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Soft Disc Brake Lever

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Soft Disc Brake Lever

Old 08-24-21, 02:44 PM
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Berge20
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Soft Disc Brake Lever

New to disc brakes, so may be a simple question. SRAM Red Hydrolic disc brakes for a road bike. Ridden it a few hundred miles with very tight brake levers (aka you touch them slightly and they grip quickly/hard). Took my new bike into my fitter this weekend (not at LBS that put it together). This required me removing front wheel and putting bike on its side in the car on a 45 minute ride with traffic both ways. Fitter made minor adjustments to the rig, including slight rotation of handle bars and adjusting the levers themselves to be closer to the bars for easier reach in the drops.

Come home and toss on the front wheel. Head out for a ride and realize that both front and rear brake pedals are soft (front) to very soft (rear) all of a sudden. I *believe* they both got progressively better over the course of a short ride but that could be my mind messing with me.

Question is am I looking at air in the lines somehow from putting the bike on its side for that short period of time in the car, or is there some other thing that happens when you adjust the SRAM AXS Red levers to be closer to your bars that may have also gotten tweaked at the fitter and I can quickly wrench on?

Likely heading to LBS that assembled it either way, but just trying to learn the ins and outs of this for my own benefit.

Thanks all for your knowledge and assistance. Hope I spelled brake right this time
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Old 08-24-21, 03:34 PM
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Air did not get into your brakes from the ride in the car...it was already there. The ride in the car may have made it move to the levers and result in them feeling 'soft'. This is similar to how a mechanic will test a hydraulic brake to see it has air someplace. You put the bike in a vertical position and pump the levers. Usually if there is air stuck somewhere in the system or in a spot inside the lever/master cylinder where it won't be a problem this will get it to move someplace where it becomes obvious what the problem is. You can have a lever feel nice and solid w/ the both wheels on the ground then pop it up on the back wheel and pump the levers only to find out you've got a bunch of air. This does make it easy to 'burp' the lever and get the air out. Have the shop that built your bike do this.
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Old 08-24-21, 05:51 PM
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I only have experience with Shimano MTB hydraulics but this is very similar. If I flip my bike up side down to do some work or on its side I get the soft brakes for a short bit. It usually works itself out quickly though. You've got some air in there as mentioned above. It worked ok at one point so may work itself out but also may have too much air in the system. It's fine if it's above the master cylinder but more air in the reservoir means it's more likely to get into the lines. Realistically you can't get it 100% out unless you bleed the brakes while flipping the bike in every direction. Pretty much not realistic. Could be you just have a bit too much air in there and just need a better bleed, also might work it's way out leaving the bike upright for a bit and working the brakes to get the air to the top.
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Old 08-24-21, 06:03 PM
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Originally Posted by Ryan_M View Post
I only have experience with Shimano MTB hydraulics but this is very similar. If I flip my bike up side down to do some work or on its side I get the soft brakes for a short bit. It usually works itself out quickly though. You've got some air in there as mentioned above. It worked ok at one point so may work itself out but also may have too much air in the system. It's fine if it's above the master cylinder but more air in the reservoir means it's more likely to get into the lines. Realistically you can't get it 100% out unless you bleed the brakes while flipping the bike in every direction. Pretty much not realistic. Could be you just have a bit too much air in there and just need a better bleed, also might work it's way out leaving the bike upright for a bit and working the brakes to get the air to the top.
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There should be NO air in the system. It is completely realistic to bleed it properly and get it all out. The air will NOT 'work it's way out'. You have to burp the lever OR bleed the system to get rid of it. Brakes w/ air somewhere in the system don't fix themselves.
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Old 08-24-21, 06:14 PM
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Originally Posted by cxwrench View Post
There should be NO air in the system. It is completely realistic to bleed it properly and get it all out. The air will NOT 'work it's way out'. You have to burp the lever OR bleed the system to get rid of it. Brakes w/ air somewhere in the system don't fix themselves.
Oh good it's you lol. I do enjoy our exchanges 🤣. I suggest you take that up with Shimano then and tell them they designed their parts wrong. I level the lever as best I can but the bleed port isn't right on the end of the cylinder. So unless 8m reorienting the bike during the bleed process it's nearly impossible. I go back and forth with the fluid and do what I can but it's not 100% doable to get all the air out. Probably not a bad thing to have a small bubble of air above the master cylinder anyways to deal with thermal expansion. There's no problem having a bubble there and saves blowing a seal if the fluid gets hot... which would just suck air back in when it cool.
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Old 08-24-21, 07:52 PM
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Originally Posted by Ryan_M View Post
Oh good it's you lol. I do enjoy our exchanges 🤣. I suggest you take that up with Shimano then and tell them they designed their parts wrong. I level the lever as best I can but the bleed port isn't right on the end of the cylinder. So unless 8m reorienting the bike during the bleed process it's nearly impossible. I go back and forth with the fluid and do what I can but it's not 100% doable to get all the air out. Probably not a bad thing to have a small bubble of air above the master cylinder anyways to deal with thermal expansion. There's no problem having a bubble there and saves blowing a seal if the fluid gets hot... which would just suck air back in when it cool.
Uhhh yeah, there shouldn't be air in the system. If properly bled there is no air. If you follow the instructions (Park Tool has an excellent video) you should be ok. Doing something wrong and making excuses to make it seem right isn't a good working solution.

