ADVrider

Go Back   ADVrider > Bikes > GSpot > Parallel Universe
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 11-09-2010, 07:55 PM   #46
LaPorte
Gnarly Adventurer
 
LaPorte's Avatar
 
Joined: Jul 2006
Location: Northern Ca.
Oddometer: 492
Thanks boy's for your suggestions. Like I said I used a screw driver ( I don't think it was metric, but it did have a yellow handle) to spread the brake pads more than once. Calliper woun't spread to full open????????????????? Next day I could spread it to full open with my thumbs. Might be something with the Master cylinder and removing the cap, hell I don't know????????????????

Wish you guys were there, we could of scratched our heads together!!!!! Even better you could have kept me company on those DARK, TWISTY, BACK ROADS where there wasn't a sole but me for 50 miles. You think I was nervous, you bet I was.

LaPorte
__________________
If you don't know where your going don't lead!
LaPorte is offline   Reply With Quote
Old 11-09-2010, 11:14 PM   #47
EnderTheX
Drunken Squirrel
 
EnderTheX's Avatar
 
Joined: Mar 2009
Location: DFW Area, TX
Oddometer: 2,715
You guys totally lost me, and/or I'm kinda drunk, reading about not being able to spread the pads... ???

1. I have always been able to spread the pads with my special metric screwdriver!

2. Brake wear is accounted for by the black bladder in the fluid reservoir, there should be no pressure/vacuum on the system at idle.

3. If weird shit is happening with your brake system your lines or valves may be stuck or clogged (and I really hope there is no air/water in your system)... time has nothing to do with hydraulics.

4. Where the hell is my beer? Did I finish it already?
EnderTheX is offline   Reply With Quote
Old 11-10-2010, 12:38 AM   #48
The Griz
North Forest Rider
 
The Griz's Avatar
 
Joined: Nov 2008
Location: Minnesota
Oddometer: 3,779
Quote:
Originally Posted by EnderTheX
Brake wear is accounted for by the black bladder in the fluid reservoir
Sorry but that makes no sense. That black rubber seal in the reservoir is not to account for pad wear, it is simply a seal so no air gets into the system. No more, no less.

Quote:
there should be no pressure/vacuum on the system at idle.
That depends on whether or not you're squeezing the brake at idle or not!

This all works via a displacement of brake fluid from one side of the system to the other by applied outside pressure: the human squeezing the lever. That is all. Regardless of whether or not the bike is in motion, running or not, at any RPM, if you're not squeezing or pressing the brake, no no displacement of fluid is taking place.

Simply put, squeeze the lever and you're displacing fluid from the lever end of the brake system down to the caliper end, pressing the calipers and pads up against the rotor. When you release the lever, the spring or whatever return mechanism in the lever (typically a spring) moves the lever back out. This creates a void/vacuum in the lever end of the system drawing the fluid back up to the lever/reservoir end. No air. Just movement of fluid from one end to another.

Quote:
3. If weird shit is happening with your brake system your lines or valves may be stuck or clogged (and I really hope there is no air/water in your system)... time has nothing to do with hydraulics.
The line being 'clogged' is highly unlikely. Unless he opened the reservoir cap and put some stuff in there purposely. Something being 'stuck' is even more unlikely.

However, if air got into his system, thermal expansion of the air molecules may have created a higher pressure within the system. When the air within the system cooled down, there was less pressure within the system.

Just a theory LaPorte. If you experience this issue again, I'd bleed the brake lines and start over with new brake fluid. This way you'll know for sure there is no air within the system. Air within hydraulic brake systems can cause all kinds of weird problems including thermal expansion.
__________________
PAUL BUNYAN FOREST RIDERS MC
2013 KTM 300 XC-W
2014 KTM 690 Enduro R
The Griz is offline   Reply With Quote
Old 11-10-2010, 05:56 AM   #49
digdesign
Hack
 
digdesign's Avatar
 
Joined: Jun 2010
Location: Boston
Oddometer: 151
Quote:
Originally Posted by The Griz
However, if air got into his system, thermal expansion of the air molecules may have created a higher pressure within the system. When the air within the system cooled down, there was less pressure within the system.

