F/ Disc brake hub centralised?

When lacing up the front wheel, the rim isn't central to the flanges of Norton's disc brake hub 062867. This causes an undesirable stress pattern in the spokes.
I am pondering, if the wheel is laced such that the rim is central to flanges, would it be possible to machine the hub and provide spacers for fitment in the Roadholder fork, while retaining the disc brake?
A different type of caliper may be required.

Please share your views. Has someone performed this mod?

- Knut

mdt-son said:

When lacing up the front wheel, the rim isn't central to the flanges of Norton's disc brake hub 062867. This causes an undesirable stress pattern in the spokes.

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The offset causes no problems as far as I'm aware, plus the original disc-side spokes are 8 SWG.

mdt-son said:

I am pondering, if the wheel is laced such that the rim is central to flanges, would it be possible to machine the hub and provide spacers for fitment in the Roadholder fork, while retaining the disc brake?

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That would be a solution in search of a problem in my opinion.

mdt-son said:

A different type of caliper may be requiresd.

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It would, as the hub offset provides the necessary spoke clearance for the Norton Lockheed caliper.

Thanks, Les.

I do see some benefits if caliper clearance can be resolved. For instance, using 40 spokes of equal length and SWG instead of 4 different types, making wheel lacing a breeze. More important are the safety aspects of course:
When braking hard, spoke tension is distributed on 20 spokes instead of 10 only.

The use of SWG 9 spokes in a disc brake wheel is almost loughable and a sign of an initial design for a low torque braking system. In a modern design (4 piston caliper, 320 mm brake disc), SWG 7 spokes would be used.

A zero offset modification was performed by member Ludwig many years ago, if I'm not mistaken.

- Knut


[Edited]

I use twin discs with Lockheed calipers. My rim is centralised, I simply re-engineered the caliper mounts. Never do a bodge job on your front brake - you need it too much. My front forks are Ceriani from a 450 Ducati. and my yokes are Yamaha TZ350 - there is still plenrty of room for the calipers.

The original Dunlop MC275 rim is bulged and drilled for the dish of the front wheel, so you are also looking at replacing that item. I would agree with a complete remove and replace of the original forks with something compatible is the only safe way to do this.

mdt-son said:

I do see some benefits if caliper clearance can be resolved. For instance, using 40 spokes of equal length and SWG instead of 4 different types, makes wheel lacing a breeze. More important are the safety aspects of course:
When braking hard, spoke tension is distributed on 20 spokes instead of 10 only.

Click to expand...

Where is the evidence that the standard disc wheel is in any way unsafe?

Somewhere around 30,000 Commando disc front wheels must have been produced and as far as I'm aware I've never yet heard of one collapsing with the puny original disc or an uprated disc assembly.

mdt-son said:

The use of SWG 9 spokes in a disc brake is almost loughable and a sign of an initial design for a low torque brake system. In a modern design (4 piston caliper, 320 mm brake disc), SWG 7 spokes would be used.

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Yes, but it isn't a "modern design", therefore doesn't need more than 9 SWG spokes (on the non-disc-side and heavier 8 SWG on the disc-side spokes) for the puny original Lockheed brake. In my opinion 40x, 9 SWG would have been more than adequate.


If you were to seriously upgrade the brake then the complete front end would need a rework including changing/widening the forks and fitting a completely different disc brake but that's a different subject to moving the hub of the original wheel assembly for what I would consider to be to no advantage, safety or otherwise.

Jdub said:

The original Dunlop MC275 rim is bulged and drilled for the dish of the front wheel, so you are also looking at replacing that item. I would agree with a complete remove and replace of the original forks with something compatible is the only safe way to do this.

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True, a new rim would need to be drilled slightly different to the original. No big deal. Dimple pattern 1 x 1 remains as is.

- Knut

"This causes an undesirable stress pattern in the spokes."

Please list where/how/when this has been a problem in functionality.

One of the simpler solutions is to use a Production Racer front wheel, which is centered, along with its splined mount disk and a period AP Lockheed caliper, all of which are still available from suppliers like Andover and Norvil. You can either use a PR fork leg with it's integral caliper mount, or and adapter for the standard Commando fork leg. It does take a little machining, but nothing complicated.



Ken

You beat me to it Ken !

And there’s the option of very light discs from Norvil.

But whilst at it, why not stick another lightweight disc in t’other side ?!

It seems I have poked a holy cow!

Les, I never claimed the original design is "unsafe", that's your wording. Wheel design seems to have been dictated by the puny 10" disk and Lockheed caliper.

I didn't bring the theme up to remedy a deadly shortcoming in the original design. However, it's a fact many owners seek to improve the original system by fitting huge disks and 4-6 piston calipers, still keeping the original hub and wheel, and it frightens me.
A venture like this is risky, hence the idea to modify the hub and spoke pattern to increase the safety margin.

A wider fork would be fine, but it doesn't produce a better of safer braking system. If I can make the improved system work for 7-3/8" fork tube spacing, why bother with wider forks?

Ken, Eddie: Yes, if a twin disc system is desirable and I wanted preserving the classic Norton connection, a Norvil production racer hub and braking system is the only viable solution. It's rather expensive though (£1800-1900).
Many riders find a single disc system good enough.

- Knut

mdt-son said:

Les, I never claimed the original design is "unsafe", that's your wording.

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Well, you did say...:

mdt-son said:

More important are the safety aspects of course:

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...Which to me, implied you thought there was an underlying issue of "safety" with the existing wheel assembly.

mdt-son said:

Wheel design seems to have been dictated by the puny 10" disk and Lockheed caliper.

