[987kmns]

It's been a while - hope everyone is doing well! Tonight Ion and I did some interesting work on his Boxster, so I figured I'd throw some pics on here.

For those unfamiliar with brake rotor changes on a 986/987/many other Porsches, they involve removing the brake caliper. Not a big deal. The brake caliper is attached to the aluminum wheel carrier with two bolts. Normally this job takes 30 seconds +/- 5 seconds depending on whether you are over-beered or under-beered. This job suddenly takes much longer though if all the aluminum threads in the wheel carrier happen to come out with the caliper bolt. It makes it slightly more difficult to torque the caliper bolt back to spec (63 ft-lbs). It actually makes it impossible - as you hopelessly watch the bolt twist forever in the de-threaded hole. Sadly, this is a known problem with these cars Some folks convert to caliper studs, to avoid this episode altogether. N0tt0n is a big proponent of studs.

All right...you get the backdrop. On to the solution. Ion did some research and he decided that he was going to attempt to repair the de-threaded hole through the use of a Time-Sert - a metal sleeve that is threaded both on the outside and the inside. This is a common repair method for stripped threads and it allows the final ID and threads in the bore to be left at original spec.

The procedure goes like this:

1. Drill out remaining threads and enlarge bore to OD of Time-Sert
2. Thread new bore to outside thread spec of Time-Sert
3. Insert Time-Sert into bore
4. Install original hardware into Time-Sert

The trouble with drilling into the wheel carrier is that the tolerance for the caliper bolts is very tight, so it is preferable to keep the enlarged bore perfectly concentric with the original bore. This also means drilling perfectly square to the surface of the wheel carrier. To make sure that we could achieve said requirements, we decided to make a small tool to use as a guide. We started with a piece of 1 1/4" square steel tube and drilled two holes into it, spaced at the same distance as the brake caliper mounting holes. We drilled one hole to the OE spec for the caliper bolts (M12) and the second to the OD spec of the Time-Sert. The correct distance between the centers of these two holes is 130mm.

Here is Ion drilling the holes on a drill press.
And here is the finished guide. The hole on the left is a little larger than the OE-sized hole on the right.
Next, we attached the guide to the carrier using the bottom hole, which still had good threads.
And now, post drilling, you can see the slightly larger hole without threads at the top versus the original hole and thread at the bottom.
Since the Time-Sert has a small flange, a counter-sinking tool is used to create space for the flange.
Next, Ion tapped the new hole to the OD thread spec of the Time-Sert.
Finished threads.
All that is left is to drive down the Time-Sert into the threaded bore. A special tool is used, which pushes the outer threads of the Time-Sert against the bore, capturing the sleeve in place. With the special driver removed, the Time-Sert is now captive in the bore.
Here is the finished product. Nice and flush with the surface of the wheel carrier.
And the damn rotor finally on for good.
Finally, here is what the Time-Sert kit looks like, including the actual Time-Sert sleeve used in this install (top left).

For this project, we used a 24mm Time-Sert. The inner thread spec is M12 with 1.5 pitch.

Hope nobody encounters these pesky stripped threads in the wheel carrier, but if you do, to us it seems like the Time-Sert option is worth considering. Total work time, including making the guide tool was 2 hours.

[HoodPin]

Well done! Its nice to know that specialized tools are out there, and how well they can work. Thanks for sharing.

[Dandelion]

Nice job! Yeah, I preemptively went to studs as the 981/991 require you to remove the caliper for brake pad changes.

ed

[N0tt0N]

Nicely done! As expected.

What's the opposite of Studly? Figures Ion would have his holes surgically enhanced.

[Vicegrip]

Good write up on a often seen issue that is not just Boxter related! Did you have any issues when drilling the carrier? I had to make a short drill bit so the cordless drill could fit in the fender wells. For track cars I can see where installed studs would be a good idea.

[spiffyjiff]

i had my fronts 'certed (even the brake line bracket into the caliper) a few yrs ago after i heard creaking during braking. one of the bolts came out along with all the caliper threads. yay! anyway, i prob should have had rears done at same time. is this a better way to go vs. studs? was thinking about that route too.

[N0tt0N]

Time-serts have many advantages, like nothing to bang into other things with exposed threads, OE instructions a garage can follow (torque is 54ftlbs for nuts on studs, for instance), less expensive, less complexity for regular inspection. If you have them on the front I'd put them on the rear.

Also you have to have existing thread to put in studs so one may not be an option. I like studs because everything stays in place when doing work yourself.

[cmartin]

Nice write up. Good work on the template/tool.

[Dandelion]

Another advantage of caliper studs - give you a place to hang the caliper.

ed

[N0tt0N]

Yay! HOF!