Brake Confusion

[W.E.G.]

It is apparent that people are confusing terminology between V8 cars and V6 cars.

The bolts that attach the caliper to the steering knuckle on cars with either motor require genuine manly torque. The replacement bolts for the front come with thick threadlocker pre-applied. These are grade 10.9 bolts, and they are stout.

I’m no metallurgist, but I question the proposal that these 10.9 bolts are”yielding” at 44# plus 90. You are screwing them into ALUMINUM. If anything is “yielding,” it is the aluminum caliper. My theory on the reason GM wants you to replace the bolts is to be sure the correct threadlocker is used. Now, that doesn’t explain why they want you to replace the rear bolts (which do not get threadlocker, but which are tightened to a lesser torque than the front bolts). Leave that one to ponder.

[W.E.G.]

Bolts used to attach caliper to knuckle on SS model.

These particular bolts came off a 2015 SS.
Identical in every respect to bolts that I also removed from a 2011 SS.

Rear caliper bolt on left.
Front caliper bolt on right.

[W.E.G.]

The minimum yield strength of a grade 10.9 bolt is 940 megapascal.

Megapascal is a PRESSURE value, and does not seem to translate directly to a TORQUE value. If anybody has the mathematics knowledge to determine how much megapascal PRESSURE is generated by 44 foot pounds plus 90 degrees, please chime in.

I can tell you that based on my personal experience torquing fasteners, the amount of ugga-duggas I was having to pull to get that extra 90 degrees on the caliper bolt felt like it was in the 170 foot-pound range. The tricky part of it is trying to figure how much of that resistance was the THREADLOCKER fighting back. Anytime you have a sticky foreign substance on a fastener, the torque you feel while pulling is going to give you a somewhat false reading (higher reading) than you would have gotten if the threads had been clean.

I have a hard time believing that a grade 10.9 bolt is deforming in any serious manner at just 170 foot-pounds.

[Rock-It Man]

Originally Posted by W.E.G.

It is apparent that people are confusing terminology between V8 cars and V6 cars.

The bolts that attach the caliper to the steering knuckle on cars with either motor require genuine manly torque. The replacement bolts for the front come with thick threadlocker pre-applied. These are grade 10.9 bolts, and they are stout.

I’m no metallurgist, but I question the proposal that these 10.9 bolts are”yielding” at 44# plus 90. You are screwing them into ALUMINUM. If anything is “yielding,” it is the aluminum caliper. My theory on the reason GM wants you to replace the bolts is to be sure the correct threadlocker is used. Now, that doesn’t explain why they want you to replace the rear bolts (which do not get threadlocker, but which are tightened to a lesser torque than the front bolts). Leave that one to ponder.

The installation instructions for the Brembos are to torque to a spec and then an additional 1/4 turn. That is the typical method for TTY fasteners.

But you're right about the threadlock. That is the other reason to use the specified bolts once only.

Now someone will say...just use loctite instead. I will resist the temptation to give a talk about loctite. There are many kinds but none cure well in aluminum holes or helicoils. So please, people, go by the book; it was written by engineers.

[jrisebo]

Originally Posted by W.E.G.

It is apparent that people are confusing terminology between V8 cars and V6 cars.

The bolts that attach the caliper to the steering knuckle on cars with either motor require genuine manly torque. The replacement bolts for the front come with thick threadlocker pre-applied. These are grade 10.9 bolts, and they are stout.

I’m no metallurgist, but I question the proposal that these 10.9 bolts are”yielding” at 44# plus 90. You are screwing them into ALUMINUM. If anything is “yielding,” it is the aluminum caliper. My theory on the reason GM wants you to replace the bolts is to be sure the correct threadlocker is used. Now, that doesn’t explain why they want you to replace the rear bolts (which do not get threadlocker, but which are tightened to a lesser torque than the front bolts). Leave that one to ponder.

Correct, My car is obviously not an SS.

Im cleared up on the issue. Just going to weld the piss out of them and be done. next guy can deal with it.

