Seeley - Norvil Front Hub Dual disc spoke-caliper clearance

I am working on a Suzuki 500 racer build at the moment. I have had to space the disc over, machine material off the fork leg, but I still had to machine the AP style caliper. There is very little difference between the CP2195 and CP2696 modern replacement in the critical dimensions applicable here.

Don't be afraid to do this it, is a standard approach on many race bikes. Though I don't think you need 3mm, 2mm is enough, maybe less!

Machine at the 12 degree angle used on the casting where it is impacting the spokes. Though in the end I set mine nearer to 10 degrees with the 19" rim I am using. There is a caliper drawing available. You will need to chamfer the hex bolt heads as well, but not so much you don't get a full head grip for tightening.

Because I only have a small mill I split my caliper to do it, with then only the rear of the caliper mounted on an adjustable angle plate. With a bigger mill you won't have to split the caliper and you can machine the bolt heads in situe.

If you want to minimize the machining on the caliper you will need to combine a little of each, disc spacing, leg machining and caliper machining!

You need to do this all in a progressive process, spacing over the caliper as needed to keep the disc central in the caliper! Measure, set next dimension, machine, measure, set next dimension.......you may need to space teh calipers from the mounting bracket!

I was able to take 3mm off of my fork leg, used a 6mm spacer and only have a small clearance disc to fork leg, then took maybe 2mm off the caliper, but this is a different application.....

springer said:

Thanks Chris for taking the time to write, i will post tomorrow with more info about the hub and more. Spokes are not a problem. Last solution will be a new custom fork yoke from minnovation . Calipers are NOS AP 2195 original so will be definitely on the bike. Discs and carriers are also origina 11.5 Norvil from Mick Hemmings , would like to use them too .Could modify Hub maybe. Write tomorrow, thanks

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Here is my Norvil Twin disc Hub. Also My lower Ceriani GP35 forks are 52 mm in diameter. For people that have the CB750 Hub , i d like a favour: to measure for me what is the distance of the effective hub flanges meaning how far apart are the spoke heads on the opposite sides of the hub. Marked as distance A in the photo.
I d like to know , if i am to modify (narrow) the hub what is a good working distance of the spokes at the hub and the hub still is doing ok as with an existing hub (like the CB 750 Hub)

kommando said:

2 CB750 hubs both identical but 1 up and 1 down, 40 spokes and 2 flat disc mounting surfaces even if they are offset slightly.

Distance between 2 disc mounting surfaces

Overall

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THANKS You are great! Can you give me the distance between the flanges where the spokes go ?

SteveA said:

I am working on a Suzuki 500 racer build at the moment. I have had to space the disc over, machine material off the fork leg, but I still had to machine the AP style caliper. There is very little difference between the CP2195 and CP2696 modern replacement in the critical dimensions applicable here.

Don't be afraid to do this it, is a standard approach on many race bikes. Though I don't think you need 3mm, 2mm is enough, maybe less!

Machine at the 12 degree angle used on the casting where it is impacting the spokes. Though in the end I set mine nearer to 10 degrees with the 19" rim I am using. There is a caliper drawing available. You will need to chamfer the hex bolt heads as well, but not so much you don't get a full head grip for tightening.

because I only have a small mill I split my caliper to do it with the rear of the caliper mounted on an adjustable angle plate.

If you want to minimize the machining on the caliper you will need to combine a little of each, disc spacing, leg machining and caliper machining!

You need to do this all in a progressive process, spacing over the caliper as needed to keep the disc central in the caliper! Measure, set next dimension, machine, measure, set next dimension.......you may need to space teh calipers from the mounting bracket!

I was able to take 3mm off of my fork leg, used a 6mm spacer and only have a small clearance disc to fork leg, then took maybe 2mm off the caliper, but this is a different application.....

Click to expand...

This forum and all of you are great. Thank you! I ll probably narrow my hub as the first item but do you know actually how much material there is on the caliper back where we want to machine? i dont want the caliper to lose strength and be prone to fail> If you removed maybe 2mm how much was left.
I begin to think that we ll have to do 2 or 3 mods to everything and gather 2 mils here 1 mil there to achieve the result. I need overall about 4 millimeters each side. And i cannot space the discs apart because if i do they touch the lower fork legs

The distance as you shown is 65mm, further down where the head spokes holes are : 68.12mm (but bear in mind it's the "top" of the hole and the head spoke will go further in )........hope this help , sorry not clever enough to post pics (and no smartphone , old fart you know!)
as mentioned by Steve the two hex bolts are prone to hit the spokes (on that way the grimeca is better)but you may notice there are two washers , so take one out , or both , and add loctite.......

springer said:

THANKS You are great! Can you give me the distance between the flanges where the spokes go ?

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At the circle defined by the centres of the spoke holes from flange outer side to flange outer side is 67mm. So this plus the diameter of the outer spokes is the largest size.

Hmm, In that respect the Norvil Hub is almost the same, almost 65 mm . So the diference is the way the Norvil discs are attached and that these discs are vey thick, i don t have them with me but i believe they are 8 mm thick.

marinatlas said:

The distance as you shown is 65mm, further down where the head spokes holes are : 68.12mm (but bear in mind it's the "top" of the hole and the head spoke will go further in )........hope this help , sorry not clever enough to post pics (and no smartphone , old fart you know!)
as mentioned by Steve the two hex bolts are prone to hit the spokes (on that way the grimeca is better)but you may notice there are two washers , so take one out , or both , and add loctite.......

