Brake Calipers - FYI

[07_SKY_RL]

Thought I'd polish my brake calipers.

Turns out they aren't aluminum - a magnet sticks to them.

I didn't check the rears - only the fronts.


Would that make them cast iron? Cast steel?

[Skip]

I would think that they are cast iron for the heat and to reduce warpage. And yes the rears are same metal as front. And remember that e-brake hooks to the rear and is a pain if it is misadjusted....Skip...Oh and yes you take them off they have to be bleed....

[larry4pyro]

Hi,

Wow, that really strange, I can tell you both the front and rear calipers on my NA Sky are aluminum. I just went down to the garage a few minutes ago - a magnet didn't stick to either front or rear.

I tried to polish them last week. The rears shined OK, but the fronts seemed to be made of softer aluminum and I couldn't get the scratches out. So I just painted them.

[07_SKY_RL]

OK. This is really odd.

Maybe I'm a little obsessive, but I keep a Sharpie and paint pen handy and mark parts as I take them off.

I marked both front calipers and their brackets, LF and RF. Left being the driver side and right being the passenger side.

I took the calipers home, and noticed the brackets are stamped L and R - only they're stamped opposite from what I wrote - and I double checked when I marked them.

The calipers appear to be identical castings, but there are two bosses for the bleeder screw fitting, marked L and R. The one that has the bleeder hole bored in the R boss is the caliper I marked Left, and vice versa.

Am I going crazy?

The brackets are nearly identical, other than a locating boss that the caliper sits on - the car isn't worn enough for the bracket to have marked either caliper body.

The calipers, however, can only go on one way with the bleeder screw facing up, which it has to in order to get the air out, and they were oriented that way when I took them off.

The caliper with the bleeder bored in the R boss has to go on the driver side, and the caliper with the bleeder bored in the L boss has to go on the passenger side.

There are part numbers stamped on the calipers - 22731035 on the one I marked R, but is marked L, and 22731036 on the one I marked L, but is stamped R. Part numbers aren't valid on gmpartsdirect.com or partszoneonline.com.



One thing I considered was the calipers came out of the parts bin and nobody noticed the casting stampings were wrong. Still, for that to be the case, the calipers would have to be mounted on the front of the disks rather than the backs, and I've never seen a GM car like that, although anything is possible.

There are some factory pen marks that touched both the caliper and its bracket. One side is green, the other blue, so I know my brackets and calipers are matched to their correct mate.

Any ideas? Do I have the R and L sides of the car mixed up or did GM suddenly change orientation on me?

[07_SKY_RL]

Originally Posted by larry4pyro

Hi,

Wow, that really strange, I can tell you both the front and rear calipers on my NA Sky are aluminum. I just went down to the garage a few minutes ago - a magnet didn't stick to either front or rear.

I tried to polish them last week. The rears shined OK, but the fronts seemed to be made of softer aluminum and I couldn't get the scratches out. So I just painted them.

Weird. I haven't yet checked the backs, but I double-checked the fronts - they're sitting right next to me. They are definitely attracted to magnets - and I checked the outboard side to be sure I wasn't getting a false reading off the piston.

I wish they were aluminum, from a polishing standpoint. Its a lot easier.

I'm still going to try and smooth off some of the casting (or maybe its forging - I don't know) flash and maybe the sand pattern (I guess if they spent the $$ for forging dies, they'd have a nicer finish), but I'll probably paint them. They look pretty nice right now, and I think they've been coated with something, but once the rust starts, they'll look like heck and I'm not sure its worth clear coating polished steel/iron.

I've used the G2 products in the past - they're a two-part epoxy, a bit pricey, but I think that's a better coating than the Duplicolor, which is just ceramic-enhanced enamel. My first intent was to do them in red, but I'm starting to think that's too ricey on a midnight blue car. There's enough bling with the chrome wheels.

I think I'm going to pick up the G2 silver and some G2 black and mix them up so I get a dark metallic grey - sort of that of the darker silver Sky color. That should be nice and understated, to keep focus on the wheels, but still have a level of detail and "cleanability" not present on the stock calipers.

Also, I noticed the rear driveshafts have rusted quite a bit, I'll be cleaning them off and hitting them with the same coating, along with the rotor "hats" that show against the wheel, and maybe a few other undercarriage odds and ends (being careful not to paint mating surfaces).

[07_SKY_RL]

Rear calipers on the Red Line are aluminum.

[GaryH]

I don't know what their made of but, a magnet sticks to the front ones but does not stick to the rear ones.

[ggccg]

Originally Posted by GaryH

I don't know what their made of but, a magnet sticks to the front ones but does not stick to the rear ones.

Magnets are not the ultimate test for steel. Steel that has been heated to its transition temperature and then quickly cooled will show no attraction to magnets.