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1988 Mercedes 500 sec
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Discussion Starter #1
Rebuilt all my calipers on the sec, I believe when putting the two halves of the calipers together the rear caliper 4 bolts are torqued down to around 35nm or 25llb/ft
I cant seem to find the torque setting of the bolts for putting the two halves together on the front bendix caliper. Does anyone please have this torque setting
 

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1988 Mercedes 500 sec
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Discussion Starter #3
Thanks the rears were done to 25llb/ft but unable to find front bendix torque
 

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350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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If ti's the same bolt (diameter and thread) in the same application than the same torque should be fine. It depends more on the bolt and application (shear vs. tension) than anything else.
 

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1988 Mercedes 500 sec
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Discussion Starter #5
bolts on te rear caliper take a 10mm socket and are thinner the front calipers take a 17mm socket but told by two brake companies to thighten front and rear bolts the same to 35 to 40nm which is what i did
 

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Discussion Starter #7
thanks couldnt see any torque settings it says not to seperate,will see how i get on once plumbed in
It says if there is leaking then torque is incorrect, i put new o rings between the calipers and they were raised slightly before joining the calipers together
 

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350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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bolts on te rear caliper take a 10mm socket and are thinner the front calipers take a 17mm socket
Don't make the mistake of confusing the socket size with the bolt size. What matters is the diameter of the shank of the bolt.
It says if there is leaking then torque is incorrect,
I agree if it leaks (with new o-rings) then the torque is not correct, but if it doesn't leak that doesn't mean it's right. When you apply the brakes the pistons try to force the halves apart. The torque (tension) on the bolt has to be enough that the hydraulic force cannot make the halves separate. The total pressure exerted by the pistons (psi x area) has to be less than the tension in the bolts (psi x cross sectional area x number of bolts)
 

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1988 Mercedes 500 sec
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Discussion Starter #9
The bolt size is much thicker on the front than the rear i have been trying to find this torque figure for the front and told by a brake company the torque figures are the same for front and back
 

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350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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Can you give me the diameter and thread pitch of the bolt? Are there any markings on the head of the bolt, like 10.9?
 

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1988 Mercedes 500 sec
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Discussion Starter #11
the bolt says 11.9 on it, diameter is 9.85mm, i dont know the pitch but will try put up a pic approximately threads are 1mm apart
 

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1991 500SEC 55K mi. 1987 560SEC Now 153K mi. 2020
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You'll need to put a thread pitch gauge on it for true accuracy.

They usually reside in any METRIC Tap & Die set... Perhaps even, a local hardware store or European auto repair shop local to you.

Hang in, and stay safe!

M
 

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350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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the bolt says 11.9 on it, diameter is 9.85mm...
Well, sounds like you have a 10mm bolt there. I've heard of grade 10.9 and grade 12.9, but never 11.9. Are you sure? Common thread pitches are 1.25 and 1.5, so, since you're estimating 1.0, most likely yours are 1.25. Can't make a recommendation, though, without knowing the grade.
 

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350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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OK, I did a little research. European markings are a little different than SAE markings. Bolts could be made to an 11.9 spec if the manufacturer wanted them to be. The appropriate torque would be slightly less than midway between 10.9 and 12.9. Those bolts were cad plated when new, but the plating has worn off, so, my recommendation would be to oil the threads with engine oil (don't get any in the brake cylinders themselves) and torque them to about 50 ft-lbs or 68 Nm.
 

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Discussion Starter #16
I will have a look at the bolt again i had them shotblasted then plated so possibly 10.9
50 sounds a fair bit
If i bolt them to the car can i toruqe them then prob is u used threadlock at 25 do i need to open and clean all the bolts again
 

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350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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If you had them plated then the torque is different (more, actually). I suggested oiling them to eliminate variables, but if they're newly plated then they should be installed dry. Liquid thread locker probably puts you back in the same ballpark as oiled.

25 ft-lb is way to low for a 10mm bolt loaded in tension. The tension in the bolt has to be greater then the hydraulic force trying to push the halves apart. If they're 10.9 then about 45 would be good.
 

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Discussion Starter #18
Ok thanks will do 45 calipers willl
Be going on in 5 weeks can i just nip upto 45llb/ft or do i need to undo the bolts clean and then tighten
 

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Do they have Loctite on them? If so, you have to break them loose before you can retorque them. What I would do is remove one bolt. Clean the loctite off with acetone and swab the threaded holes out with a q-tip soaked in acetone. When it's dry, apply new loctite and reinstall it with 25 ft-lbs if that's what you used before. Then, repeat with the other bolt. Torque that one to 45, then torque the first one to 45. If you're concerned, use 40 ft-lbs, but I wouldn't go lower than that.
 
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