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SRAM Guide R engagement point adjustment?

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RACERX70

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Discussion starter · #1 ·
Gent's,

Is there a way to adjust the engagement point on my SRAM Guide R brakes? Ever since new, the free travel of the lever is such that I can come very close to contacting the handle bar if pulling the lever hard enough. I prefer the engagement point to be almost immediate. Besides adjusting the reach knob, is there a way to adjust the engagement point on the Guide R's?

Thank you.
 
#2 ·
How far do the pads / pistons travel before they contact the rotor?

You can decrease the distance by removing the caliper and stroke the lever (move pistons / pads out) when there is just enough clearance to slide the caliper back on there should be less lever travel assuming there was a lot before moving the pistons.
 
#3 ·
With a Guide R, there isn't any contact point adjustment per se.

A normal bleed block pushes the pistons back into the caliper all the way, so they'll have maximum distance to go before contacting the rotor. If your pads are worn, it will take longer for the pads to contact the rotor.

So, to get the pistons/pads closer to your rotor, you could use a thinner bleed block (or even an old rotor) to basically leave the pistons set to a closer contact point.

Its kind of like over-filling the master cylinder, except its more like filling it to the correct level but with worn pads. But just know if you do this, if you install new pads and have to push the pistons back in all the way, it could overflow. But if you had the bleed kit installed when you do that, it wouldn't cause any problems.
 
#4 ·
ocnLogan said:
With a Guide R, there isn't any contact point adjustment per se.

A normal bleed block pushes the pistons back into the caliper all the way, so they'll have maximum distance to go before contacting the rotor. If your pads are worn, it will take longer for the pads to contact the rotor.

So, to get the pistons/pads closer to your rotor, you could use a thinner bleed block (or even an old rotor) to basically leave the pistons set to a closer contact point.

Its kind of like over-filling the master cylinder, except its more like filling it to the correct level but with worn pads. But just know if you do this, if you install new pads and have to push the pistons back in all the way, it could overflow. But if you had the bleed kit installed when you do that, it wouldn't cause any problems.
Click to expand...
Overfilling the hyd. system w/ worn pads will not decrease pad to rotor clearance. Want to decrease pad to rotor clearance see reply # 2.
 
#5 ·
keen said:
Overfilling the hyd. system w/ worn pads will not decrease pad to rotor clearance. Want to decrease pad to rotor clearance see reply # 2.
Click to expand...
As I was the third post, I did read your first post before responding.

Pistons extending further takes more fluid volume compared to pistons being all the way reset/pushed back into the caliper. Having a totally full master cylinder seems to help the contact point with worn pads feel similar to a fresh set of pads in my experience. Maybe because there is less air in the system? Not sure, just have noticed it helps for me, hence the suggestion.

Bleeding the brakes with a thinner bleed block extends the pistons farther, decreasing pad to rotor clearance, similar to what you are recommending, but for me has been easier to get the contact point right than the no bleed block method, where it's a bit of "guess and check".
 
#6 ·
ocnLogan said:
As I was the third post, I did read your first post before responding.

Pistons extending further takes more fluid volume compared to pistons being all the way reset/pushed back into the caliper. Having a totally full master cylinder seems to help the contact point with worn pads feel similar to a fresh set of pads in my experience. Maybe because there is less air in the system? Not sure, just have noticed it helps for me, hence the suggestion.

Bleeding the brakes with a thinner bleed block extends the pistons farther, decreasing pad to rotor clearance, similar to what you are recommending, but for me has been easier to get the contact point right than the no bleed block method, where it's a bit of "guess and check".
Click to expand...
I don't agree w/ your assessment of hydraulic operation. There are loads of information on hyd. principles concerning fluid volume, timing, piston area, stroke etc. available. Might want to take a read here :
https://www.servicearchive.sram.com/sites/default/files/techdocs/sm_hydraulic_disc_brake_v06.pdf

For bicycle disc brakes excessive lever travel will occur if there is air within the "working" fluid or fluid bypass, too much rotor to pad clearance, hose expansion or too much "Deadband" in the lever. Deadband can only be adjusted w/ adjustable "bite point" levers.
 
