Caliper Support Bolt Replacement (2004 X5 3.0i)

[2004bmwx53i]

Originally Posted by StephenVA

Reuse the bolts for the bracket to hub. Replace the pins that hold the caliper to the bracket. Replace the caliper mounting boot as well. Reinstall the new pins DRY.

Note: At 100K I personally replace all bolts, boots, lines, rebuild the calipers etc at the brakes. The replacement bolts use a male TORX head, so you will in the future need a FEMALE Torx socket. The ability to torque and unbolt is improved moving forward at the socket self centers on twist.

?????
We are discussing #3 on Image below I looked up the costs from a local dealer.
Hex bolt M12X1,5X41 ZNS3 4 11/2005 34116767217
The cost is
Disc Brake Caliper Bracket Mounting Bolt - BMW (34-11-6-767-217)

MSRP: $17.98
Discount: $3.59 (20% off)
Sale Price: $14.39

I think to OP clicked on the assembly part (Bracket, bolts,etc) number #2

Would you please share the retailer info. Thanks

[2004bmwx53i]

Originally Posted by andrewwynn

They are not torqued near yield I reuse. Does BMW recommend non reuse? They often do for CYA legal reasons in suspension parts.

From TIS:

2AZ
Brake caliper to steering knuckle
(screws lightly oiled, contact surfaces between brake caliper and steering knuckle cleaned and grease-free)

110 N·m.

It states if self locking or microencapsulated replace them.

I'm not aware that E53 uses either.

I reuse them.

Thanks for the input. As for the yield point, how would we know that at 110 Nm the material would not be at or passed yield.
Also, would you please explain what is meant by microencapsulated.
BTW, my mileage is 167000 miles!
Thanks

[andrewwynn]

I'm not even sure what BMW means by microencapsulated but I think it's a special treatment that distresses the metal "one time" to lock it. These bolts aren't.

I use an app called iEngineer to look up bolt stress/yield etc.

I think those bolts are M12 front axle maybe M10 back.


Over 5 tons of force at normal torque.

The spec torque for 10.9 M12 is 122 N·m. That is 75% of yield 160 ish should be yield hence "nowhere near". You can stress a steel bolt effectively ∞ times if below 75% of yield. It acts just like a spring.


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[bcredliner]

Micro-encapsulated bolts have Loctite or similar on them. That's why the bolts are special. I re-use them but apply blue Loctite before doing so. Calipers are subject to lots of vibration, shocks and heating and cooling cycles. I wouldn't reuse them without a new application of Loctite.

[2004bmwx53i]

Originally Posted by andrewwynn

I'm not even sure what BMW means by microencapsulated but I think it's a special treatment that distresses the metal "one time" to lock it. These bolts aren't.

I use an app called iEngineer to look up bolt stress/yield etc.

I think those bolts are M12 front axle maybe M10 back.


Over 5 tons of force at normal torque.

The spec torque for 10.9 M12 is 122 N·m. That is 75% of yield 160 ish should be yield hence "nowhere near". You can stress a steel bolt effectively ∞ times if below 75% of yield. It acts just like a spring.

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This is first class response! Thank you.

[2004bmwx53i]

Originally Posted by bcredliner

Micro-encapsulated bolts have Loctite or similar on them. That's why the bolts are special. I re-use them but apply blue Loctite before doing so. Calipers are subject to lots of vibration, shocks and heating and cooling cycles. I wouldn't reuse them without a new application of Loctite.

Just for the sake of technicalities, I would say that if bolts are torqued to specification they would not necessarily need extra locking measure. The torque supposedly has already taken vibration into account. This is my pure guess.
Adding thread lock does no harm at all. I'll do that. Thanks.

[andrewwynn]

Originally Posted by bcredliner

Micro-encapsulated bolts have Loctite or similar on them. That's why the bolts are special. I re-use them but apply blue Loctite before doing so. Calipers are subject to lots of vibration, shocks and heating and cooling cycles. I wouldn't reuse them without a new application of Loctite.

That is not bad advice. I will add however that after remove and replace roughly 100-120 caliper bolts. 100% of the time it took more torque to remove them than the torque they were set with. E.g. I'm not concerned about adding thread lock though I certainly would not advise against it. Very good idea. Actually on a recent job where the bolts were so rusted I had to cut new faces on the bolt to remove: I added thread lock to ironically make it easier to remove next time.

(Nexuses the thread lock fills the gap that allows water/air ingress to cause the rust lock)

[andrewwynn]

Originally Posted by 2004bmwx53i

Adding thread lock does no harm at all. I'll do that. Thanks.

I've rarely added but after that last job from hell (took a couple hours to remove two caliper bolts after somebody else rounded off the bolt heads on some M14 bolts), just to keep out the rust is a good reason.

[2004bmwx53i]

Originally Posted by andrewwynn

I'm not even sure what BMW means by microencapsulated but I think it's a special treatment that distresses the metal "one time" to lock it. These bolts aren't.

I use an app called iEngineer to look up bolt stress/yield etc.

I think those bolts are M12 front axle maybe M10 back.


Over 5 tons of force at normal torque.

The spec torque for 10.9 M12 is 122 N·m. That is 75% of yield 160 ish should be yield hence "nowhere near". You can stress a steel bolt effectively ∞ times if below 75% of yield. It acts just like a spring.
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Just to be nerdy, I found some info regarding the yield of 160. Yield is stress with units of pressure like psi, torque is of unit length x force. So they can't be compared. Please have a look at the link below (the tables) and let me know what you think (I get yield of 940 and proof load of 630 MPa). This has become an interesting discussion.Thanks

https://www.boltdepot.com/fastener-i...ade-Chart.aspx

[crystalworks]

Ever since having a caliper bracket bolt back out on my Mom's Infiniti FX35 (was torqued to spec), I use a bit of red locktite every time I do a brake job. Didn't do any real damage, just gouging on wheel barrel, but could have been very bad. I've never had that happen on a BMW, but I take no chances now.