Unsticking caliper with a 2x4

[sam000lee]

My front disc brake was stuck after sitting for the winter. I bled and replenished the brake fluid but it was still stuck. After watching this video, I tried the 'hitting it with wood' trick. When I do this, my wheel frees up nicely, but if I reapply the brake it sticks again until I readminister the wood. What is going on here?

[Steve]

Clean/rebuild your caliper.

.

[tkent02]

And the rest of the brake system.

[CivilRock]

To answer your question; your caliper is sticking. Most likely from corrosion/rust between the piston and caliper (slave cylinder).

1. take the caliper off the rotor.
2. pump the brake lever until the piston comes out of the caliper.

From there you'll understand the problem. You'll need more brake fluid and some emery cloth to polish the piston/caliper. When you order the new seal and boot to reassemble, go ahead and order the rubber parts for the master cylinder too.

Brake fluid is hygroscopic and collects water from the air. That's why you're supposed to change the brake fluid every 2 years. It's usually not the brake fluid that fails, it's all the water in the fluid that rusts and corrodes your brakes from the inside. In a 30 year old GS, chances are it's been 19 years since it was last changed, if ever.

-Kevin

[sam000lee]

Okay thanks, good answer. I'm also just wandering what smacking the caliper is doing that frees it up momentarily.

[blowerbike]

use a plastic hammer unless you enjoy handling wood
the shock from what ever you use shakes the piston back in the bore enough to remove the pressure on the rotor.
simple eh?

[tkent02]

1. take the caliper off the rotor.
2. pump the brake until the piston comes out of the caliper.

From there you'll understand the problem. You'll need more brake fluid and some emery cloth to polish the piston/caliper. When you order the new seal and boot to reassemble, go ahead and order the rubber parts for the master cylinder too.

Brake fluid is hydroscopic and collects water from the air. That's why you're supposed to change the brake fluid every 2 years. It's usually not the brake fluid that fails, it's all the water in the fluid that rusts and corrodes your brakes from the inside. In a 30 year old GS, chances are it's been 19 years since it was last changed, if ever.

-Kevin

All very true, but consider a new master cylinder, they are cheaper than the parts to rebuild your old one. Just bought one for $20 and it even came with a rebuild kit.

[CivilRock]

Well, there's just a teensey tiny bit of pull back from your master cylinder trying to spread the pads off the rotor. The corrosion is preventing that. When you smack it, you overcome the corrosion's grip and the pads part from the rotor. Not sure how to explain it if that doesn't make sense.

Have you ever had a tank slapper? That's when the front wheel violently oscillates like a shopping cart caster wheel. The force on the caliper is so great it can push your brake pistons back into the calipers giving you a ghost brake when you most need it. Not really like hitting it with a 2x4, but it just came to mind. If you do ever get a tank slapper, test the brakes on the straights before you get to a corner. You might need to pump it a couple times.

There's another possibility that the little relief hole in the master cylinder (MC) is blocked, plugged, or corroded and is not letting the brake fluid back into the MC. But since you freed it with a "whack" to the caliper, it's probably not the problem.

I encourage you to take it apart and see how it all works. It's a pretty simple device, and pretty hard to get wrong. I like to see exactly what I'm doing before I order the parts if it's my first time, or you can be bold and order all the parts you think you'll need and have them at hand when you dive in. While you have it apart, blow on one end of the brake line and make sure it's not collapsed on the inside. Crappy old DOT3 can eat the insides of rubber lines and you'll never know from looking at it.

[blowerbike]

is this where i insert.....while your rebuilding your system to go a head and flush with rubbing alcohol and change over to silicone dot 5 fluid.
dot3/4 draws moisture and causes all these problems.
dot 5 does not and you will never have a stuck caliper or damaged paint again

[CivilRock]

Yes. I didn't know that about DOT 5.

I thought it was just higher boiling temp or something.

I've lost a lot of rattle can paint from spilling DOT4.

-Kevin

[tkent02]

Dot 5 doesn't eat paint?

[blowerbike]

Dot 5 doesn't eat paint?

no way jose...
corvette's and big HD'd come with dot 5.

[Steve]

No, it doesn't eat paint. Nor does it absorb water, but that doesn't mean there are no problems with water.

Any water that does find its way into the system will tend to puddle at the lowest point. In this case, it's the calipers. Which also happen to get warm on heavy braking. It's possible that they might get hot enough to boil the water, leading to instant MUSH for brakes.

[Grimly]

Okay thanks, good answer. I'm also just wandering what smacking the caliper is doing that frees it up momentarily.

You've likely got the standard Tokico crappy caliper on the LH side. They're fine, they do the job, but they wear in one or two/three spots that cause them to stick.
First, as has been mentioned, they get sticky pistons, but that's not really all that common on a bike that's in regular use.
Of more common occurence is the propensity of many owners to lose or toss away the little steel sliders the pad ears sit on. Without those sliders, the pad ears wear a groove in the alloy body of the caliper bracket - and they stick.
Of even more common occurence is the tendency of many owners to not bother re-greasing (or wrong grease) the sliding pins every year (essential maintenance) and the pins get worn, but not as much as the holes get worn in the soft alloy caliper bracket - and they stick, because the whole shooting match is actually twisting when you brake.
So, it's a crappy design and with a lot of miles on it's even more crappy.
Having said that - if you rebuild them (and assuming you can find very low mileage brackets), they can be good brakes - just keep an eye on them and maintain them, unlike the last owner.
I'm going through a brakefest with mine - I've decided to stick with the OEM brakes and keep them good, but if the supply of good used bits dries up, will look at better, later calipers from something else.

[earlfor]

Dot 5 doesn't eat paint?

Nope, it's silicone based. However, it is ABSOLUTELY incompatible with types 3 and 4. It'll turn the brake fluid into peanut butter if you mix them.