Dual Rotor Commando, that looks almost stock

M

motoalchemist

VIP MEMBER
Joined
Jun 13, 2010
Messages
395
Country flag
Hello,
wanted to post some pictures of the Dual disc Conversion Ive been working on the past 6 months. The rotors are RGM as is the hub and spokes. You may not be alble to see it, but the spokes all lace from outside -in. Not sure how sturdy this will be, but was necessary to make room for the CP2696 calipers. the fork ends are from Andover and the mounting holes required a bit of oversizing. I had to use a 19mm radial master cylinder and custom stainless hose to get the proper feel. The shimming process was slow and cumbersome, but if anyone else want to do this ill disassemble the axel and show measurements. lots of fettling to get this to all fit. But its been worth it.
 

Attachments

  • Dual Rotor Commando, that looks almost stock
    PXL_20250816_235926673.MP.jpg
    385 KB · Views: 436
  • Dual Rotor Commando, that looks almost stock
    PXL_20250816_235820648.jpg
    374.2 KB · Views: 416
  • Dual Rotor Commando, that looks almost stock
    PXL_20250816_235849971.jpg
    228.7 KB · Views: 351
  • Dual Rotor Commando, that looks almost stock
    PXL_20250816_235837085.jpg
    279.5 KB · Views: 317
  • Dual Rotor Commando, that looks almost stock
    PXL_20250816_235815709.jpg
    277.5 KB · Views: 421
In the photo of the whole bike, the rear tyre looks a bit odd, what size is it? 18"? Also the fast back tail fairing looks to be angled downhill, That is usually an indicator of a bent rear frame loop.
 
Moto,
Could you tell me what a radial master cylinder is. I have been reading about them for years and have no knowledge about them and how they work.
Thanks,Mike
 
The older master cylinder as per Commando is an axial arrangement, the piston is moved at 90 degrees to the movement of the hand on the lever. Radial is where the movement of the hand is applied directly to a piston that moves in the same direction. The elimination of the 90 degrees changes the feel and action.
 
You must have a lot of travel in your master cylinder. I use two Lockheed AP calipers with a master cylinder designed for one. I use the front brake with my forefinger, while the other fingers operate a quick-action twin cable throttle.
 
A very nice arrangement.

I raced with a similar dual AP Lockheed caliper setup on my PR somewhere back in the mid '80s. I used the original PR slider switched over to the left side, and a repro right side slider from Mick Hemmings, along with the original PR splined disk on one side and a second one on the other side. I first used the original AP Lockheed 9/16" master cylinder that the bike came with came with, which gave a very light pull when used with the dual disks. I liked the light pull, until I crashed during a race at Willow Springs after a panic grab at the lever locked up the front wheel at the end of the front straight. After all the broken ribs and collar bone healed, I replaced the master cylinder with a similar AP Lockheed one with 5/8" bore, the one originally meant for the Norvil dual disk setup. I was much happier with that. It required a more normal pull on the lever, but gave really good feedback. I raced with that setup several times, until I crashed at Daytona when the Hemmings repro slider broke through the axle hole going into the hairpin turn. I think it was probably my fault because of some machining I had done to the slider. But I didn't uses that setup again, because I was switching over to 18" mag wheels with slicks and a Ceriani front fork with a different pair of disks. But I still had the AP calipers and 5/8" master cylinder, and it still worked very well.

Edit - Corrrection - The 5/8" bore master cylinder was not the one meant for Norvil dual disk setup. Norvil listed the 9/16" bore master cylinder for both the single and dual disks. I think it was Mick Hemmings who recommended going to the 5/8" bore for the dual disks. Or maybe I just decided it was a good idea, tried it, and liked it. That was all a long time ago, and my memory is no longer as reliable as it used to be. I'm passing on info based on my own experiences, and do my best to correct anything I get wrong.

Ken
 
Last edited:
' they'd done em , back then . Mr Schmarts H2 SEELY kwickersaki .
Dual Rotor Commando, that looks almost stock


As in there were Handed R & L ' Norvil TYPE roadholder legs . incidently MANX were FORGED .
Something else to worry about . were Norvil . ?

Dual Rotor Commando, that looks almost stock
 
Dual Rotor Commando, that looks almost stock

both legs the same , ere .

Dual Rotor Commando, that looks almost stock

READS .

