Replacing master cylinder
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Road Warrior
Joined: Aug 2020
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From: NC
Replacing master cylinder
Wanting to replace my front MC (1988 FLHTC Electra glide) as the PO converted to single disc (replaced caliper with a Wilwood), the brake lever is very hard pull with almost 0 travel, wanting to go to a smaller bore MC (5/8) , would like to use Harley MC, anyone know what MC that would bolt up? Thanks.
Last edited by Ghetto blaster; Oct 15, 2020 at 10:21 PM.
HDF Community Team
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From: USA
Something isnt adding up right here, hydraulically, with a heavy lever and near zero movement on a single caliper downgrade.
Have you pulled the caliper to make sure the pistons and pads are actually moving?
Have you pulled the caliper to make sure the pistons and pads are actually moving?
Seasoned HDF Member
Joined: May 2008
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From: South Carolina
Even a 5/8" bore M/C will have a heavy pull, that is how the single disk bikes were configured through `95 (and the brake feel sucks on those bikes).
`96 and later single disk bikes use a 9/16" bore master cyl.
But the best thing to do would get back to a dual disk setup...
It makes perfect sense, the previous owner deleted a caliper and kept the same master cylinder...that would equal a harder pull and less travel of the brake lever.
Simple hydraulics...
`96 and later single disk bikes use a 9/16" bore master cyl.
But the best thing to do would get back to a dual disk setup...
Simple hydraulics...
Last edited by Dan89FLSTC; Oct 16, 2020 at 09:32 AM.
HDF Community Team
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From: USA
Deleting a caliper does not reduce hydraulic pressure from the master cylinder. It does reduce volumetric flow requirements though, so lever throw is reduced.
However, that is actually not what happened here. Both calipers were removed, and a single unspecified Wilwood caliper was installed. Presumably larger, with comparable hydraulic area to that of the combined oem calipers.
So Ill stand with my words and recommendation to check caliper piston motion.
However, that is actually not what happened here. Both calipers were removed, and a single unspecified Wilwood caliper was installed. Presumably larger, with comparable hydraulic area to that of the combined oem calipers.
So Ill stand with my words and recommendation to check caliper piston motion.
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From: poway
Deleting a caliper does not reduce hydraulic pressure from the master cylinder. It does reduce volumetric flow requirements though, so lever throw is reduced.
However, that is actually not what happened here. Both calipers were removed, and a single unspecified Wilwood caliper was installed. Presumably larger, with comparable hydraulic area to that of the combined oem calipers.
So Ill stand with my words and recommendation to check caliper piston motion.
However, that is actually not what happened here. Both calipers were removed, and a single unspecified Wilwood caliper was installed. Presumably larger, with comparable hydraulic area to that of the combined oem calipers.
So Ill stand with my words and recommendation to check caliper piston motion.
OP can got through the math on piston surface area, but that is only if he want the force of the pads to be the same as original. Chances are he needs more. FWIW if doing the calcs,you only want the area of the pistons one side of dual acting brake.
Seasoned HDF Member
Joined: May 2008
Posts: 21,132
Likes: 12,691
From: South Carolina
Deleting a caliper does not reduce hydraulic pressure from the master cylinder. It does reduce volumetric flow requirements though, so lever throw is reduced.
However, that is actually not what happened here. Both calipers were removed, and a single unspecified Wilwood caliper was installed. Presumably larger, with comparable hydraulic area to that of the combined oem calipers.
So I’ll stand with my words and recommendation to check caliper piston motion.
However, that is actually not what happened here. Both calipers were removed, and a single unspecified Wilwood caliper was installed. Presumably larger, with comparable hydraulic area to that of the combined oem calipers.
So I’ll stand with my words and recommendation to check caliper piston motion.
My Softail had a 5/8" bore master cyl.
I noticed no difference between the Wilwood caliper and the OEM caliper. The front brake still sucked.
The way I cured the front brake was to go to a smaller bore master cylinder (9/16"). After that the front brake works great.
I`m not speculating or presuming anything here, I have the hardware on the bike.
But...
The OP has a bike that is set up for dual disks, that is the direction he should be going, not putzing around with a different master cylinder to make a jury rig single disk brake system work...
Thread Starter
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Road Warrior
Joined: Aug 2020
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From: NC
Yes, the caliper is working as normal and has no problem bringing the bike to a halt, just the lever has almost 0 travel and this is not what I am used to, I am not your typical E glider, as of now I am stripping the bike down to the bare essentials (no bags, fairing, hand controls, etc.) so I will be losing close to 60 to 70 lbs kinda big boy bobber, may throw a small tach on it, might see if I can find a good used 9/16 and give that a try.
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HDF Community Team
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From: USA
That last post doesnt read the same as the first post. At least to me.
If a disc brake system is in optimal condition, there will be nearly zero pedal/lever motion. Its kinda the holy grail of disc brakes. You get pedal/lever play from sticking caliper pistons, disc runout, air entrainment, linkage clearance, etc.
Your first post said the lever was very hard to pull, but your second post says it had no problem bringing the bike to a halt.
Before you go replacing master cylinders, if a different size is available, check with Wilwood on this caliper or kit. They may have a specific caliper recommendation. They may also have different pads. Different pads can create a very different feel.
If a disc brake system is in optimal condition, there will be nearly zero pedal/lever motion. Its kinda the holy grail of disc brakes. You get pedal/lever play from sticking caliper pistons, disc runout, air entrainment, linkage clearance, etc.
Your first post said the lever was very hard to pull, but your second post says it had no problem bringing the bike to a halt.
Before you go replacing master cylinders, if a different size is available, check with Wilwood on this caliper or kit. They may have a specific caliper recommendation. They may also have different pads. Different pads can create a very different feel.
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Seasoned HDF Member
Joined: Dec 2005
Posts: 19,894
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From: poway
That last post doesnt read the same as the first post. At least to me.
If a disc brake system is in optimal condition, there will be nearly zero pedal/lever motion. Its kinda the holy grail of disc brakes. You get pedal/lever play from sticking caliper pistons, disc runout, air entrainment, linkage clearance, etc.
Your first post said the lever was very hard to pull, but your second post says it had no problem bringing the bike to a halt.
Before you go replacing master cylinders, if a different size is available, check with Wilwood on this caliper or kit. They may have a specific caliper recommendation. They may also have different pads. Different pads can create a very different feel.
If a disc brake system is in optimal condition, there will be nearly zero pedal/lever motion. Its kinda the holy grail of disc brakes. You get pedal/lever play from sticking caliper pistons, disc runout, air entrainment, linkage clearance, etc.
Your first post said the lever was very hard to pull, but your second post says it had no problem bringing the bike to a halt.
Before you go replacing master cylinders, if a different size is available, check with Wilwood on this caliper or kit. They may have a specific caliper recommendation. They may also have different pads. Different pads can create a very different feel.
