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Is it possible to bleed disc brakes without the expensive kit?

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Is it possible to bleed disc brakes without the expensive kit?

Old 10-06-13, 10:50 PM
  #1  
bobotech
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Is it possible to bleed disc brakes without the expensive kit?

I'm building up my old Hardrock with some upgraded parts. My Hardrock has disc brake tabs so I put disc brakes on it.

We recently got a donation of some disc brake parts including a complete front/rear set of Avid Juicy 7 brakes with rotors and a disc brake wheelset. They are all mounted on my bike now however the front one need to be bled badly, it doesn't even work.

I found out that the bleeding kit costs roughly 60 dollars and that is quite a bit of money that I don't have. I'm used to bleeding car brakes which is pretty simple. You pump the brakes a few times, hold the pedal to the floor, open the bleeder valve on the caliper, and repeat til air no longer spits out of the bleeder valve. Is bleeding a hydraulic bike brake system anything like that?
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Old 10-07-13, 01:43 AM
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It is probably possible to do it without a kit but it may be messy and results may vary. I understand your point as $60 seems a bit excessive. If you are going to have your bike for a while I recommend investing the $19 for a bleed kit so you have the tools to do the job conveniently whenever you need to.

https://www.amazon.com/Avid-Brake-Ble...cy+7+bleed+kit

Here are some links to guid you through the procedure:
https://www.youtube.com/watch?v=6mg6NbIjmOM

https://www.parktool.com/blog/repair-...-bleed-service

-j
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Old 10-07-13, 01:54 AM
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The key difference between bike hydraulics and car hydraulics is "open" vs "closed" system. A car system is open, meaning the reservoir isn't under pressure and that the main cylinder will be refilled from the reservoir when the lever is released.
A bike system is closed, meaning there really isn't a reservoir to draw from. The system is blocked off at both ends, all the time.
If you think of bleeding a bike brake as first adding a reservoir, then the rest is pretty much like bleeding a car brake.
Some recommend that you should create some suction as well, to make it easier for any air bubbles to escape. The argument being that with the small volumes used in a bike, flow enough won't get rid of the bubbles as it does in a car.
Bleed kits do make the job easier and less messy, but if you look at the instructions you'll soon notice that the main part of the bleed kits are the syringes. And syringes you can get elsewhere, for less money. I've gotten mine from pharmacies and lab equipment suppliers.
With a bit of luck, you can jam them into the bleed ports well enough to get the job done w/o any further equipment.
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Old 10-07-13, 02:33 AM
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Looks like a much cheaper option.
FYI, when bleeding car brakes, don't push the pedal to the floor, you can actually do more harm that way as the Master Cylinder rod can get gunked up. Only push it down as far as you would normally during braking.
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Old 10-07-13, 10:37 AM
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Originally Posted by Greenfieldja View Post
It is probably possible to do it without a kit but it may be messy and results may vary. I understand your point as $60 seems a bit excessive. If you are going to have your bike for a while I recommend investing the $19 for a bleed kit so you have the tools to do the job conveniently whenever you need to.

https://www.amazon.com/Avid-Brake-Ble...cy+7+bleed+kit

Here are some links to guid you through the procedure:
https://www.youtube.com/watch?v=6mg6NbIjmOM

https://www.parktool.com/blog/repair-...-bleed-service

-j
Awesome, much cheaper than buying the 60 dollar kit at the bike shop.

Originally Posted by dabac View Post
The key difference between bike hydraulics and car hydraulics is "open" vs "closed" system. A car system is open, meaning the reservoir isn't under pressure and that the main cylinder will be refilled from the reservoir when the lever is released.
A bike system is closed, meaning there really isn't a reservoir to draw from. The system is blocked off at both ends, all the time.
If you think of bleeding a bike brake as first adding a reservoir, then the rest is pretty much like bleeding a car brake.
Some recommend that you should create some suction as well, to make it easier for any air bubbles to escape. The argument being that with the small volumes used in a bike, flow enough won't get rid of the bubbles as it does in a car.
Bleed kits do make the job easier and less messy, but if you look at the instructions you'll soon notice that the main part of the bleed kits are the syringes. And syringes you can get elsewhere, for less money. I've gotten mine from pharmacies and lab equipment suppliers.
With a bit of luck, you can jam them into the bleed ports well enough to get the job done w/o any further equipment.
Yeah, the more I look at the kit, I already have everything except for the actual fittings that screw into the ports. Its a shame you can't get just the brass fittings. I have the syringes, the tubes, and even a pile of those plastic click hose clamps. Hmmm. I wonder if I can get a small car bleeder screw to fit into the bleed port of the caliper? In that case, I already have all the parts necessary.

I have the syringes since I used them to bleed oil injection pumps on 2 cycle engines.

But then again, 19 dollars isn't bad for the whole kit.
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Old 10-07-13, 11:39 AM
  #6  
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We recently got a donation of some disc brake parts including a complete front/rear set of Avid Juicy 7 brakes with rotors and a disc brake wheelset
Who is WE? CO OP? , Get the kit, pay if forward, donate it. Its a CO OP .
you snagged the brakes someone else donated.


Wouldn't call them expensive plastic hoses and plastic disposable medical syringes
and a fitting to screw into the fill connection

tidy is another syringe and fitting and push the bubbly fluid into it, so as to not make a mess .


DOT fluid eats paint, clean that up.