Just a theory LaPorte. If you experience this issue again, I'd bleed the brake lines and start over with new brake fluid. This way you'll know for sure there is no air within the system. Air within hydraulic brake systems can cause all kinds of weird problems including thermal expansion.
Dude, come on. Now you're really reaching here. The volume of air that would need to be in the system in order for thermal expansion to have an effect is probably the size of an aircraft hangar. And even if it could have an effect the fluid would simply back up into the resivour.
__________________
2010 F800GS
2009 Buell XB12Scg FOR SALE
1990 E30M3 track rat
digdesign is offline   Reply With Quote
Old 11-10-2010, 06:02 AM   #50
digdesign
Hack
 
digdesign's Avatar
 
Joined: Jun 2010
Location: Boston
Oddometer: 151
Quote:
Originally Posted by The Griz
Sorry but that makes no sense. That black rubber seal in the reservoir is not to account for pad wear, it is simply a seal so no air gets into the system. No more, no less.
It makes perfect sense. The bladder is there for pressure relief. When fluid is drawn down the bladder expands and does not allow a vacuum to be created in the system. It's purpose is to keep the fluid clean and dry while it equalizes pressure between the reserve fluid and atmosphere through the hole in the cap.
__________________
2010 F800GS
2009 Buell XB12Scg FOR SALE
1990 E30M3 track rat

digdesign screwed with this post 11-10-2010 at 06:08 AM
digdesign is offline   Reply With Quote
Old 11-10-2010, 08:11 AM   #51
The Griz
North Forest Rider
 
The Griz's Avatar
 
Joined: Nov 2008
Location: Minnesota
Oddometer: 3,779
Quote:
Originally Posted by digdesign
Dude, come on. Now you're really reaching here. The volume of air that would need to be in the system in order for thermal expansion to have an effect is probably the size of an aircraft hangar. And even if it could have an effect the fluid would simply back up into the resivour.
I said it's just a theory 'dude'. Chill out!

And, no, you wouldn't need an "aircraft hanger" full of air. That's ridiculous. Now you're "reaching". Even the slightest bit of air in a hydraulic brake system will cause all kinds of problems. I've heard motorcycle mechanics say this many times. I've experienced it and had to bleed the brake lines. I've also experienced it on my mountain bike which has Hayes hydraulic disc brakes.
__________________
PAUL BUNYAN FOREST RIDERS MC
2013 KTM 300 XC-W
2014 KTM 690 Enduro R
The Griz is offline   Reply With Quote
Old 11-10-2010, 08:11 AM   #52
The Griz
North Forest Rider
 
The Griz's Avatar
 
Joined: Nov 2008
Location: Minnesota
Oddometer: 3,779
Quote:
Originally Posted by digdesign
It makes perfect sense. The bladder is there for pressure relief. When fluid is drawn down the bladder expands and does not allow a vacuum to be created in the system. It's purpose is to keep the fluid clean and dry while it equalizes pressure between the reserve fluid and atmosphere through the hole in the cap.
So now we're talking about the large round piece of rubber that you put on top of the reservoir bowl first before you screw on the cap? If so, yes.

I've never heard of it being called the "bladder" by any motorcycle technician or the like. Didn't know what Ender was talking about.
__________________
PAUL BUNYAN FOREST RIDERS MC
2013 KTM 300 XC-W
2014 KTM 690 Enduro R
The Griz is offline   Reply With Quote
Old 11-10-2010, 09:58 AM   #53
EnderTheX
Drunken Squirrel
 
EnderTheX's Avatar
 
Joined: Mar 2009
Location: DFW Area, TX
Oddometer: 2,715
Quote:
Originally Posted by The Griz
So now we're talking about the large round piece of rubber that you put on top of the reservoir bowl first before you screw on the cap? If so, yes.

I've never heard of it being called the "bladder" by any motorcycle technician or the like. Didn't know what Ender was talking about.
Might be my own terminology but yeah, that thing expands into the reservoir as you wear your pads... I just called it a bladder because it is flexible and seals the top of the reservoir, may I should have called it a membrane instead

Anyway I think we are all on the same page
EnderTheX is offline   Reply With Quote
Old 11-10-2010, 10:06 AM   #54
The Griz
North Forest Rider
 
The Griz's Avatar
 
Joined: Nov 2008
Location: Minnesota
Oddometer: 3,779
Quote:
Originally Posted by EnderTheX
Might be my own terminology but yeah, that thing expands into the reservoir as you wear your pads... I just called it a bladder because it is flexible and seals the top of the reservoir, may I should have called it a membrane instead

Anyway I think we are all on the same page
Agreed.
__________________
PAUL BUNYAN FOREST RIDERS MC
2013 KTM 300 XC-W
2014 KTM 690 Enduro R
The Griz is offline   Reply With Quote
Old 11-10-2010, 05:52 PM   #55
Bayner
Beastly Adventurer
 
