I’m going to be a little more longwinded than usual, but hear me out. On Tuesday I took the Beast to the MB dealer in Germany for the usual annual service before going into storage for the next 7 months. While there was only about 3000 miles on the clock since last year’s service, I requested that in addition to an engine oil change (Mobil 1 0-40wt which I provided), the 722 transmission fluid be drained and replaced with Fuchs 4134 ATF (which I provided) and a new filter, of course. Finally replace the current EBC Reds running on EVOSPORT lightweight rotors with EBC Reds (which I provided for the front and rear) and the front wheel bearings as they are inexpensive and after 70K it’s just a preventative item for me. Alright, so far, so good. The work was to have been completed by Wednesday afternoon. Upon my return on Wednesday I am informed that one of the 12mm 8.8 rated bolts which fasten the caliper to the support snapped when being tightened with a torque wrench (In Germany I think they even tighten light bulbs with a torque wrench). So, was this a one-off defective bolt, or is something else afoot here? Stay tuned. After looking at the broken bolt it looked like as if it failed due to fatigue. I know for a fact that all 4 fastening bolts on the front calipers had to have been tightened 4 times during the course of their life so far. Once at the initial installation, 2 front rotor replacements and 1 wheel bearing replacement. Amazingly these are only grade 8 rated bolts. The next thing I am told by Mercedes Benz is that replacement bolts are not available and that I must replace the entire caliper which comes with new bolts for about 1000 Euros - - - yeah right. I said fellas’, these are calipers made for Mercedes by Brembo and I will have a set of 12.9 bolts by Friday as I have no intention reusing any of the original bolts after seeing what just occurred and that’s exactly what I did. I replace all 4 bolts with high quality German 12.9 rated Allen head 12mm x 70mm bolts with a 1.5 pitch. Each bolt has a tensile rating of 175K lbs., and I instructed that they be torqued to 135nm (100 ft lbs) with LocTite, but even then Mercedes Benz had me sign a waiver releasing them from any liability because I refused to replace the caliper.

Consider this; all 4 of the existing bolts are reused and retorqued for the 4th time, but don’t snap. So, are they right at the breaking point; will a hard braking application cause them to fail; do you really want to take that chance? My recommendation: replace ‘em the next time you have the calipers off.

And couple of a last minute comments: EVOSPORT does not recommend EBC pads, however these EBC Reds were on from the beginning and after 15K miles the rotors are perfect.

The Mercedes Benz dealer did not believe me when I told them the calipers were made by Brembo. How could a German car possibly have Italian brakes (and bolts)? They actually called AMG today who confirmed this to be true.

 

 

I've always been told not to use hardened bolts on suspension and brake parts. Hardened bolts are more likely to shear because of how the load is applied in these applications.

 

I've had a few brake bolts break on a few different cars. Once I only knew because the broken piece got jammed in between the caliper and disc and made a weird noise. It's really not that big of a deal since there is more than one bolt and three other brakes. Not to mention, the brakes are clamped to the rotor and stay that way even without bolts.

 

Chances are the Tech used the wrong setting on the torque wrench.

 

Most standard bolts, do not even have a shear strength specification even though the bolt may be used in shear applications. In this case, properly torqued, there is no load in shear, although a 12.9 bolt in a single or double shear application will be significantly stronger than an 8.8 rated bolt. It is not the shear load that will result in a fracture of 12.9 bolt, it would be a load causing the bolt to bend. No doubt, a 12.9 bolt will fracture if a high enough bending force is applied.

The torque setting was correct. I feel the failure was a result of too many tightening cycles (4 that I'm aware of).

 

Really, were you on the end of the torque wrench or was the tech, you state he was tightening the caliper to the support, I could have bought a breakage on the support to the spindle support, but the small fasteners? chances are he messed up. Another case of do it yourself, its your car, the tech does not have to pay for his mistakes now does he.
As far as you 4 times theory, many MB owners must now replace all wheel studs because most have been torqued far too many times with guys running through tires in 3-5k miles range?JMO

 

Besides you do not want a bolt to shear in this case I would prefer to bend and still have some fastening component.

 

for those wondering, these bolts, 001 990 08 14 can be purchased for about $5 each at www.oediscountparts.com

 

Wat!? There's a Brembo logo on the inner side of the caliper.

 

The next time you have a look at a Ferrari 430, Maserati, Audi RS line, Porsche and a few others, have a look at the front calipers - notice anything familiar, except painted in red?

 

And there's no room on the AMG kompressor signature plate for the Ishikawajima-Harima Heavy Industries Co., Ltd. logo either.

Bend . . . in this type of application?

No, I was not on the end of the torque wrench and neither was I in the forest when a tree fell, so I don't know if it made a sound. And in support of your scenario of me not being on the end of the torque wrench, than it is reasonable to assume that all 4 bolts have been previously subjected to over torquing and would be subject to failure.

The fact is, the old 8,8 bolts have been replaced with M12 (12.9) bolts with LocTite and torqued to 135nm (100 ft lbs). I see no future need for concern.

 

either way, still quite informative with the bolt sizes incase if anyone ever need to replace them.

 

Why all the fuss? The bolts for the front and rear are available from MB. Your guy must have told you wrong.

Front caliper to spindle bolt- A 001 990 08 14
Rear caliper to spindle bolt- A 2110 423 00 71


These bolts are micro encapsulated with thread lock. They should be replaced every time per MB.

 

I know this thread is old, but here I am ready to replace my front brakes and don't have caliper bolts on hand. I just did the brakes on my GL63 and the 'kit' from FCP Euro came with new caliper bolts. The same kit for the E55 does not.

Knowing MB I'm sure they will recommend replacement, but I'm curious how many of you actually replace these every time. I spent 10+ years w/ ASE master techs who swore it was unnecessary, but those were Subarus.

I was planning on thread-locking and reinstalling the bolts, vs waiting another week for new bolts to arrive or spending half a day and $60 driving to the dealer to get them.

Also - is the 100 ft lbs recommended in this thread correct for torque? On the GL63 it's only 59 ft lbs plus 45 deg turn.

Any input appreciated!

 

I replaced my brakes and rotors about a year ago. I reused the old bolts both front and back, except for one in the rear. It was difficult to remove, chewed up a bit so it was replaced.

 

The torque specs for the front E55 AMG is 135ft lbs single stage. Note, it is different for the AMG model. Also the AMG model uses a 14mm bolt compared to the 12mm for the non-AMG models. The unofficial procedure I follow is to reuse the mounting bolts after cleaning both the bolt and female receiver of the bolt with a wire brush/tap to remove all old lock tight and apply new lock tight. I tend replace the bolts if I don't know how many times they have been torqued.

 

I accidentally broke a caliper bolt because I stupidly kept trying to tighten it instead of break it loose (I guess I was distracted). I was able to heat the caliper and work the broken part of the bolt out and the threads were in good shape. My local dealer had bolts in stock though only because someone ordered them and never picked them up. That's when I looked into it and found that you are supposed to replace them each time. I find that excessive but maybe it's worth it because the bolts aren't too bad if you buy them ahead of time. Aren't the latest MB bolts 12.9?

 

I reused these bolts too when I did seals and clean out on my front calipers.


I dont see any issue reusing those bolts as long as they all measure the same when removed and look in good order.



You would have to be doing hundreds of thousdands of kms on corrugated outback roads like in the middle of nowhere in Australia or something for those bolts to come out at 135lb/ft. Its just not going to happen loctite or not. MB is just covering their *** from you litigus yanks.