motorbyclist
7th January 2009, 21:38
Feel free to make any corrections or ask any questions :)
Right, so here's my how-to on replacing all the seals in a floating caliper hydraulic brake setup, but is basically the same process across the entire hydraulic caliper type range.
I'm not a brake expert, and this was my first time, but it's not difficult and I'm not entirely stupid either so hopefully by making all the mistakes I can prevent others from doing the same. Think of this as a handy reference:)
I did this without disconnecting the lines as I'm a lazy bugger and there's no real cause to. If you DO separate the lines the copper washers at the joints are actually gaskets and should be replaced. If you seem to have a pressure leak somewhere these may be the cause - Ive seen spurts of fluid come out before but it might not be so obvious.
For the record, brake fluid DOES strip paint, and can do so very quickly in some cases. As with most things it's not good for skin either but after spending a day in contact with the stuff I'm still ok.... I meant to wear latex gloves to see if they survived but never got round to it.
Look at the pictures in part six (a few posts down the page) for a very handy tip when it comes to safely pouring brake fluid.
Always use the specified grade of brake fluid from a fresh (unopened) container - Brake fluid is hydrophillic; it loves moisture and will draw it in from the air around it.
If the new fluid is a different colour to the old stuff this helps you see when you've bled all the fluid through;)
Also, while my yamaha manual gave full instructions on how to do this, I ignored them and read afterwards - there was more about safety warnings and 'replace with new' than actual instructions...
Foreword: Brake Bleeding, because your brakes are spongy or soft and/or the fluid is old
Brakes can become spongy or soft over time for any number of reasons, including air bubbles and old fluid. Old fluid can be particularly dangerous as water may does get in over time and if it boils from the heat of braking your brakes will lock solid.
So if you are simply bleeding your brakes, without any seal work or replacing the pads, you need should not even remove the calipers - just fit a clear tube to the nipple and route it to a receptacle then use the 'as per the manual' method: open nipple - pull lever - close nipple - release lever - repeat - don't forget to keep topping up the reservoir!
<img src="http://www.kiwibiker.co.nz/forums/picture.php?albumid=1366&pictureid=14329">
The clear tube lets you see the bubbles coming out and keeps things clean. Afterwards give the area a thorough clean with soapy water to stop the paint peeling off. The nipple is operated like a tap, a quarter turn anticlockwise is enough to open it, and just nip it tight to close. When you're done tighten it properly but don't go overboard.
Brakes will always be slightly soft when using standard brake lines as they will expand/stretch under pressure, and more so as the lines age. Stainless steel braided lines or even just a harder rubber line will improve the 'feel' of your brakes dramatically.
If you do elect to remove the calipers first, ensure that the pistons can not accidentally push out or you will have a bit of work ahead of you ;)
Part One: The Problem - Brakes Lose Pressure
So to begin, I did this for a number of reasons, and on two of the same bike.
My bike, which I did first, had nothing 'wrong' with it but a squishy feel due to not being bled or having fluid replaced for years - a job which should be done annually - but now being eleven years old I decided I should do it while parts were still around, and seeing as I had to do my brother's bike anyway this way we could compare between working brakes and buggered brakes if anything got difficult.
My brother's bike had a problem whereby the system would loose pressure while sitting and while in use. He had bled the system several times to no avail and then his fork seals went and dumped fork oil all over his brakes anyway. I'm told oil is not good to brake seals, just as brake fluid is Not Good to everything else.
Right, so here's my how-to on replacing all the seals in a floating caliper hydraulic brake setup, but is basically the same process across the entire hydraulic caliper type range.
I'm not a brake expert, and this was my first time, but it's not difficult and I'm not entirely stupid either so hopefully by making all the mistakes I can prevent others from doing the same. Think of this as a handy reference:)
I did this without disconnecting the lines as I'm a lazy bugger and there's no real cause to. If you DO separate the lines the copper washers at the joints are actually gaskets and should be replaced. If you seem to have a pressure leak somewhere these may be the cause - Ive seen spurts of fluid come out before but it might not be so obvious.
For the record, brake fluid DOES strip paint, and can do so very quickly in some cases. As with most things it's not good for skin either but after spending a day in contact with the stuff I'm still ok.... I meant to wear latex gloves to see if they survived but never got round to it.
Look at the pictures in part six (a few posts down the page) for a very handy tip when it comes to safely pouring brake fluid.
Always use the specified grade of brake fluid from a fresh (unopened) container - Brake fluid is hydrophillic; it loves moisture and will draw it in from the air around it.
If the new fluid is a different colour to the old stuff this helps you see when you've bled all the fluid through;)
Also, while my yamaha manual gave full instructions on how to do this, I ignored them and read afterwards - there was more about safety warnings and 'replace with new' than actual instructions...
Foreword: Brake Bleeding, because your brakes are spongy or soft and/or the fluid is old
Brakes can become spongy or soft over time for any number of reasons, including air bubbles and old fluid. Old fluid can be particularly dangerous as water may does get in over time and if it boils from the heat of braking your brakes will lock solid.
So if you are simply bleeding your brakes, without any seal work or replacing the pads, you need should not even remove the calipers - just fit a clear tube to the nipple and route it to a receptacle then use the 'as per the manual' method: open nipple - pull lever - close nipple - release lever - repeat - don't forget to keep topping up the reservoir!
<img src="http://www.kiwibiker.co.nz/forums/picture.php?albumid=1366&pictureid=14329">
The clear tube lets you see the bubbles coming out and keeps things clean. Afterwards give the area a thorough clean with soapy water to stop the paint peeling off. The nipple is operated like a tap, a quarter turn anticlockwise is enough to open it, and just nip it tight to close. When you're done tighten it properly but don't go overboard.
Brakes will always be slightly soft when using standard brake lines as they will expand/stretch under pressure, and more so as the lines age. Stainless steel braided lines or even just a harder rubber line will improve the 'feel' of your brakes dramatically.
If you do elect to remove the calipers first, ensure that the pistons can not accidentally push out or you will have a bit of work ahead of you ;)
Part One: The Problem - Brakes Lose Pressure
So to begin, I did this for a number of reasons, and on two of the same bike.
My bike, which I did first, had nothing 'wrong' with it but a squishy feel due to not being bled or having fluid replaced for years - a job which should be done annually - but now being eleven years old I decided I should do it while parts were still around, and seeing as I had to do my brother's bike anyway this way we could compare between working brakes and buggered brakes if anything got difficult.
My brother's bike had a problem whereby the system would loose pressure while sitting and while in use. He had bled the system several times to no avail and then his fork seals went and dumped fork oil all over his brakes anyway. I'm told oil is not good to brake seals, just as brake fluid is Not Good to everything else.