Nerding out on Brakes shall we? Not another tech deraliment

mtbjoe wrote:

Interesting thoughts but I will tell you that I cannot turn the bite point in all the way now or the brake locks up. That tells...

Interesting thoughts but I will tell you that I cannot turn the bite point in all the way now or the brake locks up. That tells me the above explanation about bite point adjustment not moving pads is incorrect 

kane wrote:

https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Fbikeadvice.in%2Fwp-content%2Fuploads%2F2010%2F11%2FMC-6.jpg&f=1&ipt=57742ea1c1bad29ad4d3d164cf3bfb106b5def254e069f0a329bd992ed16a566This diagram shows an open master cylinder design. The bite point adjust changes the position of the piston to the right of the port. If...

https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Fbikeadvice.in%2Fwp-content%2Fuploads%2F2010%2F11%2FMC-6.jpg&f=1&ipt=57742ea1c1bad29ad4d3d164cf3bfb106b5def254e069f0a329bd992ed16a566

This diagram shows an open master cylinder design. The bite point adjust changes the position of the piston to the right of the port. If you extend the adjuster and push the piston in too far it will be past the port and engauge the caliper pistons, effectively making a closed system. 

mtbjoe wrote:

Nice picture. Are you sure that’s the design of the brake? 

kane wrote:

What you describe with lengthening the bite point screw to change the feel of the brakes isn't really consistent with how hope brakes, or open hydraulic...

What you describe with lengthening the bite point screw to change the feel of the brakes isn't really consistent with how hope brakes, or open hydraulic brake systems in general, work. 

The bite point screw doesn't change the position of the pads; this is determined by the seals in the caliper and the gap to the disc will be the same for any disc thickness. What the bite point screw does is change the position of the piston in the master cylinder relative to the reservoir bleed port so that more or less lever throw is required before the master cylinder piston passes the port and starts to move the caliper pistons. Once this happens the brake will behave in the same way regardless of the starting position unless there isn't enough fluid in the reservoir and then air will enter the system. This is why Hope recommend adding extra fluid in the V4s when using 1.8 or 2.3 mm discs.

I'm not really sure what is going on with your brakes to make them feel different with the modification you made but I would guess it comes down to the bleed or setup not being perfect. Hope Tech 4s don't have a very firm lever feel compared to others, even with everything setup correctly and the caliper pistons perfectly centered.

Pedal Bob wrote:

That sounds weird to me, because that would mean that the bite point control dial is just a second reach adjust. From what I can understand...

That sounds weird to me, because that would mean that the bite point control dial is just a second reach adjust. From what I can understand of what you're saying, the bite point control dial is simply adjusting a deadzone buffer before the master cylinder piston starts pushing actual brake fluid. 

My general understanding of hydraulic brakes was that obviously the seals is the first step of determining where the pistons will end up. Adding a bite point control dial would be the second step of giving you some fine tuning, and not only when everything is brand new and fully serviced. 

The lever reach should just be to place the lever where it suits you personally.

That's at least how I've looked at it till now, and obviously I understand there can be different ways of doing things from manufacturer to manufacturer, but I just find it a bit odd if what you claim is actually true that you're only adjusting a deadzone of the master cylinder piston. 

HexonJuan wrote:

All a bite point adjust does is move the MC piston position relative to the timing port holes in the MC. The smaller the gap between...

All a bite point adjust does is move the MC piston position relative to the timing port holes in the MC. The smaller the gap between the primary seal on the MC piston and those ports creates a shorter throw before engagement. Generally, adjusting it won't alter the lever's home position, with Shimano being an exception in that regard. Shimano requires adjusting reach to maintain the desired home position when their bite point adjust is fiddled with. All that is to say yes, bite point adjust=deadband adjust. If one can't get the activation point they're looking for using that, then there is/are other factors at play, from simple (improper setup at install, bad bleed, kinked brake line, excessively worn pads and/or rotors) to the harder to diagnose (manufacturing dimensional issues within the system, assembly issues at build). 

AndehM wrote:

Regarding contact adjust, I've read multiple places that the way that works on SRAM RSC-style brakes is different.  On those, it changes the rotation of the...

Regarding contact adjust, I've read multiple places that the way that works on SRAM RSC-style brakes is different.  On those, it changes the rotation of the eccentric cam that the lever uses to drive the master cylinder piston.  This cam has varying amounts of mechanical advantage throughout its rotation.  Winding the C adjuster out on these brakes decreases the mechanical advantage, making the lever pull effectively more linear (ratio of lever movement to piston advancement gets closer to 1:1).  So the distance you have to pull the lever in order to make the pads contact the rotor gets shorter, but the amount of finger force needed increases because it loses mechanical advantage over the system drag.  Conversely if you run the C adjuster all the way in, you gain maximum mechanical advantage so the pull is lighter but has to move further to hit the contact point.  Think of a simple lever over fulcrum setup - C adjuster fully out is short lever arm, C adjuster fully in is longer lever arm.