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Precisely, so it's not practicable to try to move the hub unless the complete brake assembly is changed.

mdt-son said:

However, it's a fact many owners seek to improve the original system by fitting huge disks and 6 piston calipers, still keeping the original hub and wheel, and it frightens me.

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But it isn't known to cause any problems whatsoever as far as I'm aware, so maybe your fears (which I don't share even though all the front spokes of my Mk3's front wheel are 9 SWG) are unfounded.

mdt-son said:

A wider fork would be fine, but it doesn't produce a better of safer braking system. If I can make the improved system work for 7-3/8" fork tube spacing, why bother with wider forks?

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Simply because you then have more space to centralise the hub as you seem to consider that to be important.
The whole reason the existing hub is offset is to provide sufficient space for the Norton Lockheed caliper and the caliper can't be moved further out because the face of the disc is already close to the fork slider.

"
still keeping the original hub and wheel, and it frightens me.
A venture like this is risky, "

Help me understand, what it is you are afraid of?

mdt-son said:

It seems I have poked a holy cow!

Les, I never claimed the original design is "unsafe", that's your wording. Wheel design seems to have been dictated by the puny 10" disk and Lockheed caliper.

I didn't bring the theme up to remedy a deadly shortcoming in the original design. However, it's a fact many owners seek to improve the original system by fitting huge disks and 4-6 piston calipers, still keeping the original hub and wheel, and it frightens me.
A venture like this is risky, hence the idea to modify the hub and spoke pattern to increase the safety margin.

A wider fork would be fine, but it doesn't produce a better of safer braking system. If I can make the improved system work for 7-3/8" fork tube spacing, why bother with wider forks?

Ken, Eddie: Yes, if a twin disc system is desirable and I wanted preserving the classic Norton connection, a Norvil production racer hub and braking system is the only viable solution. It's rather expensive though (£1800-1900).
Many riders find a single disc system good enough.

- Knut

Click to expand...

FWIW, my experience with my PR was that the original single disk was more than enough for the period (treaded) race tires. I didn't go to two disks until switching to slicks and 920 engines. I think the single PR (Norvil) setup is a superb brake, and all I would ever need on a street bike. It's significantly superior to the standard Commando disk setup.

I also have looked at the stock front hub and wondered if it would work to machine the disk mounting side and lace a new rim (wider, in my case) to convert it to symmetric lacing, but never gave it a try. It looks like it could be done, though. I think the only problem might be, as you mentioned, finding enough clearance between caliper and spokes. The PR setup did require machining the inside of the slider to clear the disk, as well as a bevel on the back of the caliper to clear the spokes. You might have to do something similar when using the stock caliper. It does look like an interesting project to try, though.

If you go for it, please post the details for the rest of us.

Ken

This is an 11" disc with the AP Lockheed caliper. It does the job absolutely fine. No the wheel is not offset, nor is the caliper machined.

And actually, to create the pad track for the lightweight alloy carrier, a stock Commando disc was cut down and used. I still have this disc. For me, it is pretty good evidence that a Commando disc is not as the OP stated 10"!

The hub is a Seeley copy, same bolt pattern as Rickman hubs and discs. Rickman discs were 10" until late 1975 when the front went to 11" at the same time the forks were changed from Rickman 41mm to Betor 38mm. The current forks are 35mm Maxton, which use 600 Honda style cartridges. And no, the larger diameter forks were not stronger, because the 41mm tube wall thickness was pretty thin!

Recently I have changed the disc for another alloy carrier with a PFM pad track, which is both a fraction thicker and marginally larger in diameter, really, marginal it is still a nominal 11" disc. With the new disc, I am using different pads for great feel and stopping power. This is mainly to reduce lever effort for my small and ageing hands!

But the most important component in this system is the correct size master cylinder!

Is your front tyre really that sticky?

mdt-son said:

Les, I never claimed the original design is "unsafe"

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This causes an undesirable stress pattern in the spokes.

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I read this the same way as LAB, an undesirable stress pattern is the same as saying unsafe.

SteveA said:

This is an 11" disc with the AP Lockheed caliper. It does the job absolutely fine. No the wheel is not offset, nor is the caliper machined.

The hub is a Seeley copy, same bolt pattern as Rickman hubs and discs. Rickman discs were 10" until late 1975 when the front went to 11" at the same time the forks were changed from Rickman 41mm to Betor 38mm. The current forks are 35mm Maxton, which use 600 Honda style cartridges. And no, the larger diameter forks were not stronger, because the 41mm tube wall thickness was pretty thin!

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Yes, it can be done using different parts, however, that's drifting away from the original question about whether it's possible to do so by machining the original hub.

mdt-son said:

...would it be possible to machine the hub and provide spacers for fitment in the Roadholder fork, while retaining the disc brake?

Click to expand...

L.A.B. said:

Yes, it can be done using different parts, however, that's drifting away from the original question about whether it's possible to do so by machining the original hub.

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Yes, I know it isn't directly relevant. Mea Culpa.

Really, I was just reacting to the statement that the Commando has a 10" disc.

Thanks for the drawing, which eloquently illustrates my point. It has a 280mm disc (11.023622047 inches)

kommando said:

I read this the same way as LAB, an undesirable stress pattern is the same as saying unsafe.

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Yes, but as British chaps, instead of saying 'unsafe' we might state: 'it isn't as safe as it might be'. Very little is.

A solution might have been moving the fork legs further apart and allowing the hub and rim to run central. But that might have been seen as 'overengineering'.

Certainly expensive, and possibly ugly?