Think I saw a picture of Williams , at Imola or the Bol dor with dual 11 inch discks , recently . Maybe L & R legs ? mighta bin Croxford . 75 ? P R Commando Works Bike anyway.

s'nuther .
Dual Rotor Commando, that looks almost stock


good Job , anyway . they reckon they ' steered ' with ONE Disc . If you tried real braking - twisted the forks .
THATS why you pull the pinch bolts on the clamps down , after theyve ' settled in . Can set e ' just pinched '
untill youve run a few miles , so it IS tightening in the right ' set ' .

you can do handstands now ! Stoppies , is it .
 
Last edited:
Yeah, some interesting oddities in the way Norton fitted the dual Norvil disks, using two of the same sliders as in the single disk that was standard on the PRs. It had the caliper in back of the slider on one side, and in front on the other. You could buy three types of kits from Norton to convert a Commando front end to a "750 Racer" or "750 Formula Racer" configuration. First was kit No. 9, to convert to a single Norvil disk setup. Next was kit No. 10, to convert to a dual Norvil disk setup. And finally, kit No. 11, to convert a single Norvil disk to a dual Norvil disk setup. I've attached the pages from the Technical Release N3/12 showing the three kits.

Page 14 1200.jpg


Page 15 1200.jpg


Page 16 1200.jpg


Ken
 
Last edited:
A note of interest for anyone wishing to make this sort of conversion, in case you haven't noticed. The original Norton parts list shows the dual disk setup using two identical sliders, part no. 063547, which puts the caliper in front on one side and in back on the other. As shown in the original post, the sliders Andover Norton now supplies are available in two configurations, 06.3547/L and 06.3547/R, so you can put the calipers on in a symmetrical arrangement, like the one this thread is about. I think that's a much superior design compared to the staggered calipers shown on Mick Grant's bike in Matt's post.

Ken
 
My current set up.
I experimented with a radial m/c but got it wrong and the braking was decidedly mediocre!
It was a 21mm m/c and adjustable down to 18mm.
I recently saw huge improvements with it by reducing it to 18mm, but next I’m swapping the radial m/c for a ‘normal’ Brembo of 16mm diameter which, according to the charts, is the correct size.

IMG_7626.jpeg
 
Last edited:
lcrken said:
A very nice arrangement.

I raced with a similar dual AP Lockheed caliper setup on my PR somewhere back in the mid '80s. I used the original PR slider switched over to the left side, and a repro right side slider from Mick Hemmings, along with the original PR splined disk on one side and a second one on the other side. I first used the original AP Lockheed 9/16" master cylinder that the bike came with came with, which gave a very light pull when used with the dual disks. I liked the light pull, until I crashed during a race at Willow Springs after a panic grab at the lever locked up the front wheel at the end of the front straight. After all the broken ribs and collar bone healed, I replaced the master cylinder with a similar AP Lockheed one with 5/8" bore, the one originally meant for the Norvil dual disk setup. I was much happier with that. It required a more normal pull on the lever, but gave really good feedback. I raced with that setup several times, until I crashed at Daytona when the Hemmings repro slider broke through the axle hole going into the hairpin turn. I think it was probably my fault because of some machining I had done to the slider. But I didn't uses that setup again, because I was switching over to 18" mag wheels with slicks and a Ceriani front fork with a different pair of disks. But I still had the AP calipers and 5/8" master cylinder, and it still worked very well.

Edit - Corrrection - The 5/8" bore master cylinder was not the one meant for Norvil dual disk setup. Norvil listed the 9/16" bore master cylinder for both the single and dual disks. I think it was Mick Hemmings who recommended going to the 5/8" bore for the dual disks. Or maybe I just decided it was a good idea, tried it, and liked it. That was all a long time ago, and my memory is no longer as reliable as it used to be. I'm passing on info based on my own experiences, and do my best to correct anything I get wrong.

Ken
Click to expand...
I keep all of my fingers of my right hand around the quick-action throttle except for the forefinger. And I never grab the brake. My first race bikes had drum brakes, which could heat-up and crash me. When I race, the front brake needs to be that sensitive. I am not slow and steady. I have never liked entering corners behind other guys. With discs, I can brake in mid-corner. When I had drum brakes, it was a nightmare. I usually ride a slower bike faster. The Seeley 850 is a very easy ride for me. There is no way it can crash. With my 500cc Triton, there were many ways.
 
Back
Top