Issue with spongy rear brakes after tube change

Hello All,

This is the 2nd time I am noticing this on my Stromer ST1 and I wonder if I am doing something wrong.

I decided to replace the tube on my rear tire for which I ended up having to remove the rear wheel. When I put it back, I noticed that the rear disc brake had suddenly become super spongy. It definitely wasn't that way prior.

This is the 2nd time this is happening. I am having to perform a bleed, but because of the co-incidence with the tube change, I wonder if I am doing something wrong. Are there adjustments other than removing air from the brake line that could potentially address this issue?

I have standard Shimano brakes that take mineral oil.

Many thanks
 

fooferdoggie

Well-Known Member
flipping will make it worse if there is air in the line. touching the levers yep. I knew about that I once took the pads out to check the wear saw I needed to put new ones in so I settled the bike to shift down then squeezed the lever. oops.
 
I tried the quick bleed (the one where I pour in oil using the funnel and then flick the brakes to release trapped air) and it did not work. Looks like I need to do the full bleed...urghh
 

PedalUma

Well-Known Member
Region
USA
City
Petaluma, CA
Do you have a brake blead syringe? Interesting thing. If you put the mineral oil in a stopped syringe and pull back the plunger bubbles will appear like ginger ale. If you hold it in that position, under suction, for an hour in a vice you will extract all of the dissolved gasses. And will avoid getting another vapor gap in the line. I believe @fooferdoggie has not tried this and thinks that it is nutty. If you try it you will see that it is real and that it works.
 

fooferdoggie

Well-Known Member
Do you have a brake blead syringe? Interesting thing. If you put the mineral oil in a stopped syringe and pull back the plunger bubbles will appear like ginger ale. If you hold it in that position, under suction, for an hour in a vice you will extract all of the dissolved gasses. And will avoid getting another vapor gap in the line. I believe @fooferdoggie has not tried this and thinks that it is nutty. If you try it you will see that it is real and that it works.
or just pump enough new fluid in the fully replace the old? that would be far faster.
 
Do you have a brake blead syringe? Interesting thing. If you put the mineral oil in a stopped syringe and pull back the plunger bubbles will appear like ginger ale. If you hold it in that position, under suction, for an hour in a vice you will extract all of the dissolved gasses. And will avoid getting another vapor gap in the line. I believe @fooferdoggie has not tried this and thinks that it is nutty. If you try it you will see that it is real and that it works.
Something like this:

Do I need to tinker with the brake pistons etc. for this approach? And do I really need a bike stand to tilt the bike?
 

PedalUma

Well-Known Member
Region
USA
City
Petaluma, CA
Something like this:

Do I need to tinker with the brake pistons etc. for this approach? And do I really need a bike stand to tilt the bike?
Yes, Exactly. You don't need a stand. You can just have the bike against a workbench or even a wall. The syringe technique really works to get the air out. As the guy in the vid says do it a few times. Some of them have an extension tube with a locking crimp. Get to the part where he does the half-pull.
 

PedalUma

Well-Known Member
Region
USA
City
Petaluma, CA
1652216195854.jpeg
 
Yes, Exactly. You don't need a stand. You can just have the bike against a workbench or even a wall. The syringe technique really works to get the air out. As the guy in the vid says do it a few times. Some of them have an extension tube with a locking crimp. Get to the part where he does the half-pull.
Got it....seems a lot easier than a full bleed...which is do-able, but something I have absolutely no time for unfortunately. I will give this a shot before attempting a full bleed. Waiting for the Royal Blood oil to arrive in a couple of days.
 
I ended up doing a full bleed (super messy given it's my first time, but I now get it).

Turns out I have sticky pistons as well, which I will tackle next.

Also: I have the issue of aligning the disc to the pads. Question about this: can I do this with my bike turned upside down? Now that (hopefully) all the air is out of my brake lines, I am hoping this is ok...otherwise I can't think of an easy way to align my wheel/brake disc with the brake pads/calipers.

Thanks!
 

fooferdoggie

Well-Known Member
I ended up doing a full bleed (super messy given it's my first time, but I now get it).

Turns out I have sticky pistons as well, which I will tackle next.

Also: I have the issue of aligning the disc to the pads. Question about this: can I do this with my bike turned upside down? Now that (hopefully) all the air is out of my brake lines, I am hoping this is ok...otherwise I can't think of an easy way to align my wheel/brake disc with the brake pads/calipers.

Thanks!
Iowuld do the alignment with the bike in the normal position. it would be easier I would think.
 

PedalUma

Well-Known Member
Region
USA
City
Petaluma, CA
With the bike right side up apply slight pressure to the lever with a Velcro strap or rubber band. Loosen the mounting bolts partially. Then slowly and evenly tighten the mounting bolts as you turn the wheel with your free hand. That is it! It will be aligned.
 
All done....really enjoyed the process and learned a lot as well.

General question for you guys. When doing full bleeds, do you prefer removing the calipers or the wheels? Based on my current experience, personally, I feel for the rear brakes, removing calipers is easier because the rear wheel is super heavy and a pain to re-install. But when I bleed the front brakes next, I might just remove the tires....saves me another round of aligning.
 

fooferdoggie

Well-Known Member
All done....really enjoyed the process and learned a lot as well.

General question for you guys. When doing full bleeds, do you prefer removing the calipers or the wheels? Based on my current experience, personally, I feel for the rear brakes, removing calipers is easier because the rear wheel is super heavy and a pain to re-install. But when I bleed the front brakes next, I might just remove the tires....saves me another round of aligning.
I remove the caliper to get the angle of the line better. I don't remove the front.
 

m@Robertson

Well-Known Member
Region
USA
I try to remove nothing. Only re-orient the lever so the reservoir hole is the highest point of the assembly. However there's a lot to be said for removing the caliper and its something I should do since its so easy to re-align Magura calipers.. This vid gets into why you remove the caliper (fluid release from the opened caliper). It also shows you how to do a full bleed for push thru and pull back. I use a simple syringe up at the lever, not an expensive bleed kit.


If I am doing a quick bleed, I still put the open syringe at top in the reservoir, halfway fill it, and then tap on the calipers and flick the levers to get most of the bubbles out. This quicker method works 'good enough' almost always.
When you pull a wheel off, its normal on hydros for the lever to be really spongy as the pistons often expand and that makes it seem like the brakes have failed. After installation, squeeze the levers a bunch of times and the system will come back.
 
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