The bolts in the photo have no markings on their heads, so they are most likely rubbish.
In most cases (such as this one), bolts are more used to clamp two objects together (with some washers in between in this case).
Shear is then transmitted between the two objects via friction. Clean and rough (sandblasted is good) surfaces help to enhance friction.
Depending on the amount of shear force to be transmitted, and the grippiness of the friction surfaces, the required clamping force can be estimated.
From the required clamping force, the size and grade of bolt needed can be found.
The bolts themselves are not loaded in shear.
Thankfully finally someone on this forum understands bolts are never designed to transmit Sheer forces but to apply clamping forces...Hallelujah. Still, keep that ganky brake adapter off the roads near me, have a proper spacer added and welded in so that the bolts can do their designed job of Clamping. that adapter looks like going all the way to 95% and fukking off at the last bit.
While it’s true that a properly bolted (or riveted) connection imparts friction forces in the joint, bolted connections can also be designed for shear in the bolts. Typically the allowable shear in a bolt is 60-70% of the bolt’s yield strength. So if the bolt diameter is large enough and its strength is high enough and it is properly torqued, you can design a bolted connection for shear forces, only. An example of this is bolted steel beams that frame into the web or flange of a steel column. The bolts in those joints are designed for shear, not friction.
Olejoedad is right, the connection between the stock callipers and the knuckle are designed for shear to resist the rotational forces that occur when a clamping force is applied to the rotor by the calliper when the brakes are applied.
Now, would I use the adapters to attach callipers? Not without knowing the grade of bolts and steel used and going through the calculations to convince myself that the connection is safe.
Mike in Sydney U.S Registered & Licensed P.E.
[This message has been edited by Mike in Sydney (edited 07-02-2023).]
While it’s true that a properly bolted connection imparts friction forces in the joint, bolted connections can also be designed for shear in the bolts. Typically the allowable shear in a bolt is 60-70% of the bolt’s yield strength. So if the bolt diameter is large enough and its strength is high enough and it is properly torqued, you can design a bolted connection for shear forces, only. An example of this is bolted steel beams that frame into the web or flange of a steel column. The bolts in those joints are designed for friction, not shear but during assembly the bolts will be in shear. It they aren’t properly torqued, they remain in shear.
The connection between the stock callipers and the knuckle rely on the clamping forces from torquing the bolts to spec and shear to resist the rotational forces that occur when a clamping force is applied to the rotor by the calliper when the brakes are applied is overcome.
Now, would I use the adapters to attach callipers? Not without going through the calculations to convince myself that the connection is safe.
Mike in Sydney
[This message has been edited by Mike in Sydney (edited 07-02-2023).]
Actually Mike you are right but also wrong in this application, once the braking force has over come the bolts clamping force and has to rely on sheer, this bracket affair has already failed.
There's a big difference between a building structure and an automotive bracket like this.
I suppose that in a building where the joint supports a lot of dead load, if loading is high enough to overcome friction, the parts shift one time into their final positions and then stay there.
In an automotive bracket like this, the loading is variable and often reversed (i.e. not constant), so if there is any slippage, then the parts will make an unpleasant toc-toc sound as they shift back and forth, and soon things will degenerate as the bolts loosen and everything comes apart.
I work in automotive; I don't know how building structures are done.
There's a big difference between a building structure and an automotive bracket like this.
I suppose that in a building where the joint supports a lot of dead load, if loading is high enough to overcome friction, the parts shift one time into their final positions and then stay there.
In an automotive bracket like this, the loading is variable and often reversed (i.e. not constant), so if there is any slippage, then the parts will make an unpleasant toc-toc sound as they shift back and forth, and soon things will degenerate as the bolts loosen and everything comes apart.
I work in automotive; I don't know how building structures are done.
True that. If you hear 'toc-toc" the joint has failed and in this case, I suspect that shear forces will come into play as the part is loaded and unloaded. Like you said, if this happens everything soon comes apart. So the answer is use the proper size and grade of bolt and torque it properly.
I worked in building engineering (civil / structural) and you are spot-on on your statement about the joint connections in building and structures.
I can tell you 100% for sure those are not Fieroaddiction Corvette brake upgrade brackets for the 88. I have a set and they are completely different (1 piece and no offset).
