Check your front brake anchor arm.

CAB · Post by **CAB** » Thu Apr 22, 2010 8:32 pm

Hello gents.

The bolt did not fail, it was the end of the brake stay. It must have fatigued over time, fractured from the lower edge of the hole to form a hook and then the hook must have straightened out. I distinctly felt two events before the front wheel locked. I will post some photos when I download them.

I have since spoken to the club and Steve Surbey. Apparently AMC modified the brake stay (but kept the same part number) so that it had a bulbous end around the bolt. Steve sells one like this but made from thicker material as well. Guess which one I'm buying? Steve also said that he had seen plenty of original ones with elongated holes and won't sell them second-hand.

The stay looked reasonably new, I would imagine it was a replacement part or a rechromed original. I bought the bike from a chap who didn't really get on with it (it was a bit of a let down compared to his previous bike). The owner before him did the bike up (I think) but then moved abroad.

I keep the bike at my dad's and we have been sorting out the bugs (new carb, setting up the electronic ignition, clutch, rewiring it, solid state regulator, LED stop light, halogen bulbs, bigger AGM battery etc). It's only done a few short runs and was going very well compared to when I first had it (always spitting back/cutting out, sooty plugs, would not hold a charge). On Thursday we did about 20 odd miles and it was holding charge with the pilot light on or dipped main beam on all the time. We did a nut and bolt check and gave it another run on Friday of about 30 miles and it let go about a quarter of a mile from home. I'm glad it happened to me and not dad as I don't think he would have bounced as well as me.

I think we need to make a safety critical page on the forum for things like this and the rear hub issue especially for new club members like me. I will also submit the photos for the magazine showing the original and replacement parts.

I don't remeber seeing a washer but Steve Surbey said that there should be one. I'm not sure I like the idea of a serrated shake-proof washer damaging the surface and setting up fatigue cracks.

I don't suppose anyone has a spare CSR fork slider do they...?

CABEdited by - CAB on 22 Apr 2010 7:33:43 PM

itma · Post by **itma** » Thu Apr 22, 2010 10:10 pm

quote: I think we need to make a safety critical page on the forum for things like this and the rear hub issue especially for new club members like me.

there is no need; sensible use of the frequent question and search facility will throw up a selection of answers to just about any question.

this brake stay problem has been covered many times over the years; the only "safety critical" factor involved is the mechanical competance of previous owners [or even the present].

So many people don't know the difference between a set bolt and a set screw, too many think that stuffing a stainless item in is good engineering; excessive chromium replating will take its toll;
preventative maintenace such as a weekly check of all fixings is not high on a lot of riders lists of things to do betwen polishing it.
secondhand parts bought from the ignorant at jumbles or off ebay dont help either.

your item failed because it was subject to the stresses generated because the bolt in the end was loose/defective or badly fitted in some way, not because it "fatigued"
sorry to sound a bit harsh on a newcomer but as your profile is blank there is no way to judge your own ability.

these "special washers" are just internally toothed shakeproof washers; certainly I would not use one, and if the late Biscuit, our resident ace engineer[ among others] didn't either, then I am doubly convinced they are not necessary.

top tip
never buy a bike that is described as having "been done up"
dead cert its a wreck under the paint

CAB · Post by **CAB** » Fri Apr 23, 2010 12:24 am

Sorry Itma I strongly disagree.

You can only use the search function to find a problem if you know specifically what to look for. If there was a page labled as "Safety Critical Checks" it would be obvious and may prevent death or serious injury to both new comers and you old timers alike. There are pages and pages of information on here. How many people have trawled through them all?

I know the difference between a set screw and and a bolt.

The bolt was not loose, the bolt did not fatigue, the lug at the end of the brake stay did. The item itself is in tension every time the brake is applied. The presence of the hole acts as stress raiser and there is insufficient material around the hole anyway. The fact that the component was redesigned by the factory suggests that there was a problem with the OE part.

I'm afraid I don't know anything about your ability either but I'm an aerospace stress engineer and I'm sure it is a fatigue failure.

I don't want to get into an argument with you, my day job is designing primary structure for civil aircraft where safety is the primary concern and that was my reason for starting this thread. If you can offer practical advice with regards to fitting these parts correctly then please do so.

CAB

wilko · Post by **wilko** » Fri Apr 23, 2010 12:37 am

This is a subject for mythbusters.Can we pick up two tons weight hanging from a brakestay, I'll get back to you! I have a spare one to play with.

itma · Post by **itma** » Fri Apr 23, 2010 12:39 am

"If you can offer practical advice with regards to fitting these parts correctly then please do so."

I have done so.
if you disagree thats fine by me.
no offence meant

the reasons for the failure of this part and its redesign are well documented.

In 40+plus years of AMC ownship I have never had a problem with this item, old type or new.

I'll repeat my assertion that the 'critical safety factor' is generally the previous owner[s] who 'did it up' there is no way to cover all the permutations of bodgery I have seen committed on these bikes.
You want to make sure its safe? take to bits and start over again.

The search facilty works well enough on key words or phrases, granted it could be improved a bit.
You don't have to read the lot.

John Donne · Post by **John Donne** » Sun Apr 25, 2010 12:18 pm

If you have this problem, then fit the later P11 item, part number 021474. These were fitted to all the P11 models, and the G80CS models with the later 5 fin hubs. Use the bolt 014807 with a lock washer 014119, with this hub, or it may be a retro fitted to the earlier hubs. Also the top of the anchor arm bolts onto stud 01624, with a nut 000004, and a lock washer 014117. I have never had this problem, and the P11 is really under braked, with the 750 Atlas engine fitted, expecially when carrying a passenger. AMC had a fix for all the later bikes. This problem is the same as that other road kill problem, the rear wheel bearing, oil seal and cup reversal issue. I had some of these stays made a few years back, and had them chromed, but no one was interested in buying any of them.

wilko · Post by **wilko** » Sun Apr 25, 2010 11:51 pm

I just informed this old codger at a british rally yesterday that he had his brake on the wrong side and that it was dangerous for the brake stay to be under compression. HIS REPLY WAS THAT THEY FITTED THEM BOTH SIDES so i just walked away....

dave16mct · Post by **dave16mct** » Mon Apr 26, 2010 12:18 am

Take a look at this on ebay now, 290428989143. The brake stay is not only on the wrong side but is held on by a nut and bolt. It even looks wobbly in the picture! I've sent an email but don't know what the reaction will be.

Don Madden · Post by **Don Madden** » Mon Apr 26, 2010 3:29 am

Wilco, we old codgers are a very positive lot--Just as positive when wrong as when right! Stays should alwas be in tension, never compression--Hic! Cheers, Don.

SPRIDDLER · Post by **SPRIDDLER** » Mon Apr 26, 2010 10:57 am

quote:
Stays should alwas be in tension, never compression--Hic! Cheers, Don.

Shame no-one pointed this out to Nora Batty