Brake Pad Knock Back

[Ccitis]

I have been chasing some a pesky fork vibration for a few years now. I get it on heavy braking and at higher speeds. Now I notice I am getting some pad kick back, what I mean is I have good lever feel, then suddenly it will go soft but the next pump is firm. Bled the brakes, same deal. Took the master cylinder apart cleaned it up and put it back. Lever feels fine at a standstill. Just goes soft after rolling or riding, every once in awhile. I can only think that is some piston kick back. Are bad rotors the only thing that does that? I don't want to buy expensive new rotors if I should be looking at something else?

[DEEBS11]

Old rubber brake hoses can cause these symptoms.

[LAB3]

Do you live in the mountains? Could be they're getting hot from over use. Helped out someone from Alabama a couple of weeks ago, her SUV has an automatic transmission and she never drove in the mountains of Western NC before, I could see her discs glowing cherry red!

[Socer4m]

second on Deebs,,,replace hoses if old,,,ebay has good, cheap braided stainless brake lines, various lengths if needed,,,also check axle bolt, caliper bolts and front fork brace bolts for tightness,,,maybe give the brakes another bleed, keep us informed, Mike in S.Diego and Pa.

[Radioguylogs]

Moisture in the caliper can cause that. It vaporizes when the brakes get hot.

More of a problem with DOT5 than DOT 3/4.

[Ccitis]

Brakes lines were new in 2018, as per the date on them. I don't use Dot 5... Dot 3 usually, sometimes 4. Sea level. Has not been hot. Have been through the front end many times making sure torques are correct. Its a bit of a mystery to me. Brake rotors warped?

[bikerphil]

You should be able to determine if the rotors are warped when coming to a slow stop, 5 MPH down to zero you should be able to feel it using the front brake only.

[Ccitis]

You should be able to determine if the rotors are warped when coming to a slow stop, 5 MPH down to zero you should be able to feel it using the front brake only.

I agree. I am doubtful it is that. (BTW on another note, I just bought a 09 Tiger 1050... really enjoying that bike!)

[bikerphil]

It is more like 15 MPH down to a stop to feel the rotor warp, rather than 5 which I stated above.

[Ccitis]

Went through it again. Took the front end apart, and put it back together as per the manual and torque specs. Ensured left fork was lined up properly. Bled the brakes and master cylinder bolt some more. May take the line off and bench bleed the master cylinder, but the intermittent nature of this makes me turn away from air in the system. It happens when the wheel is in motion. At a standstill the lever feels fine. And I cannot see any runout, nor am I getting pulsing. A real mystery. Bike is off the road for now, the fact one second the lever is firm, the next it goes to the grip is super unsafe. A shame... it is riding season.

[bikerphil]

Maybe time to try a different master cylinder. If you're running SS lines and your bike is a Standard, 14mm would be the correct bore size. Who knows with the old m/c, the bore could be scratched causing it to fade.

[Ccitis]

Maybe time to try a different master cylinder. If you're running SS lines and your bike is a Standard, 14mm would be the correct bore size. Who knows with the old m/c, the bore could be scratched causing it to fade.

Yes, it is likely I will have to start part swapping. Hoses are not SS... but they are 2018 new rubber. Why the PO did not put SS on, I have no idea.

[DEEBS11]

Ccitis, 2018 OEM rubber or Chinese rubber?

[bikerphil]

Ok, if using rubber hoses, I would use a 16mm (5/8") or 17mm (11/16") bore, the 14mm will make the lever too spongy.