Brake caliper torque values

IIRC, there is a (steel) helicoil in the Aluminum upright so it's not quite as bad as threading an M12 steel bolt directly into an M12 Aluminum thread.

What is your reference for the 58 ft-lb specification? (Found the 72 ft-lb spec in the 308GT4 WSM)

Agree with you that maybe they erred on the "too much" side initially -- isn't it an M12 x 1.25P thread (which makes the threads smaller and magnifies the force for a given torque)? Perhaps they backed off a little in something published later -- just a thought...

 

Nope



Books were all wrong.


Even 58 is dicey.

 

When I did my rears this summer I found helicoils in there... and, as is the nature of helicoils, they came out with the bolts. I replaced them with TimeSerts... Much better.

 

Could be a factor (allowing them to feel OK about backing off the spec at the rear when they figured out that the original design, even with the helicoil, couldn't take that higher torque value ), but there's less of a problem at the front with the front steering knuckle being steel (IIRC) rather than aluminum.

Very likely. Can you post a scan of the page, or have a link to that "Service Bulletins All Models through 1980" document?

No need to change it -- that's the (now) recommended value

 

Helicoils do not come out when properly installed. Those were installed improperly by whoever stripped out the original aluminum threads.

Hundreds, if not thousands of those uprights have either been helicoiled or swapped side for side because someone in the past actually believed the silly torque figure. All information in Ferrari manuals needs to be put to the smell test.





The incorrect rear caliper bolt torque figure is a rather well known and often quoted mistake in the Ferrari manuals.

We used it regularly to rub Ferrari's nose in their lousy books.

 

Are you saying that ALL of the 308 (and other F models from the same era) SPC books that show helicoils in the rear upright figure are wrong? I have no problem believing that F over-estimated the permissible torque originally and did a later SB to reduce it, but I doubt that they added a component that didn't exist to an SPC figure and assigned it a PN.

 

Yes and no. Helicoils were used, sometimes, but you never knew when without looking. Many had plain aluminum threads. Never an explanation.

Manual 550/89 even shows 2 lines in the torque specs for helicoiled threads and aluminum threads but no spec for with helicoil.

The uprights are symetrical and all 4 ears are threaded. Many people just swapped them side for side when a thread stripped.

In any event 10kpm was too high and was simply copied from another source based only on application. Ferrari books are not the work of engineers.

 

No argument there.... I long ago took PO's mechanic off my Christmas card list.

 

I know the feeling.

 

So let me understand this, you go from an emphatic:

to

I've no doubt that many rear uprights have been swapped side-to-side and redrilled, and would even believe that very, very early 308 might have been sans helicoil (since it doesn't seem to be used on 246), but, unless you (or someone else) can post a photo of, say, a 308QV rear upright with only two caliper mounting holes and no helicoils, I'm going to believe that all of the later 308 do/did have the helicoils at birth -- but always glad to be convinced otherwise.

 

My no was not intended to mean never. Never is a word I seldom apply to Ferrari.


What I will say though is that helicoil use is shown from the earliest GT4 parts books to the latest QV parts books. And the only Ferrari reference I know of admitting to use of aluminum threads is the last book published in 1989, long after the cars in question were produced.


Again, in any event 10 kgm is too high, helicoil or not.

 

Funny, I draw the exact opposite conclusion from your photo based on the shape (see photo) and the color of the threads (which look more silver-shiny, like a drawn steel wire material, than the dull matte grey appearance of bare Aluminum):

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But do you remember where you found it (or, if anyone knows, please post where)? It doesn't seem to be up on Ben Deetman's www.ferraridatabase.com site -- and it should be!