I wouldn't be blowing seals unless they ask you to do it and they aren't drunk or high on seal drugs.
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Old 08-24-21, 08:54 PM
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Originally Posted by veganbikes View Post
Uhhh yeah, there shouldn't be air in the system. If properly bled there is no air. If you follow the instructions (Park Tool has an excellent video) you should be ok. Doing something wrong and making excuses to make it seem right isn't a good working solution.

I wouldn't be blowing seals unless they ask you to do it and they aren't drunk or high on seal drugs.
Im not talking about air in the system, I'm talking above the master cylinder. There's gotta be some give, other wise your brakes would just cease on, on a hot day as the fluid expanded until expansion exceeded that forcing oil out of the seals, or the brake line would rupture or crack a housing if the forces got too great. All car braking systems have an air gap above the master cylinder, as do crane hydraulic systems, and fork lifts, and any other industrial or commercial hydraulic system I've dealt with, and so does my bike because Shimano designed it that way. If they truly wanted zero air above the master cylinder they made a good effort to put the port in the wrong spot, I doubt that's true. But even still they'd have to add a mechanism to deal with expansion, a lot of effort to engineer around what an air gap does by nature.
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Old 08-25-21, 05:07 AM
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Ah, I'm learning! Had flipped the bike upsidedown to get a closer look at a tire valve giving me issues right before the ride. Now realize how that could shift some of that air within the system around in an unhelpful manner.

Thx all. Still may have the LBS guys have a look if it doesn't return to normal after some upright time and some work.
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Old 08-25-21, 07:56 AM
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Try holding the brake lever on with a strap and left overnight. Leave the bike upright and when releasing the strap let the lever quickly snap back. This can sometimes release an air bubble trapped at the master cylinder. It also may help to tap the brake line with your finger a couple times while the lever is clamped to help move any air to the top.
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Old 08-25-21, 07:16 PM
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Thx, will give it a go.
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Old 08-25-21, 07:19 PM
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Originally Posted by Crankycrank View Post
Try holding the brake lever on with a strap and left overnight. Leave the bike upright and when releasing the strap let the lever quickly snap back. This can sometimes release an air bubble trapped at the master cylinder. It also may help to tap the brake line with your finger a couple times while the lever is clamped to help move any air to the top.
Usually when I flip the bike upside down to do something quick the brakes come back to normal after working the lever a dozen times or so. If it ever happens it doesn't I'll keep this in mind. Thanks!
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