I spent the day yesterday installing new Porterfield pads on my rear calipers. I did not open the brake lines.

Installation went relatively smoothly. Venting clearances are spot on at .008 for both inner an outer pads. I went for a test drive last night. My brakes are very spongy. They are much less effective than before the pad change.

The old calipers are pretty crusty, but they were still working before the pad switch. The original plan was to rebuild them over the winter.

Any ideas on what happened and/or corrective action?

Can't say I've ever changed pads without also bleeding.. I would "internet guess" that in spreading the pistons to get the larger pads in, that you introduced spongyness at that time. You don't mention when the last time they were bled.. Also, if you are running the same pads on the front as well? or since the rears aren't bedded in yet? it could feel "spongy" for those reasons too...

That may be too much venting clearance...move it to .004 on inner and outer. IIRC a recent thread referenced that. Good idea "while you're in there" to crack the bleeders & let any possible bubble out...
Also possible is that fresh pads on used rotors need solid bedding to get full contact...power brake a bit to help that...

I think you will find that most advise 0.004. (which in my view is a German engineer's way of saying "as close as possible without rubbing").

Also I'd suggest do 3 or 4 decent hard decelerations from about 35 mph to warm em up and bed em in. Do this 1st - easier than adjusting venting clearances!

Hope this helps

DaveO

It is very typical with older crusty calipers for the seals to be damaged when recessing the piston which could let in air.

Of course check the venting clearance and bed in the pads as suggested. The Porterfield's are great but they do need to be properly bedded and they tend to work better as they warm up.

Also if you loosen the outer pad adjusting too much you can let air in. So just to be sure I would recommend a bleed.

Thanks for the replies.

After some thought, it just didn't make sense NOT to rebuild the calipers at this time. I already had the rebuild kits. I estimate that they sat dormant for 10 years before I started driving the car. I'm probably lucky they still worked.

I found this kick ass video from Eric Shea - thanks Eric!:

https://www.youtube.com/watch?v=dm_DnizKOZM

It guides you through the entire process. I took the laptop to the workshop and just followed along.

Naturally, I picked two of the hottest days of the year to tackle this project.

One side is done and I'm heading out to assemble the other side this morning.

Click to view attachment