Brake Calipers Question

J

Jon Nelson

New member
I picked up some NAPA rebuilt calipers today, to replace the ones on my car that I suspect are dragging.

My question is this:

Is there some way I can ensure that the pistons do not "stick", and that I can be sure the calipers release properly? I've had a lot of brake wear, the hardware is all new and freely functioning the way Honda intended, I'm sure the brakes drag enough to prevent proper cooling, basically they are always building more heat.

I was considering dissassembling the new calipers and running the hone though them until they go together nicely and I can move the pistons easily, by hand.

The pistons in the rebuilds are stuck in there well enough that I cannot budge the pistons, even when sticking a pen through the line connection hole.

Any thoughts?

Thanks;

Jon Nelson
 
Be careful Jon!

Whether the calipers are brand new, or are slightly worn, there will be considerable drag on the pistons. This is normal. When I install new brake pads, I can't push the pistons back by hand. I have a piston retracting tool to drive them back. I doubt that you can push the old pistons out by pressing on the back of the piston thru the brake line hole since this will cause the piston to cock slightly and bind up. A better method is to use compressed air and blow the piston out, or (and this is kind of messy but guarenteed to work) remove the brake pads with the caliper still installed and pump the brake pedal until the piston pops out. Don't mess around with a hone as you'll only increase the clearences and reduce the effectiveness of the seal. The only area that you need to worry about in terms of sticking is on the pins that the caliper slides on. Make sure they are clean and use the proper grease (it's listed in the shop manual). If these pins get worn, you'll start to get more caliper flex and a springier brake pedal.

Lastly - a slight amount of piston drag is not a bad thing. It keeps the pistons from getting knocked back into the calipers from rotor run-out. If this happens, you have to pump up the brake pedal a couple of times at the end of before they work! Not a good thing!
 
Thanks, Greg, for the advice.... yes, I plan to be careful!!

The old calipers (on the car still) are even difficult to retract with my big ass c-clamp, one side more so than the other, more than normal(I have changed plenty of pads in my time)... hence the rebuids. I'm in the midst of performing some pretty major repairs, to I chose to get the rebuilds rather than do them myself. I've done it in the past, and yes, the compressed air trick is the way to go.


I simply thought there might be a trick to prepping the calipers for race use. Nothing else seems to escape some sort of special prep or modification, why should they be any different?

The pins and sliders do seem to have a certain amount of play, even on the rebuilds, so we'll see about that, I can't think of anything short of having the caliper bodies bushed and machined to help in that dept, but perhaps it owuld be worth the trouble. I;ve been getting some brake wear that might indicate a bit of calper flex.

Thanks,

Jon
 
Here's my 2 cents worth...
The difference between a race car and a street car are that a street car rarely has the caliper apart, is rarely bled, has old, rusty fluid, lots of street grime, gook; and a race car typically has clean fluid, is bled frequently, very little contamination and gook, but is subjected to very high temperatures. As a result, the only real maintenance that the caliper requires is new piston seals and dust boots, since these will distort or break down over time from the heat. I can honestly say I have never had a caliper piston seize up on a race car, including the time I welded the piston to the brake pad backing plate (This was during the era of Showroom Stock OEM pads...and 20 laps at Blackhawk was about 5 laps too many!!!). I would expect a street car or a boneyard caliper to be a problem initially, but once the old piston is out, as long as the bore is clean and you use new pistons and seals, the piston should move pretty freely. Was the caliper ever dropped or hit or something that might have distorted the cylinder bore?

Heat is also an issue with the guide pins. On a racecar, they don't really wear out, but the heat does cause them to become sloppy. This sloppiness causes caliper flex which results in a spongy pedal. Next time you are bleeding your brakes, try this little experiment. Put new pads in, bleed, and watch the calipers flex while the brakes are pumped and released. Now put old pads (at least 50% worn) and repeat the test. You be amazed at how much more the calipers flex. For this reason, I have a set of shims made up from used backing plates, ground down to various thicknesses starting at 1/8" in 1/16th inch increments. As the pads wear down, I install a thicker shim between the outside pad and the caliper. This keeps to piston pushed in further and keeps more of the caliper pin engaged to minimize flexing. I can run the pads until they are almost gone and they work fine. The pads seem to wear more evenly as well (less tapered wear).
 
Good thread. I'm just sorting my car out, and this gives me good useful information.


------------------
1994 Civic DX - ITA #93
 
Greg;

The calipers on my car WERE the originals. The car's been in the family since new, and sat for a year or so before the conversion to race car. Since the calipers weren't completely seized, and didn't leak, I cleaned/lubed the guide pins and the pad seating areas, and left it at that.

Worked pretty well for a season, but....

Since then, I have found that my car is incredibly hard on brakes. It could be me, I do use them hard, but I went through 50-60% of a set a Hawk Blues and a set of rotors in a weekend and a half.

I'm happy to report that the rebuilt calipers fit the guide pins better, and came with a new slider for the lower side, AND the pistons move quite freely, so hopefully my brake woes are fixed.

If that doesn't do it, I have yet to get any cooling air to the brakes, this is a pretty obvious thing to do, I know, but I've been resisting this, cause I've seen way too many cars running around with brake ducts hanging/dragging/tangling/falling off.

for now,

Jon
 
after my weekend of running closer to the front, I'm convinced your brake wear is abnormal, as my hawk blacks STILL have well over half the pad material left.
That said, I'm going to be running blues next event, we'll see how well things stand up
 
In the absence of any real trick setup info, I chose to paint the calipers red. Should be good for 10hp (at the wheels)!!

Seriously, though, I'm hoping my brake wear improves, I'd really don't want to spend any more money on pads this year.

How did the blacks hold out? You've got, what, three weekends on them? 4?

Why the switch to blues?

Jon
 
Jon, be carefull about painting the calipers as a lot of times the paint interfers with heat transfer and causes fluid to boil easier. just my thoughts.

------------------
Gordon Galloway
Honda CRXsi
IT2 #32
 
The paint can work both ways, as a conductor and as an insolator. I used gold colored engine enamel on mine since this is pretty close to the quasi anodized look of the factory OEM calipers. Got to be worth at least 2 tenths of a second....

I have never had a problem of boiling my brake fluid on my ITC Civic. I run at Blackhawk & Road America (Two of THE toughest tracks in the country on brakes!). I have been too lazy to repair my air dam with integrated brake ducts after an off course agricultural excursion last year so I haven't had any cooling air to my brakes at all this year. I have 4 weekends (7 races) on my Hawk Blues and they have over 75% material left on them. My rotors are worn slightly but are not scored. I haven't had a problem with melting the boot seals. If I have the time and patience to install the boots when I rebuild the calipers, I do. If I'm in a hurry (or get pissed at them because they won't go in, and I'm getting eaten alive by mosquitos while trying to do a rebuild in my driveway) then I will probably leave them off. I run Wilwood 575 fluid.
 
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