Rear Brake Caliper Retaining bolts **WARNING**

Just carrying out some routine maintenance last week and was re-attaching my rear brake caliper when one of the bolts sheared.

The picture below shows you the bolt and also the other one which I removed to inspect. As you can see the other has also started to 'stretch'.

I was using a torque wrench so wasn't over-tightening them. Next time you have yours apart give the bolts a good look over.

Will be sending them to Suzuki to see if they have anything to say about them.

BTW they are off a SV650S (2000).

[embee]

This doesn't surprise me.

I haven't liked the "feel" of the (front and) rear caliper bolts when trying to tighten to the manual's torque settings, so I've used a slightly lower value (still torqued, but a bit less). Similarly pinch bolts on yokes etc.

The question of whether they are lubed will influence the torque/tension curve. Torque figures are "usually" given for "lightly oiled" condition, this relates to the protective oil fasteners usually come with from the manufacturer. Manually oiling or using copper grease etc will reduce friction relative to this.

However it would be normal for fasteners to have enough strength in-hand to still be within the elastic limit even allowing for oiling.

I'd be interested to know what grade those fasteners actually are. I'd expect this sort of application would normally use a grade 8.8 as a good strength/toughness compromise.

Looking at the photo, there seems to be some evidence of stretching (narrower diameter of the bolt, wider spacing of the threads).

It'll be interesting to see Suzuki's comments, when you receive their reply.

Thanks for the warning.

A

To be honest the bolts have obviously been overtightened and their response will be to that effect and that it's all your fault.

They will neither care nor believe the fact that they've been torqued up correctly each time so I wouldn't have thought that there was much point complaining about them.

Not wishing to cause trouble but, perhaps more importantly, why haven't you actually looked at them when they've been out before torquing them up? Stretching like that should be obvious with a glance.

Don't worry I've been there as well. I managed to snap a caliper bolt and a pinch bolt on my race CBR600 within ten minutes of my first ever wheel change. The rest of the bolts were between 6mm - 8mm longer than they should have been!

Out of interest how good a quality is your torque wrench?

I have a Draper one which is okay. Had the calipers off my race SV650 about a dozen times last year and had no signs of stretching the bolts.

I agree that I should have noticed it before and I'm also not expecting much of a reply from Suzuki.

The bike was a couple of years old when I got and it's also had the back wheel taken off by tyre fitters so there's been plenty of cases for others to over tighten them.

The torque wrench I use is the low range one from Halfords.

Finally had a reply from Suzuki Customer Services today: -

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Thank you.........

I must advise you that based on your information it would seem your motorcycle was not manufactured for the United Kingdom market.
I have therefore spoken with my Aftersales colleagues who have advised me that in light of the above, Suzuki is unable to justify any request for financial assistance.

In closing........

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Now my letter to them made no request for financial assistance or in fact anything to do with money. All my letter was about was the safety factor of bolts that could shear whilst riding along and that I would await their investigation into an apparent weakness with interest.

Another letter is required I think.

Oh and they kindly sent the bolts back to me

I would say that the torque your using is far too much. What torque have you been tightening them to? and what size bolt is it?
I can look up the charts to see what the correct tightening torque is for a mild steel bolt.
Personally I would never bother with a torque wrench for these bolts, After all they only have to be tight.

Originally Posted by derbybiker

I must advise you that based on your information it would seem your motorcycle was not manufactured for the United Kingdom market.
I have therefore spoken with my Aftersales colleagues who have advised me that in light of the above, Suzuki is unable to justify any request for financial assistance.

sv not made for the uk market?, i could have told you that by the way the crappy ally bolts fluff up when you say "winter"

in all seriousness what does the uk market have to do with caliper bolts torque settings?

IMO those bolts do look like they have been overtorqued, maybe they havent been hardened correctly? who knows

oh blimey i recently had a rear tyre fitted,as i watched what the tyre fitter did throughout i was amazed when the following day my rear brake pedal felt strange upon going home after work. when i got home and inspected, the bolt holding my stableising arm to the rear caliper was missing and my caliper was completely twisted around the brake disc luckily the hose stretched but did not break.after untwisting and refitting a new bolt i wondered wether the tyre fitter (ageing hells angel who looked like he knew what he was doing) did it or as i have just read maybe a bolt sheared off! i wonder if this has happened to anybody else!

interestingly, the K3's haven't got a torsion arm... maybe suzi realised a design fault???