Torque specs for Caliper halves bolts

g96818

Funny thing, i was wondering the same, but decided to just take a torque wrench and measure the torque.


The rear calipers are 32 ft-lbs.
I was going to measure the front calipers tomorrow.

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Rusty

How did you measure the torque?

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g96818

Since there are 4 bolts per caliper, i just picked a starting point and increased the torque value until the bolt started turning and i took the last value (32 ft-lbs) and checked it on the remaining bolts and then incremented it to 33 ft-lbs and checked to make sure they turned a little before clicking.
They all clicked at 32 ft-lbs and turned at 33 ft-lbs so the rear bolts are 32 ft-lbs.


You could also buy a digital torque reader or analog torque wrench to measure it, but i wasn't going to spend that money.

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Rusty

That's in the ballpark of what I had posted of 40 lbs. On the chart I linked. 32 ftlbs is for a lubed torque spec, and 40 ftlbs is for a dry torque spec for the same bolt. The factory uses a wet spec because of them using a thread locker of some kind.

The bolts are a 8.8, or a 9.8 class.

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g96818

There's no marking to determine the grade of the fastener.

I measured the front bolts at 63 ft-lbs.

Didn't feel like there was thread locker, but if so then it would already be dry by now and the torque values would be wrong since those would now be considered the breakaway torque.

According to this video, there's no thread locker on the bolts. skip to 2:50.
https://www.youtube.com/watch?v=artb4VxLaig

front caliper bolts are 63 ft-lbs
rear caliper bolts are 32 ft-lbs

These are definitely not class 8.8 or 9.8 since the head size doesn't match.
The head size for a Class 8.8 M10 is 16 mm and M12 is 18 mm. My caliper bolts are 14mm and 17 mm so these are based off the old standard.

Also the chart you linked to doesn't apply since that chart is for hex head bolts, where as the caliper bolts are hex flange bolts. Hex flange bolts are torqued higher.
https://www.swtc.edu/Ag_Power/diesel...e%20values.pdf

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Rusty

I know there is no markings on the bolts for what grade they are. I don't think Nissan would use the lowest grade, or the high grade bolt for this application. So I picked one in the middle, which would be 8.8.

The torque reading you are getting fall in line. Remember that you are not dealing with everyday bolting. This is Nissan speced. So the head size may not be what you are expecting. Car companies do some strange stuff.

I've rebuilt 4 sets of calipers so far. Of that. 3 had some type of thread locker on the threads. Most likely a triple boiled linseed oil. When I worked for Elliott TurboMachinery. We used to use this stuff all the time. Great thread lube until it drys.

Since the chart I linked to doesn't work. What chart would you use? And what torque would you use?

I hate to tell you. Those calipers in the video. Already have been apart, and cleaned. Plus when he took them apart. Where's the brake fluid? They have new pistons and seals already in them. The threads on the bolts have been wired brushed. The guy just took one side apart as a show and tell. He already screwed up in that video. He didn't put any brake fluid on the o-ring that goes between the halves.

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Rusty

I just found the spec's I was looking for.

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g96818

The torque chart with head sizes are in the GI section of the FSM

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JARblue

Here are the torque specification and bolt discrimination pages from the FSM.

Attached Files

Bolt Torque-Discrimination Chart.pdf (239.3 KB, 15 views)

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Rusty

Page 19.

That where I found everything last night.

There is 2 standards. The PREVIOUS STANDARD, and the new NEW STANDARD BASED ON ISO. The caliper bolts are under the previous standard. As "g96818" found out. The 10mm is 14 mm across the flats amd the 12mm is 17mm across the flats. Under the new standard. The 10mm is 16mm across the flats and 12mm is 18mm across the flats.

No markings or a 4 on the head of the bolt would be a 4T grade. If the head had a 7 or 2 dots, 180 degrees apart. The bolt grade is 7T. If the head has a 9 or 3 dots, 120 degrees apart. The grade would be 9T, the strongest.

On the 4 sets of calipers I have rebuilt. I've never seen a marking on the bolt heads. Has anyone else seen any markings? So, given this information. I would say the bolts are a 4T grade. So the torque would be for the 10mm hexagon flange bolt is 26 ftlbs. For the 12mm hexagon flange bolt would be depending on thread pitch 41 ftlbs for the 1.75 pitch, or 48 ftlbs for the 1.25 pitch. I don't know what the thread pitch is.

Anyone else think that is right or wrong. Post up.

The chart I posted earlier is close to the 7T grade torque spec's, 10mm 41ftlbs, and the 12mm at 74 ftlbs. The chart listed 40 and 70 ftlbs.

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JARblue

Confirmed just now that there are no markings on any of the bolts holding the front or rear Akebono caliper halves together on my 2011.

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g96818

The only markings on the bolts are "L" and "S" and only on the front calipers, rear caliper bolts have no markings. I have no clue what that means. I'm going off a whim and saying the nissan torque specs don't apply, since these are built by akebono so we need to find akebono's torque chart. If I had the exact material compositions, then I could try to calculate the torque values.

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Rusty

But in the mean time............what spec's? The 4T or the 7T?

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g96818

That's the million dollar question that i do not know the answer to. If anything, I would assume 4T since there are no markings, which was why decided to just measure the torques. Like i said, these probably don't follow the nissan chart since theses are akebono calipers and nissan buys them already assembled.


I emailed powerstop tech support to see if they can give me the spec since they "reman" these calipers, even though they supply you with brand new calipers without the akabono tag.


I'll post back if they are nice enough to give me the spec, if not then I'm planning on going with what i measured and tossing some blue loctite on the bolts.

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SouthArk370Z

This may or may not help in your research but bolt torque is an indirect measure of bolt stretch.

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