www.boxertrix.com

Is it true that you can't use stainless bolts in caliper mountings because they don't have enough tensile strength ?

You can work it out yourself. It is the shear strength that comes into question when using it as a brake mounting bolt.

https://www.boltdepot.com/fastener-info ... chart.aspx

http://www.bssa.org.uk/topics.php?article=127

It is usually used where corrosion is a concern. Stainless is not recommended for brake caliper mounting. The 8.8 grade bolt is recommended for 11S.

fontana wrote:Is it true that you can't use stainless bolts in caliper mountings because they don't have enough tensile strength ?

I have used stainless on calipers for over 30 years.

There are people...usually clued-up engineer types...who will say you'll definitely die if you do, theoretically. And there are real-world riders who, like Boxadog, have used them with impunity for a very long time. I understand the metallurgical argument for not using stainless....the same as I also understand why I perhaps shouldn't do thousands of miles on a repaired rear tyre. I think, as with many things in life, it boils down to personal choice. And, of course, the same adage applies to using stainless bolts as it does to repairing tyres - if the doom-mongers were right, and somebody really had definitely died because they made their own mind up....we'd know about it. Definitely.

Pete

What about titanium ( my favourite metal as it happens ) ?

kfrogzx7 wrote:What about titanium ( my favourite metal as it happens ) ?

Ti is fine as its shear/tensile characteristics are equal too or better than Grade 8.8 steel ( I think )

I have Ti caliper pinch bolts and mounting bolts

DT

Stainless comes in various grades or can be described sometimes as quality. It also has some characteristics unique to it apart from the resistance to corrosion. Leaching chromium in a electrolyte. Work hardening and with it the metal can become brittle (not unique to it but depending on the forces and work rate the surface can break down). Stainless can also transfer electrons to another stainless steel component it is in contact with and over time it forms one item. Useful to know and to use an insulator material between the 2 items. Can't remember the correct term for this type of corrosion. Depending on the material the brake caliper is made of corrosion can occur on the anode with an electrolyte even with the stainless steel fastener. The risk of corrosion between stainless and carbon steel to aluminium is less with carbon steel in an electrolyte environment.

As for the stress either shear or tensile? For shear stress you need a less brittle material. Maybe irrelevant for the application of brake caliper mount on a R1100S being ridden on the road but the weakening of the material over time would be more of a concern.

One other thing to consider is torque value. The torque values supplier by the manufacturer is for the recommended grade bolts. If you change the material of the fastener the relevant torque value needs to be adjusted. Just like the difference between wet and dry torque. You are messing around with the elastic range. Having less stretch on a bolt made from harder less elastic material does not equal the stretch and security of a more elastic material.

In short I would stick to the recommended grade bolts in this appliction. Just give them a coat of Hammerite silver next time it comes off.

milleplod wrote:There are people...usually clued-up engineer types...who will say you'll definitely die if you do, theoretically. And there are real-world riders who, like Boxadog, have used them with impunity for a very long time. I understand the metallurgical argument for not using stainless....the same as I also understand why I perhaps shouldn't do thousands of miles on a repaired rear tyre. I think, as with many things in life, it boils down to personal choice. And, of course, the same adage applies to using stainless bolts as it does to repairing tyres - if the doom-mongers were right, and somebody really had definitely died because they made their own mind up....we'd know about it. Definitely.

Pete

Well put Pete, and, like Bob (Boxadog) I too have used them for years, and at times have been known to ride hard ... ish and my brake calipers/forks have never (yet) parted company

milleplod wrote:I also understand why I perhaps shouldn't do thousands of miles on a repaired rear tyre.

It's been a long time since I had a tyre properly repaired, but back then, it was perfectly safe to repair a tyre from inside provided it was done professionally.
I once fixed a puncture at the roadside, with the help of a very helpful dispatch rider who had one of those roadside repair kits.
They're supposed to be a temporary get you home solution, but I rode a further 4,000 miles on it without issue.
Not a very good idea I know, but I was young, skint, and not very sensible back then.