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I'm just wrapping up brake refurb job (new hoses, rebuilt and repainted callipers).
I hesitated about whether to use the pad dampers - extra expense and others seem to manage fine with just copper grease on backing pads, but I thought I'd go by the book.
The front 36mm dampers are giving me trouble. On both 36mm pistons they are popping out of the pistons. All the other dampers just snapped in and seem very secure.
I'm worried about a damper coming out of the piston when driving, and not pulling the pad back on that side, to extent that I may pull out all the dampers (not pulled off paper adhesive cover yet) and try copper grease.
Has this happened to anyone else? What should I try on the spider at back of the troublesome pads to persuade them to stay in? Squeeze them inwards or prise them further out?
The piston inner bores are clean and dry, so they're not losing purchase on grease or anything.
Maddening!
Edit: I've just realised that on the other caliper I had same problem, and sourced non-Porsche dampers from another supplier selling Hamburg-Technic branded parts and they worked fine. They were on last caliber I was working on, so what's happened is that the other caliber where I used 36mm Porsche dampers and they seemed ok, it's those dampers which are now popping out as I'm test fitting the new pads. Grr I'm going to have to get another couple of those Hamburg-Technic dampers.
I had this problem a decade or two ago, tossed the dampers in the trash and never looked back. I use a bit of copper hi-temp anti-seize on the back and edges of the pads, and haven't had any squeak problems.
My assumption at the time was that the dampers were the wrong size, too large for the bore in the caliper piston. I never figured out whether I mis-ordered or Porsche mis-labeled them, they worked fine in the trash can.
A couple of caveats: Some pads just squeak, dampers or not. I have used PBR, Porterfield R4S, and now Textar (stock) pads all with good results. (PBRs were too soft for hard driving).
And any pad will squeak if not bedded. New pads on used rotors need to be driven moderately until the pads wear to match the grooves in the rotor surface, new pads and smooth rotors can be used hard from the beginning. And they need a few hard stops to bed in: When the pad heats up some of the pad material transfers to the rotor and creates a better braking surface. The brakes work better and are quiet also.
This needs to be repeated occasionally, as driving around town with cold brakes will wear the rotor back to a clean polished surface. A few stops from 80 to 20 on a deserted road will do it.
I installed Hawk Plus pads in my GTS front calipers 10 years ago when I acquired my current 928. Boody things squealed like a pig under light braking- very annoying. Last year I decided t o do something about it and cleaned everything up on the front and rear brakes. I purchased new dampers all round and found that the rear ones were relatively easy to fit but the front ones were a bit of a sod along the lines Adrian and Jim experienced cursing and swearing at the things.
In the end I used some double sided tape to temporarily stick them to the back of my PK Bumpstick handle and used that to help push them with "brute force"- it worked. No way could I have got them in with my finger pressure.
Bottom line the Hawk pads that I had cursed for 10 years suddenly went as quiet as a Church Mouse. I did damage the sticky coating on one of the pads and in the end stuck some silicon RTV over the remnants of the sticky surface.
The sticky pads work by retracting the pads with the pistons, rather than relying on the pads to fall away from the moving rotor on their own. Actually withdrawing the pad reduces the risk of casual glazing of the friction surface, something that reduces available braking force plus adds risk of noise. Plus it can cut down on some of the dusting.
Adding copper grease, common pad anti-squeal compounds etc to the back of the pads helps with the noise only, does nothing to help pull the pads clear of the spinning rotors.
I use the factory-style dampers. At my first brake pad replacement at around 40k on the car, I bought all new ones, but decided to experiment with some hi-temp RTV to hold them to the back of the new pads. Worked quite well until the next pad replacement, when I had to separate them from the worn pads again with a painter's spatula. This second replacement included a lot of system PM, caliper overhaul, etc. I decided to install the NOS dampers this time rather than re-glue the old ones back on, for no reason other than convenience. Could have easily re-used the original pieces after clean-up and another bit of hi-temp RTV to stick them to the new pads.
Really interesting to read all the experiences here - thanks all for comments.
I've ordered a couple more of the 36mm Hamburg-Technic products, and Dr Bob's comments on glazing make me feel slightly better about it. Now I've invested in all the other dampers it seems better to carry on this path.
Incidentally all the dampers were easy to push in with firm shove. The 44mm Porsche ones I had bought years ago and kept stored went in and stayed in fine, it was the Porsche supplied 36mm - all four of them - which gave problems. Tried bending the spider legs every which way to fix the problem but to no avail.
All the rears were the Hamburg-Technic product. I noticed installing them that they went in with lovely snap - as did the H-T 36mm pair I had. The 28/30mm rears ones were marked with 996 part numbers (996 352 086 00, 996 352 086 02), but PET doesn't show them as OK for 928 even though they go in the same Brembo pistons, and were provided by supplier (Euro Car Parts) based on a MY91 928 S4 so the parts world is aware they are suitable. The design of them is in some subtle way better than the Porsche-supplied parts.
I gave up installing the pad dampers when the price went up to around $25.00 each. I use a paste that my father used for decades (bearing grease and copper anti-seize) and smother it on the back and edges as mention above and nary a squeak to be heard.
I was doing some brakes in a later 911 this week and it had a combination of the style we have and this style on the brakes. Sorta liked them but doubt we can use them.
Anything Hamburg-Technic is crap - use at your own peril.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
You see the full range of parts Roger, and with experiences gathered from many, many installations. You are bound to be correct about majority of H-T parts as your view is based on hard evidence. All I can say is their pad dampers seem fine - install very positively and firmly.
On the issue with my Porsche 36mm dampers not staying in, I have suspicion that I may have installed the different ones for pre-89 car. I know I had some in my parts stash, but maddeningly I tossed the little bags they came in so can't confirm if error was mine.
On the issue with my Porsche 36mm dampers not staying in, I have suspicion that I may have installed the different ones for pre-89 car. I know I had some in my parts stash, but maddeningly I tossed the little bags they came in so can't confirm if error was mine.
Your late caliper 36mm pistons should have a 20.5mm internal diameter so for your theory to be correct you'd need to have used the pad damper for a pre-89 28mm piston caliper which has a 20mm internal diameter so slightly smaller. Presumably that'd be for a rear caliper rather than front. Could that be possible?
When I did my front brake job earlier in the year the dampers were a very tight fit in the pistons. Can't remember off hand where I got them from but it would either be ECP or Rose Passion. Probably the latter.
No it's not possible I tried to insert dampers from rear! I have that service bulletin but hadn't read it so closely to realise how much narrower the ID of the newer pistons is. Great spot thanks.
It must just be that the batch of Porsche 36mm I had (dated 1999!) are somehow not fitting well. All other sizes front and rear fine, whether Porsche or ECP/Hamburg Technic. I have another couple of H-T ones to replace them with at weekend. I know Roger not fan of Hamburg-Technic in general, but the dampers at least stay in the damn piston.
09-03-2016, 09:36 AM
Pad dampers popping out!
George Layton March 2014