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

[moto748]

Even the better grades of stainless are nowhere near as strong (in shear or tension) as the steel used in plated allen screws (Grade 12.9).

I'd bear this in mind when considering replacing any bolts.

I'd be wary of replacing caliper clamping bolts at the best of times, though. They will have been carefully torqued up to equal tightness.

[Edited on 7-11-2005 by moto748]

[Nattyboy]

Jasper - the rusty bolts on my own brembo billets is a constant source of frustration (although when cleaned up and WD40'd they look fine from a distance), but when I mentioned to Rich L (Louigi) about replacing them his response was very cautious. My hand may be forced though coz the r/h caliper is weeping a small amount of fluid (im guessing there is an o ring behind the bolts) so i'll let you know what I do..

Nat

[Jasper]

I have talked to a few people and have now even got the torque settings.I am going the A4(high tensile) stainless route,removing one bolt at a time.I can't see this being a problem.The calipers should not move with three other bolts holding them together.I hope.

[bolds]

From http://www.easywebstore.co.uk/stigfa...tID~34484.aspx

"Is stainless suitable to replace high-tensile bolts?
No. The vast majority of stainless fasteners listed on this site are grade A2-70, and have approximately 85% of the tensile strength of grade 8.8 steel bolts. As such, stainless fasteners are only recommended for non-stressed applications, which effectively rules out brake calipers, suspension mountings, brake discs, seatbelt anchors and propshaft bolts. We cannot advise on the suitability of replacing any OEM fasteners with stainless, or accept any responsibility for your actions in so doing. On your own head be it...... "

[Jasper]

I am replacing with A4 not A2.

[GeoffDuk]

For SS specs etc check out this website for advice.
http://home.jtan.com/~joe/KIAT/kiat_2.htm

[Steve M]

This is a reply I did from a similar post a bit back -


normal Zinc plated bolts have a tensile strength of 500 Newtons/mm2
stainless steel basically starts at 500 N/mm2 for class 50 up to 800 N/mm2 for class 80.
High tensile bolts are about 800 N/mm2 - usually stamped 8.8 on the head.
So if you want to be really sure about the strength get some stainless steel grade A4 class 80. Alloy fasteners have a huge range due to the various metals available, but are unlikely to be over class 80 on a bike.

also you have to be carefull about putting stainless bolts into alloy as disimilar metals react with each other causing corrosion, this can be prevented using copaslip or similar, you then have to reduce the tightening torque to copensate for the lubricate tread - to about 60% of the stated torque.

[ali]

Jasper, let me know what you eventually end up with as I'd like to order some. I've had a brembo billet on the shelf in my living room for the last year (the pair to my DD l/h caliper) and even the bolts on that have gone rusty!!

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

Cheers,

Ali

[guest1]

I seem to recall that we had problems previously when using s/s in the presence of ammonia - the s/s apparently becomes brittle to the point of useless.
Granted it was a saturated area inside a glovebox but just a thought if your cleaning the s/s with ammonia based product.
There's never a chemist around when you want one is there.

[Felix]

Their top spec race calipers use titanium bolts (unless they're monoblocs, of course). Why not use some of those?