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MG MGF Technical - Ap Racing 304mm disc offset?

Question is in the title - anyone know what the offset of the AP 304mm brake disc?

Hmm - thinking about it, I am not 100% sure that I know what the offset of the OEM 240mm disc is either!

Anyone got access to these figures?

Cheers
Rob Bell

According to the EBC catalogue, the 'height' is 39mm. HTH
Mike Hankin

which can be found over here:

click on the relevant catalogue

http://www.ebcbrakes.com/catalogues.html
David Peters

22mm FMM
d mottram

Lots of such data is obtainable on the DBA )disc brakes australia)website under applications or replacement discs. Well worth a bookmark.
d mottram

I phoned AP on Friday, and here's the details that I got off Pete:

Disc dimensions: 304 x 24mm
Offset: 32mm +/- 0.5mm

The pads are 46mm.

Interestingly, AP do have a floating rotor of these dimensions - namely 304mm diameter and 24mm thick. It has a 12-point mounting with a PCD of 7.5" (Part numbers CP4348-938CGA for RH and CP4348-939CGA for the LH). They're not in stock, and thus will need to be made to order. Ģ150 each. Then add on a pair of mounting bells (offset details to your specification) coming in at about Ģ80.

Weight saving per corner - approx 1kg.

Given that you can buy a pair of AP discs for 150 for a pair, the option I am thinking about isn't what you'd call cheap - certainly not worth it for the 1kg weight saving alone. But saving a further 4kg by not using Trophy or TF 11-spokes will mount up to a saving of 5kg per corner unsprung weight...

The next trick will be to measure up the offset and ensure that it clears all the suspension components...
Rob Bell

Very interesting... I guess you'll need a spacer plate for the caliper mounting that matches the adjustment to the rotor offset? That would seem more efficient than a spacer on the wheel mounting?

The frankly quite obese unsprung weight is my only criticism of the AP / Trophy rim combo, if you can get the same with Cup alloys I'll be seriously envious...
Mike Hankin

Spacer might be required, but what I am hoping for is to simply bolt the caliper to the opposite side of the hub carrier (in much the same way as caliper spacers are usually mounted.

At the moment, this is more of a mental exercise - there are quite a few problems to consider - not least being how to bolt the caliper in place with the rotor mounted to the hub... Fun and games! :o)
Rob Bell

Rob, could you clarify what you mean by "offset". IMO this is the distance between the caliper mounting face and the middle of the disc. Often confused with the height of the hat (or bell)of the disc
David Peters

Rob, I just checked the DBA website for the standard disc dimensions. The disc is 22mm thick and is moved inwards by the top hat a distance of 22mm making the distance from the outer face of the tophat to the innermost face of the disc a total of 44mm.

As to the AP discs................I don't know as they are not listed.

David
d mottram

>>I guess you'll need a spacer plate for the >>caliper mounting that matches the >>adjustment to the rotor offset?

Isnīt that what all after market brake kits do comprise of? The bracket does not only account for the bigger disc diamter, but also arranges the correct offset.


>>bolt the caliper to the opposite side of >>the hub carrier

Arenīt the Ap calipers mounted on the inside of the hub? So the opposite side would give you even less clearance? not?
David Peters

>> Rob, I just checked the DBA website for the standard disc dimensions. The disc is 22mm thick and is moved inwards by the top hat a distance of 22mm making the distance from the outer face of the tophat to the innermost face of the disc a total of 44mm. <<

Thanks David - although I am sure that the standard 240mm disc offset is greater than that? Shame that the AP disc is not currently listed, although with the number of aftermarket discs for this caliper now coming onto the market in the UK, it will only be a matter of time I am sure.

>>
>>I guess you'll need a spacer plate for the
>>caliper mounting that matches the
>>adjustment to the rotor offset?

Isn't that what all after market brake kits do comprise of? The bracket does not only account for the bigger disc diamter, but also arranges the correct offset. <<

Yes, but we can have considerable flexibility with floating rotors, as the alloy mounting bell can be manufactured to suit what ever offset you need. :o)

>>
>>bolt the caliper to the opposite side of
>>the hub carrier

Aren't the Ap calipers mounted on the inside of the hub? So the opposite side would give you even less clearance? not? <<

No, the AP caliper is actually mounted, as per the standard sliding caliper, on the outer face of the hub carrier. Mounting it on the inside will enable a much larger offset to be used - and hence clear the wheel spokes of the standard "Cup" alloy.

However, the problem then is to ensure that the disc then doesn't foul suspension components, particularly on full lock or suspension movement. More measurements to be done I think!!!
Rob Bell

I can feel about 25mm clearance between the inner face of the rotor and the lower balljoint, the gap on the upper balljoint seems about the same. Torrential rain stopped play before I could get the wheel off for a proper look though...

Given that the caliper would usually bolt to the outer side of the carrier, there's potential for nuts to be welded there instead and the caliper bolted through from the inside. A bolt of carefully chosen length, naturally ;o)
Mike Hankin

Only 25mm? I shall have to be careful as mounting the caliper to the inside face of the hub carrier could result in an approximate 25mm increase of offset - there may be inadequate clearance :o(

The other alternative would be to have a bracket made up that bolts to the standard locating mounts, and rotates the caliper upward and round so that the caliper mounting face is in the same plane as the hub carrier (if you can picture what I mean - and here a drawing would explain better what I am thinking of...)

Again, this may foul a suspension component... I guess what is needed is some time spent under the wheel arch of my car and another with AP brakes already fitted!

All this before even thinking of using 260mm Rover 800 rear discs for the back end...
Rob Bell

This thread was discussed between 30/06/2006 and 05/07/2006

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