Commando drum brakes

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JimC said:
I've asked this before. Does anyone know why Norton first put the disc on the right side? Why are all the rest, that I know of, single discs on the left side? My guess is Norton first put the disc on the right because it was cheaper to do so.
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The answer is quite simple, Norton could use the same left hand lower fork leg with either a drum or a disk, both of which were produced at the same time.

Jean
 
Jeandr said:
The answer is quite simple, Norton could use the same left hand lower fork leg with either a drum or a disk, both of which were produced at the same time.
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When Norton changed from a right-hand front disc to a left-hand disc for 1975, they just swapped the fork legs over, so they could have done that in 1972 if they had wanted to.
 
It appears that Norton didn't realize, until 1975, that the front disc was to be on the left side. If it made no difference Norton sure as heck would not of changed from right to left side. Now, the question is, why are front discs on motorcycles on the left side? I have a 72 Combat with right side disc and it handles and stops fine, with a much upgraded front brake system.
 
JimC said:
I believe all single disc brakes are on the left on today's bikes, regardless of rear brake position. I have never seen a motocrosser with a right front brake.
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Buell's front disks are on the right, and their back brake is on the opposite side. I'd say Eric Buell knows a little bit about handling, too.
 
JimC said:
It appears that Norton didn't realize, until 1975, that the front disc was to be on the left side.
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But they didn't use a rear disc until the '75 Commando which, for whatever reason, apparently made the change necessary? One theory I heard is because disc brakes are 'outboard' of the wheel, the force exerted during braking twists the forks more than a drum brake that operates on the centre line of the wheel, even though a drum back plate still requires some form of torque location to the leg?
 
Buell's front disks are on the right, and their back brake is on the opposite side. I'd say Eric Buell knows a little bit about handling, too.
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I didn't know that. With the exception of the Buell, are there any other with a right side single disc up front? Eric Buell marches to a different drummer, that's for sure. Since all master cylinders are on the right it would be simpler, hence cheaper, to not crossover. I know there are motorcycles with both front and rear brakes on the same side, but still maintain a left side front brake.
 
Maybe the whole right-side / left-side thing is balancing all the parts on the bike left to right?

Master cylinder & lever on the right, disc & caliper on the left = closer balance instead of lopsided to the right?

Eh. Whatever. They all seem to work relatively well regardless of what side they are on.
 
ludwig said:
LAB, dthis is not correct . Only 2 things matter : the contact point of the tire with the road and the anchor point of the brake at the fork leg . the location of the brake is irelevant .[
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Well, as I said, it was only "One theory I heard"
 
L.A.B. said:
Jeandr said:
The answer is quite simple, Norton could use the same left hand lower fork leg with either a drum or a disk, both of which were produced at the same time.
Click to expand...


When Norton changed from a right-hand front disc to a left-hand disc for 1975, they just swapped the fork legs over, so they could have done that in 1972 if they had wanted to.
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Yes, but the reason the caliper on the Norton was on the back of the fork leg from the get go was to bring it's mass closer to the steering axis, when Norton changed to a left side caliper, some beleived the handling suffered because the weight of the caliper was further away from the steering axis, not to mention it did not look as good (to me). If you look at modern bikes, their calipers are always close to the steering axis, or if you prefer, on the back of the fork legs. Norton was right back then contrary to the accepted standard of the Hondas which had positioned their calipers on the front of the fork legs.

I don't know what prompted the move to the left for 1975, probably they had fired the engineers and the factory squatters thought they would sell better, but if you look at pictures of those bikes, you see the drain plugs were not relocated, so it was just assembled left to right. Probably they could relocate a bit of weight to the left to ofset the weight of the back caliper and at a time the factory was not doing too well, there no money to be invested in a new lower left fork leg which would have required a new or differently machined right lower fork leg. The only screw up Norton had made was with that ofset hub which precluded easily going to dual disks. No one would need two front disks anymore than operating a PC with more than 640Kb :lol:

Jean
 
My understanding was that the forces induced by the brake were better dealt with by mounting the caliper(s) aft of the fork leg(s), so that the mass of the fork leg structure could serve as a larger area for dissipation.

In other words, caliper(s) mounted ahead of the fork leg(s) have only the small amount of material on the casting enclosing the mounting bolts to absorb all of the braking force and transfer it to the mass in motion (the bike, through the forks).

So, on a bike with a single front disc brake caliper held on by two bolts, the entire braking force is transferred through the small amount of aluminum surrounding each of the two bolts!

Anyone see a problem with this?
 
grandpaul said:
So, on a bike with a single front disc brake caliper held on by two bolts, the entire braking force is transferred through the small amount of aluminum surrounding each of the two bolts!

Anyone see a problem with this?
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I have been a little concerned by that, and would be more so, if a considerably more powerful disc/caliper combination was used on the left side?

But has anybody known the mounting lugs to break when used with a left-hand disc?
 
Norton found by swapping the caliper over to the other side stopped the Commando pulling to the left when riding with "no hands". I have seen the calcs why, but hell who cares just keep both hands on the bars.

Cash
Mk3 that runs straightish some of the time and stops on a tanner.
 
Anyone see a problem with this?
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The theory is good if you are trying to stop a 10,000 lb motorcycle and have a caliper and and servo assisted mastercylinder with a tire contact patch equivalent to a tank tread.

Seriously, the walls of the fork leg are thinner and weaker than the caliper mounts. If you applied enough force to break the mouinting lugs, the legs would have disintegrated a long time before that.

I'm convinced the whole thing was decided in the styling department. I'm not so sure an engineer had anything to do with designing that set-up. If one had it would work better! :wink:
 
I don't know about sides, but I always want the calipers behind the fork legs. This for mass centralization (buzz word), lowering the Moment of Polar Inertia of the fork assembly. The farther away weight is from the steering stem, the worse it is. Front mounted calipers also move weight farther from the CG, also bad. Are there currently ANY front mounted calipers on modern bikes?
 
Michael "Mercury" Morse is the guy we send our drum brakes to be put right.
 
MercuryMorse,
Welcome to the forum! Your expertise here is greatly appreciated. Your theory makes the most sense, keeping the weight as near the line of the steering stem as possible.

As far as Norton is involved, I still believe the stylists made the change from right to left.
 
Ron,

I agree that stylists may of made the right to left decision on the Norton, but did stylists account for the major motorcycle manufactures chosing to mount the single disc on the left? I really think there is some technical reason for doing so.

I, too, appreciate Michael Morse's expert input.
 
Only two out of the four Japanese manufacturers of that time (72-75) actually put their front disc brakes on the left-hand side, and that was Honda and Kawasaki. Yamaha (TX/XS/RD models) and Suzuki (GT models) didn't, although all of them were leading caliper designs.
 
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