I ended up using a grease gun to force mine out, but my system has been apart for many, many years.

If your brakes are still connected just pump your brake lever gentle to move the pistons out, but could be messy!

 

They move out, its just pushing them back in thats the problem. I only mentioned that I had access to an air compressor as a few help sites I've visited mentioned that I may need to use on to force out a stuck piston. From what I've seen (just by holding it in my hand and shaking my head) it appears that they should come out with a bit of tugging. I'm assuming that the previous owner neglected to maintain the brakes on this bike not noticing the declining performance in stopping power over the years.

I spoke with one of the mechanics at my LBS this morning. He told me that the majority of bikes he sees are running poor performing brakes - the owners basically neglect to service them because they seem to work just fine. He was working on an older Goldwing and pointed out the problem areas (related to the brakes) on the bike and added that even though he had pointed these things out to the owner, the guy just wanted his carbs fixed so "he could go ride".

With only 14,000 miles on my bike, I'm figuring its gunk I need to clean out rather than worrying about replacing pistons at this point in time... or at least I hope... for now.

 

"...a stitch in time..." Preventitive maintenance is the best way to ensure long life of your charished possesion. A quick seal replacement may be all you need, but I have seen the cash-strapped simply clean and re-use old seals.

 

Took the calipers apart this morning. Loosened the bolts that secure the two halves of the caliper. "Gunk" was clogging the small openings where it appears that brake fluid should flow through. Used brake cleaner to get the "gunk" out. Cleaned what I could on the outside surfaces. All 4 pistons are stuck so I will be trying the air compressor trick this evening, hopefully that will do the trick by first following the guidelines on the XJ CD.

 

FYI, I think I found my problem today. Taking Robert's suggestion, I completely bled the lines. Not only was the fluid filthy, but eventually I came across water in the brake fluid! I drained a few cc from both sides. How the heck did water get in there, condensation? So, I fear what the insides of the callipers look like. I haven't actually taken the calipers apart yet - tomorrow my stomach could only handle so much in one day.

So, at the least I'm looking at the caliper seal kit, like this, right? http://www.oldbikebarn.com/part.php?id=2336

Likely, I'm looking at a new cylinder or two - which seem to be really hard to come by. I've checked the sources in the 'Links' section and a few others. Anyone have any leads?

 

Yes, you would need those, and source new pistons while your at it, but hold off until you varify they need replacement. I would HIGHLY suggest rebuilding the system (master cylinder too) in the interest of keeping your hide intact. Water in the system is a bad sign. It has a realy bad habit of eating the pistons and anything else that is vital in the system with the exception of the rubber hoses, ozone and UV take care of those instead. Looks like your on the right path. How was the effort at getting to the master cylinder resevoir? There is another thread on this topic floating around here, I just wrote and posted earlier today on approaching this very issue. Check it out.

 

The pistons didn't look as bad as I expected. Two of them were wedged in there pretty tight. Cleaned both calipers, all four pistons, and checked the seals. Next item on the order list will be a new set of seals even though nothing appeared cracked or missing.

I did reassemble everything as I wanted to make sure I could actually do it (because I do have an appointment at the LBS in case I fail). Used the brake bleed kit I picked up at Sears. Followed the directions and after three trys, the brakes felt solid. Took it for two short runs (25mph) around the neighborhood - stopping and checking with a flashlight to make sure nothing was leaking or spraying all over the bike - and everything seemed intact. I also wanted to take it slow because I installed new pads as well as a new tire. Tomorrow morning I will check the floor around the bike to see if I can spot any new leaks.

So I'm thinking, new master cylinder kit, new caliper seals, and maybe new brake lines??? I'm considering keeping my appointment at the LBS just so the mechanic can take a quick overall look at the bike to see if he can spot something I missed. Good idea?

 

"An ounce of prevention is worth a pound of cure" is a great motto. Sure it's a great idea (if you can afford it). I would just wipe/wash each of your unions down with alcohol and check for wetness after a few uses (brake cleaner is good too but ruins paint jobs). Make sure you check with your pad manufacurer for pad bedding instructions, it is important. Got to break them in correctly. Good luck!

 

If you are refering to taking it to a mechanic as "if you can afford it"... well, I can and I can't. I can't afford to overlook something that, if neglected, would cost me $$$ in the near future. On the other hand, my wife and I are in our last year of graduate school so we have very little money to burn (hense the 20 year old second hand bike instead of buying new).

I will definately take your advice and wipe down the areas w/ alcohol pads tomorrow morning.

Do you have a book of quotes sitting next to your computer? I like them, keep 'em coming.

 

Thank you for your compliment, but credit is due the author. Poor Richard's almanac is a classic American publication started by our very own Bejamin Franklin. It is filled with sage advice and sound suggestions. He can be quoted for most everything in it or he collected it to include in his book. It has been in use for the better part of two centuries. Good stuff, it helps in times of quiet (like in the loo). I haven't a copy but the few times I read it have been indelibly marked in my mind (a rarity in my advancing years). I agree with your logic concerning can and can't afford the investment. Your well-being is priceless, I agree. A few well spent dollars now will pay off in confidence in your braking system being there when you need it and will perform as advertised. You seem to have the issue well in hand and I'm certain your mechanic will appreciate your interest in keeping him employed to check your work (he's bills to pay too). Nothing wrong with a second opinion from a knowledgable source. You have developed a sense of what you are comfortable with and that indicates intelligence. With time you will also develop a sense of what you can do for yourself with confidence. I expect that will be a very short learning curve. Good luck to you sir, I think your doing swell!