Dorkiphus.net - bolt anti-corrosion coating

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Quote:

Originally Posted by Jabs1542 (Post 595378)

A bending moment plus a shear force causes a weakened area at the edge of the shear where the moment creates a tensile stress. Better yet: tensile stress plus shear stress is worse than shear stress alone. Think Von Mises.

I'm trying to understand why Porsche set up their caliper studs that way, it's SOP on all the Cup cars. I assume that the bending load is insignificant compared to what they gain by having the stud slightly downsized - but what is that gain? For reference, my caliper bolts (which fit tightly through the caliper hole with zero slop) are 12 mm in diameter whereas the GT3 studs are 10 mm in diameter.

Please pardon layman terms. The shoulder gives location alignment between the two parts. Necking the stud moves the stress concentration area from the threads to the necked area and tunes the clamping forces over the temp range.

Removing an aluminum caliper can be a chore once the two have been together a while and some AlOx builds up on the studs which remain in place. Sometimes Porsche does not get all fiddly when it is not needed.

Quote:

Originally Posted by trytryagain (Post 595379)

I’ve been contemplating a move to caliper studs to avoid frequent bolt removal/replacement. However, looking at the stud pictured, it won’t work for my situation due to the 14mm spacers used to position my calipers outward on the larger than stock girodisc rotors. In effect, the shoulder on the stud would “capture” the spacer, but not the caliper.

Anyone know of studs that provide a snug fit to the caliper holes similar to the stock caliper bolts as Jay mentions?

Are you running with these as well? Worked just fine for me. Not sure about 981 calipers.
http://www.tarett.com/items/un-assig...bcs-detail.htm

^Thanks Martin! I did not know about these. Will give Tarett a call.

Quote:

Originally Posted by Jabs1542 (Post 595378)

Agreed. But that is not what your post stated.

The GT3 studs work, they just leave a little 'slop' at the connection. BTW - someone mentioned that this slop was dialed in on purpose in order to make it easier to align and mount the calipers.

I have Gyrodisks with the required spacer as well, that alone is a huge reason to go to studs (fitting that spacer/washer between the caliper and upright, while sliding in the bolt, and holding everything in the exact correct position is a PITA) as well as concern about cross drilling the aluminum hole in the upright.

Quote:

Originally Posted by trytryagain (Post 595379)

I’ve been contemplating a move to caliper studs to avoid frequent bolt removal/replacement.

Have you been doing most of your pad changes yourself? Factory torque setting each time?

I've seen/heard ugly failures with the uprights even when fresh bolts are installed for each change. I'd go with studs for sure but consider the existing wear on the upright if you've been taking the caliper on/off pretty frequently.

I’ve had about 5-6 caliper on/off cycles on the fronts, only 3 on the rears. I have always hand threaded the bolts back in and torqued to factory spec. I’ve used brand new bolts once.

At the tech session on Saturday I discussed with Geoff whether it would be a good idea to time cert the uprights when installing studs. He seemed to think it was okay just to install the studs as is, given the degree of usage and care to date.