Brake Bolts

I am rebuilding a T3.

Somewhere in the back of my mind I have the idea that it is not recommended to use stainless bolts to hold the brake calipers on because of the risk of them shearing under braking.

Is this a figment of my imagination or are there real safety issues ?

Thought it was better to ask the group then to find out the hard way.


I have used stainless steel bolts (grade A2) on my calipers with no problem (touch wood)

Think the caliper bolts are M12, if you can shear that by applying the brakes, you have better brakes than I have, Gunga Din!

I have also used stainless, As Duffo said, it is unlikely you are going to shear 2 10mm stainless steel bolts.
Just wish I had ordered some stainless allen head bolts as well for the caliper joints so they matched.


I have just been looking at it. Yer right about the bolts not shearing. The castings would give up long before the bolts will.

The stainless shearing thing must be a pigment of my illumination.

re: Duffo and the stainless caliper joint bolts, I just went into an industrial nut and bolt supplier with a list. He sent me round the back to pick it myself, then weighed it and gave me every SS nut bolt and washer I needed for the entire bile (except the 2 engine bolts) for £15. I came out with a smile …

Might be worth popping into you local industrial bolt supplier.

Just worth saying, stainless not having the same tensile strength of mild is not a figment of your imagination. I’m no expert, so Google it, plenty of info out there.

Tony is correct however like the others I have used Stainless for 30+ years with no problems.
Use copperslip as well.

Tensile strength and sheer strength are not the same. Stainless is more brittle than mild steel. For brake mountings in my opinion stainless is fine, for racing with carbon discs and trick pads then maybe not, but with P08 Brembo set up it shouldn’t be a problem.

Of course sir, if your bolts sheer off as you are hurtling down to a mountain hairpin bend, just bring them back!

Recent experience, Mo?

As above. Not recommended and yet not a problem in my experience.
A couple of things to bear in mind;
Only use good quality A2 stainless bolts. I’ve seen/bought bolts marked as A2 that were very poor quality. Best get them from an engineers merchants rather than a car boot sale :astonished:
Stainless is used on oil rigs and yet it’s prone to being affected by salt. Worth keeping them clean and greased in the winter.

All the best

Re the above, if you fit a stainless front engine mounting bolt to your Tonti it still needs plenty of grease/copperslip. Don’t bother with the annual turning of the bolt as this just tends to wipe away the grease. Grease up well and leave till needed to be removed.


I fitted stainless bolts to my T3’s calipers, and to lots of other things, back in the early 80s - still going strong.