Front disc upgrade

Andy Higham · Saturday at 6:17 AM

I have found a reasonably easy doner disc for a front conversion.
Suzuki VZ1600 Marauder. 320mm diameter, 61mm bore, 13mm offset and 5 hole fixing.
I can make a centering ring to suit the Norton hub and then pop the rotor on the dividing head to drill the mounting holes, half way between the existing ones.
I bought a cheap Chinese rotor to play with, if it works well I can buy a higher quality rotor

concours · Saturday at 7:40 AM

Andy Higham said:
I have found a reasonably easy doner disc for a front conversion.
Suzuki VZ1600 Marauder. 320mm diameter, 61mm bore, 13mm offset and 5 hole fixing.
I can make a centering ring to suit the Norton hub and then pop the rotor on the dividing head to drill the mounting holes, half way between the existing ones.
I bought a cheap Chinese rotor to play with, if it works well I can buy a higher quality rotor

Are you going to fit two discs? For symmetry?

Andy Higham · Saturday at 7:44 AM

I would love to but that is a mahoosive job

B+Bogus · Saturday at 8:44 AM

concours said:
Are you going to fit two discs? For symmetry?

I like a bit of symmetry.
Symmetry and weight.

Fast Eddie · Saturday at 8:46 AM

Symmetry. With less weight…

Andy Higham · Saturday at 9:02 AM

Asymmetry with even less weight.
100g of thick cut smoked bacon please?

20260214_155633 by Sigma Projects, on Flickr

MexicoMike · Saturday at 9:08 AM

What are you converting FROM?

Andy Higham · Saturday at 10:21 AM

Standard Norton iron non floater and calliper to 320mm floater with Yamaha 4 pot calliper (gold spot)

Dedubyah · Saturday at 12:31 PM

I am going to convert to RGM's 12" disc. I have considered Don Penders conversion but don't like the look of a disc that large, haven't decided on whether to keep the std caliper or go to a 4 pot Brembo

acotrel · Saturday at 12:58 PM

If you are going to use the bike at high speeds through a lot of corners, you will need twin discs. A Commando engine is heavy. DO NOT use cast iron discs - only steel. The discs on my Seeley 850 are from a 1970s Suzuki 750. They ARE NOT CHROMIUM PLATED. I still had difficulty finding pads which were effective. I use 2 AP Lockheed calipers with a master cylinder which was designed for one. My front brake is one-finger operation and I use a Yamaha twin-pull quick action twist-grip. The rider should not have to think about what their hands are doing, when riding fast The quick action twist grip avoids having to move the hands on the grip. With my motor, the throttle needs to be wound-on in a controlled fashion. I have 3 fingers and a thumb around the throttle, and use the front brake with my forefinger. If I grabbed the brake with all fingers, I would crash. Using restraint is psychological. Never panic, always calculate. Disc brakes do not change much as they heat up.

Andy Higham · 2026-02-15T06:31:50-0700

I have been working out details of the calliper mount and centering ring using CAD.
Keeping 2mm clearance between the calliper and spokes and 2mm clearance between disc buttons and fork leg, when I build the wheel I can move the hub 3mm towards the disc side. This will add an extra bit of cone to the disc side spokes, which has to be a good thing.
I have sent a DXF file to the laser cutters for the calliper bracket, getting it cut in 5mm aluminium for a trial to see if everything works as it should. Once it's right it will be 10mm 6082-T6

grandpaul · 2026-02-15T07:23:47-0700

I used to just send my OEM discs out to DBR to have them drilled.

I even came up with my own pattern once.

Before & after-

Plain rear, fancy front-

Dedubyah · 2026-02-15T18:19:46-0700

acotrel said:
If you are going to use the bike at high speeds through a lot of corners, you will need twin discs. A Commando engine is heavy. DO NOT use cast iron discs - only steel. The discs on my Seeley 850 are from a 1970s Suzuki 750. They ARE NOT CHROMIUM PLATED. I still had difficulty finding pads which were effective. I use 2 AP Lockheed calipers with a master cylinder which was designed for one. My front brake is one-finger operation and I use a Yamaha twin-pull quick action twist-grip. The rider should not have to think about what their hands are doing, when riding fast The quick action twist grip avoids having to move the hands on the grip. With my motor, the throttle needs to be wound-on in a controlled fashion. I have 3 fingers and a thumb around the throttle, and use the front brake with my forefinger. If I grabbed the brake with all fingers, I would crash. Using restraint is psychological. Never panic, always calculate. Disc brakes do not change much as they heat up.

This is a 1973 Norton 850 Commando I am talking about, not a sport bike. If I wanted to ride like that, I would have not sold my Ducati 999R.

Front disc upgrade

Andy Higham

concours

Andy Higham

B+Bogus

Attachments

Fast Eddie

Andy Higham

MexicoMike

Andy Higham

Dedubyah

acotrel

Andy Higham

grandpaul

Dedubyah

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