When I used to have Code RSCs, I didn't realize this and ran the C all the way out to make them bite quickest like I was used to from Maguras or Shimanos, and would get wicked arm pump on relatively short descents.  Years later after I learned this and got Mavens, I run the C all the way in after a bleed and only adjust outward a little to balance feel, and never get arm pump.

That said, the bite point adjust on other brake systems sometimes works differently (directly advances the MC piston - Hayes' version does this).

Robstyle wrote:

The easiest way to check if the master cylinder piston has gone past the reservoir port is to whip the wheel off and see if you...

The easiest way to check if the master cylinder piston has gone past the reservoir port is to whip the wheel off and see if you can push the pistons back. Yes=Gtg no=err maybe don't ride on them 

 

HexonJuan wrote:

For all things mechanic wise, assume you're the weak link in the process and do your best to strengthen your knowledge of fit and process. RTFM...

For all things mechanic wise, assume you're the weak link in the process and do your best to strengthen your knowledge of fit and process. RTFM, RTFM again, RTFM one more time for good measure. And read it, don't skim (done it, bit me in the ass a couple times, and it was embarrassing). If all that fails, reach out to tech support. The folx working phones and computers are generally hella helpful and quite likely more experienced in the set-up of their wares and definitely know of any potential manufacturing issue that's preventing you from getting the ideal you're looking for. Don't be afraid to be wrong in your thinking either. Sometimes it turns out what you were looking for was not the way a system was designed to operate.

Be curious, be reasonable.  

AndehM wrote:

Regarding contact adjust, I've read multiple places that the way that works on SRAM RSC-style brakes is different.  On those, it changes the rotation of the...

Regarding contact adjust, I've read multiple places that the way that works on SRAM RSC-style brakes is different.  On those, it changes the rotation of the eccentric cam that the lever uses to drive the master cylinder piston.  This cam has varying amounts of mechanical advantage throughout its rotation.  Winding the C adjuster out on these brakes decreases the mechanical advantage, making the lever pull effectively more linear (ratio of lever movement to piston advancement gets closer to 1:1).  So the distance you have to pull the lever in order to make the pads contact the rotor gets shorter, but the amount of finger force needed increases because it loses mechanical advantage over the system drag.  Conversely if you run the C adjuster all the way in, you gain maximum mechanical advantage so the pull is lighter but has to move further to hit the contact point.  Think of a simple lever over fulcrum setup - C adjuster fully out is short lever arm, C adjuster fully in is longer lever arm.

When I used to have Code RSCs, I didn't realize this and ran the C all the way out to make them bite quickest like I was used to from Maguras or Shimanos, and would get wicked arm pump on relatively short descents.  Years later after I learned this and got Mavens, I run the C all the way in after a bleed and only adjust outward a little to balance feel, and never get arm pump.

That said, the bite point adjust on other brake systems sometimes works differently (directly advances the MC piston - Hayes' version does this).

HexonJuan wrote:

For all things mechanic wise, assume you're the weak link in the process and do your best to strengthen your knowledge of fit and process. RTFM...

For all things mechanic wise, assume you're the weak link in the process and do your best to strengthen your knowledge of fit and process. RTFM, RTFM again, RTFM one more time for good measure. And read it, don't skim (done it, bit me in the ass a couple times, and it was embarrassing). If all that fails, reach out to tech support. The folx working phones and computers are generally hella helpful and quite likely more experienced in the set-up of their wares and definitely know of any potential manufacturing issue that's preventing you from getting the ideal you're looking for. Don't be afraid to be wrong in your thinking either. Sometimes it turns out what you were looking for was not the way a system was designed to operate.

Be curious, be reasonable.  

TEAMROBOT wrote:

Hadn't encountered the phrase "RTFM" yet. Thank you for sharing this gift with me.

mtbjoe wrote:

Random thought: I think the replacement of the bladder at the end is the most difficult part to avoid any air. Why not bleed upside down...

Random thought: I think the replacement of the bladder at the end is the most difficult part to avoid any air. Why not bleed upside down and use the caliper bleed port to make sure absolutely no air? 

mtbjoe wrote:

Random thought: I think the replacement of the bladder at the end is the most difficult part to avoid any air. Why not bleed upside down...

Random thought: I think the replacement of the bladder at the end is the most difficult part to avoid any air. Why not bleed upside down and use the caliper bleed port to make sure absolutely no air? 

mtbjoe wrote:

Random thought: I think the replacement of the bladder at the end is the most difficult part to avoid any air. Why not bleed upside down...

