vintage drum vs. disc

Hi, everyone.

I'm working on my '73 cb350 twin for the spring, and I have a couple of
concerns:

The stock disc/single piston caliper was poor last year, at best.
Honestly, do you think that I'll get better performance from the cb350's
TLS drum, or the classic caliper with a new ferodo pad and a deglazed
rotor? I've also noticed that the disc's performance was especially poor
in the wet. Will a drum exhibit this behavior? What about said disc
brake with the pad and deglaze?

Also, I need to pick a pair of tires. I've fitted new 2.15" x 18" hoops.
I want as sticky a tire as I can get for the street. I've heard good
things about the Avon Roadrunners, but have no experience. How about
sizes? I'll be running stock forks, with my new 1/2" longer-than-stock
koni shocks out back. what do you think about 90 section up front, 110 in
back?

Thanks!

-Sean

 

cb350's TLS drum, or the classic caliper with a new ferodo pad and a
deglazed rotor?

I would stick with the disk brakes, drums suck. The only reasons for
using drums is that you're riding a classic bike that you want to keep
original or you're racing in some vintage class that won't let you
update your machine...

If you can find some higher friction pads, you'll get better brakes at
the expense of more lever effort and quicker wear on the rotors. Back
in the mid-1970's knowledgeable riders would switch to Ferodo pads to
get a harder pad with more "feel", and the Ferodos were just the ticket
to replace those soft original equipment pads that were so grabby
they'd make the front end dive going into corners...

Front end dive makes riders nervous because 1) they feel like they are
going over the handlebars and 2) the reduction in rake and trail
changes the steering feel too much...

For better braking performance, you might try semi-metallic or even
sintered metal pads. The semi-metallics offer more friction, and
increase rotor wear. The sintered metal pads have the most friction,
but they will wear the rotor out rapidly, and if you don't have a stack
of old rotors handy, you'll be upset at the price of a new one every
year

Have you tried using the front brake lightly to skim the water off the
surface, before applying it harder to stop?

Poor wet weather performance was one of the reasons why we used to
drill holes in our disks. The other reasons were that it made the
rotors lighter and they looked "trick", just like the racers had in the
magazines...

When the Brit bikes came out with Lockheed brakes in the late 60's,
they used a cast iron rotor, which has better friction characteristics
than the slipprier stainless steel rotors that Honda and other Japanese
manufacturers chose. Stainless steel will discolor and turn brown if
you heat it too much, but at least it won't rust...

There was a manufacturer of cheap aftermarket iron rotors in the
1980's, but I don't remember who it was. I wasn't paying attention when
my rear brake pads wore out once and the steel-against-steel contact
gouged the rotor badly. Stainless steel is harder than that, it
wouldn't have been so badly damaged...

Stainless steel is so tough, it's hard to drill holes in it. You need a
drill press, a bunch of those hard black drills, lots of cutting oil,
and patience, patience, patience. You can apply machinist's blue to the
rotor, divide the brake surface into as many segments as there are
spokes in the rotor carrier that's riveted to the rotor, and scribe a
pattern of arcs from the inside edge to the outside edge using the same
radius as the outer edge of the disk and start center-punching pilot
holes at regular intervals on the arcs you've scribed. Then drill small
pilot holes at each punch mark and use larger sizes to make the holes
whatever size you want. I've seen guys drill so many 3/8th inches holes
in their rotors they looked like swiss cheese...

So far as wet drum brakes are concerned, if you ride your Honda trough
a puddle deep enough to immerse the brakes, you won't have any brakes
until you dry them out by dragging them for a few miles and they might
be very grabby during that time...

Drum brake grabbing is normal for that design. When you first apply the
drum brake, only part of the brake material on the shoe comes in
contact with the rotating drum. There is a self-energizing effect as
more and more of the brake material comes in contact with the drum...

And drum brakes were always high effort brakes. There was lots of
friction in the cables and the linkages, and racers had to anticipate
stopping early, so they could plan to "throw out the anchor"...

Well, you can do that on a race track, you know what's ahead of you and
there are flagmen to warn you about unseen problems ahead, but what
about the street?

Racers wanted more of that self-energizing effect I mentioned above, so
they experimented with higher friction brake pads. The retarding force
that you get on the brake from the force applied by the friction
material is called "mu" (uprintable Greek letter). If you get 1/3 of a
pound of retardation for a pound of pressure, that's 0.3 mu...

Those 0.3 mu pads would sometimes have so much self-energizing effect,
they would lock up completely and stay locked...

I talked to one guy who rode a chopper in the 1970's. Chopper riders
didn't like front brakes, though. He only had the drum brake on the
rear, and he fitted it with sintered metal brake shoes so he could ride
the mountain roads everyday. The sintered metal shoes wore his brake
drum out rapidly...

What about said disc brake with the pad and deglaze?

I used to deglaze the *brake pads* on my *undrilled* stainless steel
rotors annually. The pads would glaze and begin squeaking so I knew it
was time to sandpaper them. The de-glazed pads would clean the rotors
off, I never sanded the rotors...