This annoys me intensely both brakes.
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Can they be replaced?
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[/URL]Can they be replaced?
- Joined
- Dec 29, 2013
- Messages
- 6,156
- Location
- Kidderminster Worcestershire UK
- Car
- Mercedes W124 260E M103
Well you now that nuts and bolts are only plated . Me , i would get some stainless bolts if its bothering you . Remove and replace them. Ho sorry it looks new ,if it is , and the cost of these dream machines ,then i to would complain . Get them at MB to change them for free..
hotrodder
Active Member
'Stainless' covers a LOT of ground but the vast majority of stainless fasteners are significantly weaker (yield and tensile strength) than high tensile carbon/alloy steel and definately not suitable for things like brakes, wheel bolts, suspension fasteners etc. Complain to MB and/or paint the head of the bolt but do not swap it for one made from stainless...
A class 8.8 fastener is made from quenched and tempered carbon steel and has a min UTS of 800 MPa, a min yield of 640 MPa and proof strength of 660 MPa for the sizes commonly found on cars. Bolts holding wheels, bits of suspension or brakes together are typically stronger than this, commonly class 10.9
Common stainless bolts are made from austentic grades (for corrosion resistance) which are not hardenable by heat treatment. These are covered by different standards... the material grade is called out as A2 or A4 etc and the strength properties are given by a suffix so for example
A2-50 is a fastener made from 304 stainless which has a min UTS of 500 MPa and a min proof stress of 210 MPa. There is no quoted yield strength as stainless steels have a different stress-strain behaviour to carbon steels i.e. there is no distinct yield point
A4-70 would be a 316 bolt with a min UTS of 700 MPa and 450 MPa min proof strength
Off the top of my head A2-70 and A4-70 are the most common flavours of 'stainless' bolts offered. -80 strength classes also exist which match the min UTS of class 8.8 but not the yield strength and they aren't that commonly offered. 'Proper' high strength stainless bolts are harder to find and made from different flavours of stainless which have less corrosion resistance [/gross generalisation]
This is why, in the old days, MB wheel bolts used to have a stainless cap glued/bonded/friction welded to the head of a carbon steel class 10.9 bolt
A class 8.8 fastener is made from quenched and tempered carbon steel and has a min UTS of 800 MPa, a min yield of 640 MPa and proof strength of 660 MPa for the sizes commonly found on cars. Bolts holding wheels, bits of suspension or brakes together are typically stronger than this, commonly class 10.9
Common stainless bolts are made from austentic grades (for corrosion resistance) which are not hardenable by heat treatment. These are covered by different standards... the material grade is called out as A2 or A4 etc and the strength properties are given by a suffix so for example
A2-50 is a fastener made from 304 stainless which has a min UTS of 500 MPa and a min proof stress of 210 MPa. There is no quoted yield strength as stainless steels have a different stress-strain behaviour to carbon steels i.e. there is no distinct yield point
A4-70 would be a 316 bolt with a min UTS of 700 MPa and 450 MPa min proof strength
Off the top of my head A2-70 and A4-70 are the most common flavours of 'stainless' bolts offered. -80 strength classes also exist which match the min UTS of class 8.8 but not the yield strength and they aren't that commonly offered. 'Proper' high strength stainless bolts are harder to find and made from different flavours of stainless which have less corrosion resistance [/gross generalisation]
This is why, in the old days, MB wheel bolts used to have a stainless cap glued/bonded/friction welded to the head of a carbon steel class 10.9 bolt
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