Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > General Motorcycles only > Stainless bolt replacement in calipers?

[Jasper]

Felix,i was looking at doing that but then this corrosion/reaction of metals raised it's head!!I'm still convinced SS is an option if the correct spec is used,as is Ti.

[rcgbob44]

Just use A4 S/S with some copper slip and you will have no problems, most suppliers of S/S will offer either A2 or A4, S/S is not expensive but never use S/S for engine bolts as it has a courser thread than normal metric engine bolts and hence can work loose easier.

I found this out when I bought a set to put on my Jota and was warned about this problem by a very knowlegable chap many years ago, remember that S/S does not have the same tensile streanth as mild steel for such applications like retaining bols etc.

You will have no trouble with A4 on your calipers.

[moto748]

Originally posted by rcgbob44
as it has a courser (sic) thread than normal metric engine bolts and hence can work loose easier.

Sorry but this simply isn't true. Stainless steel is a material, not a 'type' of bolt. Thread patterns are manufactured to to fixed standards: a metric coarse thread is a metrids coarse thread, whether the bolt is made from stainless steel mild steel, brass, or Plasticene.

That's not to say that you can't get a bolt in stainless with a different thread to normal metric coarse, but the idea that stainless threads are intrinsically different is just plain wrong.


And I re-iterate that even A4 stainless is nowhere near as strong as the stuff steel allen bolts are made from.

[Steve M]

Originally posted by moto748
And I re-iterate that even A4 stainless is nowhere near as strong as the stuff steel allen bolts are made from.

A4 does not determine the strength of the bolt, it's the class that does that eg. an A4 class 80 bolt has a very high tensile strength - see my post a bit higher up .

[Jasper]

I have ordered some A4 class 80 bolts.I am pretty damn sure that they will be strong enough for this use and am willing to take the risk.Especially as there are a few people out there that have done it with no significant problems(as long as well coppaslipped).I may go the Ti route if i can find some money!!

[Steve M]

They will be absolutely fine

[yeti]

Originally posted by ali
Incidentally, I'll be out at the brembo factory shortly so I'll ask why they fit such crappy bolts!

Ask them how they machine the piston pockets in monoblock calipers! I've been an engineer, admittidly aircraft, for 30 odd years and I'll be jiggered if I can work out how they do it.

[Jasper]

Right,you can't get A4/80-non in the country!!You can get A2/70-80.A4 is marine(nothing to do with the strength!!).So,a2 70-80 it is!!Here is some reading:

If Stainless isn’t as strong as high tensile steel is it going to be strong enough?
This is our MOST faq. Firstly it should be made clear that if for whatever reason you require high tensile (HT) bolts you should use original equipment. Secondly if we believed a bolt was not strong enough for a particular application we would not sell it to you. HT steel is used by factories because it is cheap, convenient and saves assembly time. We ran a motorcycle fitted with standard A2 bolts on discs and fork castings etc which were tested on a daily basis for many months and found no problems whatsoever. Not really a surprise when you consider both the hub and the yokes are low tensile cast alloy - the threads on the fastener are actually stronger than the threads in the material. If you need further reassurance - in the seven years we have been selling stainless we have not had a report of a single failure because the bolt wasn’t strong enough.

A2 Class 70-80 (BS970 bar & hexagon equivalents T303/T304)
The 'A2' denotes the alloy type. A2 is often referred to as 18/8 (18% Chrome/8% Nickel) or Type 304. This is the most common form of stainless steel fastener fabrication, it offers excellent general corrosion resistance and is the minimum specifcation we supply. Class 70-80 refers to the strength range. There are two strength ranges available, Class 60 and 70-80. Unlike some of our competition we sell only fasteners made from the higher strength range.

A4 Class 70-80 (BS970 bar & hexagon equivalents T316)
A4 is also referred to as 18/10/3 (2% extra Nickel added 3% molybdenum) or Type316. This is regarded by specifiers as 'marine grade' or 'enhanced corrosion resistant' stainless and is designed for constant immersion in salt water or 'stronger' acids.


I have had to bulk order these(3 sets) so if anyone wants 8.let me know(Yes Rob,your first!!)

[GeoffDuk]

You can purchase A4 fasteners from RS components, however there is minimum order quantity. They only go up to 6mm diameter - length 40mm. A bag of 50 costs £10 +VAT

[GeoffDuk]

Mistake. RS components sell Hex socket in A4 available from M3 to M12 however they become expensive as you move up in size. For example M12 * 70mm (MOQ 10) costing £41 + VAT for 10