S4 Front Caliper Rebuild Problem (pics)!
 

Front inner pads were wearing less than outer by about a third, looked to be a sticky caliper piston(s) issue. I ordered the repair kits from Pelican, only supplier I could find that carried Brembo dual piston kits for the '89 928. New pistons are the correct diameter, but different configuration. ID is smaller so now my anti-squeal pads will not fit. The seals, both 36mm and 44mm, fit the inside of caliper correctly - Yay! Problem is the dust seals dont fit. Old ones were just a metal rimmed circle. New are rubber covered and mate to a groove in the caliper piston. Old dust seal's outside diameter(s) were 44.27mm for 36mm piston, and 52.27mm for 44mm piston. New are 45.8mm and 53.5mm. I can not get them to fit in the caliper recessed openings as they are cut to 44mm and 52mm respectively. I already bunged up one of the small seals trying out my BFH. :icon501: Seriously, I used the grease supplied with the kits, placed the caliper in a padded vice, used a piece of 1x wood stock sandwiched between vice jaw and seal, then tried to gently and evenly press it into the recess. It would either cock sideways or pop back out.

I called & emailed Pelican but they've gone stealth on me. Can't find anything on the net to explain it. Did find couple other suppliers who sell the same kits - look like the same dust seals from the pics.

So, does that mean the new dust seals are supposed to fit & I just haven't figured out the right technique for installing them? Or did I get the wrong sized dust seals? Here's all the info I could put together on caliper piston & seal:

Front caliper - inner section: ('brembo' in raised letters) # 20.4565.00, (88 stamped inside a circle)
Front caliper - outer section: ('PORSCHE' in raised letters) # 20.4564.00 (87 stamped inside a circle)

Original piston & seal...
Caliper piston small, 36mm outside diameter, 1.265 length
Caliper piston large, 44mm outside diameter, 1.260 length

Dust seal small, 44.27mm outside diameter
Dust seal large, 52.27mm outside diameter

Numbering on small dust seal: 20 4513 72 - 10
Numbering on large dust seal: 20 4513 82 - 11
==============================
NEW PARTS
Pelican caliper kit-36mm, 951-351-919-10-OEM
Pelican caliper kit-44mm, 928-351-919-10-OEM

Caliper piston small, 36mm outside diameter, 1.262 length
Caliper piston large, 44mm outside diameter, 1.260 length

Dust seal small, 45.8mm outside diameter
Dust seal large, 53.5mm outside diameter

Numbering on small seal: 20 4872 44
Numbering on large seal: 20 4872 48

Is it possible that the kits you got are for the rear calpiers?, The new pistons are definitly smaller in diameter at the working part, Just a thought. Hummm

Hawkeyes: try zeckhausen.com/brembo/consumables.htm#rebuild - They may be able to answer some questions if nothing else. I also found a site last week where they will swap out (I believe) your rebuildable calipers for like.....$90.00 IIRC! If I can find that site again I'll post that info too.

Paul Barrera
'91 $4

Does this help?
http://billsworkshop.com/P928S4/xpics/89%20Brakes.doc

You appear to have early version calipers. Odd. I thought all 89s should have new caliper version, but it appears the change broke part way in MY89. What is your VIN number?

I have more info coming.

From service bulletins...Note the VIN break at 282 (2nd footnote, last page). I hate it when they do that!

Bill, you are the MAN! Now the problem is obvious - the Porsche Nazi's did it to me again! :grr: I mean, how could I be so uninformed as to simply believe that my 1989 model would take parts designed for a 1989? And not even the dealer lists Front Caliper Repair Kit #95135191901 for the 1986 thru MID YEAR 1989. No, no, no, they list it for 86-87, and 88 (why not 86-88?). The part number for 89-95, to make it even more error prone, simply reverses the last 2 digits 01 to 10. Couldn't they have just agreed that 02 follows 01?

Anyway, now I have to decide whether to try and exchange my calipers for the 'new improved' model, or just order the correct repair kits. Price is approximately equal, if Paul is correct. Anyone notice any braking performance gains between the 86-88 models and the 89-95's?

Thanks,
Hawk

They changed the piston size 42mm to 44mm for more even pad wear.

Don't know if you'll see any performance change from the scraper vs dust cap, except for longevity by keeping things cleaner.

Nice job Bill your, library is awesome, with out your assitance this might not have been resolved , AAAA++++ , Stan

Hawkeyes: The place to go is rockauto.com! Go through the normal bs of make model etc, click on brakes, then calipers and you will see it. FYI for other lurkers: this is a deal where you send your calipers in, they remanufacture and send back to you. Rears are $93 and fronts are $119 plus core & shipping. This works for big brakes too but i'm confident that you probably can buy without a core at a good price too. Check it out and good luck! :thumbup: BTW I'm an old Healey 3000 ('61 & '65) and jag ('64 & 71 XKE) guy too. Got REAL tired of Lucas Electrics and BMC quality control but had a lot of fun. The 928 though, is still twice the car even with it's quirks. P.S. Stay off the bridges, man!

Paul Barrera
91 $4 a/t Black

No you can't. They will tell you they have no cores.

It's no secret that 90% of my library is the Jim Morehouse CDs. That's where this came from.

Bill, you're amazing. I'm sure glad you hang out in my neck of the woods. Don't get a big head though. Everyone agrees, a little head is a good thing. ;>)

You're screwed. You can only do the full rebuild with new pistons all around to update them to the new style. I searched a long time and never found any source for the older style. When I did my "rebuild" I ended up using all the old seals over again and just cleaning the snot out of everything. 2 seasons of auto-x later and everything is still fine.

fraggle,

Pelican carries both old and new and in-between. They just have them listed incorrectly in their catalog. The correct kit is shown as an '88, 36mm and 44mm - around $100 per caliper. The Rock Auto deal is legitimate, but you send in your calipers for the rebuild...heck, I can rebuild 'em & price is about the same. You are correct however in that one cannot upgrade the existing caliper to the new style. I'm not going to worry about it, have sent back the old repair kits for credit & Pelican has sent me the correct ones. BTW, Bill was the only person out of 3 dealerships and 2 928 suppliers to correctly identify the mid-year caliper piston design change.That is awesome...thanks a million Bill! :jumper: :jumper: