Turning Front Drum Brakes:

Greetings ;

Well, I went through a period of time where I decided to sell my beloved 'strunzo'. Thankfully, a couple of long rides on perfect days cured me of that passing fancy. It's been especially nice to get out and ride given that I have everything (exept for a weeping kickstart shaft) sorted out nicely... as far as I got on my restoration. It's a one kicker, pulls strongly and hasn't let me down on the side of the road for quite a long time.... and OH that exhaust rumble.......

It's time to turn my attentions to refining some of the areas that I didn't do before. One glaring issue is the front brakes. (drum :TLS) When I got the bike , there was standing water on a section of the braking surface and it had rusted a bit. I had access to a lathe when the hub was disassembled so I LIGHTLY turned the rusted area to get it smooth again. Then relaced the wheel, new shoes and a few internal parts.... the front brakes stop pretty well .. but it pulses, meaning I should have kept going on the lathe, but I didn't trust my skills.

.....so that's the LONG winded intro to my two -part question: 1: is there enough steel on the braking surface of a Commando front drum to get them properly lathe-turned AND.....2: do you know who might specialize in doing such work? I e-mailed Buchanans but their website doesn't mention machine services so I'm assuming not.

as always, thanks for your valuable opinions and collective wisdom

Karl:

and thanks to the Access Norton member ( you never gave me your user name: is it RX7171?) who's e-mail in part helped me with my decision to hang on to my baby. (he intercepted my CL ad...mentioned here in a couple places.) 8)

Try Vintage Brakes http://www.vintagebrake.com/ The guy is very knowledgeable and helpful, should be able to answer all of your questions and I would expect that late fall would be a good time to ship them out to him. He gets pretty busy.

Dave

Thanks, Dave:

i sent them an e-mail to check it out. i can't believe I'm the only one who'se ever thought to have the front drum turned.....

thanks again.......any other opnions on this?

karl

I arced the shoes, but apparently my rim was OK. I don't have any pulsing. You may want to try the shoes before you get into the hubs. I just glued (tacky glue from a sewing shop) #60 sandpaper in the hub and ground the shoes to fit. Took about an hour, turning the wheel by hand and adjusting the front brake adjuster to keep grinding the shoes down. It sure improved the front brake. I remember it was like dragging feet before and now it works. It hauls me down from 60 real fast. But don't expect it to do it time and time again, it fades pretty quick with heat. And that's with the high friction RGM shoes. At least I can use them now.

Dave
69S

I've got a Bear disc/drum brake lathe in my shop and am always willing to try to cut a drum or rotor for an unusual application that might come through the door, UNLESS we can't establish the manufacturer's maximum finishing diameter (for drums). I have no idea how far the 8" Commando can be safely cut but, that aside, I would think there must be a shop in your area which would be willing to try but there is a caveat. On my machine, for example, there is no way to cut it with the wheel still laced, but I suspect you're anticipating that.

A dedicated brake lathe is the way to go if possible rather than a regular lathe since it doesn't produce a continuous cut - there is a break in the advance of the cutter in each revolution which produces a finish which is not trying to "screw" the shoes in the direction of the cut.

DogT has a good point as well; after you cut the drum the shoe will only contact the swept area in its center. Re-arcing the shoe to fit the new diameter helps but, of course, most techs won't do that anymore because of the airborne particulates generated. Man, I remember working the special machine we had to re-arc shoes when I was a kid in my Dad's shop and we would just blow the dust off. I still have the machine but it hasn't seen use in decades.

It is important to find someone who can turn the drum while the rim is still laced on.
The spoke tension can distort the drum enough to pull it out of round.

I dont think you will find anyone who will spend the time to set up a complete wheel to machine the drum, anyone prepared to do that will be few and far between, if you find some one be prepared to open your wallet.
I've machined heaps of Norton front drums with out problem , the Norton front drum is a sturdy bit of gear, it will take some good spoke pulling to pull it out of shape, I manufacture my own shoes and "arc" them myself personally, I had to do this coz the ones available "genuine" Norton , Ferodo etc were all under size before you fit them, the ones I bought and measured were half worn out before you start, I'm not the only one to confirm this, I would guess that when these shoes were made , probably in Asia somewhere they were probably made for 200mm not 203.2mm (8") hence most of your adjustment is taken up before you start,

If you think the Norton drum is OK to machine without the rim, that's fine. I'm going by what several racers recommended, people who have plenty of experience setting up drum brakes.
The guy who did my Honda charged me $60 I think ( a few weeks ago) I can't remember exactly how much he charged, but I don't recall it being expensive. We are fortunate here in Brisbane to have some brilliant engineers who like bikes and charge reasonable prices. The guy who did mine used to be Phil Read's mechanic on the Grand Prix circuits.

Thanks, I'm from Brisbane also.

Thank you for your replies, all. So turning the drums can and has been done... good to know. I already knew that I'd have to disassemble the wheel. This isn't a problem for me because I've laced dozens of wheels (admittedly competition bicycle wheels ) My nephew , a fresh graduate of the motorcycle institute laced and trued them for me originally (because I didn't have a motorcycle truing stand) and there is the chance that he didn't get the tensioning nice and even, and that might be responsible for some of the pulsing I'm feeling. Before going to the machinist, I think I'll pop off the tire, throw it on a truing stand re-true/retension it and see if that takes carte of the pulsing. It's stopping pretty well but the pulsing is moderately bothersome. I'm from the 'rumble around at 45-50 all day " school rather than someone trying to do vintage racing. but brakes is brakes.... gotta have them!

thanks again:

Karl

I've resurrected a few drums with a rust mark on the bottom.. a die grinder with a flapper wheel and some gentle hand work. Yes, it's ghetto, (or as we say here, "Hillbilly") yes, the purists will faint dead away like the old biddy in the Polaner All Fruit comercial, but it has worked for me. And worked well. JFWIW

Concours, I notied that your from Cow Hampshire.... so , like me, your remedy would indicate that you're a 'parsimonious northerner" (translated cheap-ass yankee........as I am) 8)

Actually, I did that as well to knock down the rusted area in addition to minor turning. brake works fine except for the pulsing. I'm going to look towards the truing issue first before complete dissassembly/turning.

thanks

Karl

Karl,
About that weeping kickstart. I cured mine quite simply (albeit after putting up with it for years) by changing to a 25mm x 4mm O ring. It's a tighter fit in the groove than the standard imperial one.

Martin

thanks......I love 'over the counter auto parts store' fixes...... I'm going to put a drip pan under it for the rest of our riding season (which on Cape Cod is through November) .....then I'm going to cure that ill as well.

kfh