Random thought: I think the replacement of the bladder at the end is the most difficult part to avoid any air. Why not bleed upside down and use the caliper bleed port to make sure absolutely no air? 

Primoz wrote:

How do you intend on pushing oil to the caliper and out the bleedport?

mtbjoe wrote:

I invertered my bike for 2 hours and opened the caliper port. Sucked out a little air and replaced same volume with fluid. 

It’s amazing now 

mtbjoe wrote:

I invertered my bike for 2 hours and opened the caliper port. Sucked out a little air and replaced same volume with fluid. 

It’s amazing now 

Johnboy wrote:

When you say inverted, do you mean this  Or this....  

When you say inverted, do you mean this 

 

Or this.... 

 

TEAMROBOT wrote:

Hadn't encountered the phrase "RTFM" yet. Thank you for sharing this gift with me.

AndehM wrote:

Regarding contact adjust, I've read multiple places that the way that works on SRAM RSC-style brakes is different.  On those, it changes the rotation of the...

Regarding contact adjust, I've read multiple places that the way that works on SRAM RSC-style brakes is different.  On those, it changes the rotation of the eccentric cam that the lever uses to drive the master cylinder piston.  This cam has varying amounts of mechanical advantage throughout its rotation.  Winding the C adjuster out on these brakes decreases the mechanical advantage, making the lever pull effectively more linear (ratio of lever movement to piston advancement gets closer to 1:1).  So the distance you have to pull the lever in order to make the pads contact the rotor gets shorter, but the amount of finger force needed increases because it loses mechanical advantage over the system drag.  Conversely if you run the C adjuster all the way in, you gain maximum mechanical advantage so the pull is lighter but has to move further to hit the contact point.  Think of a simple lever over fulcrum setup - C adjuster fully out is short lever arm, C adjuster fully in is longer lever arm.

When I used to have Code RSCs, I didn't realize this and ran the C all the way out to make them bite quickest like I was used to from Maguras or Shimanos, and would get wicked arm pump on relatively short descents.  Years later after I learned this and got Mavens, I run the C all the way in after a bleed and only adjust outward a little to balance feel, and never get arm pump.

That said, the bite point adjust on other brake systems sometimes works differently (directly advances the MC piston - Hayes' version does this).

HexonJuan wrote:

Been a spot since I popped a pair of Sram's apart, but I recollect the dial interfacing with another component that interfaced with a threaded unit...

Been a spot since I popped a pair of Sram's apart, but I recollect the dial interfacing with another component that interfaced with a threaded unit that did in turn advance or retreat the MC piston. I could be wrong and if so I expect to be enlightened.

Eae903 wrote:

I got my hands on some Maven bases the other day. First impressions after bedding in the rotors and test riding them are that they feel...

I got my hands on some Maven bases the other day. First impressions after bedding in the rotors and test riding them are that they feel like a slightly more powerful Code, definitely did not have that immediate grab of the Maven silvers. Lever pull did feel a bit lighter, but not as light as my Dominions, and then the bite point was a bit vague and and there was a good amount of squish after the bite. 

Eae903 wrote:

I got my hands on some Maven bases the other day. First impressions after bedding in the rotors and test riding them are that they feel...

I got my hands on some Maven bases the other day. First impressions after bedding in the rotors and test riding them are that they feel like a slightly more powerful Code, definitely did not have that immediate grab of the Maven silvers. Lever pull did feel a bit lighter, but not as light as my Dominions, and then the bite point was a bit vague and and there was a good amount of squish after the bite. 

iceman2058 wrote:

Maven Bronze you mean? I'm currently on a pair with a couple of rides on them, they feel about the same in terms of lever squish...

Maven Bronze you mean? I'm currently on a pair with a couple of rides on them, they feel about the same in terms of lever squish compared to the Maven ULT (i.e. not much squish at all!). Are you sure they had a good bleed?

Eae903 wrote:

I got my hands on some Maven bases the other day. First impressions after bedding in the rotors and test riding them are that they feel...

I got my hands on some Maven bases the other day. First impressions after bedding in the rotors and test riding them are that they feel like a slightly more powerful Code, definitely did not have that immediate grab of the Maven silvers. Lever pull did feel a bit lighter, but not as light as my Dominions, and then the bite point was a bit vague and and there was a good amount of squish after the bite. 

iceman2058 wrote:

Maven Bronze you mean? I'm currently on a pair with a couple of rides on them, they feel about the same in terms of lever squish...

Maven Bronze you mean? I'm currently on a pair with a couple of rides on them, they feel about the same in terms of lever squish compared to the Maven ULT (i.e. not much squish at all!). Are you sure they had a good bleed?

Eae903 wrote:

Nope, I mean maven base. Came stock on the Sram 90 build Hightower that we got in. I'm pretty confident in the bleed, since I did...