Last edited by fietsbob; 10-07-13 at 11:50 AM.
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Old 10-07-13, 11:48 AM
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Originally Posted by dabac View Post
The key difference between bike hydraulics and car hydraulics is "open" vs "closed" system. A car system is open, meaning the reservoir isn't under pressure and that the main cylinder will be refilled from the reservoir when the lever is released.
A bike system is closed, meaning there really isn't a reservoir to draw from. The system is blocked off at both ends, all the time.
If you think of bleeding a bike brake as first adding a reservoir, then the rest is pretty much like bleeding a car brake.
Some recommend that you should create some suction as well, to make it easier for any air bubbles to escape. The argument being that with the small volumes used in a bike, flow enough won't get rid of the bubbles as it does in a car.
Bleed kits do make the job easier and less messy, but if you look at the instructions you'll soon notice that the main part of the bleed kits are the syringes. And syringes you can get elsewhere, for less money. I've gotten mine from pharmacies and lab equipment suppliers.
With a bit of luck, you can jam them into the bleed ports well enough to get the job done w/o any further equipment.
There are open systems in the bicycle world too. Shimano would be the most obvious and common example.
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Old 10-07-13, 11:52 AM
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disc brake have expansion tanks in their master/levers, a rubber diaphragm
covers the fluid so there wont be air introduced when the bike is not upright.

Cars dont really get flipped over in normal operation.

Last edited by fietsbob; 10-07-13 at 11:57 AM.
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Old 10-07-13, 12:04 PM
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Originally Posted by bobotech View Post
Awesome, much cheaper than buying the 60 dollar kit at the bike shop.


Yeah, the more I look at the kit, I already have everything except for the actual fittings that screw into the ports. Its a shame you can't get just the brass fittings. I have the syringes, the tubes, and even a pile of those plastic click hose clamps. Hmmm. I wonder if I can get a small car bleeder screw to fit into the bleed port of the caliper? In that case, I already have all the parts necessary.

I have the syringes since I used them to bleed oil injection pumps on 2 cycle engines.

But then again, 19 dollars isn't bad for the whole kit.

Are your syringes threaded to connect to the fitting that attaches to the caliper bleed port?

-j
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Old 10-07-13, 12:14 PM
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Originally Posted by fietsbob View Post
Who is WE? CO OP? , Get the kit, pay if forward, donate it. Its a CO OP .
you snagged the brakes someone else donated.


Wouldn't call them expensive plastic hoses and plastic disposable medical syringes
and a fitting to screw into the fill connection

tidy is another syringe and fitting and push the bubbly fluid into it, so as to not make a mess .


DOT fluid eats paint, clean that up.
Actually that is my plan. I'm going to get a kit or build a kit and donate to the co-op. If I ever needed to use it again, we have it at the shop. We had someone donate 4 sets of nice hydraulic disc brakes and like 12 or more nice disc rotors, 5 nice mountain bike derailleurs (deore and xtr level), and 3 decent forks including one 29er dual air chamber fork. We were tickled to have such a nice donation, that normally doesn't happen to us.
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Old 10-07-13, 12:21 PM
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Originally Posted by Greenfieldja View Post
Are your syringes threaded to connect to the fitting that attaches to the caliper bleed port?

-j
Oh no, they aren't. They are just normal syringes with the tapered nozzle. THe nozzle is like the tapered nozzle that you find on crazy glue.
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Old 10-08-13, 05:44 AM
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Yes. I do it all the time. My kit is a big plastic syringe and a couple of short lengths of car windscreen washer hose. The purpose built kits (like a great many cycling tools) make the job faster - which is important in a commercial workshop.

A big difference between bike bleeds and cars is that with a bike you can usually contrive to make the hose run continually "up-hill" from the caliper to the lever.

Be careful if you're using dot4 fluid - protect your eyes, even if just a pair of sunglasses.
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Old 10-08-13, 11:05 AM
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Speaking of fluids, What is a good way to tell the difference between dot 3-4-5? I have read that the Juicy brakes use DOT based fluids which is fine but I'm not sure how to tell the difference, I don't think you can mix them.
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Old 10-08-13, 11:46 AM
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What is a good way to tell the difference between dot 3-4-5?
<stating the obvious> read the label on the can, once its out of the can , there is no label to read.
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Old 10-08-13, 02:31 PM
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Dot 3, 4 and 5.1 are compatible, dot 5 is not. Most bicycle brakes from after the year 2000 or so will specify dot 4 or 5.1. Some older Hayes etc brakes will say 3 or 4, but you can use the more stable 5.1.

The avid kit comes with 5.1. You must use 2 syringes for avid brakes, the top syringe pulls air from the lever as well as receiving the fluid that is pushed up from the bottom.

There are two avid kits, a cheap and less cheap one. The cheap one is ample for most. If still not cheap enough, there are a few off-brand ones around eg https://www.ebay.com.au/itm/like/180832926726?lpid=87

- joel
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Old 10-08-13, 04:56 PM
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Originally Posted by fietsbob View Post
<stating the obvious> read the label on the can, once its out of the can , there is no label to read.
Well duh!

I'm talking about not knowing what is in the brake system currently. From the other person's post, I can probably safely use DOT 5.1 fluid and have no issues.

I thought that DOT 3 and 4 and 5 were not compatible with each other and it turns out that DOT 5 isn't compatible but the newer 5.1 is so that is what I shall get at the auto parts store.
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Old 10-08-13, 05:37 PM
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Contact Manufacturer .. I dont do service on car's brakes , they are who that stuff is made for,
bikes just use it because its easy to source .
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