Help - Front caliper fail = big crash

keezx

Built up, you can't see if the brake nut is long enough.
Sloppy build>nut loosens> crash>shop to blame.

One more reason to build your bikes yourself.

markk91

Agree- very true. And you dont really want to mess with it once built up.

Beatmaker

They may come with more than one though. My SRAM always did. So if there are left overs and they are long it might suggest they did use a short one.

Ah right. Last time I purchased calipers they only came with one length.

superkenners

Sounds incredibly painful. Get well soon.

I find it hard to believe you can fit a brake caliper and only just get it to bite. Usually the thread bites well in advance of the caliper even starting to bite against the fork. In fact you would not be able to fit a caliper like that without knowing that it is incorrectly fitted IMO. So I would be enquiring about the bike shops insurance policy.

rolf_f

Superkenners wrote:

Usually the thread bites well in advance of the caliper even starting to bite against the fork. .

Yes, because usually the nut is long enough. If it's too short, it won't bite well in advance. Which is what people keep saying because it is likely the correct explanation (if the nut was long enough but loose, the caliper would be obviously wobbling around long before it had a chance to come off).

daniel_b

Beatmaker wrote:

They may come with more than one though. My SRAM always did. So if there are left overs and they are long it might suggest they did use a short one.

Ah right. Last time I purchased calipers they only came with one length.

My Ultegra 6700 and 6800's both came with, IIRC, 3 different lengths of the recessed type bolt - to cater for different fork setups one would assume.

superkenners

Rolf F wrote:

Superkenners wrote:

Usually the thread bites well in advance of the caliper even starting to bite against the fork. .

Yes, because usually the nut is long enough. If it's too short, it won't bite well in advance. Which is what people keep saying because it is likely the correct explanation (if the nut was long enough but loose, the caliper would be obviously wobbling around long before it had a chance to come off).

Yep, agree with that. Point was that the person installing it would have struggled to fit it with the short nut (if it was literally attached by a thread), which in itself should have triggered alarm bells. Ultegra (all Shimano in my experience) brakes come with two or three different nut lengths so no real excuse on that front. So in terms of the sloppy mistake/negligent scale, I would side towards the latter and not cut them any slack (if only for sake of other potential customers).

flanners1

Get well soon.

Have scanned most of the posts. Do you have the caliper? May be worth examining the thread to see if it was stressed/thread was stripped etc. Nasty experience. Having built a fair few bikes I was amazed the different length bolts needed for differing forks.

markk91

Flanners1 wrote:

Get well soon.

Have scanned most of the posts. Do you have the caliper? May be worth examining the thread to see if it was stressed/thread was stripped etc. Nasty experience. Having built a fair few bikes I was amazed the different length bolts needed for differing forks.

Thank you flanners and for all those whom have replied. Will visit the shop again today.....

veronese68

markk91 wrote:

Will visit the shop again today.....

Good luck, let us know how you get on.

dyrlac

How bad was the femur fracture? Did mine in July (fairly clean but fully displaced distal third, fitted with an antegrade intermedullary nail and a total of 5 locking screws). Off the bike for effectively three months (ill-advised turbo sessions midway through notwithstanding), but back on since the beginning of November, still looking for missing watts. GWS!

bigmat

It sounds to me like most likely cause is using a caliper nut that was too short and only attached by a couple of threads. As a result either those threads were under a lot of force and suffered from premature stress failure, or maybe the nut didn't engage the threadlocked part of the bolt and therefore worked loose. If you still have the caliper then you should be able to work out how far the nut was threaded on, and compare this with standard length nuts / depth of your fork to establish what length was most likely to have been used and whether this was the probable cause of the accident or not. If you went the legal route you would probably get a metallurgy expert to look at the parts and come to a conclusion. I should add that I have had to order longer nuts for certain bike builds and always err on the side of caution - it should be pretty obvious if a nut and bolt "only just" engage and common sense says this is not acceptable. For the injuries you have suffered I would certainly consider looking to the shop / its insurers for compensation. Only you can say what the real cost of the accident is but could poetentially include significant loss of earnings, loss of amenity, long term health implications etc as well as immediate pain and suffering. Not good!

darkhairedlord

I would not try and refit any parts to see how they go or start trying different length nuts. If you do you may damage any evidence of negligence on the part of the mechanic. Get lawyer-ed up, you are in hospital because someone else wanted to finish off quick and go to the pub instead of concentrating on their work. If you can find the nut in the vicinity of the crash site that would help, so go borrow a metal detector and get looking. However, for a sleeve nut with threadlock to come undone requires some effort on the hex wrench. The only way its coming off by accident is if it was never on properly.

mac9091

Come on we're all gagging for a picture You got an X-Ray??? Anyways get well soon, must have been some crash.

As for the threading of the cylinder bolt: You should be able to see where it was tightened up to by either a bit of rust on the exposed threads or a small amount of grease build up. A pic may be useful.

