SS brake caliper bolts

['15 LS3-1LE]

So I've ordered a full, rotors and pads front and rear brake kit but upon research found a daunting issue about the caliper mounting bolts which many swear must be replaced anytime they're removed.

No big deal, that's fine. They're just cheap bolts however, FRONT bolts show available but REAR bolts are nowhere to be found!! Is this because it is identical bolt sets front and rear?? I'm losing my mind over this which is silly because I know worse case scenario I can just mark the bolts to their position as is and put back to said mark and it would work but it's the principle here.. Why can't I find REAR caliper mount bolts?? Are they in fact just identical?? Also, what the hell is 44ft/LBS-90°(front)and 30ft/lbs-90°(rear)Wth does 90° mean?

[Deputy347k9]

Originally Posted by '15 LS3-1LE

So I've ordered a full, rotors and pads front and rear brake kit but upon research found a daunting issue about the caliper mounting bolts which many swear must be replaced anytime they're removed.

No big deal, that's fine. They're just cheap bolts however, FRONT bolts show available but REAR bolts are nowhere to be found!! Is this because it is identical bolt sets front and rear?? I'm losing my mind over this which is silly because I know worse case scenario I can just mark the bolts to their position as is and put back to said mark and it would work but it's the principle here.. Why can't I find REAR caliper mount bolts?? Are they in fact just identical?? Also, what the hell is 44ft/LBS-90°(front)and 30ft/lbs-90°(rear)Wth does 90° mean?

First (quote): "but upon research found a daunting issue about the caliper mounting bolts which many swear must be replaced anytime they're removed"

It's not that "many" swear the bolts are to be replaced, this is a factory specification. The bolts are called "torque to yield". Sometime back I believe I posted a picture of a new OEM caliper torque to yield mounting bolt standing next to a one time used caliper torque to yield bolt, there was a slight difference as the used bolt thread appeared to have been slightly stretched. Was it stretched to the degree that the bolt would fail the next usage? I don't know that but I am not willing to find out either, also why I don't drive without insurance!

Second:

There IS an obvious difference in the size of the front bolts and the rear bolts. The rear OEM GM part number is 11515781. I just checked Amazon and eBay, both sites have plenty of the OEM rear bolts, don't know why you can't find them?


Third (quote): You stated; "Also, what the hell is 44ft/LBS-90°(front)and 30ft/lbs-90°(rear)Wth does 90° mean?"

ANSWER: The correct torque for the front is 44 foot pounds PLUS 90 degrees, rear torque is 30 foot pounds PLUS 90 degrees not minus! This torque value is telling you to first apply the precise torque value of either 44 or 30 foot pounds then tighten the bolt ANOTHER 90 degrees! Your best bet is to take some red finger nail polish and apply marks so you will know exactly where 90 degrees is, then tighten the bolt that further distance! Put some lead in your back pockets because you will need the extra weight when you apply that 90 degrees, you won't do it with a 6 or 10 inch wrench!

Fourth:

If you use the "search" tab you will find an abundance of material relating to all facets of the brake system. Guarantee every question you may have regarding the breaks will be answered. It's also great reading.

How that?

Larry


Guess my first note should have been welcome to the forum?

[hesster]

I think this is the part needed in the link. These are technically TTY Bolts, which are recommended to be replaced and not reused since they are "stretched" when tightened down to achieve the torque spec or actually the desired clamp load. Endless arguments on reuse, if you do reuse apply Blue Lock-tight. They are NOT the same as the fronts.
The Torque to Yield Spec for the Fastener (Torque + Specified Angle) means Torque the REAR Bolt to 30 Ft Lbs (Fronts are 44), then tighten it ANOTHER 90 degrees. There is a special tool that can be used on a Torque Wrench for this, or the easy way is Torque it to 44 Ft Lbs, then with a white paint pencil marker mark the bolt head and a adjacent spot on the Caliper, then mark another spot on the Caliper 90 degrees CW from the initial mark, then keep tightening the Bolt until the marks align again. See the Pic as a example on a suspension bolt.
https://www.nationalgmparts.com/oem-...-bolt-11515781

[gtstorey]

Torque plus angle is not necessarily torque to yield.

https://dannysengineportal.com/torqu...lus-angle-faq/

https://www.onallcylinders.com/2016/...gle-fastening/

I actually haven't checked the service manual to see if it list caliper bolts anywhere as actually TTY. I look at the direction of load to determine if I'm going to replace (and how often I'm going to have them apart) to determine whether I think I'm going to replace. Internal engine fasteners that are in tension, I would definitely consider TTY and only use once. Bolts like caliper bolts that are in shear and I'm taking apart fairly often, I reuse. I think the factory guidance of replace is because of the locking compound on the bolts and lawyers. Of course I may slam on the brakes during my next drive, lose the brakes and die.

