Front brake drag...

[motopsycho87]

Has anyone else experienced brake drag on an ec? I've rebuilt my caliper, master cylinder and changed the hose but I still only get about 3 turns on a good spin on the front wheel?

Everything is moving smoothly, pisonts etc, pins are clean and greased, disc is true to 0.2mm, but the wheel doesn't turn under the weight of a padlock on the disc!

I've completely run out of ideas! Bracket appears to be true also. And there is free play in lever.

 

[pscook]

Check that your pads are flat as well as pistons are returning. I assume that you cleaned the pistons in the caliper when you rebuilt it, you might want to make sure that there isn't any crud built up on the pistons.

Regarding pads, if they warp, they won't seat properly, and can drag against the rotor. It's worth it to check. Bent pads will cause poor brake performance that feels like air in the system as well.

 

[motopsycho87]

The pads looked pretty flat last time I had them out, I had them on a flat table and did figure 8's on emery paper. I'm down to my last resort now, waiting for new pads haha.

Can anyone please record a video of spinning their front wheel after applying the front brake? Would be nice to see comparison, and if I'm just being anal!

Problem has been after the bike gets warm it binds more and more...

 

[(F5)]

Could be the return path in the master cylinder. Tiny hole can get blocked up, there should be a big hole & a very small hole.

 

[bowhunter007]

Have you spun the wheel with the caliper unlbolted & set aside...just to rule out drag at bearing/axle assembly?

 

[motopsycho87]

Yeah, new bearings too, spins lovely with the pistons pushed back.

How do you go about cleaning this return path? When the pistons are being pumped up from being pushed back in the caliper they move in sync as they should, and retract slightly when the lever is let go as they should. This would say the return path is fine?

 

[Zman]

I have seen that after a few crashes the bark busters can move in an contact the lever end. It can put pressure on the system and cause drag or in some cases can apply lots of drag.

 

[JP4]

If your master cylinder is overfilled it won't allow the pistons to fully retract, thus causing drag. Maybe have a check and draw off a little fluid from the m/c.

 

[jostby]

another thought is to make sure the brake lever adjuster screw is backed out enough to let the piston in the master cylinder to fully retract when the lever is released. That can cause bleeding issues also but that's another topic.

 

[(F5)]

Yeah, new bearings too, spins lovely with the pistons pushed back.

How do you go about cleaning this return path? When the pistons are being pumped up from being pushed back in the caliper they move in sync as they should, and retract slightly when the lever is let go as they should. This would say the return path is fine?

Mmm, the above doesn't preclude a blocked path, they will retract slightly when you let go of the lever.

but:
If the return is blocked it will be quite hard to push the pistons back. Quite hard.
You'd be tempted to resort to brutal force or opening the calliper bleeder.

You can also test it by connecting a length of empty brake hose to the mc & blowing through it to make bubbles. Most common cause is no freeplay at the lever to piston, but you've covered that you say.

 

[motopsycho87]

When bleeding, air freely flows to the reservoir, so I doubt its blocked. I use grips to return the pistons, the both move in and out freely, I blasted them with an airline and they pop right out.

I pushed the pistons back a couple mil before replacing the reservoir cover, so it can't be that. There is 2mm play in the lever before contacting the master cylinder piston.

Ive taken it for a spin after remachining the rear pad land, it's a lot looser, but still only spins about 3 times...