#7 ·
keen said:
I don't agree w/ your assessment of hydraulic operation. There are loads of information on hyd. principles concerning fluid volume, timing, piston area, stroke etc. available. Might want to take a read here :
https://www.servicearchive.sram.com/sites/default/files/techdocs/sm_hydraulic_disc_brake_v06.pdf

For bicycle disc brakes excessive lever travel will occur if there is air within the "working" fluid or fluid bypass, too much rotor to pad clearance, hose expansion or too much "Deadband" in the lever. Deadband can only be adjusted w/ adjustable "bite point" levers.
Click to expand...
Thank you for the document. I'm always open to learning more, and it was an interesting read. And surprisingly well done/understandable for a tech document. Now I know a few specific terms that I wasn't aware of previously.

After a bit more thinking, I do think I was conflating a few things after too few hours of sleep last night (4). I was confusing a few things with closed systems (which, according to the document, do work how I was explaining), but thats not as relevant for a system with a resevoir of course.

I think we're both saying that without contact point adjustment (deadband, the new word I learned today), the most you can do is try to get the pistons to the correct placement in the seals to eliminate excessive lever travel before contact.

This actually lead me to another question for the OP though. Are the pistons and seals nice and clean? If they're gunked up, it might be preventing the pistons from re-centering in the seals correctly, and make the deadband/lever throw longer than it should be, as it should be doing that by itself.

Also, for whatever reason, when pads get worn, I find that bleeding with a thinner bleed still block works better for me than using a full block, and then resetting the pistons by cycling the lever a few times, just because other times in the past I've pushed the pistons out too far, and had to push them back in further to have enough space to put the pads back in.

After thinking about it for a while, the only reason I can think that may be so, is perhaps because the resevoir is low enough in volume that it gets easier to injest air into the "working fluid" through the timing ports because of expansion/contraction, or due to the bike being stored in different orientations (I store my bikes vertically by the front tire). Not sure which, but since its worked for me so far, I'll likely continue for now.
 
#8 ·
Yep its a good read.

If properly bled there should be no introduction of air into the system no matter what the pad wear. Bicycle calipers are just plain finicky due to their compact size. I believe manufacturing tolerances contribute to un even & lazy piston operation. No doubt replacing piston seals is a good idea on older brakes but ime Sram brakes are questionable.
 
#9 ·
I'm quite sad that I went for the code R and I seem to have to throw the lever an 1" before they engage! I tried to put a piece of aluminium can behind the pads and that helped, but also felt like an inadeqeust solution. I may go back to it though.

Just like you can adjust the lever distance; could you somehow block the lever from returning all the way? I have them set virtually all the way out so when they engage they won't bottom out. But I wouldn't mind just pre-moving the lever like it's already 3/4" engaged... if that makes sense?

I could see playing around with some kind of a wedge to stop the full return of the lever, but it also seems like a less than perfect solution.

BTW, they were like this the moment they arrived; both front and rear. I've bled them as I have many systems before, and they are the same. They are great brakes when they engage; they just have a preset that is way too far away from the rotor so you have to throw them a 1/2 mile before they work. :ROFLMAO:
 
#10 ·
thegallery said:
I'm quite sad that I went for the code R and I seem to have to throw the lever an 1" before they engage! I tried to put a piece of aluminium can behind the pads and that helped, but also felt like an inadeqeust solution. I may go back to it though.

Just like you can adjust the lever distance; could you somehow block the lever from returning all the way? I have them set virtually all the way out so when they engage they won't bottom out. But I wouldn't mind just pre-moving the lever like it's already 3/4" engaged... if that makes sense?

I could see playing around with some kind of a wedge to stop the full return of the lever, but it also seems like a less than perfect solution.

BTW, they were like this the moment they arrived; both front and rear. I've bled them as I have many systems before, and they are the same. They are great brakes when they engage; they just have a preset that is way too far away from the rotor so you have to throw them a 1/2 mile before they work. :ROFLMAO:
Click to expand...
If you haven't solved your issue yet, I recently found a product that does EXACTLY what you are looking for.
Been working well for me. It clips on tight, no fear of it rattling off, and it literally is a wedge to stop the lever from returning all the way back.
 
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