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SRam Hydro brakes…

Old 05-14-22, 11:41 AM
  #1  
Fentuz
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SRam Hydro brakes…

After a winter of mud, i noticed that the rival brake lever were getting closer to the handle bar. The squeeze increased as the pads wore out.
I aware that the reach is adjustable but the issue more the added degree of rotation.

Although I do most servicing/repair/upgrade myself, i took the bike to a pro shop for the yearly inspections (bb swap, wheel check, fluid bleed). The bike shop said the brakes were fine and it is just a result of the wear and tear.

so to get the brake feel back as I like it, new pads seemed to be the answer but was it?
the pads lost 0.15mm per side (2.05mm material left), discs are 0.05mm worn (0.2mm above minimal thickness).

So I took my filler blade and found there was just above 0.13mm clearance between pads and disc on either side.
pick up a can of coke (best and cheapest 0.1mm shim material) and cut some pads back shims (pad backing plate contour) as fitted a shim on either side.
results is good; brake feel is back to how I like it…
cost: not much
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Old 05-15-22, 09:59 PM
  #2  
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Hydraulic brakes are self-adjusting (or should be) so if the pads are not as close to the rotor and the lever feels soft, you probably need to bleed the brakes. You could also have a warped rotor causing what you are describing.
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Old 05-16-22, 02:25 AM
  #3  
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Originally Posted by Chilepines View Post
Hydraulic brakes are self-adjusting (or should be) so if the pads are not as close to the rotor and the lever feels soft, you probably need to bleed the brakes. You could also have a warped rotor causing what you are describing.
Discs are fine (dti clocked when the wheel were checked) , fluid was bled by a pro, yes twin pot calipers self adjust but I found that you can feel a difference when the pads start to wear. I used to feel the same on my race car with twin pots and no servo despite bleeding and reverse bleeding. When I fitted brand new pagid rs14, it was rock solid with very little pedal travel and after a couple of races, the travel was longer despite bleeding and use or 660 racing fluid.

Note that on the bike, the feel is not spongy, the braking power is still there and does not fade, the lever just travels more possibly because the pots retract back to much in the caliper housing. May be, when there is not pressure, the retracting springs are too strong causing the pads to retract back more than they really need. I have always wondered why Bike hydro calipers required those pad springs, cars don't need it and I don't believe motorbike have them either. Are these springs artefact of the mechanical disc system (like on some car hand brake/ebrake/parking brake)?

I also noticed that on the gorilla pads I currently use, the pots created an indent in the coating of the back plate (didn't get that on galfer or sram pads). I'm not to concern about that as it can help locating the pad on the piston/pot reducing potential movement /rattling when pressure is not applied. (known issue with AP twin pot calipers and the good old girling).

Last edited by Fentuz; 05-16-22 at 02:31 AM.
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Old 05-16-22, 04:28 AM
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Originally Posted by Chilepines View Post
Hydraulic brakes are self-adjusting (or should be) so if the pads are not as close to the rotor and the lever feels soft, you probably need to bleed the brakes. You could also have a warped rotor causing what you are describing.
I can tell you from experience that SRAM road hydro levers are not self adjusting. The lever throw gets longer as the pads wear, until you have to replace the pads because the levers are hitting the bars.
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Old 05-17-22, 02:41 PM
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Originally Posted by dsaul View Post
I can tell you from experience that SRAM road hydro levers are not self adjusting. The lever throw gets longer as the pads wear, until you have to replace the pads because the levers are hitting the bars.
SRAM disagrees with this statement.
https://www.sram.com/en/service/arti...e%20pad%20wear.
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Old 05-17-22, 03:29 PM
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Originally Posted by Fentuz View Post
After a winter of mud, i noticed that the rival brake lever were getting closer to the handle bar. The squeeze increased as the pads wore out.
I aware that the reach is adjustable but the issue more the added degree of rotation.

Although I do most servicing/repair/upgrade myself, i took the bike to a pro shop for the yearly inspections (bb swap, wheel check, fluid bleed). The bike shop said the brakes were fine and it is just a result of the wear and tear.

so to get the brake feel back as I like it, new pads seemed to be the answer but was it?
the pads lost 0.15mm per side (2.05mm material left), discs are 0.05mm worn (0.2mm above minimal thickness).

So I took my filler blade and found there was just above 0.13mm clearance between pads and disc on either side.
pick up a can of coke (best and cheapest 0.1mm shim material) and cut some pads back shims (pad backing plate contour) as fitted a shim on either side.
results is good; brake feel is back to how I like it…
cost: not much
I can't believe I'm typing this, but I would definitely recommend you remove the DIY Coke can shims you installed, and figure out what is causing the problem and fix it. SRAM brake systems are poorly designed and notoriously difficult for inexperienced shops to troubleshoot. If your shop is sending you home with malfunctioning brakes and just telling you it's normal, you need to find a new shop that has experience working on SRAM hydro brakes. The lever bottoming out is not normal, nor is it caused by worn pads. SRAM brakes (like nearly every hydro brake system out there) are supposed to self adjust to compensate for pad wear. If your system isn't self-adjusting, something is probably stuck/broken or the contact point/reach adjustement has been changed, etc.. My guess is you've got a stuck piston(s).
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Old 05-17-22, 07:31 PM
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Originally Posted by msu2001la View Post
I can't believe I'm typing this, but I would definitely recommend you remove the DIY Coke can shims you installed, and figure out what is causing the problem and fix it. SRAM brake systems are poorly designed and notoriously difficult for inexperienced shops to troubleshoot. If your shop is sending you home with malfunctioning brakes and just telling you it's normal, you need to find a new shop that has experience working on SRAM hydro brakes. The lever bottoming out is not normal, nor is it caused by worn pads. SRAM brakes (like nearly every hydro brake system out there) are supposed to self adjust to compensate for pad wear. If your system isn't self-adjusting, something is probably stuck/broken or the contact point/reach adjustement has been changed, etc.. My guess is you've got a stuck piston(s).
Yup! Or contaminated pads and/or rotors also.
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Old 05-17-22, 10:47 PM
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Like I said, there is no brake fade, just longer travel.
i looked at the pistons and they move freely, they are clean. I cannot see and issue with the system, it works similarly to a AP or Brembo or Girling setup from a caliper system point of view.
the only thing different is the pads back spring.

Why did sram put that there? The spring keep pushing back the pad backing plate again the caliper housing. Basically, for those you have replace pads on cars, the spring is doing what you would do to push back the piston is the housing before fitting new pads.

self adjusting should/would work if there was nothing constantly backing the pads back
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Old 05-18-22, 03:11 PM
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Originally Posted by Fentuz View Post
Like I said, there is no brake fade, just longer travel.
i looked at the pistons and they move freely, they are clean. I cannot see and issue with the system, it works similarly to a AP or Brembo or Girling setup from a caliper system point of view.
the only thing different is the pads back spring.

Why did sram put that there? The spring keep pushing back the pad backing plate again the caliper housing. Basically, for those you have replace pads on cars, the spring is doing what you would do to push back the piston is the housing before fitting new pads.

self adjusting should/would work if there was nothing constantly backing the pads back
That spring is definitely not exerting enough force to displace the pistons, so I think you’re creating your own boogieman here…
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Old 06-01-22, 02:12 PM
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The spring is just there to prevent the pads from rattling in the caliper. If they were allowed to move freely on the retainer pin, they'd buzz the rotor every time you moved the bike side to side and you'd slowly lose your mind. BTW, cars do use anti-rattle springs, here's one on a typical BMW brake:



It's the skinny metal part clipped onto the two vertically oriented metal holes. I've left one off by accident, believe me, you know it.
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