Front brakes dragging......again!

[Conrad]

vacuum out the res. first without taking too much out and allowing air to enter.  Fill res. and move to slave and bleed.  No point in dragging all that rubber and such through the whole system.

I just assumed that he knew to vac out the old fluid first. I guess I shouldn't do that eh?

[Conrad]

Awesome!  I was hoping for that!  The fluid looks pretty dirty in the reservoir, so I might as well clean it up.

I just did my clutch, and the brakes, recently. The clutch fluid was a mess!

[VirginiaJim]

Clutch bleeding is a different topic...start a new thread guys.

[B.D.F.]

This is hard to quantify but <a little> fluid movement would be OK and even expected due to the reservoir being higher than the bleeder(s). What you are really looking for is substantial pressure (I know- again hard to quantify), say enough to spit a bit of brake fluid up and out of the bleeder. That would be too much pressure.

Another quick and easy test would be to check the effect of that pressure on the brake drag directly. If you are finding the front wheel dragging, you could ride the bike and check the brake drag without touching the brake system. Then crack the top bleeder and see if the front wheel is any easier to turn or coasts any further. If it does, then there was some effect of hydraulic pressure left in the system. If opening the bleeder has no noticeable effect on the front wheel that you can feel, the cause of the brake drag is something other than the brake hydraulics.

There is always some drag from disc brakes and the front wheel will not free- wheel and spin a long time even on a bike with a perfectly functioning brake system. That said, you should not feel any resistance from the brakes when you try to turn the front wheel by hand.

Finally you can also check your front wheel bearings and seals for any damage and to make sure both sides are well greased (both bearings and seals).

Brian

Well last night I tried Brian's suggestion of cracking the bleeders to see if there was pressure.  Guess what?  There was a little.  I cracked both and though I didn't get the 'rush' of oil I anticipated, there was some.  Since I had my bleeder kit connected, I went ahead and bled both sides.  I actually flushed a fair amount of oil through both calipers.  I didn't see any dirt or anything peculiar.

The brakes did release some, and now only slightly drag.  A modest spin of the front wheel yields maybe 3/4 to a full rotation.  I think it should be even more free, but I don't have anything to compare it to.  But the biggest change is in the lever!  At the lever it used to feel very tight, as in there was no lever action.  It felt 'pumped up' all the time.  Now they feel more 'normal' in that there is a lever 'action', you have to squeeze and you feel the lever applying pressure to the brakes.

I do not declare victory, as I still feel like there is something binding, but I feel better that I am at least close to the issue.  Maybe I have the same problem Steve was having with his, I don't know, but I should think that if it happens again, I will pull the lever to see if that releases the pressure.  If it does, then I will KNOW what my next step is.

[stlheadake]

Thanks for the info Brian, that is EXACTLY what I love about this forum.  That and the gashole issues   There really wasn't THAT much pressure, it probably was more related to gravity, and less to pressure.  However, as I mentioned before, I did flush a bunch of fluid through, and that has seemed to help. 

If it comes back, I'll try some different 'tests'.  I checked the bearings and seals (habit) when I re-installed the wheel on Monday.  I had just had new kicks installed.  I always check the bearings by inserting a finger and rolling them a couple of turns.  I feel for 'grit' or something not smooth.  It's not a highly scientific method, but it makes me feel better.  As far as the brakes go, all I know is they are better than they were.

This is hard to quantify but <a little> fluid movement would be OK and even expected due to the reservoir being higher than the bleeder(s). What you are really looking for is substantial pressure (I know- again hard to quantify), say enough to spit a bit of brake fluid up and out of the bleeder. That would be too much pressure.

Another quick and easy test would be to check the effect of that pressure on the brake drag directly. If you are finding the front wheel dragging, you could ride the bike and check the brake drag without touching the brake system. Then crack the top bleeder and see if the front wheel is any easier to turn or coasts any further. If it does, then there was some effect of hydraulic pressure left in the system. If opening the bleeder has no noticeable effect on the front wheel that you can feel, the cause of the brake drag is something other than the brake hydraulics.

There is always some drag from disc brakes and the front wheel will not free- wheel and spin a long time even on a bike with a perfectly functioning brake system. That said, you should not feel any resistance from the brakes when you try to turn the front wheel by hand.

Finally you can also check your front wheel bearings and seals for any damage and to make sure both sides are well greased (both bearings and seals).

Brian

[martin_14]

Thanks for the info Brian, that is EXACTLY what I love about this forum.  That and the gashole issues   ...

So you have gashole issues, uh? Tell us about it... 

[TownsendsFJR1300]

I would think just removing the brake lever on the bars would release any pressure (if that's where the problem is coming from.) 

If the front brakes are linked to the rear, are they linked to both front disc's or just one? If so, could the rear MC be applying pressure to the fronts when not applied?

As an FYI, I just rebuilt the dual, front, 4 pot calipers in my bike (was just starting to drag-about 3/4 free turn).  With new seals and assembling with Permatex brake lube:
 ( http://www.amazon.com/gp/product/B0018PSASU  ).   I now get just over three full spins on the front wheel.  That's with the lever being normal pull/distance (fronts are NOT linked to the rear wheel, non-ABS).  This lube is made for brake pistons/pins, etc and so far works extremly well.  There's a PDF link on the spec's of the brake lube..

Just make sure nothing is accidentally applying your brakes

[Fretka]

How about this: As you ride down the road various bumps and flexing, including normal fork action, introduce some "instantaneous and short term' flexing of the caliper in relation to the rotor. This is normal and all is well.

This Y axis or sideways force to the rotor  causes the brake caliper pistons to retract or get bumped back slightly vastly lessening the drag of the pads on the rotor, again all is normal.
So what I am saying is a little rotor warp + suspension movement is a good thing as it retracts the pistons a very small amount ( in addition to the hysteresis of the piston seals themselves).
So ..... every time you attempt to measure the brake drag, you do this just after applying the brakes as you pull into your garage...right? Of course they will show some brake drag because the conditions of normal riding down the road and the resultant effects have not occurred yet, so the brakes seem tight.
You end up chasing your tail!
The point is this

Whatever brake drag you feel with the bike sitting in your garage will not be present once you start riding as the forks, caliper, wheel, triple clamps bearings frame etc... begin to flex slightly.

Measuring brake drag after coming to a stop will always give you a false reading.
Just ask racers who have had a heroic save from crashing only to find that the save was so violent that it pushed the pistons waaayyyy back into the calipers and now they have no brakes!

Fretka

[Fretka]

No comment?  Seems I am a thread killer


Bruce

[VirginiaJim]

No, you're not.  That's my job, although I prefer locking them.

I guess there's drag that may be normal and drag that could be abnormal.  For instance, when I bollocksed up my fronts by having too much fluid in the reservoir you could tell it was dragging...not a little, but a lot.  Some drag on a disc system I would think is normal.  I guess you would have to be there to know that it's too much.