Anyone know anything about disc brakes?

Anyone have any idea why my rear brake locks up?

Avid BB7 Road S. Cable actuated with SRAM S500 lever. I start a single track run with it working normally, by the bottom of the run it's damn near locked up. I have to dial the pad out to get it working again. It's hot but not outrageously so.

The front never does this and I use them both a lot because I'm scared.

Wheel moving in the dropout and jamming the rotor against the caliper? Or loose caliper bolts? Or are both pads tight on the rotor? Could be a sticky cable?

I have DT Swiss RWS skewers done up pretty tight, so I hope it's not moving in the dropout. I did worry about that before as I was having definite wheel location issues but they seemed sorted with those skewers.

The caliper has been adjusted as per some guy on youtube so the caliper bolts and pads should be all good.

Sticky cable is a possibility I suppose but it's housed all the way to the caliper. Jagwire foo'

It feels like it's a heat thing as it's progressive and it goes back to normal after a while. Actually that's a good point, I don't know that for certain as I usually fettle with it to get it working again. I have to dial the outside pad out to actually get the wheel rotating again, it's clamped on that much.

I changed the rotor to a different SRAM one and next I'll try some new pads. Really annoying when it seizes completely on!

Pro disc brake tip

Don't accidentally pop the presser foot out of your BB7 at 11pm the night before you're off to Scotland. Unless you want a crash course in their design and servicing of course.

had been looking for this but it was not on this thread, it was hidden on the Di2 thread instead.

@alb posted this a while ago

"Got shown a neat trick that improves lever throw (shortens it) on both ST-RS685/ST-RS785:

Un-screw free-stoke adjustment screw almost fully. Remove bleed screw and add reservoir topped with oil.
If it's a brand new install then bleed the system as normal until no air bubbles in either syringe or rising up through the bleed reservoir at the lever end. Close system @ caliper end remove syringe but leave bleed reservoir topped with oil in place. (if already bled got to No.4)
Clean caliper and add pads (leave the wheel/rotor out)
Cycle the pistons out by squeezing the lever a few times (without the rotor/wheel fitted). Use a piston press or clean (careful not to contaminate pads) flat head screwdriver to reset pistons each time. Check both pistons are moving freely with equal movement. Repeat 3-4 times. Air can be trapped behind the pistons - this effectively 'burps' them - you'll likely get a big ol' air bubble escaping up through the bleed reservoir on first go.
With bleed reservoir still in place slowly wind-in the free-stoke adjustment screw whilst flicking the lever blade. You should get tiny air bubbles escaping as the air is forced out/screw wound-in.
Remove bleed reservoir replace bleed screw closing the system
Re-fit wheel/rotor. Set brake"

typically i couldn't find it while i was just installing a new lever on the commuto x bike but it may be of interest to @hippy and others using rs685 and rs785 STIs

I've got used to mine but thanks for the heads up. We fucked around with a similar process in the first instance although I think we did the throw screw and lever flicking at different times so it possibly wasn't as effective.

Cheapest I can find an M615 brake with the right hand lever I need is chain reaction but it's a rear so I'll need to shorten the hose. CRC are out of stock of the correct (I think) BH90 olive and barb but they have the BH59-63 in stock. The BH90 has a 2.1mm bore diameter and the BH59-63 is 2.3mm.

Chances of being able to smash it together?

I've cut barbs out of hoses before and reused them and the olives so could just do that...

Ignore me.

shimano complete brakes normally come with a spare barb and olive in my experience.

I have a spare if you really need?

@hamrack I'm in Glasgow not London but thanks.

@chiroshi CRC specify no olive but are about £20 cheaper than anywhere else so...

185mm caliper on a 180mm rotor, certain death?

Really grabbing it might angle the piston. Doing something similar on a cross bike because lazy and it's for emergencies only

Cheers, found a cheap avid one on eBay so have splashed out.

Must've been really cheap for such a reaction.

Someone has an experience with recent Sram HydroR Caliper ? Mine were mounted with CPS washers on IS->Post adapter (160 mm). The pads do not fully engage the rotor. Should I remove the CPS washer ? The SRAM guideline specifies two different types of caliper : CPS and standard.

CPS washers

Maybe on top?
http://forums.mtbr.com/brake-time/can-i-loose-cps-washers-864387.html

Any #protips before I break out my new mount facing tool on a steel frameset?

Apart from cutting oil and "measure twice, cut once" obvs.

@coldharbour plz.

I could try this ! Thanks.

Is it a 2 in one jobbie, in that it faces both mounts at the same time? If so it's pretty hard to fuck it up (not a challenge), if not, just remove as small amount of material as possible.

not a challenge

In an ideal world, my first go wouldn't be someone else's £4k build, but hey-ho...

Thanks, will take it slow.

Ulegra groupset with
RS685 STI with RS805 callipers £670
Vs
105 with
RS505 STI with either RS785 Callipers £570
Vs
105 with
RS505 STI with either RS505 Callipers £500

What's the best value? Others here have said The Ultegra option levers are much better but thought I'd ask on the specific thread.
I'm a total noob at this so go easy.

calipers:
the flat mount rs805 and rs505 (and probably rs405) are for all practical purposes the same. So any of them or cheapest ones

Any idea on the shifters??