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My bike's front brake dooesn't have the stopping power it did before. The last couple rides out, stopped on an incline, I had to really squeeze down on the lever to hold the bike where I'd normally not apply so much lever pressure to hold it. Coming up for a normal stop they don't have the same power either.

I have not opened the system up, so I'm baffled how air could 1) gotten in or 2) lasted so long if it was already in there.


I'm going to open it up and rebleed , but I got to thinking, could this be a glazed pads occurrance? The lever feels to have adequate pressure. There is no noise or break squeaks/squeals.

Could be many things. Glazed pads(or shoes) and dirty fluid are most common causes. Inspect pads for glazing and cleanliness. Use brake parts cleaner and Nitrile gloves(they may just be dirty but if youre this lucky go directly to the nearest gambling)
Bleed system making sure outcoming fluid is not contaminated. ( in addition to air free)Make sure to use right fluid most cars use DOT3 Some DOT4 bikes may use dot3,dot4,dot5 or dot5.1 It is OK to use a higher number than required but not lower. If fluid is milky it is bad and system needs flushed. You could even have a bad master cyl. but this is uncommon. Once I saw brake line clog up completly.

ABS and tied brake systems have their own unique problems.

slimcolo wrote:Some DOT4 bikes may use dot3,dot4,dot5 or dot5.1 It is OK to use a higher number than required but not lower.

WARNING WARNING! BAD INFO!

DOT 5 and DOT 5.1 are totally different from, and completely incompatible with, DOT 3 and DOT 4 brake fluids.

DOT 3 and 4 are glycol-based, water-soluble brake fluids. DOT 5 is silicone-based and not water-soluble. You CANNOT use DOT 5 in a system designed for DOT 3 or DOT 4 and vice versa.

DOT 3 and DOT 4 are interchangeable with each other.

Shorts wrote:My bike's front brake dooesn't have the stopping power it did before. The last couple rides out, stopped on an incline, I had to really squeeze down on the lever to hold the bike where I'd normally not apply so much lever pressure to hold it. Coming up for a normal stop they don't have the same power either.

I have not opened the system up, so I'm baffled how air could 1) gotten in or 2) lasted so long if it was already in there.


I'm going to open it up and rebleed , but I got to thinking, could this be a glazed pads occurrance? The lever feels to have adequate pressure. There is no noise or break squeaks/squeals.

You probably just need to bleed the system and remove the old fluid. Shouldn't be more than a 15 minute job with a helper.

The MC and fluid are relatively fresh as I installed a new Nissin mc in mid-March. There shouldn't be a breakdown in either if those items in less than 4mths, but I won't write it off completely. Stranger things have happened

I'll rebleed the system in a few hours before the ride, as well as do a deglaze down the street. See how those improve the performance.

I'm just confused as to why there'd be any issue with them in such a short amount of time since last work done. The pads have a good amount of meat left on them as well.

Edit: I use DOT 4 as that's what is recommended on the bike and that's what I can readily find locally.

Sorry what jonnythan said is true of the dot 5 but not the dot 5.1 which is non silicon but meets dot 5 boiling.
Until I got a Beemer (these Euro bikes use dot 4, like VW) I always kept two brake fluids one dot 3 for cars and one dot 5 for bikes. I've seen quite a few Harleys get brakes messed up by puting in dot 3. Especially true of drum brakes.

Bleeding is not a bad plan at all. A loose banjo connection or such could let air in when the lines are flexed or turned just right while being applied or let go. It's unlikely, but possible.

If that fails, de-glaze the pads and rotors.

Did you wash the bike and not get all the soap off the brakes?

Pissoff the old man or somebody? A quick spritz of Armour-All on the rotors can get someone some payback, if you know what I mean.
J/K... I really doubt that's what happened, but careless use of WD-40 or something can do the same thing.....

slimcolo wrote:Sorry what jonnythan said is true of the dot 5 but not the dot 5.1 which is non silicon but meets dot 5 boiling.
Until I got a Beemer (these Euro bikes use dot 4, like VW) I always kept two brake fluids one dot 3 for cars and one dot 5 for bikes. I've seen quite a few Harleys get brakes messed up by puting in dot 3. Especially true of drum brakes.

I did not know that about DOT 5.1. Seems unfortunately named to me.

slimcolo wrote:Sorry what jonnythan said is true of the dot 5 but not the dot 5.1 which is non silicon but meets dot 5 boiling.
Until I got a Beemer (these Euro bikes use dot 4, like VW) I always kept two brake fluids one dot 3 for cars and one dot 5 for bikes. I've seen quite a few Harleys get brakes messed up by puting in dot 3. Especially true of drum brakes.

Yup, but it's usually a bad idea to put 3 in a dot 4 system as it has a lower boiling point. I think you said that already though.

Do Harley's have a lot of hydrolic drum brakes? The only place I've seen those (I've never really worked on Harley's) is older quads.

if they are relatively new you might still need to seat the pads, a few hard stops (brake until just before the back tire raises up) from 60 or 80 to 5mph spaced a minute apart should get them sticky again and burn off anything thats been left on there. good practice anyways.
it could also be that you got high performance pads, which dont work as well at lower temperatures (not stopping as hard from as fast) and the old pad material was still on the rotor so you got the lower speed brake grip from that till it either burned off or was replaced by the higher performance pad material on the rotor.