Joined: Mar 2008
Location: Penticton, BC
Oddometer: 1,484
Quote:
Originally Posted by The Griz
When you release the lever, the spring or whatever return mechanism in the lever (typically a spring) moves the lever back out. This creates a void/vacuum in the lever end of the system drawing the fluid back up to the lever/reservoir end.
Well, you're pretty close Griz. What actually happens is that the lever is returned to it's resting position by the spring behind the piston in the master cylinder bore. Pressure is thereby released on the caliper's piston and the remaining drag is removed by use of a square-cut and particularly formulated seal around the caliper piston.
'Dirt' in very small amounts can clog the passages in the ABS body/valving and can come from a wide range of sources either introduced or the interior surfaces of all the brake components exposed to the fluid. It's not very common however. Once a piston starts to corrode a little, whatever the cause- but typically old fluid, it can hang up a bit on the seal making it difficult to retract initially as the crud binds against the seal. Once you have forced it past, the symptom disappears. These bikes are too new for that to be an issue I would think.
Bayner is offline   Reply With Quote
Old 11-10-2010, 08:00 PM   #56
The Griz
North Forest Rider
 
The Griz's Avatar
 
Joined: Nov 2008
Location: Minnesota
Oddometer: 3,779
Quote:
Originally Posted by Bayner
Well, you're pretty close Griz. What actually happens is that the lever is returned to it's resting position by the spring behind the piston in the master cylinder bore. Pressure is thereby released on the caliper's piston and the remaining drag is removed by use of a square-cut and particularly formulated seal around the caliper piston.
'Dirt' in very small amounts can clog the passages in the ABS body/valving and can come from a wide range of sources either introduced or the interior surfaces of all the brake components exposed to the fluid. It's not very common however. Once a piston starts to corrode a little, whatever the cause- but typically old fluid, it can hang up a bit on the seal making it difficult to retract initially as the crud binds against the seal. Once you have forced it past, the symptom disappears. These bikes are too new for that to be an issue I would think.
Right on Bayner. I do understand, and did say that the lever returns via a spring, and that that creates a vacuum at the upper/lever end of the sealed system. This vacuum relieves pressure on the caliper, yes, and also sucks/pulls the caliper back to the "null" position.

Pascal's Law of Hydraulics:

__________________
PAUL BUNYAN FOREST RIDERS MC
2013 KTM 300 XC-W
2014 KTM 690 Enduro R
The Griz is offline   Reply With Quote
Old 11-10-2010, 08:12 PM   #57
MCMXCIVRS
Beastly Adventurer
 
MCMXCIVRS's Avatar
 
Joined: Nov 2006
Location: Calgary, Alberta, Canada
Oddometer: 1,218
Quote:
Originally Posted by Bayner
Well, you're pretty close Griz. What actually happens is that the lever is returned to it's resting position by the spring behind the piston in the master cylinder bore. Pressure is thereby released on the caliper's piston and the remaining drag is removed by use of a square-cut and particularly formulated seal around the caliper piston.
'Dirt' in very small amounts can clog the passages in the ABS body/valving and can come from a wide range of sources either introduced or the interior surfaces of all the brake components exposed to the fluid. It's not very common however. Once a piston starts to corrode a little, whatever the cause- but typically old fluid, it can hang up a bit on the seal making it difficult to retract initially as the crud binds against the seal. Once you have forced it past, the symptom disappears. These bikes are too new for that to be an issue I would think.
Finally, an accurate answer. I've been following this thread and cringing at the inaccurate information and hypotheses that were being shared. I haven't had time to put together a detailed response of how disk brakes function. Give the man a gold star.
MCMXCIVRS is offline   Reply With Quote
Old 11-10-2010, 08:40 PM   #58
The Griz
North Forest Rider
 
The Griz's Avatar
 
Joined: Nov 2008
Location: Minnesota
Oddometer: 3,779
Quote:
Originally Posted by MCMXCIVRS
Finally, an accurate answer. I've been following this thread and cringing at the inaccurate information and hypotheses that were being shared. I haven't had time to put together a detailed response of how disk brakes function. Give the man a gold star.
Quote:
Originally Posted by The Griz
squeeze the lever and you're displacing fluid from the lever end of the brake system down to the caliper end, pressing the calipers and pads up against the rotor. When you release the lever, the spring or whatever return mechanism in the lever (typically a spring) moves the lever back out. This creates a void/vacuum in the lever end of the system drawing the fluid back up to the lever/reservoir end. No air. Just movement of fluid from one end to another.
I'd say my response prior to Bayner's (sorry Bayner) is pretty spot on and in fact accurate. I've thrown out a couple of hypotheses about why LaPorte was experiencing his issue, but my explanation of how the brake systems work has been accurate. I'll take that gold star now.


