Brake Lever “Throw” for Hydraulic Disc Brakes?

Discuss light weight issues concerning road bikes & parts.
PyreofFyre
Posts: 17
Joined: Thu Apr 12, 2018 6:43 am

by PyreofFyre

Hi all,

So I’m putting together a new disc braked bike, following years of meddling with rim braked bikes. Have looked through the threads and couldn’t find a suitable response.

The question goes like this.

I typically prefer a shorter “throw” at the brake lever, between fully released to fully engaged. For a rim braked bike, all one needs to do is to loosen the cable bolt, squeeze the calipers, pull the cable tight and re-tighten the cable bolt.

How does one achieve a similar outcome with hydraulic disc brakes? With the brakes fully bled, the levers still travel about half the distance between fully released and fully engaged. Can I shorten this somehow, to say a quarter of the travel?

Thanks.
PoF

PaulH
Posts: 41
Joined: Mon Jul 10, 2017 9:50 pm

by PaulH

If it’s shimano they have a travel adjustment screw below the lever


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by Weenie


PsyDoc
Posts: 74
Joined: Thu May 06, 2004 4:14 pm
Location: Valdosta, GA

by PsyDoc

The screw has limited adjustment and, although I have not measured mine, I don't see how you could possibly get it down to a quarter of the travel. The same goes for the reach adjustment...there is some, but not much.

PaulH
Posts: 41
Joined: Mon Jul 10, 2017 9:50 pm

by PaulH

All you can do the. Is give them a very good bleed , and use the business card trick to space the pads this will give you minimal throw , however if you do run the pads that close you will get some rub after long descents due to rotor expansion. I used to be like you but now I run with a lot of travel as the modulation is far superior with disc brakes.


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TobinHatesYou
Posts: 1693
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Perform a bleed with the bleed blocks, but do not reset the pistons before replacing the bleed port covers. After replacing the bleed port covers, then reset the pistons. This will result in a miniscule amount more fluid being in the system.

I use SRAM HRD and I find a properly bled system to require a very short amount of throw. I have to use the contact point adjustment to increase the throw to my liking.

Also as mentioned, shortening the throw negates some of the modulation benefit of disc brakes.

PyreofFyre
Posts: 17
Joined: Thu Apr 12, 2018 6:43 am

by PyreofFyre

Hi all,

Thanks for the replies and inputs! I should have mentioned earlier, that I only wanted to reduce the "throw" or the travel of the brake levers without having to mess around with the travel adjustment, but it looks like that's not possible. I did try to go the route advise by PaulH, but still no go.

Oh well...

Thanks for all the comments!

PoF

BTW, for the moderators, not sure why there's now 2 separate threads for this one. Is there a way to fold the one below, into this one?

https://weightweenies.starbike.com/foru ... 6#p1419366

NickJHP
Posts: 106
Joined: Wed Feb 14, 2018 2:22 am

by NickJHP

My Sram eTap HRD brakes have two separate adjustments on the lever, a reach adjustment and a contact point adjustment.

TobinHatesYou
Posts: 1693
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

A correctly bled eTap HRD system won’t have the short travel he desires, even with the contact point adjustment turned fully counter-clockwise. And reach adjustment is irrelevant.

He could try bleeding with the contact point adjustment turned clockwise a bit, keeping the lever squeezed while he turns the adjuster counter-clockwise again.

PyreofFyre
Posts: 17
Joined: Thu Apr 12, 2018 6:43 am

by PyreofFyre

Thanks Tobin!

Could I trouble you for a bit of a backgrounder, on why this would work? Just so I get a better understanding of the intricacies of disc brake maintenance.

Much appreciated,
PoF

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ergott
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Joined: Tue Apr 18, 2006 3:03 am
Location: Islip, NY
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by ergott

Why are there two duplicate threads?

Nevermind, you already asked this.