The only way to really determine if the bolts are TTY is to measure before installation and upon removal and see if they are longer.

[hesster]

Good articles. I simply made the decision to replace all Torque and Angle Fasteners during my Suspension Build, assumed they stretched in some amount, yield point or not, and had piece of mind in avoiding failure.

[ChibiBlackSheep]

I just bought them last week from gmpartsstore.com

Part Number Part Name Price Quantity Total
11570788 Disc Brake Caliper Bracket Mounting Bolt $6.74 4 $26.96
11515781 Gear Assembly Mount Bolt $2.62 4 $10.48

[hesster]

So, not to belabor things, how does one know if these TTA Fasteners are ALSO TTY and "should be replaced?

"You can identify a torque-to-yield or stretch-style fastener by the narrow shank just below the washer face and before the thread run. A bolt of this design is intended to be installed in the plastic range and cannot be reused after being tightened once."

So that is most if not all of the assorted suspension bolts. And certainly Caliper Bolts. I rounded up one of each of my old Suspension Fasteners and tool a pic. Caliper Bolts on the Bottom.

[gtstorey]

Originally Posted by hesster

So, not to belabor things, how does one know if these TTA Fasteners are ALSO TTY and "should be replaced?

"You can identify a torque-to-yield or stretch-style fastener by the narrow shank just below the washer face and before the thread run. A bolt of this design is intended to be installed in the plastic range and cannot be reused after being tightened once."

So that is most if not all of the assorted suspension bolts. And certainly Caliper Bolts. I rounded up one of each of my old Suspension Fasteners and tool a pic. Caliper Bolts on the Bottom.

Was that quote taken from here?
https://www.hemmings.com/blog/articl...lts-fasteners/
If so it's interesting that its buried in a section on cylinder head bolts and I'm not sure if it was meant to apply to all bolts. Maybe.

Of course I don't even use a torque wrench on suspension or brake bolts, so I may die the next drive.

['15 LS3-1LE]

Thanks for all the feed back! I have a 20" or so torque wrench for the job so I got that covered. My point on the 90° part is that would make a much greater torqued amount they could call said x number of foot pounds, wtf is an extra 90° equating to in torque specs, really? Then just call it and extra 1/4 turn of the bolt.

I guess I'm supposed to open the bleeder valves as I compress the pistons, right? ( As I'll use my racheting dual sided caliper piston tool) If not recommended to open the bleeders, I will definitely take it straight to a shop to get the whole brake fluid system flushed

['15 LS3-1LE]

Originally Posted by gtstorey

Torque plus angle is not necessarily torque to yield.

https://dannysengineportal.com/torqu...lus-angle-faq/

https://www.onallcylinders.com/2016/...gle-fastening/

The only way to really determine if the bolts are TTY is to measure before installation and upon removal and see if they are longer.

I will do this, along with documentation of my findings. When I bought the bolts at my Chevrolet dealership parts counter the guy said they're certainly not reusable bolts, they get stretched upon installation torque. I will say, the front and rear bolts are damn near identical tho. Different part numbers, as that wonderful lil chart referenced earlier here correctly indicates. Visually no real discernible difference to the eye

[gtstorey]

Originally Posted by '15 LS3-1LE

I will do this, along with documentation of my findings. When I bought the bolts at my Chevrolet dealership parts counter the guy said they're certainly not reusable bolts, they get stretched upon installation torque. I will say, the front and rear bolts are damn near identical tho. Different part numbers, as that wonderful lil chart referenced earlier here correctly indicates. Visually no real discernible difference to the eye

It will have to be the same bolt installed then removed to check. The amount of stretch will be less than the manufacturing tolerance of the bolts. I found one source that quoted 0.2% of "plastic deformation" or permanent stretch is considered yield.