Click to expand...

I have removed the caliper piston and roughly measured the thickness of the caliper back material. It varies from 6 mm to 8.5 mm , so i believe there are two milimeters to cut from there. Mine have a single washer of 2 mm thickness , so maybe i can replace with a singele half the thickness and chamfer the hex heads

You can get flanged head bolts so no washer needed, but make sure they match the current bolts spec ie 8.8 or 10.9. .

springer said:

I have removed the caliper piston and roughly measured the thickness of the caliper back material. It varies from 6 mm to 8.5 mm , so i believe there are two milimeters to cut from there. Mine have a single washer of 2 mm thickness , so maybe i can replace with a singele half the thickness and chamfer the hex heads

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You answered it yourself, and from memory I had similar figures. Certainly not a problem to take 2mm off. 3mm is unlikely to be much of a problem either, but little steps is better. I did 1mm then re mounted the caliper and checked and then removed another 1mm. The second cut is actually when I changed the angle to 10 degrees.

Hi

Springer,
Discs are 6.5mm thick.
Back of the carrier to the front of the disc is 22mm. The splines for the floating disc?
The carrier itself is 11mm thick.
If you have the new AP replicas of the original calipers you can use button head fasteners. The back of the caliper can be machined. I angled the cut to suit the spoke angle on this Honda K4. Mind you it is a Grimeca.

Norman White has a double disc brake kit including a hub that looks just like a Norvil hub, only narrower. He might be persuaded to sell it separately.

Chris said:

Hi

Springer,
Discs are 6.5mm thick.
Back of the carrier to the front of the disc is 22mm. The splines for the floating disc?
The carrier itself is 11mm thick.
If you have the new AP replicas of the original calipers you can use button head fasteners. The back of the caliper can be machined. I angled the cut to suit the spoke angle on this Honda K4. Mind you it is a Grimeca.View attachment 15559

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Thanks
i have the 2195 original calipers but bolts are similar. They have a 2mm washer and one "curly" lockwasher, i think i can put a 1 mm washer and loctite. I ll take all these into consideration . I just dont want to have only 1 mm of clearance everywhere. I can sure take 2 mm off the calipers and maybe 2 from the hub each side so i believe it can be done but marginally. i ll keep the thread posted.

johntickle said:

Norman White has a double disc brake kit including a hub that looks just like a Norvil hub, only narrower. He might be persuaded to sell it separately.

Click to expand...

Thanks , i ll see that also, or at least take it s measurements.

I have heard of folks using HD front hubs...

grandpaul said:

I have heard of folks using HD front hubs...

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΅Well the thing is , i have all the parts and try to make it as much as possible to the initial idea, otherwise it ll be easy to used more modern discs which are thinner and other calipers.

grandpaul said:

I have heard of folks using HD front hubs...

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Yes , I had fitted one with all the spokes innerwards (no outer spokes ) usefull ....

springer said:

Does the CB 750 hub fits the Norvil carriers and discs? which cb 750 hub is it exactly? It is a good idea, or else maybe i will try to modify my hub narrow it ,since i already have it . That is one option but has to be done carefully because it is a 3 piece interference fit. We have to de-press it with heat , modify it and then re press it together again with the same orientation of the spoke holes.

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I use Ceriani forks and A CB750 hub, with Yamaha TZ350 fork yokes. The front end was originally off a 450 Ducati, but I replaced the yokes to get the trail right. The distances between centres and diameters, all remained the same. The forks don't have provision to mount callipers, so I use an arrangement of aluminium plates. You will find that if you fit the callipers behind the sliders, you can space them out to suit the disc positions. Your problem seems to be the width of the hub. The CB750 hub with two Suzuki steel discs does not foul the sliders.

acotrel said:

I use Ceriani forks and A CB750 hub, with Yamaha TZ350 fork yokes. The front end was originally off a 450 Ducati, but I replaced the yokes to get the trail right. The distances between centres and diameters, all remained the same. The forks don't have provision to mount callipers, so I use an arrangement of aluminium plates. You will find that if you fit the callipers behind the sliders, you can space them out to suit the disc positions. Your problem seems to be the width of the hub. The CB750 hub with two Suzuki steel discs does not foul the sliders.

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I myself thought that the problem is the hub but considering i want to use my norvil discs and carriers and my my Lockheed calipers, The hub is not a problem. After measurements , it is comparable to the CB 750 hub and considering that i would have to make carriers that would fit the Norvil disc (for the cb 750 hub) the result would be the same. The main problem is that the Ceriani GP35 lower slider is 52mm in diameter and that is that limits most other clearances. Anybody could measure me the Norton Fork slider?
It seems that i have to cut 1-2-3 mm from each component in order to fit what i have...

Hi Springer
I will measure my Norvil fork leg tomorrow.
Ps in my garage I have a brand new set of Minovation yokes for 41mm BMW forks. Elliptical spacers?
Chris