Front Brakes

[billg302]

Good evening gents, since it was colder out today, I spent the day installing new front rotors, new Galfer (3 piece) front brake lines and a new Galfer clutch line. Got the clutch system to bleed perfectly, (seems like there's a little more pull effort required, maybe due to the line not expanding like the stock did but the clutch works great. Moved over to the front brakes to bleed them, they bled normally and got all air out. Problem I'm having is the front brakes still feel spongy, not as solid as before. I bled with a MityVac for awhile and then went over to a hose in brake fluid for good measure. It got to the point I didn't see any air bubbles at all out of either side. As I squeeze the lever, I do see fluid shooting out of the little orifice in the master only for the first 3 - 4 squeezes, then it stops. If I remembered right, the clutch master would shoot fluid out every time you squeezed the lever. I'm thinking my front brake master is bad. I did take her out for a test ride after and it will lock the brakes if squeezed hard enough but it takes more squeeze than before for a normal stop. I'm using Brembo DOT 4 fluid. It just feels like the first 1/2 of lever travel is soft and then it gets more resistance after that. I did bleed some more but still not seeing any air. That's what leads me to believe the master cylinder is bad. Any thoughts?

 

[billg302]

Doesn't make a ton of sense to me but I just went out and cycled the master again (it's been 3 hours since I did it last) and it feels normal now. I did do the new rotor bed in process when I drove it earlier so everything got pretty hot. I'm thinking getting the fluid hot and letting it cool down while leaving the master cylinder at the highest point may have got rid of some air that I couldn't otherwise.

 

[MaxMidnight]

Problem I'm having is the front brakes still feel spongy, not as solid as before. I bled with a MityVac for awhile and then went over to a hose in brake fluid for good measure. It got to the point I didn't see any air bubbles at all out of either side.

Still has microscopic bubbles in the system.

As I squeeze the lever, I do see fluid shooting out of the little orifice in the master only for the first 3 - 4 squeezes, then it stops. If I remembered right, the clutch master would shoot fluid out every time you squeezed the lever.

Normal. This happens because you are displacing fluid from the callipers and line. As the pistons do not return to the original position after several squeezes no more fluid is displaced. They will return as the wheel rotates and the pistons are knocked back.
With the clutch the diaphragm spring pushes the slave system back so when you pull the lever there will always be some fluid displaced.

I'm thinking my front brake master is bad. I did take her out for a test ride after and it will lock the brakes if squeezed hard enough but it takes more squeeze than before for a normal stop. I'm using Brembo DOT 4 fluid. It just feels like the first 1/2 of lever travel is soft and then it gets more resistance after that. I did bleed some more but still not seeing any air. That's what leads me to believe the master cylinder is bad. Any thoughts?

If you are using stainless covered lines they will give a firmer lever

Doesn't make a ton of sense to me but I just went out and cycled the master again (it's been 3 hours since I did it last) and it feels normal now. I did do the new rotor bed in process when I drove it earlier so everything got pretty hot. I'm thinking getting the fluid hot and letting it cool down while leaving the master cylinder at the highest point may have got rid of some air that I couldn't otherwise.

Yep, those micro bubbles have made it to the top and have now dispersed so the lever feel 'normal'.
You can also remove them by cable tying the lever back and leaving it over night.

 

[billg302]

Still has microscopic bubbles in the system.

Normal. This happens because you are displacing fluid from the callipers and line. As the pistons do not return to the original position after several squeezes no more fluid is displaced. They will return as the wheel rotates and the pistons are knocked back.
With the clutch the diaphragm spring pushes the slave system back so when you pull the lever there will always be some fluid displaced.

If you are using stainless covered lines they will give a firmer lever


Yep, those micro bubbles have made it to the top and have now dispersed so the lever feel 'normal'.
You can also remove them by cable tying the lever back and leaving it over night.

Good info. I've rebuilt my share of automotive calipers, replaced lines etc but was always able to get them bled 100%. Cars with ABS I use my scan tool to cycle the ABS module to get the system fully bled. I did ride the bike today and the brakes are perfect. Stainless braided lines give the system a better feel for sure. Now to move on to the rear brakes next weekend.