T-bar is a part of a socket wrench kit.
You use it for crude application of raw force.
That's why it's also sometimnes called breaker bar.
Breaks stubborn bolts loose. Sometimes breaks stubborn bolts. Cheaper to replace than the ratchet wrench if the breaker bar breaks
Bolts: (Can't find the original thread)
The first digit of the x.x mark on
non stainless bolts stands for the ultimate tensile strength of the bolt x100MPa
the second digit gives the factor to calculate the yield tensile strength of the bolt.
The ultimate tensile strength gives the force that ruptures the bolt.
The yield tensile strength gives the force that will permanently deform the bolt.
Examples:
Your 4.6 bolt: T&he ultimate strength is 400 MPa
The yield strength is: 0.6 x 400MPa = 240MPa
This lies anywhere between wet spaghetti and quality chewing gum.
The bolts will readily snap if you only show them a spanner.
They are made by children in Chinese backyard sweatshops using a 90% recycled cardboard 10% zinc alloy that only visibly resembles steel
Compare: A decent 8.8 (pretty much an industry standard) bolt:
The ultimate strength is 800MPa
The yield strength is 0.8 x 800MPa = 640MPa
It is almost three times as strong as the rubbish they sold you
And now a high tensile 12.9 (highest grade commercialy available) bolt:
The ultimate strength is 1200MPa
The yield strength is 1080MPa
4.5 times stronger than your Chinese zinc cardboard fasteners
Stainless (actually corrosion resistant) bolts only give a quality grade ranging from A1 (lowest) to A5 (highest) and the ultimate strength in x10 MPa to tell them apart from the others. A typical denomination would be A2-70.
It's important to know a few things about these stainles steels before wildly bolting a bike together using them:The quality grading refers to corrosion resistance and NOT necessarily to strength of the bolts although higher quality grade corrosion resistant bolts usually have a higher ultimate strength too.
Commercially widespread are the qualities A2 and A4. A2 is permanently resistant to corrosion at room temperature if exposed to the elements (NOT sea water, it will show surface corrosion). A4 is often dubbed "acid resistant" and does not corrode if exposed to sea water or weak acids.
Typical quality stainless bolts would be A2-70 and A4-80
The yield strength of the corrosion resistant steels used is only about 60% of their ultimate strength.
Means although an A4-80 bolt has the same ultimate strength as an 8.8 it has considerably less yield strength (480MPa vs. 640MPa) which obviously is much the more important figure.
A further important issue of stainless bolts is their increased tendency to develop fatigue failures. A good reason not to replace any structural fasteners (brakes, chassis, suspension, engine mounts, handlebar clamps etc.) on your bike with stainless bolts.
Topic: The DRZ Thread (Read 53976 times)
