Potential catastrophic brake failure.

[Flange]

This post relates to an 03 Suzuki SV1000s - it may or may not apply to other bikes as well.

Back from a fairly quick 300km ride yesterday, cleaning the bike like all good SV owners do when I notice one of the front brake calliper mounting bolts missing !

Castigating myself for being a dickhead and not securing it properly I looked closer to find that in fact the bolt had shorn off, leaving the threaded end in the caliper.

So, here's a heads-up for all those who don't fancy the idea of a caliper detaching. See the photo which shows the remains of the shorn bolt, plus a bolt from the other caliper. Note that the intact bolt is showing clear signs of stretching just out from the shoulder area - the waisted area is over 1mm thinner than the area which threads into the calliper. The other two mounting bolts are showing the same signs to a lesser extent.

Mine is an 03 model, and the calliper mounting bolts have only ever been touched by two people, one being the person who assembled them in the factory and the other, myself. I have been meticulous in correctly tightening these bolts and have always used a low-strength Loctite to ensure that the bolts don't require excessive tightening to do their job. So the stretching is not due to over-tightening.

Which leaves just one possibility which is that the bolts are not sufficiently strong for the purpose.

So, is it just my bike which got a set of poor grade bolts, or does yours also suffer the same ?

I would strongly recommend that SV owners (and probably owners of Suzukis with non-radial mounted Tokico callipers) check their brake calliper bolts for any signs of stretching. If you don't know what to look for, take the bike to a competent mechanic and have them checked.

The consequences of a calliper detaching at speed are about as bad as it gets on a bike..

Cheers
Flange

[The Stranger:Me]

So what torque setting did you use?

[imdying]

The bolts are more than strong enough, diameter and grade, which only leaves overtightening.

[Ixion]

The broken bolt does not appear to have broken at the waisted section. Counting the number of threads its's about two thirds down the threaded section. The threads at the end opposite the break look rather mungy too

Just a though - is it possible these are those damn 'torque to yield' bolts ?

[slimjim]

The bolts are more than strong enough, diameter and grade, which only leaves overtightening.

humm would say no to this. grade bolt should be a star or stamped with 8 ..i would only think that bolt in picture to be only 4.5grade...don't belive that a grade8 bolt is used on brake mount..correct me if wrong...however overtighten would snap after heat transfer ..stretching is more than likely a fault of bolt material...would strongly report this to bike dealer, could well be factory fault...as it happen's more often than not..recalls on bikes..had one on 2003vl 1500..petrol tank under seat needed rubber pads fitted to chassis frame to stop wearage of tank and subframe movement..

[The Pastor]

so what torque setting did you use?

it was the tight as a nuns fanny one i thinks

[Maha]

it was the tight as a nuns fanny one i thinks

Thats funnier than you think, considering Flange started the thread...

[imdying]

Just a though - is it possible these are those damn 'torque to yield' bolts ?

No.

humm would say no to this. grade bolt should be a star or stamped with 8 ..i would only think that bolt in picture to be only 4.5grade...don't belive that a grade8 bolt is used on brake mount..correct me if wrong...

Suzuki don't mark their caliper bolts in the traditional fashion, but regardless, they're not underspecced.

Best place to start is having the calibration on the torque wrench snapped, assuming it was used correctly (dry threads?).

[tri boy]

Flogged/ovaled caliper holes?

[Brian d marge]

Cant really see the break clearly but is that rust , ie from a stress raiser ( thread root ) fatigue has worked its magic and why is the threaded portion taking a load??

Still good job keeping the eyes open ,,it could have been alot worse

Stephen

[Max Preload]

That texture on the fracture site looks like brittle failure which would indicate a flaw in the bolt itself, which has propagated. Most of the other damage is post-failure (deformation of the thread profile) which would indicate it's been that way for a little while.

Lucky there are 2 bolts... was this the leading or trailing?

[AllanB]

The consequences of a calliper detaching at speed are about as bad as it gets on a bike..

No disrespect intended Flange, but I believe that it would be worse if you had you bike up on a rear stand, oiling the chain while you are nude and you got your dick caught between the chain and the rear sprocket as you rotated the rear wheel.

[cs363]

No disrespect intended Flange, but I believe that it would be worse if you had you bike up on a rear stand, oiling the chain while you are nude and you got your dick caught between the chain and the rear sprocket as you rotated the rear wheel.

Bloody hell..... I hope your not speaking from experience!!!

[scracha]

Isn't "replace the bolts every time the calipers are removed" the official factory stance ? I don't bother doing this when replacing pads but tend to do this when popping out pistons etc. I've never bothered with loctite either.

[cs363]

Isn't "replace the bolts every time the calipers are removed" the official factory stance ? I don't bother doing this when replacing pads but tend to do this when popping out pistons etc. I've never bothered with loctite either.

I think you may well be correct on that, though it varies from brand to brand.
Most people well over tighten these bolts compared to the factory torque settings.