jscott82

Had an issue today re-installing one of the front caliper bolts.. Pulled the threads right out of the upright.. Surprisingly, it never got more than hand tight, just spun and spun.. I assume they failed due to the number of times I've had the calipers on and off over the years (never cross threaded, always use a torque wrench).

So the question of the day... Replace the upright or install Timeserts? I've read that Timeserts will be stronger than the original cast aluminum and would not suffer the same fatigue from repetitive removal. Interested in your collective wisdom though.

Bonus Question: should I pull the other upright and Timesert them as well?

Vandit

How about longer bolts and a nut on the other end? Is that doable?

I ask because one of the 964 guys running 993 RS uprights had a momentarily airborne situation at the Nurburgring that caused caliper to literally break off its attachment points on the upright. He replaced the broken upright, and as additional security to prevent a it from happening again, he said he used longer bolts w/ a nut on the ends. Post #11 and #13.
https://rennlist.com/forums/964-foru...ring-trip.html

AOW162435

As long as the Time-Sert flange is not proud of the the upright surface (once seated), I can't think of a reason not to. The forces on the radial caliper bolts are axial, not outward, so I think this would be a sound solution (JMHO).

Replacing the stock-length bolts with comparable bolts & nuts should be fine - just not as elegant.

Here is a good read if you want to make your head spin: caliper mounting



Andreas

jscott82

To bring this thread full circle.....

From the "experts" I've talked to today, they all agree Timeserts are an acceptable repair if not an improvement. They also suggested I switch to studs rather than bolts to eliminate the fatigue issue in the future.

Anyone know of an off the shelf stud for this application? Rennline has a kit for 996, but nothing I've found for 993. One of the folks I talked to today was MSI Racing, they offered to make some studs for me, but have not got a quote yet....

AOW162435

What is the bolt size, length & thread pitch?

From memory, they are M12.

Some discussion on studs.



Andreas

esses

ARP has what you need

jscott82

Stock Bolt is M12 1.5 X 72

Thanks for the link... So a little more research based on it...

996 Uses the same bolt (999.067.041.09) as 993 and Tarrett offers a stud kit for the 996.. The studs for 996 neck down from m12 to m10 (even though the bolt is m12 end to end)... That is completely counter intuitive to me, would seem the caliper would be loose... Any insight why they would do this?

Funny thing is: MSI makes the studs for Tarrett, and we were looking at them this afternoon asking the same question...

jscott82

Been searching ARP catalog, even called them.. could not find anything in m12 1.5 at all... Any links/leads you have would be appreciated....

AOW162435

If the stud were left M12 end-to-end, the correct nut and appropriate socket would not fit into the recessed holes of the caliper (15mm socket for the M10 nut vs. 18mm socket for the M12 nut).



Andreas

ThomasC2

If you have the 993RS uprights I think the bolt length is 77 mm, but still M12.

Thomas

k722070

what was the end result of this?
time-sert or new carrier?
and were you able to find a caliper stud kit that fit?

jscott82

I ended up using timecerts... sort of...

I ended up taking the upright to a machine shop (MSI, the guys that make the studs) and having them make an insert. The cost of the oversized timecert + overnight shipping, it was cheaper just to have a machine shop do it all.

The 996 stud kit looks real promising. However... to make the studs work I would have to get rid of the brake hardline (the one between the caliper and shock). This would come in handy in a number of situations, so its definitely worth trying..

Maybe a winter project, if I don't sell the car in the mean time...

k722070

thanks, time-sert it is.

nine9six

Not only what Andreas said, but a helicoil or timeserted thread are supposed to be stronger than the OEM thds; especially if the parent material is alum or alum alloy bodied calipers, and a steel or SS insert is used.

Yes, I understand the OP is old, but in this instance, it does not hurt to add info.

k722070

an end note to this, great product and worth the $100 price tag for the kit.
pic of time cert installed, sits just below the surface.
time cert kit comes with all the parts you need for the size ordered plus 5 inserts.
a 1/2" drill and 1/2" t-handle tap wrench are needed.
drilling the hole is the scary part, you need to make it as square as possible, tough without a drill press.
the other steps are quick and easy, drilling to insert took less than 5 minutes.
I had to remove the wheel carrier, just wasn't enough space for the drill.