TobinHatesYou
Posts: 1693
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

PyreofFyre wrote:
Tue Aug 07, 2018 2:17 am
Thanks Tobin!

Could I trouble you for a bit of a backgrounder, on why this would work? Just so I get a better understanding of the intricacies of disc brake maintenance.

Much appreciated,
PoF

Contact point adjustment effectively changes the size of the reservoir, I think? Performing the bleed with it in a different position might increase the volume of hydro fluid in the system...and then you can dial it in and out as needed.

https://www.youtube.com/watch?v=ACGyA1QVWIg&t=7m13s
Last edited by TobinHatesYou on Tue Aug 07, 2018 4:06 am, edited 1 time in total.

NickJHP
Posts: 106
Joined: Wed Feb 14, 2018 2:22 am

by NickJHP

TobinHatesYou wrote:
Tue Aug 07, 2018 3:31 am
PyreofFyre wrote:
Tue Aug 07, 2018 2:17 am
Thanks Tobin!

Could I trouble you for a bit of a backgrounder, on why this would work? Just so I get a better understanding of the intricacies of disc brake maintenance.

Much appreciated,
PoF
Contact point adjustment effectively increases changes the size of the reservoir, I think? Performing the bleed with it in a different position might increase the volume of hydro fluid in the system...and then you can dial it in and out as needed.

https://www.youtube.com/watch?v=ACGyA1QVWIg&t=7m13s
Performing the bleed with the contact point adjustment anywhere other than fully closed risks overfilling the master cylinder reservoir, leaving no room for the brake fluid to expand when it gets hot. That can cause brake drag as the pads clamp on the rotor due to the fluid expansion.

TobinHatesYou
Posts: 1693
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

NickJHP wrote:
Tue Aug 07, 2018 4:02 am

Performing the bleed with the contact point adjustment anywhere other than fully closed risks overfilling the master cylinder reservoir, leaving no room for the brake fluid to expand when it gets hot. That can cause brake drag as the pads clamp on the rotor due to the fluid expansion.

Sure, and you and I wouldn't do that because we like modulation anyway. But he wants a short, grabby throw, so that's one way to achieve that. He could just carry a 6mm hex wrench (for eTap HRD) and loosen up the contact point adjuster even more if the pad does start to rub.

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wheelbuilder
Posts: 506
Joined: Wed Feb 08, 2017 2:10 am

by wheelbuilder

I can't figure out if this thread is about Shimano or Sram, but here is a method I use when customers want the same kind of lever feel that you are talking about. You have to be exceptionally clean and careful while doings this, as even one drop of fluid getting on pads or rotor will be disasterous as far as contamination........... This works but is not recommended as it does cause excess noise, and is possibly bad for the closed system. I don't know definitively if it is or not, but I do this occasionally to appease whiny customers. Bleed the system as usual with bleed block in place. Close the system as if you are done with bleed. Install pads and wheel. Open bleed port at caliper while syringe is attached and forcibly push fluid into the caliper until you feel a hard stop. Close bleed port while maintaining pressure on syringe. Carefully remove syringe with a rag wrapped around port/hose. This will give you the high/hard lever feel you desire, but do at own risk.

TobinHatesYou
Posts: 1693
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

All approaches just result in a slightly overfilled system. If your system has contact point adjustment, it's way easier to just do that.

In fact you can do a normal bleed and then "partial bleed" just at the lever later using the contact point adjustment method and it's super-fast / easy. Takes like 5 minutes.

--

A partial bleed being you open the bleed port at the lever, connect a syringe with a bit of fluid in it and flick the lever repeatedly while pressurizing the system by pushing/tugging on the syringe plunger lightly. Do this with the contact point adjustment "out" a little bit and then replace the bleed port screw. If you're working on the rear brake, you'll want the caliper to be detached from the bike and hanging or for the bike to be tilted up so there is no hose at the same level as the caliper. You can perform this procedure with the wheel in place.

by Weenie


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