Hey people,

Do all the bolts on a kit car have to 8.8 grade or higher or is just for the seatbelt mountings? I had a quick search through the IVA manual and the only reference to bolt grades is in the seat and seatbelt mounting section.

I have a load of Stainless bolts in marine grades (A2 etc) that I would like to use to help resist corrosion, especially on the front sus, can I not use these or can they only be used in not structural areas?

Any help apprieciated.

Cheers.

I personally wouldn't use stainless on anything to do with safety or high clamping force, everything else go for it!

Cheers

Rich

quote:

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Originally posted by CaptainWow
Hey people,

Do all the bolts on a kit car have to 8.8 grade or higher or is just for the seatbelt mountings? I had a quick search through the IVA manual and the only reference to bolt grades is in the seat and seatbelt mounting section.

I have a load of Stainless bolts in marine grades (A2 etc) that I would like to use to help resist corrosion, especially on the front sus, can I not use these or can they only be used in not structural areas?

Any help apprieciated.

Cheers.

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^^^^^^^^Save the stainless for cosmetic only.

Cheers for the advice, I will get some more 8.8 grade zinc fasteners for the important stuff.

I wouldn't call any A2 stainless bolt 'marine grade' they need to be at least a A4 to have any chance in salty enviroments (I'm designing bits for offshore platforms at the moment)
its like calling aluminium alloy 'aircraft grade', but folk forget there are lightweight, low strength aircraft grades for non-structural bits....

also the A2/A4 part of the grade is only the corrosion resistance, the number in the grade (i.e. A2-70 or A4-80 ) tells you which class of bolt it is and therfore the strength

even though an A4-80 is approx. the same design strength as an 8.8, in reality they have quite different failure behavior so you can't just swap them - it all comes down to the true elastic limit vs the 0.2% proof stress

most car makers (inc ford) use 10.9 bolts on most structural parts, but its a ballancing act if you go too strong you'll losse the toughness/ductility
(i.e. would you rather a saftey critical bolt bent/streched a bit when it failed giving a little warning or would you rather it just let go completly with no warning )
with 4.6, 8.8, 10.9, 12.9 grades the higher the first number the stronger it is, but the higher second number the less it will strech before failing



[edit]
if money is no object you could get some 'BUMAX 88' bolts, never used them myself but they claim to be direct replacments for 8.8's


[Edited on 13/11/2012 by mcerd1]

As above my understanding is especially avoid using stainless bolts in situations where they are loaded in shear

Would it be acceptable to use a bigger size bolt in stainless, for example an M12 in A4-80 rather than an M10 BZP in 8.8?

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Originally posted by smart51
Would it be acceptable to use a bigger size bolt in stainless

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Where the bolts are well over sized no problem but bigger diameter bolts have to tightened to correct ( ie greater ) torque or they will tend to work loose more easily, strange but true all to do with the amount of elastic stretch the bolt experiences when it is tightened. So using thread lock or locking tabs is advisable.