That is the question.

I got 7 of the 8 spring plate screws out quite successfully, but the 8th saved up all the hate and bit me. It's good and fully rounded out.

There are multiple solutions I've read about but it comes down to:

1) Cut a slot and turn it with a straight bit or chisel
2) Split the caliper and use an easy-out

I'm leaning toward #2 as I don't totally trust myself with a chisel but:

A) is there threadlocker on the big allen bolts that hold the caliper together?
B) putting things back together, I can make completely sure that the mating surfaces are pristine but is there a torque setting and/or recommended threadlocker for the big bolts? What's the right move for making things stay together?

Thanks, as always

 

Do not split the caliper. It will not end well for you. Instead, first heat the offending screw enough to break down the thread locker and generally "wake things up." Shield the pistons, really everything except the screw head, with foil or some other medium.

Walk the bolt out using a hammer and chisel. Aim the chisel as, intuitively, it makes sense to press on half the diameter.

I've done this a bunch of times, works just fine. Good luck!

 

I split both of my front calipers when I refurbed them about 15 years ago for exactly the same reasons as you.

The WSM says not to split them, but I couldn't think of a good engineering reason why not. Especially as the only hydraulic connection between the halves is the external pipe, so no seals to worry about. I don't know for certain if there was threadlock on the bolts but I don't think so. I used new grade 12.9 bolts bought from an engineering supplier without threadlock and monitored them for a few years afterwards. They haven't come loose. As the new bolts weren't plated (not advisable on a bolt that hard anyway) I painted the ends and heads once installed. I can't recall what torque I did them up to but I used whatever torque is in the WSM for a same thread sized bolt into aluminium. (I think it was bellhousing bolts)

 

@KevinGross : Did you chisel the screw while everything is hot?

Cheers

 

@jon928se : That's the same train of thought that I am on, with respect to screwing things up if I split the caliper. I was a little worried that there might some gaskets or something that I need to worry about but I just can't come up with a good reason why there would be any kind of cavity in that part of the caliper. I have access to a sort of clean room, so I know that I could get things really clean on the mating surfaces, but the advice of good engineers (Kevin, above) weighs heavy on my brain.

Hmmmm, decisions, decisions...

Cheers

 

Probably still warm, but not important that things be crazy hot. The heat is mostly to break down the threadlocker.

 

Zirconocene, please start at post #29 here in my thread to see my misadventures in brutality for removing spring plate screws from Brembo calipers:


https://rennlist.com/forums/928-foru...earings-2.html

 

I have often wondered why folks seem to recommend not splitting the caliper. Folks who rebuild them split them all the time with little ado about it or so it seems.

The only viable reason I could come up with was there was nothing to be achieved by doing so given they are two separate pieces that operate independently connected by the external crossover. It is not as though there is a brake fluid joint face- well not that I am aware of. If one has a problem with those set screws and one is rounded dealing with it with the caliper split would seem much easier.

 

I like the torturer's instruments laid out for spring plate screw removal.

When I refurbed all callipers it was even more violent, though over time I'd amassed from ebay a load of new plates pretty cheap, so I didn't mind about bending them. On all four calipers 3 out of 4 screws succumbed to a mixture of heat, ratchet or cutting slot and moving them with screwdriver and/or chisel.

Working on the single screws left in each caliper, it became obvious that the easiest way was to weld a nut onto top of each screw. It sometimes took a few goes to get a nut firmly on, but once that was achieved they turned out easily especially as the weld heat would have vaporised any thread lock! I had some brembo dome screws from repair kits I'd acquired over time, or I used stainless dome screws the correct size from hardware supplier. The brembo screws came ready prepared with thread lock.

 

@StratfordShark : I'd forgotten about your technique of welding a nut onto the screw. That is intriguing, but I think it was out of mind due to my not having a welder.

I have someone close by, though, that could help with this if it came to it. My understanding about welding is that I don't have to worry too much about getting splatter on the aluminum body of the caliper, as it won't stick, correct? I hope it doesn't come to that, to be honest, but I like amassing the knowledge for if/when things go well and truly pear shaped.

Cheers

 

That's correct — as the caliper is aluminium the nut is welded only to the screw head. Absolutely nothing sticks to the caliper. Just pick a size slightly larger than the head (or what's left of it). I seem to remember M8 nuts worked well. It's about the only thing I've used my welder for, apart from practicing welds! Was very glad to have it. Compared with the violence I'd visited on the other screws, it was laughably easy to remove them this way.

 

Sometimes you just have to ask yourself:
If Porsche goes out of their way to tell people not to do a particular thing, why would anyone consider doing that?
Porsche could easily sell new hardware for this. Porsche could easily tell people the torque.
Why do they not?

I believe that even once the hardware is started, there is still enough "movement" between the two halves of the caliper to allow the two pieces to move, relative to each other.
I think that Brembo has a special fixture that perfectly aligns the pistons exactly opposite of each other, with absolutely no "side loading" of the bolts.
Because no one can do this without the fixture, they tell people not to take the calipers apart.

 

@GregBBRD : That's a reason I can get behind. I'm going to try the chisel first, then weld a nut, if needed. I'm pretty confident one of those will work, I just have to put on my big boy pants and do it.

Cheers

 

I've yet to have to take a caliper apart to get this hardware out....
Of course, I live in California....the land of fruits and nuts....but no salt on the roads!