With the official start of British Summer Time, rain that isn’t absolutely freezing and other definite signs of spring being in the air, the winter of 2008 would seem to be passing into history. But today it claimed one last victim before leaving us enitrely, the Avid BB5 disc brake caliper on the rear of my Commencal Normal Disc commuting bike.
Eight months of commuting duties had worn out the front and rear Avid brake pads that came supplied with the Commencal from new, so it was time for a change. It should have been a simple job, but the rear caliper had other ideas.
Avid BB5 disc brakes have two braking surfaces; a static one and one that moves inward with the brake lever action. To compensate for brake pad wear, the static surface can be adjusted by means of a screw plate connected to a big, friendly looking, red adjuster knob. This is known officially as the “inboard pad adjustment knob”.
Avid BB5 Disc Brake (front) showing inboard pad adjustment knob
Unfortunately for me, the salt and grime kicked up from the wet winter roads into the rear brake caliper had caused the metal screw plate (that lies underneath the adjustment knob) to seize to the caliper body, and no amount of force on the adjustment knob would make it turn.
I tried the usual methods of freeing seized components: application of brute turning force with the Big Spanner, shocking them apart using hammer impacts, bathing overnight in penetrating oil (good old WD-40) but to no avail, the plate and caliper were still as one. Furthermore, the adjustment pad seems to be made of a very soft alloy and didn’t take at all well to this rough treatment, as you can see from the picture below.
Avid BB5 Disc Brake (rear) after failing to un-seize the inboard adjustment plate
Note the sheared inner and outer surface of the central Torx bolt, gouges on the plate surface and outer screw threads and the dents and paint chips on the caliper body. None of this damage took much force to inflict, so be careful if you find yourself in the same unfortunate situation.
After all this effort, I’m left with a destroyed, useless rear caliper, the expense of a replacement unit and a commuting bike lacking a rear brake and therefore too dangerous to take on to the roads.
This inconvenience and expense could have been easily avoided with a couple of simple precautions:
- Apply anti-seize compound between the caliper and adjustment pad when fitting the brake. Mine came factory fitted so I didn’t think to check, but it would have been a ten minute job to apply the compound retrospectively.
- Once a week give the adjustment knob a turn in both directions to ensure it is still moving freely. If I’d noticed the pad was in any way sticky, I could have cleaned and greased it before it got to the point of a full seize.
Preventative maintenance. You know it’s a good idea.
Same thing happened to my rear bb5 caliper after riding through a very brutal winter here in Chicago, so lots of salt.
I destroyed the little teeth on the red adjuster wheel with a big pair of pliers. I don’t have a star shaped tool to get it off either.
Your blog entry was actually quite helpful, now I know I’m not alone.
Would you believe it – the exact same problem. I was training all winter and just didn’t think to check that dial. Took off both calipers (front AND back seized up), gave them an oil bath to no avail, destroyed the plastic trim, ruined the spline nut and have basically written them off, unless the LBS guy has some sort of heavy duty wrench that can unseize it. Bought another set of BB5s second-hand for 20 EUR. Lesson learned (I hope). Winter riding is really harsh on the bike – I also had a pedal just fall apart, my SPD shoes are a mess and a chain just snapped after less than 1000km riding. Next winter I need to get some beater to do my winter training on, because this is getting very expensive…
P.S. The LBS guy managed to unseize one of the dials by treating it with some kind of anti-seize compound, forgot to ask which. So that’s worth a try if anyone has this problem. Still working on the other one…
Thanks for the info Mark, hope you get the calipers sorted out. I ended up buying new ones :/
Just had the same happen to my rear one after the bad weather. I hadn’t been checking that they could still be adjusted before they got to the point of being totally seized up either. If someone comes up with the name of an anti-seize compound that would be great – thanks.
Just to update, I got the other dial unseized too, with no damage apparently. In the meantime though I bought some cheap second-hand ones, like 25 bucks, so it was no big deal, got a spare set now for next winter :)
Sorry, keep forgetting to ask the bike shop guy what he sprayed on there…
Aligning the brake I managed to strip the teeth from inside the star-shaped adjustment bolt… nearly destroyed the red plastic piece trying to use pliers to get it unstuck. I finally oiled the dial as the force being applied to the plastic was deforming against the metal inner bolt.
It’s unstuck now but I’d actually like to replace that metal bolt that got stripped out. I guess I am back in business so long as I rely on hand-tightening the dial…