A word to the wise??? – Dropped/lost front brake calliper bolt.

[Rick Fischer]

Fortunately, not far from home on good road and loud knocking from front RH wheel well. Was a just coming up behind gentle braking. Tried again and sure enough still knock knock etc. Braking itself seemed OK. However gentle gentle take him home, use lotsa gears. A day or so earlier I had to have a full ABS stand on its nose stop.
Dropped the wheel off and found outer rim of disc abraded metal to metal and some shavings around the place. Apart from that seemed OK till I checked both calliper bolts , lower (rear) bolt head not there. Only similar bolt I had around was 10mm and found hole was 12mm ISO Course. 10mm was fine as it allowed me to discover that the bolt had gone and hadn’t left anything behind. Many of you will be aware that the calliper bolts are now 12 point heads, such that a standard 12mm ISO hex head will not fit. However, still need to get an 8.8 bolt from Bunnnings to take shear load for small time to enable getting the calliper to “Local” up the road when I received new bolts.

Calliper Bolts
The Callipers were last off at B Service – service wheel bearings, grease the hub drive spines, etc. fit new slotted discs and pads; 25 500 kms ago.
As a former LAME I use a torque wrench religiously to the point where I will torque bolts to the generic torque for the dia, thread and material of the bolt/nut if the MM does not provide a torque setting. Question here, is did I miss one? I’ll not ever know. However, given my “fitting” habits perhaps not, however, we all stuff up occasionally.
Anyway, now begs question why did it take 25 500km for bolt to drop out:


My error – missed torquing bolt perhaps,
The bolt in question “yielded” at the 80Nm as a defective at manufacture bolt,
The bolt had previously been damaged by someone using a rattle gun instead of a torque wrench and yielded at 80Nm.
Another “my error” – practise/procedure:

Remove bolts,
Clean holes and threads pre installation
Install with a dab of copper grease and torque.


(Have used copper grease religiously for 30+yrs since having great difficulty removing hex head calliper bolts on ’83 RRC, through D1 and D2 to Deffie110; but now noted in the “General Instructions” bolts are to be installed “dry” with locktite where instructed, or as one use only encapsulated bolt.)


New Bolts

Decision: Will replace all of the calliper bolts on my Deffie now, and will replace the bolts with new ones every time calliper/s need to come off.
Have found that for my VIN rear callipers bolts are encapsulated ISO fine thread and the fronts are not encapsulated ISO Course. MM doesn’t mention locktite for front. However, on mine I will use locktite.
A couple of engineering design questions that are perplexing, (to my knowledge):


Fine threads are normally used with high torque tensioning due to greater surface area of similar dia fine threads vs course, and bolt material dia is not compromised by deeper thread,
Course threads are used in softer materials at lower tensions, but on later Deffie the front callipers have ISO Course at same tension as rears, both 12mm and both 80Nm.
For my VIN the rears encapsulated and the fronts are not?


Comment?

Cheers
Rick F

[Graeme]

Use a thread locker.

[Red90]

You cannot use a normal bolt. The proper bolts are shouldered to fit the caliper. They are 13mm 12 point. You can use a closed end spanner or 12 point socket. Always carry one and a long bar. Always use thread lock and torque to spec. This is a very critical component and must be done properly.

[Blknight.aus]

lotite 263

[Homestar]

A quick story that relates to this topic. When I was working for a previous company we ran around 6 transit vans for our Field Service team from the branch - One of the other Sparkies came in complaining that something was making a horrid noise up front - when I checked I found one front calliper half hanging off with a bolt missing and the other side calliper had both bolts loose. The brake pads had just been done the day before - by the Dealer. When it was investigated they had not used any thread locker when their own service manual said to do so. Needless to say we never went back to that Dealer.

[AK83]

LOL! reminds me of my story of my dads old (Ford) Exploder.
Bro had just sold his dreadful GU, and wanted any off roader type thingy wagon just for short term use(till he got his D2).
Anyhow, he took it to his mate mechanic for a major-ish service, incl brakes(discs pads, etc, plus usual other stuff).

So off we go up into Mt Dissapointment area, just gravel tracks, no off roading so to speak.
Come to the top of a major drive up, he complains of a loud grinding noise, I reckoned it was just the usual rough Exploder V6 'silkyness' [biggrin]
Anyhow, he comes up to where I was parked and sure enough major catastrophic grindy noise on touching the brakes. I could see the caliper flip upwards as he touched brake.
It lost it's lower bolt, and top bolt about to fall off too. Too late for rim, it ground through so tyre flat too, in a matter of minutes.
Can't recall, but bolt maybe M12 or M14 in size and we had nothing remotely similar in my tool box. I scouted both cars(my D1 and the Exploder) for any not so critical bolt that may do as a temp fix to get us home.
In the end a locking pin from a D-shackle was the best I could think of. Small pinhole on the end of the shackle pin so secured it with cable tie. Drove home very slowly/carefully me in front in case, his hand on handbrake just in case.
Yep, sounds dangerous, but came good, no issue, all still attached when we got it home.

Opposite side front bolts also loose! .. yet rears were tight.

Mechanic was blasted for it, replaced damaged wheel and disc(caliper OK tho), and he told of the lazy helper/apprentice and many complaints from other customers(he was gone after that). He just didn't do them up at all.
lazy sh-ite probably did them up finger tight .. yet had the smarts to tighten up the rears!?

[Rick Fischer]

Correction!

New Bolts

Decision: Will replace all of the calliper bolts on my Deffie now, and will replace the bolts with new ones every time calliper/s need to come off.
Have found that for my VIN rear callipers bolts are encapsulated ISO fine thread and the fronts are not encapsulated ISO Course. MM doesn’t mention locktite for front. However, on mine I will use locktite.
A couple of engineering design questions that are perplexing, (to my knowledge):


Fine threads are normally used with high torque tensioning due to greater surface area of similar dia fine threads vs course, and bolt material dia is not compromised by deeper thread,
Course threads are used in softer materials at lower tensions, but on later Deffie the front callipers have ISO Course at same tension as rears, both 12mm and both 80Nm.
For my VIN the rears encapsulated and the fronts are not?


Rick F


Did find that the front caliper bolts ordered by VIN are incorrect thread! Front Caliper threads are identical to rears; .................and of course that means they are encapsulated!.......................and for both front and rear they are 12 point 12mm x 1.25 pitch ISO.

As a by the by. I did mention Loctite the original and now the generic name for 'thread locker"..................as is encapsulation.

Received second four for front and eight for Ron. Have made mine throwaway. At $2 ea why woodnya [thumbsupbig]

cheers

Rick F