PS Also, air within a hydraulic brake system creating problems is not a "hypothesis". Ask any car, motorcycle, or bicycle mechanic: http://www.ehow.co.uk/how_5955008_di...-problems.html

"Pull in the brake lever. Does the lever feel firm or does it feel soft and mushy? A soft brake lever is a sign that air is trapped in the brake line, disrupting the hydraulic pressure between the brake caliper and the brake lever. Bleed the brake line at the caliper and remove any air bubbles to restore the hydraulic pressure in the brake system."



http://en.wikipedia.org/wiki/Hydraulic_brake

System Operation

Within a hydraulic brake system, as the brake pedal is pressed/ brake lever is squeezed, a pushrod exerts force on the piston(s) in the master cylinder causing fluid from the brake fluid reservoir to flow into a pressure chamber through a compensating port which results in an increase in the pressure of the entire hydraulic system. This forces fluid through the hydraulic lines toward one or more calipers where it acts upon one or two additional caliper pistons secured by one or more seated O-rings which prevent the escape of any fluid from around the piston.
The brake caliper piston(s) then apply force to the brake pads. This causes them to be pushed against the spinning rotor, and the friction between the pads and the rotor causes a braking torque to be generated, slowing the vehicle. Heat generated from this friction is often dissipated through vents and channels in the rotor and through the pads themselves which are made of specialized heat-tolerant materials (kevlar, sintered glass, et al.).
Subsequent release of the brake pedal/ lever allows the spring(s) within the master cylinder assembly to return that assembly's piston(s) back into position. This relieves the hydraulic pressure on the caliper allowing the brake piston in the caliper assembly to slide back into its housing and the brake pads to release the rotor. Unless there is a leak somewhere in the system, at no point does any of the brake fluid enter or leave.


Watch Pascal's Law video above. Release the lever and it will hydraulically "pull" the caliper back away from the rotor. That is what "releases" the pad from the rotor. That rubber seal around the caliper piston you speak of has nothing to do with it, other than to make sure no fluid is lost and no air is let in at said caliper piston.
__________________
PAUL BUNYAN FOREST RIDERS MC
2013 KTM 300 XC-W
2014 KTM 690 Enduro R
The Griz is offline   Reply With Quote
Old 11-10-2010, 09:44 PM   #59
itsatdm
Beastly Adventurer
 
itsatdm's Avatar
 
Joined: Jun 2004
Location: Nor Ca.
Oddometer: 4,732
All interesting stuff, but none of it explains why Laporte can't pry the pads apart. But this will, since it has happened to me about 75% of the time.

The pads are held in the caliper with a pin on the top and and a tab on the pad that fits in a shallow groove in the caliper.
While wrestling 50# of tire and wheel it is very likely for the rotor to nudge the pad. There is enough slop in the pin that you are very apt to cause the tab to come off the shelf and hang down slightly. It is not that noticable, but now the tab is resting against the end of the shelf and no amount of force is going budge that pad inward.

The first time it happened to me I took the caliper off and saw the problem. Now I just expect it and put the pad back where it belongs and put the tire on.
itsatdm is online now   Reply With Quote
Old 11-10-2010, 11:01 PM   #60
tmex
Beastly Adventurer
 
tmex's Avatar
 
Joined: Apr 2006
Location: NorCal
Oddometer: 2,039
Quote:
Originally Posted by itsatdm
All interesting stuff, but none of it explains why Laporte can't pry the pads apart. But this will, since it has happened to me about 75% of the time.

The pads are held in the caliper with a pin on the top and and a tab on the pad that fits in a shallow groove in the caliper.
While wrestling 50# of tire and wheel it is very likely for the rotor to nudge the pad. There is enough slop in the pin that you are very apt to cause the tab to come off the shelf and hang down slightly. It is not that noticable, but now the tab is resting against the end of the shelf and no amount of force is going budge that pad inward.

The first time it happened to me I took the caliper off and saw the problem. Now I just expect it and put the pad back where it belongs and put the tire on.
Sounds right to me. BTW, I was meeting with some Continental engineers today, and the next big thing will be brakes without hydraulics. Yes, you heard it right - all electronic actuation. That should make you feel warm and fuzzy. Unless, of course, it scares the hell out of you. It is a lot cheaper to run wires than it is to run hydraulic lines. Don't worry, BMW knows what is best for you.
__________________
my favorite bike - R1200GS
tmex is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 06:11 PM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014