Excessive front brake drag

[d3vi@nt]

I just slapped new rotors on the front and feel that the drag when spinning by hand is excessive. I know there should be some drag, but this is pretty solid resistance.

Everything worked as expected before the rotor swap. Bled with fresh fluid after the swap, too.

How does one go about adjusting the calipers to reduce drag?

TIA

[stopintime]

Which bike, which rotors before and after? Thickness? Over filled fluid reservoirs? Caliper piston stiction?

[BK_856er]

Calipers will self-adjust to new/thicker rotors, but only if the rotor is the appropriate thickness and caliper pistons move freely.

With the front wheel off the ground I like to get a couple rotations with a manual spin of the wheel.

As stop mentioned, be sure the reservoir is not over-filled.

IME, new pads or rotors or rearranging the pads will take a few rides for everything to bed in and be normal again.

I'd start by cleaning the "calipers" with diluted dish soap solution and a toothbrush, focusing on the piston exposed areas.  First unbolt caliper and remove pads.  Get things good and clean.  Extend the pistons a bit with the brake lever and clean again.  Push the pistons back in all the way using your fingers.  Equal force required or even stuck?  Extend and clean again.  Repeat numerous times.  A special tool to rotate the pistons in situ can help.  Probably time for new seals or caliper rebuild if careful cleaning doesn't sort things out.  Eventually you pay the price for irregular fluid change and/or infrequent caliper cleaning.  The piston seal not only keeps pressure/fluid in the caliper, but it also helps to retract the piston just a little so the pads don't drag too much after you release the lever.  Dirty/corroded pistons or hardened seals will prevent this automatic retraction.

BK

[d3vi@nt]

Which bike, which rotors before and after? Thickness? Over filled fluid reservoirs? Caliper piston stiction?

Thanks for the reply. Bike is the one in my sig; '99 ST2. The previous rotors were the OE brembo's with steel carriers. They measure 4mm now, but not sure what they measured when new. They've got close to 40k miles on them.

The new are Brembo Gold Series Front Brake Rotor (78B40870). They're listed as compatible; 320mm, 6-bolt with 10mm offset. They measure 5mm on my calipers, which I'm sure is what's causing the drag. Just don't know how to adjust the calipers...

[S21FOLGORE]

Caliper cleaning
http://www.ducatimonsterforum.org/index.php?topic=61878.0

+1 on checking air gap in reservoir, do the caliper cleaning if you haven't already done.

[d3vi@nt]

Calipers will self-adjust to new/thicker rotors, but only if the rotor is the appropriate thickness and caliper pistons move freely.

With the front wheel off the ground I like to get a couple rotations with a manual spin of the wheel.

As stop mentioned, be sure the reservoir is not over-filled.

IME, new pads or rotors or rearranging the pads will take a few rides for everything to bed in and be normal again.

I'd start by cleaning the "calipers" with diluted dish soap solution and a toothbrush, focusing on the piston exposed areas.  First unbolt caliper and remove pads.  Get things good and clean.  Extend the pistons a bit with the brake lever and clean again.  Push the pistons back in all the way using your fingers.  Equal force required or even stuck?  Extend and clean again.  Repeat numerous times.  A special tool to rotate the pistons in situ can help.  Probably time for new seals or caliper rebuild if careful cleaning doesn't sort things out.  Eventually you pay the price for irregular fluid change and/or infrequent caliper cleaning.  The piston seal not only keeps pressure/fluid in the caliper, but it also helps to retract the piston just a little so the pads don't drag too much after you release the lever.  Dirty/corroded pistons or hardened seals will prevent this automatic retraction.

BK

Thanks for the info.  I put in about a 20-30 mile ride, but still felt the dragging, so I was hesistant to put in more. Up on the stand again, I can get about a half rotation if I really yank on it. It does not spin freely.

I flush the clutch and brake fluid annually. I also replaced the bleeders and old rubber lines with steel-braided just a few years back, so it's been well maintained. Fluid is not overfilled.

Calipers may need a cleaning, but everything worked fine before the swap.  The new ones stop well, they just drag too much.

[BK_856er]

Half a rotation would also concern me a bit.  You did a road test, also good to check the rotor surface temperature post-ride as that'll also give an indication of the extent of the issue and if it's restricted to one side.  Dragging brakes can be unsafe!

Are pads relatively fresh?  Newish thick pads + new rotors means that you'll be pushing the pistons in further than they have been in years, possibly into a region of the piston with corrosion or dust build up.  That could explain why you didn't have the problem before the rotor change.

Do the cleaning and see how it goes.  The link to S21's tutorial is excellent.  Also lookup a video by Dave Moss on the subject - google.  Make sure the pins, etc. are also in good shape.

Sounds like you are on top of fluid changes - good on you.  For your other question, there is no caliper adjustment - just squeeze the lever a few times and things will auto-adjust.  Sticky piston will cause excessive drag and is likely in this case.  Cleaning/manipulating might resolve it.

Just occurred to me - make sure you use correct front wheel install sequence - possible to offset the R fork leg/caliper a bit which could compound the drag.

BK

[stopintime]

............

Are pads relatively fresh?  Newish thick pads + new rotors means that you'll be pushing the pistons in further than they have been in years, possibly into a region of the piston with corrosion or dust build up.  That could explain why you didn't have the problem before the rotor change.
................

BK

(I'd also add that new rotors deserve new pads)

[d3vi@nt]

Thanks, guys.

Got it up on the stands and calipers removed. With the reservoir open I was able to open the pads more with a piece of wood and some gentle prying. Pistons and piston action all seemed fine and saw even wear on the pads.

Opening the pads, of course pushed more fluid into the reservoir, which I noticed was dark brown at the bottom --not good.  Good thing I didn't go for a longer test ride.

Bled again to get all the bad and now excess fluid out. Back together and everything is working fine with the right amount of drag. Good learning experience.

Pads are fairly new and good ferodo's from CA Cycleworks, so I'll hold off on replacing them for a bit.  I'll plan to do the full caliper clean once riding season comes to a close.

Thanks again for the info and help!

[stopintime]

Very good