Brake "anchor" bolts

[BultacoBen]

Having noticed some movement in the anchor stay against the plate I removed the anchor bolt which revealed itself to be very worn, with lots of movement in the plate.

I ordered what I suspected to be the correct part, 014807 (in fact the s/steel version 014807S) only to find it seems fractionally too large to screw in. I suspect the removed bolt is not original; it has "S CL UNF" as far as I can make out (it's quite corroded) stamped on the top.

The two offending bolts and associated plate are pictured below. Any suggestions on what the correct bolt is?

Many thanks

brake copy.jpg

[Rob Harknett]

014807 is a brake anchor stay bolt for a heavyweight front wheel, but is it a lightweight you have ?
Always best to search for the part number you need, not part description, may need 042879 rear anchor stay bolt. There will be movement fore and aft if its the rear brake, to allow for wheel/chain adjustment. A bit of up/down movement not too much to worry about.

[Andy51]

Hi, if the bolt is 3/8 UNF, then it is 24 tpi as opposed to 26 tpi for the BSC that I believe it should be. If you use a long enough spanner you can force a UNF bolt in but it will b*****r the female thread. I suspect this is what someone has done (I have found this on a bike, who knows how many bodgers have been at a bike over the last 50 years!). You could try running a BSC tap through the female thread, if it goes in easily then perhaps the bolt wasn't UNF, but if it feels as if it is cutting then you may have to helicoil or get a new brake plate. The steel inserts are very difficult to replace. Andy

[Rob Harknett]

before you do that, as I pointed out, if your bike is a lightweight try the correct bolt, not a heavy weight front anchor bolt

[Janet]

I'm sure Ben would try the correct bolt be he's probably had the same difficulty I've had in finding out what that bolt is. If anyone knows what is the bolt that fits through the front brake anchor arm into the brake plate on a 250CSR , please would they tell us.

[Rob Harknett]

EEmm. For what its worth and it may not prove much. I have just removed the front anchor bolt from my 66 G2CSR a 3/8" 26 tpi nut spins on freely by hand. Its 9/16" long under the head and I have a thick spring washer fitted. However there are hacksaw signs a PO has cut down a longer bolt. I do not believe the club stocks the lightweight part number bolt. Just a tech bit, I do have a bolt fitted. I am sure a bolt is not threaded all the way to the head, if it is, its called a screw. Am I correct??? If so the bolts pictured are screws. A bolt may fit a little tighter in the torgue arm bolt hole.

[Janet]

Thank you Rob. I could have taken mine off but I would be none the wiser to know what it was/is regarding size, threads etc although I have recently learned the difference between a screw and a bolt. I used to think that screws had pointy tips and bolts were flat.

[56G80S]

It's a long time since I had my 14CSR, which was also a 1966. But Rob's point on the screw / bolt matter is important IMHO. The fit on the stay itself is important, it takes a lot of hammer and "chattering" can lead to other problems and is perhaps less lijely with bolt as opposed to screw?

I can say that the fit on my G80S stay and bolt are very close but can't say from memory if the two bolts are the same or have differences. In my view the full depth of engagement (without bottoming) is important.

When I finish this I'm going to check the reference material because I've never fitted a washer of any description under the bolt head but have taken to using a drop of Loctite even though I'd previously found this bolt a challenge to remove. Could be I've been doing it wrong for the last 35 plus years, wouldn't be the first time.

I currently use an old hexagonal BSA ring spanner which is completely flat at the open ends, i.e. there's no slight relief at the open end as there is sometimes with sockets. This allows good purchase on the bolt head and avoids any slipping on the chrome.

Johnny B

[BultacoBen]

Janet is correct, was unable to find a parts number in my manuals for the front anchor bolt, and on AMOC spares the heavyweight bolt didn't obviously identify itself as such.

A shame spares don't carry any. The extracted UNF screw spins in very easily so I will just get a UNF replacement and see if it has any less movement.

Thanks very much for taking yours out and measuring though, Rob. 9/16" seems quite short with the stay and a thick spring washer under there as well. The one I've taken out is 3/4", and I think I'll replace with the same length.

The incorrect heavyweight front anchor bolt is really a bolt as there is an unthreaded section under the head. I agree that this makes sense for a bolt that touches the stay there. The threads on the extracted screw are very clearly worn in this area in particular.

Am also aware the movement may be caused by the hole in the stay going oval since it doesn't have enough 'meat' around it. This can, I gather, be resolved by the use of a stay in this shape http://www.amoc-parts.com/store/comersu ... duct=21383 rather than this http://www.amoc-parts.com/store/comersu ... duct=21343

[Rob Harknett]

I should re confirm, my 66 G2 CSR bolt is not original, so length and the spring washer probably incorrect. ( I have no washers on my heavyweight anchor bolts ) The lightweight parts list does give a rear anchor bolt part number, perhaps they are the same. I would also add, for quickness I tried a nut on my lightweight bolt. Never seem to be able to find my thread gauges. The 3/8" cycle nut did start to tighten near the bolt head.