High tensile or stainless steel?

PJPenrouz

I bought a second hand frame with sliding dropouts which are attached to the frame by 4 M6 x 20 bolts. The previous owner replaced the original (???) bolts with titanium ones but 2 of them are slightly rounded. I've managed to remove them and would like to replace them. Should I use high tensile or stainless steel? Should I be worried about the strength of the stainless ones and put up with the possible rust?
Cheers

nicklouse

frame?

i would not want to be using less than an 8.8 grade bolt (or equivelent)

but that is just me.

rubber side up

High tensile.

PJPenrouz

The frame is voodoo wanga.
By the way - I was told in my LBS titanium was not suitable - I always thought it was strong enough. And that's why they got rounded so easily.

rubber side up

IIRC, titanium's strength:weight ratio is very good (ie 10g steel bar is stronger than 10g of steel, but thats because theres more titanium.) but i'm not sure that its actually any stronger..

Could be wrong though.

personally, i wouldnt be using Ti bolts in high stress areas, or when they have to be tightened a lot.

John Stevenson

People have this bad habit of replacing high-strength steel with titanium in applications where it's dimensionally constrained.

High grades of titanium are stronger than most grades of steel weight for weight. But because titanium's less dense than steel you need to be a bit clever to get the advantage. This is easy in, say, frames: you just use fatter tubes.

But for bolts, bottom bracket axles, pedal axles and the like, you're snookered. They have to be a certain size and shape, and that size and shape was usually designed in steel.

So if a safety-critical part of your bike is made from steel, replace it with steel.

Titanium bolts are for bottle cages. Oh, and maybe jockey-wheels.

rubber side up

So i was right then go me!

ratty2k

I'm not a metalurgist, but theres an awfull lot of BS talked about "strength"
Its all relative to its use, bolts are in tension, so high tensile it is...... But Strength is also compression- cast iron is great stuff for this, but you wouldnt want it under a bending load.

Be carefull refering to the "strength" of a material....