stainless steel fittings/disk bolts

[speedy21]

anyone know of somewhere doing a set front and back for brake discs at a good price, ive found a set for £42 on ebay, just wandering if theres anywhere cheaper as this seems rather steep for a few bolts to me ?
thanks

[stinkwheel]

I personally wouldn't use stainless for disc bolts. It's a pretty weak metal and a safety critical, high load componant

The reason it's expensive is because it will need to be an extremely high grade stainless to even come close to half the strength a high-tensile, mild steel bolt is giving you.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[BTTD]

I've wondered about this before - is it the shear strength of the bolts that matters? Because the wheel material that the bolt is fixed into isn't as strong is it?

I've always assumed that they use plain steel bolts because they're cheaper, but then I'm not very knowledgeable on metals.

[stinkwheel]

Ought to be tensile strength if they are tightened down sufficiently. The three bits of metal (disc, bolt and hub) should behave like a single piece of metal.

So with the lowest common grade of high tensile mild steel bolt (grade 8,8) assuming it's an M8 fine pitch you have *consults tables*

8,8 means it has a tensile strength of 800Nmm^2 and should be tightened to within 80% of its elastic phase to remain tight.. So you'd do it up to 22Nm of torque.

Most stainless fasteners are grade A2 70 which has 700N/mm^2 tensile strength and needs to be tightened to 17Nm of torque.

PROBABLY enough but do we know?

The other way is to get grade 80 stainless.

The other factor is that most stainless bolts they supply for motorcycles is A2 stainless which is still going to rust when exposed to salty water and is not above seizing solid in aluminium alloy.

So, if you got grade A4/80 stainless, It ought to be as strong as the original and very corrosion resistant. Is it worth the extra cost though?
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[0l0dom0l0]

Stainless aren't great for disc bolts for the reasons highlighted above.

I've just bought a set of titanium disc bolts for the same as what you've said above, and not only it's titanium stronger than steel, it's also light and as such you save a little bit of unsprung weight. All be it, marginal but can't go wrong.

Especially as standard steel bolts are a similar price!
____________________
CBT Passed: 30/08/2009, Theory Passed: 31/08/2010, Mod 1 Passed: 6/9/2010, Mod 2 Passed: 13/09/2010. Restriction ended 13/09/2012.

Bikes: 2007 Derbi GPR 50, 1998 Yamaha Fazer 600 (written off), 2002 Yamaha Fazer 600, 1994 CBR 600F, 2003 Triumph Daytona 600, Kawasaki ZX6R J1.....Current: 2006 Yamaha FZ6, 1998 Suzuki TL1000R and a Honda VFR 400 NC30.

[Pete.]