[Hellfighter]

bolts are bolts, i figured my ZL1 is worth more money down the road in a solid state, than having 1 bolt and a pin fall out at high driving speeds or bumps and then losing my brakes, and my life.... sooo i bought the pin kit on amazon for 21$ , for the whole front system on ZL1, which has the 2 pins and the clip that goes on top of the pads, for each side brand new ACDELCO, and then going to Chevy dealership, figuring the bolts will prob run me around 10-20$for all 8.

Now again this is for ZL1... considering my brake pads costed 200$ big ass pads, so i guess with higher brake pads, having some bolts and pins replaced is just an extra insurance for high end safety measure... you get what you pay for as they always say, and i rather pay out extra 10$ for new bolts with thread lock on them... to keep me safe and alive.

[Rock-It Man]

Originally Posted by W.E.G.

The minimum yield strength of a grade 10.9 bolt is 940 megapascal.

Megapascal is a PRESSURE value, and does not seem to translate directly to a TORQUE value. If anybody has the mathematics knowledge to determine how much megapascal PRESSURE is generated by 44 foot pounds plus 90 degrees, please chime in.

I can tell you that based on my personal experience torquing fasteners, the amount of ugga-duggas I was having to pull to get that extra 90 degrees on the caliper bolt felt like it was in the 170 foot-pound range. The tricky part of it is trying to figure how much of that resistance was the THREADLOCKER fighting back. Anytime you have a sticky foreign substance on a fastener, the torque you feel while pulling is going to give you a somewhat false reading (higher reading) than you would have gotten if the threads had been clean.

I have a hard time believing that a grade 10.9 bolt is deforming in any serious manner at just 170 foot-pounds.

The strength of a bolt is measured in units of stress. The strength of a bolt is the stress at which it fails.

Stress is expressed as force/area, just like pressure.

Torque is what you apply to a bolt to generate clamping force in a joint, which is also pressure. The reaction in the bolt is tension stress, which, again, is expressed in the same units.

Therefore, as I mentioned in an earlier post, bolt torque is an INDIRECT measure of clamping.

What you "feel" the torque should be is irrelevant. Physics is about facts, not feelings. The mechanical advantage created by threads generates a tremendous load on the bolt. How much is too much depends on the bolt size and material, not on the amount of ugga-duggas.

You'er right about the friction. Depending on the conditions of the thread surfaces, a given torque results in either more or less clamping. And overcoming that difference is the whole point of the 1/4 turn of a TTY bolt. Once the bolt starts yielding, the tension in the bolt, and hence the clamping force, stays nearly level over a range of stresses. That's what gives you a window to achieve the correct clamping over a range of friction conditions.

[Dragonman]

Come on man. The ugga duggas expended to generate tremendous load to bolt failure is directly relevant. If them uggas and duggas ain't there neither failure nor correct clamping values will be achieved.

I'll let myself out.

[W.E.G.]

I find myself standing in front of the pipe racks at Home Depot, daydreaming of glorious torqueriffic back-arching, and cheater-bars to be fabricated to pay homage to the mystical spirits of UgDuggra.

[Rock-It Man]

Originally Posted by W.E.G.

I find myself standing in front of the pipe racks at Home Depot, daydreaming of glorious torqueriffic back-arching, and cheater-bars to be fabricated to pay homage to the mystical spirits of UgDuggra.

UgDuggra lives in the subterranean tunnels of Innsmouth, a town on the Massachusetts coast of the imagination, just up the road from me.

[W.E.G.]

Special chowdah to build up uggduggruscles.

[Hellfighter]

Here are the bolts that I got, total was like 22$ for the rears and front


https://imgur.com/a/Yxnf5

[jaros44sr]

Originally Posted by Test_Eng

What is radial? There are only two bolts for the caliper mounting. Snug up each one then Torque each one, then +90 degrees on each one.


Sent from my iPhone using Tapatalk

sorry, meant rotor bolts to hub

[W.E.G.]

Originally Posted by Hellfighter

Here are the bolts that I got, total was like 22$ for the rears and front


https://imgur.com/a/Yxnf5

That's a great deal if you got eight bolts for $22.

I'm not finding all eight bolts at anything close to that price.
I paid $43 for all eight at the dealership.

Where are you sourcing all eight bolts for $22?