| Author | Message | ||
     Brion |
Saturday last week (11/12/05) I was riding home crossing a two lane 5 mile bridge at approximately 50 mph. all of a sudden my front tire locked up started squeeling and immediately I was into a real steep stoppie. I tried to keep it stable, but the front tire swerved left then right, then the rear swung around tossing me off high side. I rolled down the road, got pretty banged up, but worst of all was standing in the middle of a two lane bridge, traffic backed up both directions, wondering what the hell just happened. I thought something may have went through a vent in the disc and jammed against the caliper, but there is no evidence of this. Someone told me that possibly the line returning to the reservoir may have plugged, not allowing fluid return, so when the fluid expanded from heat self applied the brakes. Has any one ever heard of something like this happening before? It happened on my 2000 S3. Brion | ||
| Spiderman |
Water in your caliper is more than likely the culprit... Glad your ok | ||
| Brion |
Spiderman, I know that water would definitely expand much faster than brake fluid,especially if it flashed to steam, but if it could return to the reservoir could it still cause the brakes to suddenly self engage full on? I am still too banged up to do much work on it. Do you know more about this sort of thing happening from water in the fluid? Thanks for the reply. Brion | ||
| Spiderman |
I have had it to me but not to that extent. Brake fluid is hydroscopic, it pulls water outta the air. So after a while it tends to build water in the lower portions IE the caliper. I don't know the exact physics of it but I do know steam takes up a lot more are than liquid causing the expansion of the pots causing break lag or lockup. That is just one theroy on what happened to your brakes not a sure thing of what really happened. | ||
| Brion |
Thanks again spiderman. It seems to be the only theory that makes sense to me. Especially once I was able to move the bike it rolled freely with no evidence that the brakes were sticking. Oddly enough I had just changed the brakes and bled the caliper thoroughly, but the week after I did so the bike sat in the storming rain from Hurricane Katrina while I was stuck at a hotel trying to seek higher ground. Nevertheless thanks for your input. I sure hope it brings to light the potential for this happening to someone else. Luckily I had on pretty good gear with the exception of my jeans and once I would have crossed the bridge I would have rolled on at a fairly decent pace. I was getting ready to transit an area of the I-10 that is still nearly desolate due to the hurricane devistation. | ||
| Natexlh1000 |
Wow. That's scary. | ||
| Bobpaul |
Brion, I had a similar problem a few years ago with a Yamaha. Even though I changed the brake fluid every 1~2 years the caliper pistons siezed up. After taking the caliper apart I found that the mositure in the air had mixed with the tiny bit of fluid that gets exposed when the piston extends to apply the brakes. After a while this reacted with the aluminum bore... fuzzing up and gripping the piston. Seemed like a strange problem to me. Since you had to push the pistons back in when you installed new pads did you notice if all 6 retracted smoothly? Another thing to look at is the freeplay at the brake handle. There should be some play between the brake handle and it contacting the piston. If not then the master cylinder piston might be partly compressed which blocks the bleed hole. Hang on - let me go look at my 00 M2... OK, it doesn't have an adjustment, but when you pull the lever it moves easily for about 1/2" and then the fluid starts to compress. If you have the cover off you'd be able to see the bleed hole open. In fact if you pull the lever with the cover off it makes a little guyser out of that hole (usually squirting brake fluid all over your tank). On more thing, are you sure you used DOT 4 fluid? and not DOT5? DOT 5.1 is ok, but not easy to find in the USA. All the tube frame bikes switched to DOT4 in 2000 MY. Bob | ||
| Brion |
Bob, The problem that you had with the Yamaha, did the brakes come on by themselves? Yes it is DOT 4 that I used. I had to split the caliper to get it off the disc to install the new pads and did not notice anything unusual, but I did not remove the pistons. This is the second time I had changed the front pads. The last time I just removed the disc instead of splitting the caliper. When I get where I can bend my knees a little (road rash is a bitch)I will take them down completely and do a better inspection. Brion | ||
| Natexlh1000 |
Split the caliper? Why on earth did you split the caliper? You don't even have to take the caliper off to change the pads on ours. They just slip out the back. | ||
| Brion |
