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Welcome to Hartech, the UK's leading Independent Porsche engine specialists, located in Bolton, UK

997 GT3 brake change

O

-ollie-

Monza
Joined
26 Sep 2018
Messages
157
Hi guys,

I'm a reasonably competent driveway mechanic and am about to refresh discs & pads on my 997 GT3.

I've heard that the 2 x 10mm hex head bolts that secure the caliper are one use only on these cars - is this true? If it is I'll replace them naturally, just sounded unusual to me having never come across this previously whilst messing around with other cars (on calipers, at least).

Any thoughts? Can anyone confirm or deny?

Cheers

Ollie
 
Unnccessary caution on Porsche's part ime. My car is tracked extensively & I don't change these bolts even though the calipers come off at least 3 times a year. What does tend to happen is the threads in the upright wear out until you cannot tighten to 85nm without stripping them. Mine are all TimeSerted now and have been no trouble since.

Using a good amount of aluminium grease (Wurth AL1100 is perfect) on the bolts when you put it all back together & you'll extend the life of the original threads but they will go in the end.
 
NXI20 said:
Unnccessary caution on Porsche's part ime. My car is tracked extensively & I don't change these bolts even though the calipers come off at least 3 times a year. What does tend to happen is the threads in the upright wear out until you cannot tighten to 85nm without stripping them. Mine are all TimeSerted now and have been no trouble since.

Using a good amount of aluminium grease (Wurth AL1100 is perfect) on the bolts when you put it all back together & you'll extend the life of the original threads but they will go in the end.
Click to expand...

Thanks Nick, useful info there.

Will get some ally grease, we talking just a slither on the thread?

So the uprights are ally, the bolts are steel - is that correct? Is it galvanic corrosion that damages the thread over time?
 
-ollie- said:
Thanks Nick, useful info there.

Will get some ally grease, we talking just a slither on the thread?

So the uprights are ally, the bolts are steel - is that correct? Is it galvanic corrosion that damages the thread over time?
Click to expand...

Yes, just grease the bolt threads, it doesn't take much.

The uprights are cast ally & the bolts are steel. It's not corrosion so much as the combination of heating & cooling plus differential material expansion rates & a relatively soft metal under a fair bit of load. A thin layer of the ally threads will adhere to the steel bolt and act as an abrasive as the bolt is screwed out.

Lubrication will minimise this but won't completely solve the problem.

It's always good practise to ensure the bolt thread is cleaned off with a wire brush before reassembly.
 
NXI20 said:
-ollie- said:
Thanks Nick, useful info there.

Will get some ally grease, we talking just a slither on the thread?

So the uprights are ally, the bolts are steel - is that correct? Is it galvanic corrosion that damages the thread over time?
Click to expand...

Yes, just grease the bolt threads, it doesn't take much.

The uprights are cast ally & the bolts are steel. It's not corrosion so much as the combination of heating & cooling plus differential material expansion rates & a relatively soft metal under a fair bit of load. A thin layer of the ally threads will adhere to the steel bolt and act as an abrasive as the bolt is screwed out.

Lubrication will minimise this but won't completely solve the problem.

It's always good practise to ensure the bolt thread is cleaned off with a wire brush before reassembly.
Click to expand...

Thanks Nick, it's interesting to learn about the little quirks on these cars as I play with it a bit more.
 
My 996 is approaching 170K miles so I've probably encountered most if not every problem possible! That said, they are incredibly well engineered & given the use mine has had, very reliable all things considered.
 
If the threads in the uprights are still good, you could go with a stud kit such as this :

http://www.rennline.com/Brake-Caliper-Stud-Kit-Cup-Car-Style/productinfo/CS-BCSK/

If the threads are questionable, than as Nick says, Timecert them and stick with the bolts, or go the belt and braces route and fit studs into the Timecerts.

As regards replacing the OE caliper securing bolts every time they're removed, I'd chuck the standard bolts and fit some decent grade replacements from your local fastener supplier, as long as the threads in the upright are Timecerted and/or lubricated with Ali paste, the bolts will last a long time...
 
Slippydiff said:
If the threads in the uprights are still good, you could go with a stud kit such as this :

http://www.rennline.com/Brake-Caliper-Stud-Kit-Cup-Car-Style/productinfo/CS-BCSK/

If the threads are questionable, than as Nick says, Timecert them and stick with the bolts, or go the belt and braces route and fit studs into the Timecerts.

As regards replacing the OE caliper securing bolts every time they're removed, I'd chuck the standard bolts and fit some decent grade replacements from your local fastener supplier, as long as the threads in the upright are Timecerted and/or lubricated with Ali paste, the bolts will last a long time...
Click to expand...

Thanks Slippy.

My bus has only covered 35K and I appear to the first owner who has "sullied" it with track use. :lol: I hope the threads are good, but have bought some ally paste and will have a good look at them upon removal.

I had absolutely no idea these caliper bolts/threads where such a "thing". Upgraded stud & nut kits for calipers - bonkers!

Genuinely makes me quote excited to learn what else is available for these things. Now if only the weather would get a little better, I could use the thing a little more.
 
Certainly on the 996 GT3, the caliper securing bolts go into open ended holes in the upright/hub carrier. The holes get full of road dirt, water, grit etc, and if the bolts/threads haven't been protected and lubricated with Coppaslip or Ali paste, the threads corrode and accelerate any galvanic corrosion.
Often the damage is done when you remove the bolts ...
IF the bolt hole ends are open to the elements, it would be a very wise investment of your time to spray the holes/bolt threads with a decent penetrating/maintenance spray (or the perennial PH favoured PAS fluid and acetone) :

https://www.pistonheads.com/gassing/topic.asp?h=0&f=140&t=974663

Spray it on a few nights on the trot before undoing the bolts and you should avoid tearing the threads out of the upright when you remove the bolts.
 
Thanks for the info Slippy.

In terms of this brake change, I think I will be "winging it" and seeing how I go.

I'll carefully remove the bolts in the hope that the threads are okay, and apply some ally paste upon refitting.

Then I'll either timecert of fit studs at the next change (if I get away with this one!)

What an unusual issue, I'm glad I researched it prior - I'm used to old M power BMW's which are broadly indestructible (unless you crash them).

Cheers
 
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