Heavy duty brakes
 

Just resealed my calipers 30-69B heavy duty brakes. Pads are about the same thickness as new not changing those have them though. Putting the calipers back on the wheel, disc thickness is within tolerance above .330, new shim installed and there is about 3/16-1/4 inch that the pistons have to come out of the caliper to take up the space, seems excessive to me, what have you all found with the heavy duty breaks?

Dan Schultz
N67S s/n 0168

Mr. Schultz,
From your picture, after you attach the backplates to the cyl assy, and torque them to spec, you will find you will have to compress the pistons / pucks a little bit to clear the wheel disc. The "excessive space" will go away.
Regards,
Randy

Pistons are flush in the housing. The issue is how far out the pistons will have to come out to take up the clearance.

Is this the first time you have done this?
How did the pistons look (spacing wise) when you took them apart?
the Parker manual shows the parts that are on the brakes. As long as you have those parts, in the correct order, the unit will function as designed.
I have the HD brakes, have redone them a number of times, my disc is probably pretty close to being replaced, and I have absolutely no issue with leaky pistons, or excessive piston clearance.
Did you remove the pistons and replace the orings / clean the pistons up, or just push the pistons into the cyl., and reinstall?
Regards,
Randy

Randy

I have all the manuals, Parker, took them apart to reseal, they were leaking, pistons were out then also. Not my first rodeo as I am an A&P and IA, old pads same thickness as the the new pads. The old original PN for the disk were about .040 thicker than the replacement disks today. I have new disks, however the old disks are about the same thickness. I guess the question is when you have replaced your disks and pads how far out do your pistons come?

Dan

Mr. Schultz
I’m sorry.
I am unable to help you.
Have a good day.
Regards,
Randy

I have a call in to Parker, will advise on what they say.

Dan

From what I see in your picture it looks about right. If you finish putting the caliper together and see what you get if the pistons are coming out 1/4 inch something is wrong. I maintained 6 with heavy duty brakes and for the pistons to come out 1/4 inch the pads and disc had to be worn out with new disc and pads the pistons were flush in the housings.
Make sure when you get them back together that the calipers are free to move and not binding and your wheel spins freely

All back together about .080-.090 of clearance that the pistons have to take up rotors are just a few thou below new and pads about 10 thou below new.

Still waiting on Parker, I still think that is a lot for the pistons to come out compared to other comparable installations.

Dan

Well, I've never done 6, but I have done 1 for 27 years, (or 27 for 1 year, your choice.)
I agree with your post.
The pucks on mine, with the calipers loose, able to float, are trouble free, regardless of the distance, (I never really gave it much of a thought, since they are pretty deep to the oring, and looked identical to what I saw coming off)
I doubt Parker will give an answer, at least one that is specific...
Regards,
Randy

Talking with Parker, with all new parts, pistons will be out of housing .020-.040.
The 07 disc today is the same as the original disc that was welded, new part disc thickness is .365, with a minimum wear down to .330.

All back together works fine

Dan