Brake calipers come with a range of bolt lengths (recent purchase of 105 groupset came with 5 lengths)

Ok so you should have made sure that your bike was race worthy but that doesn't mean that the shop can't still be at fault. When i check my bike over I don't recall ever making sure that my caliper bolts were tight, check the brakes function yes but tight no. Obviously if i had stripped the brakes out to repair/replace then i'd have subconsciously noticed if they were loose or tight on removal.

And on that note i'm off to check the tightness of all my bolts on my new build.

Semantik

Painful experience for the OP should be a lesson learned for all reluctant home mechanics- never trust someone else to do a job you can do better yourself.

And if the rest of us learn only one thing from this thread it should at least be the correct name of the part referred to, which is THE PIVOT NUT.
And the fixed male threaded part it attaches to is called the BRAKE PIVOT BOLT.

And there are five different lengths of pivot nut available for the Ultegra calliper. Torque setting is between 7.8 and 9.8NM.

Tech docs here: http://bike.shimano.com/media/techdocs/ ... 820619.pdf
http://bicycletutor.com/torque-specifications/

Barbarossa

If you were racing, you must be a BC member. Have you spoken to their legal team?

If the threadlock on the bolt isn't marked, I would take this as strong evidence that the wrong length nut was used.

on-yer-bike

Maybe the LBS used the rear caliper on the front. The only difference being the length of the fixing bolt (the threaded part that protrudes from the rear of the caliper. It would take a very long sleeve to make proper contact with the bolt in this scenario. Now that is something you could prove.

fenix

Wouldn't that mean the front caliper is on the rear ? I thought that has a longer bolt than the rear one ? It'd stand out a mile ?

lesfirth

Rolf F wrote:

Superkenners wrote:

Usually the thread bites well in advance of the caliper even starting to bite against the fork. .

Yes, because usually the nut is long enough. If it's too short, it won't bite well in advance. Which is what people keep saying because it is likely the correct explanation (if the nut was long enough but loose, the caliper would be obviously wobbling around long before it had a chance to come off).

A few months ago I was cleaning my bike when I noticed there was a 5mm gap between my forks and front brake. The nut was slack. I fitted it and I went cold when I thought of what the consequences might have been.This was about 3 months after the build and several hundred miles. There had been no juddering, no noise and the brake worked fine. It was a used caliper on a new frame and I had needed a new longer nut when assembled. The bolt went about 10mm into the nut.I used coppaslip when I fitted it . It could be me that did not tighten it enough but I certainly check it regularly now.

meanredspider

Coppaslip is an odd choice when threadlock is what they come supplied with. Have you had them seize before?

lesfirth

meanredspider wrote:

Coppaslip is an odd choice when threadlock is what they come supplied with. Have you had them seize before?

Yes. That area gets showered with water and road muck.

debeli

I, too use Copaslip and similar on these threads.

I've yet to have one come undone, but have always been able to remove them when I've wanted to.

I am told by experts that I should use Loctite or similar and I nod sagely and continue to do as I always have.

One day I am going to have a bicycle dismantle itself under me as I descend at high speed... and if I survive I shall deny ever having used Copaslip and tell everyone that this post was hacked.

But until that happens, yes I do use it.

meanredspider

lesfirth wrote:

meanredspider wrote:

Coppaslip is an odd choice when threadlock is what they come supplied with. Have you had them seize before?

Yes. That area gets showered with water and road muck.

The threadlock should stop water ingress into the mating threads.

Semantik

lesfirth wrote:

meanredspider wrote:

Coppaslip is an odd choice when threadlock is what they come supplied with. Have you had them seize before?

Yes. That area gets showered with water and road muck.

If your bike is without 'guards then you don't have to resign yourself to this problem at all. One simple but effective solution will save all that sh*t getting in there - cut a small square of electrical tape and stick it over the back of the fork covering the pivot nut - no muck can get in there once you have done this.

kayakerchris

One simple but effective solution will save all that sh*t getting in there - cut a small square of electrical tape and stick it over the back of the fork covering the pivot nut - no muck can get in there once you have done this.

I really dislike the appearance of that piece of electrical tape. The other very simple trick is to use discs.

fenix

I'd take a bit of tape over discs any day. ;-)

Semantik

Fenix wrote:

I'd take a bit of tape over discs any day. ;-)

A fair bit cheaper too.

lesfirth

Semantik wrote:

lesfirth wrote:

meanredspider wrote:

Coppaslip is an odd choice when threadlock is what they come supplied with. Have you had them seize before?

Yes. That area gets showered with water and road muck.

If your bike is without 'guards then you don't have to resign yourself to this problem at all. One simple but effective solution will save all that sh*t getting in there - cut a small square of electrical tape and stick it over the back of the fork covering the pivot nut - no muck can get in there once you have done this.

Thanks for the bright idea. I think a little circle will do the job.I will need a few. I check the nut is tight ever 2 minuets! I wish I was clever .

svetty

Helicopter tape??

homers_double

A blob of clear silicone, failing that take advice from your man Kayakerchris up there /\