I bleed my brakes today and I'm not able to get my pistons to extend. They are current retracted, but nothing gets them back out even with the air bubbles removed. Also, the brakes have no tension. I made this video that reveals what the issue and what I did. Please provide advice.
2 Answers
You're bleeding them wrong.
Tektro has been making decent hydros, but the clarity of their published bleed procedures has still left a lot to be desired, so I don't blame you.
Their published instructions differ a little across models, but what I do for most of them is put a bleed block in, position them such that the port on the lever is the highest point and the port on the caliper is the lowest point, put a syringe on each end (starting with the new fluid in the caliper end), and push the fluid up while applying gentle back pressure on the lever syringe plunger. This is where you'll see most of your bubbles. Then if what came out is dirty, I remove and drain the lever syringe, replace it, refill the caliper syringe, and repeat until I'm getting clean looking fluid all the way through. Then I push it back and forth a few times, keeping the syringes upright to collect the air. You could bonk on the caliper and lever with a soft tool to loosen bubbles if you want, but I typically find it not necessary. When you're not getting any more bubbles in either direction, remove the syringe from the caliper end first and close the port tight, then the lever end. Once both ends are sealed, squeeze the lever with the bleed block still in, and it should be rock solid. I never actuate the brake lever before this with Tektros.
If you only have one syringe (the Tektro consumer kit only comes with one), I believe you do it by setting up a collection bag at the lever end and pushing fluid up from the caliper, but to be honest I never do it this way so I may be missing something.
No bike brakes today are bled without a bleed block in place between the pistons. You don't want the pistons able to move around during the bleed process because then the fluid will be overfilled and your pad gaps will be all screwed up. You can improvise one by cramming whatever in there and holding it in with tape or a rubber band. Or, in most cases a Shimano block of the same pad type will go right in too.
Actuating the lever like you're doing in the video with the caliper bleed port still open is going to cause the exact behavior you're seeing of shooting fluid out of the bleed port without moving the pistons. The pistons have some resistance to overcome from the seals etc, but the fluid will move freely. There's not really a circumstance I can think of where it makes sense to squeeze the lever with the caliper bleed port open.
answered Aug 3, 2020 at 4:47
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2Thank you for the reply and the explanation what I did wrong. Everyone shows videos what to do, but it would be great to understand what never to do and what you described, my mistakes, makes complete sense. I saw some videos about the multiple syringe approached. It’s quite difficult with 1 person, so maybe this approach will be easier. I have a whole new bleed kit ordered and this comes with multiple syringes, bleed block and other pieces. I’ll start again Wednesday.– EvanCommented Aug 3, 2020 at 11:31
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It's definitely easy to feel like you don't have enough hands when you're still learning how to bleed brakes. Remember there's no shame in rigging something up to be able to keep the syringe upright when you have your hands off of it. When possible with this kind of two-syringe style bleed, what I do sometimes to solve that problem is use a short, stiff piece of tubing on the lever syringe, i.e. by cutting a short piece off whatever comes with the kit and using that, so that it stays upright by itself easily with my hands off of it. Commented Aug 4, 2020 at 6:17
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EDIT I did it one more time and I got it. I gave it all I could and got it done in like 10 minutes once I did it right memorized. wow! Now for a test drive...– EvanCommented Aug 5, 2020 at 4:53
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I took it out for a test drive and the back brake doesn't have the stopping power it once had. The right lever that controls my back brake still feels squishy and not firm either unlike my left brake for my front wheel is firm and has great stopping power. So, now my back brake comes to a rolling stop now. I wrote JuicedBike to let them know this brake system is compromised and I need a replacement just to be safe. One more observation, if I role my bike backwards and try to stop, my back brakes squeaks badly. I may have gotten oil on it, but still my brake level is really squishy now.– EvanCommented Aug 5, 2020 at 5:13
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I read online that if the brake lever still feels spongy, it's because there's still air trapped in the line. However, I did the double syringe effort maybe 20 times and let me tell you, it was pretty tough solo and i got all those nasty air bubbles out. I see the calipers move my break pads in and out now, too, but the break lever still feels spongy and not firm and the rolling start.– EvanCommented Aug 5, 2020 at 12:55
You might need to buy a better quality bleed kit.
I had the same problem. It was my bleed kit as the connector/adaptor was not fitting fully and was introducing air to the system. I bought a better bleed kit and followed the advice above and the brakes are better then new.