Nope, I mean maven base. Came stock on the Sram 90 build Hightower that we got in. I'm pretty confident in the bleed, since I did it myself haha. I will say I did not do the piston massage, but there was no inconsistency in the feel or pull at the lever. Maven bases use the direct link lever, instead of the swing link, which is probably the major reason they don't feel like the ultimates where the bronze do. I haven't been able to do any real trail riding on them, but I bed in the pads (metallic) and gave them as good of a power test as I could riding around outside the shop. The Maven ults had that "holy shit" power and bite, where the bases delivered way more gradually, felt like a code rsc, but the power came on a bit faster and stronger. Definitely not a bad brake, one of the best from sram and a good price too. 

Eae903 wrote:

Nope, I mean maven base. Came stock on the Sram 90 build Hightower that we got in. I'm pretty confident in the bleed, since I did...

Nope, I mean maven base. Came stock on the Sram 90 build Hightower that we got in. I'm pretty confident in the bleed, since I did it myself haha. I will say I did not do the piston massage, but there was no inconsistency in the feel or pull at the lever. Maven bases use the direct link lever, instead of the swing link, which is probably the major reason they don't feel like the ultimates where the bronze do. I haven't been able to do any real trail riding on them, but I bed in the pads (metallic) and gave them as good of a power test as I could riding around outside the shop. The Maven ults had that "holy shit" power and bite, where the bases delivered way more gradually, felt like a code rsc, but the power came on a bit faster and stronger. Definitely not a bad brake, one of the best from sram and a good price too. 

mtbjoe wrote:

Random thought: I think the replacement of the bladder at the end is the most difficult part to avoid any air. Why not bleed upside down...

Random thought: I think the replacement of the bladder at the end is the most difficult part to avoid any air. Why not bleed upside down and use the caliper bleed port to make sure absolutely no air? 

Primoz wrote:

How do you intend on pushing oil to the caliper and out the bleedport?

mtbjoe wrote:

I invertered my bike for 2 hours and opened the caliper port. Sucked out a little air and replaced same volume with fluid. 

It’s amazing now 

AndehM wrote:

Regarding contact adjust, I've read multiple places that the way that works on SRAM RSC-style brakes is different.  On those, it changes the rotation of the...

Regarding contact adjust, I've read multiple places that the way that works on SRAM RSC-style brakes is different.  On those, it changes the rotation of the eccentric cam that the lever uses to drive the master cylinder piston.  This cam has varying amounts of mechanical advantage throughout its rotation.  Winding the C adjuster out on these brakes decreases the mechanical advantage, making the lever pull effectively more linear (ratio of lever movement to piston advancement gets closer to 1:1).  So the distance you have to pull the lever in order to make the pads contact the rotor gets shorter, but the amount of finger force needed increases because it loses mechanical advantage over the system drag.  Conversely if you run the C adjuster all the way in, you gain maximum mechanical advantage so the pull is lighter but has to move further to hit the contact point.  Think of a simple lever over fulcrum setup - C adjuster fully out is short lever arm, C adjuster fully in is longer lever arm.

When I used to have Code RSCs, I didn't realize this and ran the C all the way out to make them bite quickest like I was used to from Maguras or Shimanos, and would get wicked arm pump on relatively short descents.  Years later after I learned this and got Mavens, I run the C all the way in after a bleed and only adjust outward a little to balance feel, and never get arm pump.

That said, the bite point adjust on other brake systems sometimes works differently (directly advances the MC piston - Hayes' version does this).

HexonJuan wrote:

Been a spot since I popped a pair of Sram's apart, but I recollect the dial interfacing with another component that interfaced with a threaded unit...

Been a spot since I popped a pair of Sram's apart, but I recollect the dial interfacing with another component that interfaced with a threaded unit that did in turn advance or retreat the MC piston. I could be wrong and if so I expect to be enlightened.

dancingwithmyself wrote:

I have this pasted into some notes on brakes (yes, I'm that nerdy), so I'm plagiarizing someone. I think I know who but don't want to...

I have this pasted into some notes on brakes (yes, I'm that nerdy), so I'm plagiarizing someone. I think I know who but don't want to say in case I'm wrong and this is wrong.  

"With swinglink, since the initial position of the cam profile doesn't change, the contact adjuster causes the position on the cam profile at which the pads make contact with the rotor to change. The more aggressive the ramp in the cam profile is, the more pronounced the difference in feel based on contact adjust is. The initial portion of the cam profile has decreased leverage so that the gap between the pads and the rotor can close quicker. The cam profile then transitions to higher leverage for increased braking force without an overly stiff lever. When contact adjust is wound all the way in, you transition to the higher leverage portion of the cam a little later relative to when the pads contact the rotor which results in a stiffer feel than if you wind it all the way out."