Author Topic: Rear BB7 brakes are poor  (Read 612 times)

Rear BB7 brakes are poor
« on: July 24, 2020, 11:28:35 am »
My somewhat aged BB7 brakes are not so great anymore. Rear is particularly poor. Can't lock up wheel at all.

I suspect oil contamination, which implies the need to replace the pads. Seems mad, because they are hardly worn.

they are adjusted so I can only get lever to bar with cable-snapping amounts of force.
<i>Marmite slave</i>

Re: Rear BB7 brakes are poor
« Reply #1 on: July 24, 2020, 11:36:51 am »
Does sound like contamination if the pads are pressing but not stopping, you could swap pads and rotor to confirm or eliminate them. If they are contaminated cleaning rather than replacement would be the first thing to try.

Kim

  • Timelord
Re: Rear BB7 brakes are poor
« Reply #2 on: July 24, 2020, 11:47:34 am »
As it's on the rear, it's always worth suspecting the cables.  Is it still crap if you operate the caliper manually?
Careful, Kim. Your sarcasm's showing...

Re: Rear BB7 brakes are poor
« Reply #3 on: July 24, 2020, 12:03:23 pm »
BB7 brakes have plastic inner bits that can get distorted, or can even melt, especially if you are heavy, or if you are two on the same bicycle. We changed a few years ago for TRP cable disc brakes and since had a much more constant braking quality.

A

Re: Rear BB7 brakes are poor
« Reply #4 on: July 24, 2020, 01:23:36 pm »
how do I decontaminate? I've washed the rotor with water and detergent.  I have acetone.

My cables are ancient now - still originals (so, erm, maybe 5-6 years old).

Still carp if operated manually, hence suspecting contamination.

<i>Marmite slave</i>

Re: Rear BB7 brakes are poor
« Reply #5 on: July 24, 2020, 01:38:31 pm »
If the pads are contaminated with oil/grease then they are toast.  Just get some replacements from disco brakes.  The reason the pads are toast is that the oil/grease can soak into the pad matrix which makes it very difficult to remove it.  You can clean the pad surface for sure, but then over the next few days the oil/grease contamination leaks back to the surface.

Re: Rear BB7 brakes are poor
« Reply #6 on: July 24, 2020, 01:44:51 pm »
The Shimano cable disks on my bike got worse and worse even though I changed pads, scrubbed disks etc.  Then I replaced the cables and suddenly they were good again.

citoyen

  • Occasionally rides a bike
Re: Rear BB7 brakes are poor
« Reply #7 on: July 24, 2020, 03:14:24 pm »
If the pads are contaminated with oil/grease then they are toast.  Just get some replacements from disco brakes.  The reason the pads are toast is that the oil/grease can soak into the pad matrix which makes it very difficult to remove it.  You can clean the pad surface for sure, but then over the next few days the oil/grease contamination leaks back to the surface.
Got to be worth trying though, rather than just binning them straight off.

I recently restored some pads I thought were done for and they’ve been great ever since.

MrC - light sanding and solvent cleaner are the answer. Remember to clean the rotors thoroughly as well, and go through the bedding in process as if new.
"The future's all yours, you lousy bicycles."

Re: Rear BB7 brakes are poor
« Reply #8 on: July 24, 2020, 03:17:07 pm »
if the pads are sintered they can be cleaned reasonably well  by immersing in solvent and then burning the solvent off the (wet) pad afterwards.  Repeat as necessary; the idea is that any oil will be dissolved in the solvent and then wicked to the surface where it is burnt, and sintered pads will usually survive this treatment whereas organic pads, meh, not so much.

 However an 'old brake' that is not working well always suggests that the cable could do with being replaced, so I'd do that first of all.

IIRC the only plastic parts in a BB7 caliper are the outside parts that you can see. Of these the fixed pad adjuster knob is usually the first one to start melting, and it needs to get well out of shape before it is actually a problem.

cheers

ElyDave

  • Royal and Ancient Polar Bear Society member 263583
Re: Rear BB7 brakes are poor
« Reply #9 on: July 25, 2020, 06:27:07 am »
Having just gone through this same issue on the recumbent, including checking pad wear, a slight tweak of the in-line cable tensioners mad a massive difference to performance
“Procrastination is the thief of time, collar him.” –Charles Dickens

Re: Rear BB7 brakes are poor
« Reply #10 on: July 25, 2020, 08:00:54 am »
I’m tempted to wonder that if disc brake users had put as much time and effort into maintaining their rim brakes. ( cleaning and decontaminating blocks and rims appropriately), would they have been so keen to move to discs?

PaulF

  • "World's Scariest Barman"
  • It's only impossible if you stop to think about it
Re: Rear BB7 brakes are poor
« Reply #11 on: July 25, 2020, 08:02:37 am »
I’m tempted to wonder that if disc brake users had put as much time and effort into maintaining their rim brakes. ( cleaning and decontaminating blocks and rims appropriately), would they have been so keen to move to discs?

Yes. I spend far less time tweaking disc brakes than I do rims

Re: Rear BB7 brakes are poor
« Reply #12 on: July 25, 2020, 08:48:45 am »
I’m tempted to wonder that if disc brake users had put as much time and effort into maintaining their rim brakes. ( cleaning and decontaminating blocks and rims appropriately), would they have been so keen to move to discs?

I spent far more time doing g this on my rim braked bikes. Cleaned surfaces at least once per week.

Still went through multiple brake blocks a year and rims once a year.

<i>Marmite slave</i>

ElyDave

  • Royal and Ancient Polar Bear Society member 263583
Re: Rear BB7 brakes are poor
« Reply #13 on: July 25, 2020, 08:55:15 am »
I’m tempted to wonder that if disc brake users had put as much time and effort into maintaining their rim brakes. ( cleaning and decontaminating blocks and rims appropriately), would they have been so keen to move to discs?
Yes I would
“Procrastination is the thief of time, collar him.” –Charles Dickens

Kim

  • Timelord
Re: Rear BB7 brakes are poor
« Reply #14 on: July 25, 2020, 01:02:23 pm »
I’m tempted to wonder that if disc brake users had put as much time and effort into maintaining their rim brakes. ( cleaning and decontaminating blocks and rims appropriately), would they have been so keen to move to discs?

Yes. I spend far less time tweaking disc brakes than I do rims

+1

I've only ever had disc brakes get contaminated when being careless with the GT85.  (That was a Learning Opportunity, and I only did it the once.)  Rims regularly get contaminated with oily crap from the road, at least in urban riding.  Sometimes you can ride through a muddy puddle to sort it out, sometimes it's more serious and needs proper cleaning.

Most of my disc brake fettling is adjusting for pad wear (which is usually a case of lean down and turn the knob one click while stopped at the traffic lights), occasionally truing rotors that have been bashed, and dealing with cable issues.  Rim brakes wear pads and have cables too.   *shrug*
Careful, Kim. Your sarcasm's showing...

citoyen

  • Occasionally rides a bike
Re: Rear BB7 brakes are poor
« Reply #15 on: July 25, 2020, 04:15:16 pm »
Cleaning is a routine maintenance job, whether they’re rim or disc brakes.

Of course, not all bikes get routine maintenance... I started tinkering with my hybrid hack yesterday, which hasn’t had any actual maintenance for gawd knows how long. I’d intended to spend 20 minutes max on it, but ended up getting lost in three solid hours of fettling, including restoring the brake pads (turns out they aren’t black after all, they’re orange).
"The future's all yours, you lousy bicycles."

Re: Rear BB7 brakes are poor
« Reply #16 on: July 26, 2020, 02:50:57 pm »
how do I decontaminate? I've washed the rotor with water and detergent.  I have acetone.

My cables are ancient now - still originals (so, erm, maybe 5-6 years old).

Still carp if operated manually, hence suspecting contamination.

Being porous, disc pads will also soak up soap residue. I always make sure that my brakes only see fresh water when bike washing. I learned this after a weekend left out in the rain improved my braking 100%.
Life is too important to be taken seriously.