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Measuring Brake Disc offset
Benzo - 12/4/13 at 04:03 PM

Hi,

I want to know how to measure the correct disc offset correctly?

If this diagram correct?



Inside of the mounting Fact to the front edge of the braking face?

Thanks.

Benzo - 12/4/13 at 04:29 PM

Oh, and if this diagram is correct, is it measured the same way for brakes with a Alloy centre bells?

rodgling - 12/4/13 at 04:43 PM

I think it's more usually front-edge-of-braking-surface (as you show) to the face that the wheel touches. But I guess it doesn't matter as long as the recipient of the diagram understands what you mean? Why do you ask?

Benzo - 12/4/13 at 05:12 PM

quote:
Originally posted by rodgling
I think it's more usually front-edge-of-braking-surface (as you show) to the face that the wheel touches. But I guess it doesn't matter as long as the recipient of the diagram understands what you mean? Why do you ask?


Because i want to mount my calipers to my hub, and then find discs to fit.

They are Jade 6 pots Calipers going on a 266mm disc with Ford PCD on the Triumph TR7 V8

Does anyone know of any websites or spreadsheets where I can cross reference - disc diameter / disc width/ pcd & disc offset.

[Edited on 12/4/13 by Benzo]

rodgling - 12/4/13 at 05:30 PM

Well, you can be flexible in the offset by changing your calliper bracket (assuming they don't mount straight to the hub)? Or go for custom hats and rotors, then you can specify the offset you want on the hats (I've just recently gone down this path).

rusty nuts - 12/4/13 at 06:37 PM

Try your local motor factors for an old brake catalogue, should give you all the brake disc info you need as well as part number , applications etc

Benzo - 12/4/13 at 07:03 PM

quote:
Originally posted by rusty nuts
Try your local motor factors for an old brake catalogue, should give you all the brake disc info you need as well as part number , applications etc


Thank you, I've a mate has a motor factors I'll see if he has any old catalogues!

CNHSS1 - 13/4/13 at 09:43 AM

ive emailed you a pdf that should help with off the shelf sizes and offsets

CNH

Benzo - 13/4/13 at 10:03 AM

quote:
Originally posted by CNHSS1
ive emailed you a pdf that should help with off the shelf sizes and offsets

CNH


Email received, thank Craig!

Benzo - 14/4/13 at 02:36 PM

quote:
Originally posted by rodgling
Well, you can be flexible in the offset by changing your calliper bracket (assuming they don't mount straight to the hub)? Or go for custom hats and rotors, then you can specify the offset you want on the hats (I've just recently gone down this path).


Who did you order you discs and bells from mate?

I think this will certainly be the lightest route for me to go.

Trying to work out my costs at the moment.

rodgling - 14/4/13 at 04:01 PM

Rotors are Wilwood from Rally design (£70 each), hats are custom from BG Developments (£240 for two including postage & VAT). So not a cheap option, but the end result is a total of 3.7 kg each for a pair of vented 280mm discs, which is a massive improvement over the stock discs I was using (5.5 kg). The hats are really nicely done, 360 g each !!!, top marks to BG Developments.

[Edited on 14/4/13 by rodgling]

Benzo - 14/4/13 at 04:22 PM

quote:
Originally posted by rodgling
Rotors are Wilwood from Rally design (£70 each), hats are custom from BG Developments (£240 for two including postage & VAT). So not a cheap option, but the end result is a total of 3.7 kg each for a pair of vented 280mm discs, which is a massive improvement over the stock discs I was using (5.5 kg). The hats are really nicely done, 360 g each !!!, top marks to BG Developments.

[Edited on 14/4/13 by rodgling]


Rally design do these universal bells ~£60 each..

http://www.rallydesign.co.uk/index.php?cPath=562_579

Whats your opinions? then you can have them drilled..

That is a significant saving.. did you have any feedback on the Wilwood discs before you bought them? They list what im after 266mm vented, then just order some universal bells to the right offset.

rodgling - 14/4/13 at 04:37 PM

I looked at those but they look like they need a lot of work to finish them according to this:

http://www.rallydesign.co.uk/pdf/designing_4_pot_brakes.pdf

- also some of the dimensions didn't work for me, I think the inner radius was too small to sit over the hub and the rotor PCD was not right. Also I didn't like the sound of "all bells are intentionally left with 5mm excess machining allowance on faces A, B and C" - i.e. you get to machine those bits yourself. This is what I ended up with:



which I'm very pleased with. I just went for the Wilwood rotors as they had something the right size (280 mm) and spec.

rodgling - 14/4/13 at 04:41 PM

If you do decide to go the BG route, let me know and I will send you the CAD drawing they used for mine - obviously the dimensions will be wrong for you but you will know all the dimensions you need to supply.

matt_gsxr - 14/4/13 at 04:43 PM

http://www.brakesint.co.uk/ has a good technical section showing dimensioned drawings, free to use but after your 30th (or so) search it locks you out unless you buy something.

Matt

Benzo - 14/4/13 at 05:17 PM

quote:
Originally posted by rodgling
I looked at those but they look like they need a lot of work to finish them according to this:

http://www.rallydesign.co.uk/pdf/designing_4_pot_brakes.pdf

- also some of the dimensions didn't work for me, I think the inner radius was too small to sit over the hub and the rotor PCD was not right. Also I didn't like the sound of "all bells are intentionally left with 5mm excess machining allowance on faces A, B and C" - i.e. you get to machine those bits yourself. This is what I ended up with:



which I'm very pleased with. I just went for the Wilwood rotors as they had something the right size (280 mm) and spec.


thanks for that, well i suppose im going to have to get an engineering firm to drill the PCD out.

In the TR i don't have to worry about the bells clearing the hubs as they are like the Cortina setup where the bells will bolt to the back of the hubs, in front the uprights.

like so -