User 52121

Ok so after not getting anywhere with a goofy braking issue I have - I've decided to attempt a caliper rebuild again.

(see this if you're interested in my odd issue: https://rennlist.com/forums/944-turb...al-travel.html)

I was going to go with Cardone's rebuild service but after checking around (and talking to a few different folks I know who own shops) it seems that I'll most *likely* be up a creek with them. They don't stock any parts, they just rebuild what you have. So if I have a bad piston, they just ship the old caliper back to me. IMO not worth the shipping and $50 costs.

It seems that the "early" Porsche/Brembo calipers (pre-1992?) are different from the "late" Porsche/Brembo calipers (post-1992?) As such, pistons are outrageous for the "early" ones ($50+ each) whereas the "late" pistons are less than half that cost ($15-$17 each.)

What's the difference? I've seen it noted in places, "they are different" but nobody says why or how. Anybody tried a "late" piston in an "early" caliper? One of my friends is going to order a couple of each size in early/late so we can see the difference ourselves... but it'll take a few days and I'm curious what the peanut gallery thinks.

Just looking for a cheaper alternative than paying over $800 to rebuild my stock small non-S calipers. Otherwise, to me and my twisted logic, it makes more sense to just step into a big brake kit like the Lindsey "Big Black" setup for $1600 (http://www.lindseyracing.com/LR/Pors...-86BBK-01.html)

doabarrelroll

Lol, I actually did that for other reasons (as in, go with the Big Blacks), anyways, the later model (89'+) have a dust boot as opposed to the earlier style dust "seal".

Here is a pic of the early style:


Newer style:


That's why I looked for a set of 968 rear calipers to rebuild, it's 1/3 of the rebuild cost! $240 and change for 8 dust boots, scraper rings, and pistons.

User 52121

Ok... so what's the functional difference between the "dust boot" and "dust seal"? Neither are the actual pressure seals.

Oddjob

The scraper ring style were used up thru MY88. By MY89 many of the calipers were the dust boot type. My 6/88 built 89T has dust boots in front, scrapers in back; my previous 9/88 built 89T had dust boots front and rear.

Functional difference is that the outer protective seal is stationary on the early type, so the piston slides in and out of the dust seal, hense the "scraper" type. The later dust boot is a bellows type that moves or expands out w/ the piston.

Not sure that the later design performs much better than the early style, but they are certainly cheaper to rebuild since the seals, boots and pistons are available separately.

BoostBuggy

Additionally on the much earlier (up to and including 86) "scrapper ring" style front caliper the pistons were 36 & 38 mm while the 87 on had 36 & 40 mm pistons. The dust boot sytle calipers continued with the 36 & 40 mm pistons.

Due to the rebuilding costs for the scrapper ring style calipers I wouldn't take a pr of those if they were given to me. Impossible to get parts from anywhere other than the dealer and the costs are WAY TOO high!

With the dust boot sylte you can easily source parts from several different sources. For example the Stoptech pistons, seals, dust boots etc will all fit.

Michael

Oddjob

http://www.paragon-products.com/Brem...kits-early.htm


Anyone wanting to give away scraper ring calipers can send them to me, anytime.

BoostBuggy

Evidently you haven't done the math..... $300+ minimum for parts. Those calipers are worth that much considering you can find the later calipers typically prices similarly and the minimum parts cost is more like $32

Oddjob

I understand math just fine. Look at the link I posted - seals for early and late are the same price, $15.32 each. Full piston rebuild kits are twice as much, but how often do you replace all the pistons?

User 52121

Probably not often but that was almost sorta-kinda my plan.

For the cost of the "late" pistons... why the hell not? For under $300 you can have all new parts. For the cost of "early" pistons, it becomes an expensive proposition.

Ok so I get the difference between the "scraper" and "boot". I'll take a guess that the "boot" type has a ridge or something on the end of the piston that lets the "boot" snap in... that would explain why the photos of the Stop Tech pistons look different.

What's to stop me from buying a set of boots and boot-style pistons, instead of scrapers and scraper-style pistons? Can I swap all the parts out?

I get that I couldn't use "Genuine Porsche" for the '86 calipers due to the pair of smaller pistons in the fronts... but if you can get away with Stop Tech pistons in the "late" Brembos why can't I get a set of Stop Tech 38mm pistons and boots for the '86? (And if this can't be done... I actually have a set of 40mm-equipped '87 calipers mounted on the car now...)

My buddy says he might actually have the pistons in his hands tomorrow. I'm gonna cruise down to his shop in the afternoon with my old '86 calipers and check out the major differences. My only thoughts over why they might be incompatible would be piston depth, or that the bore on the caliper where the boot/scraper sits is the complete wrong diameter.

I find it a little surprising that no one has tried this (at least as far as I can tell with the search function...)

User 52121

Ok found this link on one of the "other" boards. Very timely:

https://webfiles.uci.edu/redwards/pu...%208-12-11.pdf

TSB document describing a production change on the 944 Turbos, from "early" to "late" style. Looks like it answers my question. The caliper body itself is different, to accommodate the dust boot. Damn.

BoostBuggy

Oddjob, what it appears you are not getting is that to rebuilt the caliper you need new scrapper rings. With the exception of the 38 mm you have to purchase full pistons kits to get new scrapper rings. Therefore all the parts would be, at minimum, 4x 36 mm @ $49.80 ea = $199.20 + 4x 38 mm scrapper rings @ $20.73 ea = $82.92 + 4x 38 mm seals @ $5.00 ea = $20 = total $302.12.

OmniGLH, as you have learned you can't swap in a dust boot for a scrapper ring. Both sytle do use the same seal so that's a push. The scrapper ring calipers are a royal PITA to refinish specifically due to the scrapper rings.

Hypothetically you could you the Stoptech parts on the early calipers as Stoptech has pistons etc in a much wider range of sizes than available from Porsche however, as ALL the Stoptech calipers use a dust boot design (identical to the later Brembo/Porsche calipers) the only piece you could use would be the seals.

67King

No need to replace the scrapers unless they are damaged. The seal is the ONLY thing that needs to be replaced. However, if the pistons get damaged, the scraper style get very expensive. I've got both styles and have rebuilt both.

bimmen325

I just got all my calipers rebuilt and coated by Goldline, I just stare at the red calipers every time I walk into the shop. I have to wait untill I get new rotors and pads to install them.

minho78

Jim I used these guys. Don't remenber the price,but I think it was around $100 dollars for the 4 calipers. Just let them know the piston size.

http://zeckhausen.com/Brembo/Consumables.htm

BoostBuggy

With the age of the scrapper ring calipers the scrapper ring should be replaced with a rebuild. Not replacing the scrapper ring, which is basically a rubber seal sitting in a metal outer ring, is to invite road crud into the piston bores which will eventually create a leak. Trust me on this. I speak from experience....

As to Zeckhausen, all the parts you see listed are StopTech parts. The Stoptech parts are and always have been less expensive than the Brembo counterpart(s). That said, personally I don't feel the current light grey colored StopTech dust boots are as durable as the Brembo or the old black StopTech dust boots. That's not to say they don't work as well. But you do need to be MUCH more careful in handling/installation of them. Again I speak from experience.

Goldline does a good job for a reasonable price. I highly recoomend them.

Michael