Nate, I must be a dumbax. Since I read your reply I reread the procedure in the service manual and it states that they can be replaced from the back. When I get unbruised enough to do it I will try to get them out that way. I know that I had tried, but If I can't get them out from the back I will let you know why. Brion (Message edited by brion on November 20, 2005) | ||
| Bobpaul |
Brion, On the Yam, the brakes started applying themselves more and more each time I used them. Hey good thing it was a single cylinder bike with low power... I was wondering what the heck was going on 'cause I had the throttle half open and I was only doing 30 mph! When I pulled over I found the brake was "dragging" (as in locked up under 10mph), so I used a screwdriver to lever the pads away from the disk (push the pistons back in the bore), then I rode home very carefully using the front brake only if I absolutely had to! Natex is right about changing the pads, no reason the split the caliper. To remove the caliper you have to compress the pistons back or pull the pads so that the caliper will clear the wheel when you tilt it out of there. But to just swap pads all you gotta do is lever the pads so they compress the pistons, then pull the old pads and pop in the new ones. (removing the retaining pin, of course) The more you tell us the more surprised we are. Since you did split the caliper, you know that there are 2 o-rings sealing the fluid between the two halves. Do you think these got crushed so that they are blocking the fluid passge? If so then they might let the fluid in, when you squeeze the lever, but not return. Another thought, maybe the pad retaining pin didn't catch the hole in both pads and then one of the pads slipped out of position and jammed against the rotor? Crazy idea, but possible? If the brakes were working fine one minute and then jammed themselves on the next then it had to be either mechanical (pads moving or caliper moving out of place), or the water in the brake fluid idea. I think it would take quite a bit of heat energy to flash the water enough to overcome the vent. Before you got to the bridge was there a long downhill where you had the brakes applied? If you do figure this one out let us know. We all don't want to go through what just happened to you! | ||
| Brion |
Bob, it was a flat straight away with no one close ahead or behind. I had not used the brakes at all while on the bridge and it was a five mile bridge which I was a little past half way across. I cleaned the o-rings and stuck them in place with some o-ring lube. The pin is thruough both discs. I put approx 2000 miles on the bike since I changed the pads and it was fine. I did reread the procedure since I read Nates post and it does say that you can put them in from the back. The first time I did it was in conjunction with changing the front tire so the caliper, or the rotor had to be removed to get the wheel off. Last time I am not sure why I could not get them out that way maybe I just made an assumption and read the procedure on how to get the caliper off which states to split it. When I get a little better I will look into it some more. I am really interested in everyones opinions, because it will be on my mind when I am riding my other bike until I can get it figured out. | ||
| Brion |
Thought you guys might like a few photos. As you can see the bike faired as good as I.    | ||
| Ftd |
"Brake fluid is hydroscopic, it pulls water outta the air. So after a while it tends to build water in the lower portions IE the caliper. I don't know the exact physics of it but I do know steam takes up a lot more are than liquid causing the expansion of the pots causing break lag or lockup." Materials that absorb water are hygroscopic. Gases do take up more volume than their corresponding liquids. 18 grams/milliliters of water equate to 22.4 liters of water vapor at 1 atmosphere/32 f. One drop of water equates to ~60 cc of water vapor under these same conditions. Bottom line is water in a brake line is not good. Frank | ||
| Oldog |
"and then the fluid starts to compress." A red hair here sir, No it does not fluid does not compress at all. basic science. If the fluid is rotten with water then you could have a flash off to steam. ( gotta have lotsa heat for that ) when you remove the pads for the basic brake job you may find brake dust caked on the pistons, this can cause the brakes to "stick" because the pistons can't retract, then the fluid gets hot from dragging brakes and then expands the visious cycle starts here till lock up. the correct best fix. over haul the caliper, change the brake fluid, clean and inspect the master cylinder replace if desired or if it fails the test, bleed the system thuoroghly ( this is time consuming ) pay attention to the makeup of the brake cleaners that you use, use the correct type of fluid etc..... this may be of use.. http://www.badweatherbikers.com/cgibin/discus/show.cgi?tpc=3842&post=534665#POST534665 I had the dragging brake problem like you I just got lucky I am glad that you did not get hurt worse get well soon Ol dog.. (Message edited by oldog on November 20, 2005) (Message edited by oldog on November 20, 2005) | ||
| Natexlh1000 |
OWWW That's giving me flashbacks.  Yes, it's possible to get roadrash even if you weren't on the road  That's: (20 year old suspension)+(freshly rebuilt motor)+(whoops) | ||
| Oldog |
Ouch!: that had to hurt Nate, how'd the lower back get so skint up? | ||
| Natexlh1000 |
sliding.  | ||
| Neutron21 |
that looks nasty hope you get better quick | ||
| Bookyoh |
Here is a tech tip from American Thunderbike on potential brake lock up after replacing the pads: "By Jim Boesel Simply changing your front break pads, if they were very worn down, is simple yet could lead to a horrific accident if not done correctly. Hard to believe? When your break pads wear down enough that they noticeably need to be replaced it means you’ve worn down about ½ of total pad. This means the six pistons are sticking out an extra ¼” on each sides. As dirt and grime lands on the exposed piston the heat from the break cooks it onto the piston. When you compress the piston to make room for the new pads this baked on dirt can actually be pushed into the seal, preventing the free movement of the piston. Your breaks still work but as they heat up the pistons loose their ability to retract and you start dragging your front break. If you’re lucky you’ll notice it in time and pull over before you either warp your front rotor ($100 to replace) or god forbid have a lock up! Fortunately there’s a simple way to prevent this. After you’ve removed your front pads (consult your manual) take the time to remove the front caliper. It’s a bit tricky to find the right angle that let’s you slip it past the rim but when you find it, it slips right off. I put tape on the rim to make sure I don’t scratch it. With the caliper removed carefully pump up the pistons so they’re about ½” exposed on both sides. Be careful to use slow pulls and you’ll find they don’t all come out uniformly. Do whatever you feel you need to do to compensate. Now take a shop rag and carefully wipe the pistons clean until they shine like new. This takes a couple of minutes. Now compress the pistons, reinstall the caliper and follow the normal bleeding procedures outlined in the manual. Remember to install the new break pad before you bleed. This whole added process takes about 15 minutes." http://www.americanthunderbike.org/techtips/brakepads.php Mark Cincinnati | ||
| Oldog |
Some questions why do you need to bleed the system? is it OK to use brake cleaner and a paper towel? I did this and it did not help ( after a dragging incedent ) so as a point IF your brakes drag even one time overhaul the caliper, change fluid, check disk and pads. If you are changing pads, and there have been no incedents good idea, also if the brake fluid is 2 years old or older change it.. at 4 years the system is to be overhauled. | ||
| Brion |
Jim, Thanks for the post. I have been really troubled by this happening to me and not having a good answer. My brakes were very worn from taking a long road trip 2K miles approximately and much of it was on inclined roads in the mountains and foot hills. When I returned first thing I did was change both front and rear pads and I flushed the front thoroughly. Like I said the week after I did that my bike sat in the Hurricane Katrina rain and 150+ MPH winds. Which I thought may have someway put moisture in the fluid. Maybe by the end of the weekend my knee will be flexible enough to bend so I can get them taken down. I will definitely replace the seals, O-rings etc. and will certainly do the same on my Harley. I did notice on my Harley that the brakes seem to drag a bit the bike is not even 2yrs old, but I am on my second set of pads. Once again thanks to all for your input. I will follow up with my findings when I take it down. Brion | ||
| Whodom |
Brion, If you changed pads without cleaning the brake dust from the pistons before you pressed them back into the caliper, that's almost certainly what caused the problem. I changed the pads on my S3 without first cleaning the pistons this summer. I rode it for nearly 400 miles before I had a problem. ~250 miles from home riding in the mountains, the front brake gradually came on until the front wheel almost locked. I was clueless to what had caused it, but having run into something similar before on a 1983 Honda Ascot, I cracked the bleeder valve on the caliper and it released the brakes. I later changed the front brake fluid and re-bled the system, only to have the problem again. A week later, I got the bike home and stumbled onto the tip at the American Thunderbike site. I pulled my front caliper off, took out the pads, pumped the pistons out, and sure enough, I had a good coating of brake dust on every piston. It took a good 30 minutes of work with a shop rag to get them clean. I put everything back together and haven't had a problem in several thousand miles since. You can replace the seals if you really think it's necessary, but odds are a good cleaning of the pistons will correct the problem completely. |
