Stainless

Pull up a chair - let's talk Boxerbollox

Moderators: Gromit, Paul, slparry

fontana

Stainless

Postby fontana » Tue Jan 17, 2017 2:04 pm

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

User avatar
tanneman
Member
Posts: 1203
Joined: Wed Mar 04, 2009 8:26 pm
Location: Terra Firma

Re: Stainless

Postby tanneman » Tue Jan 17, 2017 2:20 pm

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.
'Let me check my concernometer.'

User avatar
Boxadog 2000
Member
Posts: 1908
Joined: Wed Feb 18, 2004 8:29 pm
Location: Looking over hedges

Re: Stainless

Postby Boxadog 2000 » Tue Jan 17, 2017 5:00 pm

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.

User avatar
milleplod
Posts: 866
Joined: Mon Mar 25, 2013 6:46 am

Re: Stainless

Postby milleplod » Tue Jan 17, 2017 5:17 pm

There are people...usually clued-up engineer types...who will say you'll definitely die if you do, theoretically. :lol: 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
Nocto Diuque Venamur

kfrogzx7
Posts: 254
Joined: Tue Jul 15, 2014 9:25 pm
Location: Suffolk

Re: Stainless

Postby kfrogzx7 » Tue Jan 17, 2017 5:45 pm

What about titanium ( my favourite metal as it happens :lol: ) ?
Simon.
K100rs, R1100s, R1150rs, R1200st, K1300s

User avatar
Dog Tyred
Member
Posts: 2696
Joined: Wed Jan 18, 2006 12:27 pm
Location: Tamuff

Re: Stainless

Postby Dog Tyred » Tue Jan 17, 2017 6:12 pm

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


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 :D

DT
Ride like your life depended on it.

2002 BCR

User avatar
tanneman
Member
Posts: 1203
Joined: Wed Mar 04, 2009 8:26 pm
Location: Terra Firma

Re: Stainless

Postby tanneman » Tue Jan 17, 2017 9:29 pm

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.
'Let me check my concernometer.'

User avatar
slparry
Moderator
Posts: 6688
Joined: Sat Sep 20, 2008 7:19 pm
Location: Wrexham
Contact:

Re: Stainless

Postby slparry » Wed Jan 18, 2017 1:53 pm

milleplod wrote:There are people...usually clued-up engineer types...who will say you'll definitely die if you do, theoretically. :lol: 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 :D
--
Steve Parry


Current fleet: '14 F800GS, '87 R80RS, '03 R1100S BoxerCup, '15 R1200RT LE Dynamic, '90 K1

fontana

Re: Stainless

Postby fontana » Wed Jan 18, 2017 2:08 pm

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.
:oops:


Return to “Boxerbanter”

Who is online

Users browsing this forum: No registered users and 3 guests