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V7 Special rear brake squeek

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GUZZIPETE View Drop Down
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    Posted: 03 Sep 2017 at 12:27
Just fitted a new set of rear brake shoes and now have a loud squeel. It doesn't seem to be helped by the lack of a return spring for the pedal, because it goes away if you lift the pedal whilst riding. The adjuster is backed off as far as it will go, and the brakes aren't binding specifically, but are obviously enough to cause the squeel. I have checked the shoes to make sure that the leading edge is facing the right way.
Any useful tips appreciated.

Pete.
1971 Moto Guzzi V7 Special
1976 Moto Guzzi 850T
1977 Moto Guzzi Convert
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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 03 Sep 2017 at 17:13
The shoe springs should be strong enough to return the pedal smartly to its stop on the brake light switch.or the footrest depending on adjustment.I cannot on my Loops lift the lever whilst riding as it is already as high as it can go.Are your shoe springs tired? Or perhaps one of them has become dislodged.

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1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GUZZIPETE Quote  Post ReplyReply Direct Link To This Post Posted: 03 Sep 2017 at 19:09
Thanks for that Dave.

I think the reason for the sagging pedal was that the shoes were slightly oversize for the drum. Even with the adjuster backed right off, the shoes were still binding.

I took the drum off again to look at the witness marks on the shoes. The first 1" of the leading edge one shoe showed the most wear, and the other shoe had light marks over its entire surface.

I put the drum assembly with shoes on the lathe to check for run-out, using the wheel spindle as the centre. It was only about 20 thou or so out around the circumference, acceptable limits I thought. So I took a light skim off the friction surface, maybe 0.5 - 1.0mm (sorry to mix the imperial and metric, old habits and all that). That resulted in extending that first 1" long high spot to about 2". 

After putting it all back together, I now have more adjustment, so that has taken the play out of the pedal.

I think that basic problem was that the shoes were very slightly oversize and/or not quite concentric.

I haven't road tested it yet, but no squeeking when you push the bike, which there was before.

Hopefully problem solved? Well that one anyway, it is 45 years old afterall.

Was that your GT I spotted at a gathering on FB yesterday? Recognized the Cravens.

ATB

Pete.
1971 Moto Guzzi V7 Special
1976 Moto Guzzi 850T
1977 Moto Guzzi Convert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ranton_rambler Quote  Post ReplyReply Direct Link To This Post Posted: 03 Sep 2017 at 20:24
The springs in my rear brake are incredibly strong. When it comes to replacing them I think I'll have make a tool to spread them so I can get them out. I can do the fronts with a big screwdriver, but not the rears.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 03 Sep 2017 at 22:21

Was that your GT I spotted at a gathering on FB yesterday? Recognized the Cravens.

ATB

Pete.
[/QUOTE]
I don't know Pete.I was at Baskerville Hall for the ILOC International Rally with Phil and Shaun among others.Could that have been it?

TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 04 Sep 2017 at 09:07
Slimming the friction surface to fit the drum was common practice when racing bikes had drum brakes. I remember getting my Commando 2LS done by Joe Dunphy. Made a useless brake into a slightly less useless one.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote GUZZIPETE Quote  Post ReplyReply Direct Link To This Post Posted: 04 Sep 2017 at 11:33
The springs on the shoes are different on mine, one is thinner wire than the other. I don't think that's right, as they both have the same part number in the parts book.
I have read about skimming shoes on old race bikes, it seems to make sense. It's surprising how uneven the wear can be on an old set of shoes from one end of the friction material to the other. They must start off only contacting for a small section of the friction area.
It would be good to compare two sets on the same bike, with and without skimming?

Dave, I guess that must have been the Baskers ride out, it didn't reference the location on FB. I hope you weren't the only Guzzi? Maybe the only Loop though? I hope it was a good weekend.

Pete
1971 Moto Guzzi V7 Special
1976 Moto Guzzi 850T
1977 Moto Guzzi Convert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 04 Sep 2017 at 11:56

The springs on the shoes are different on mine, one is thinner wire than the other.(Quote)

That certainly isn't right Pete.New springs required I reckon.
I don't know how to find the FB photo but never mind.It was a good Laverda rally,mine was the only Guzzi there but no one seems to mind.

TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GUZZIPETE Quote  Post ReplyReply Direct Link To This Post Posted: 06 Sep 2017 at 08:23
Stein Dinse don't seem to list the springs (12 63 62 00). I've emailed Mandy to see if they can supply them.
Sounds like you had a good weekend at Baskerville Dave, I haven't managed to get to that one yet. Good to hear you were flying the Guzzi flag.
Pete.
1971 Moto Guzzi V7 Special
1976 Moto Guzzi 850T
1977 Moto Guzzi Convert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GUZZIPETE Quote  Post ReplyReply Direct Link To This Post Posted: 06 Sep 2017 at 08:52
Mandy at Stein Dinse has come back with another part number for the springs (12 63 82 00). So I'll get a pair ordered and see if they match.

Pete.
1971 Moto Guzzi V7 Special
1976 Moto Guzzi 850T
1977 Moto Guzzi Convert
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