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MG MGF Technical - (braking) master cylinder bore size ?

Hi guys,

with respect to a brake upgrade;
What is the bore size of the Fs master brake cylinder?

would 44mm brake pistons be too big to handle?

David Peters

What are the AP calipersī piston size? anyway. Noticed two possibilities on their site 38.1mm and 44.5mm. I guess the 38.1mm is used on the F? any comments?
David Peters

>> would 44mm brake pistons be too big to handle? <<

Are we talking radii or diameter? The standard front caliper has a diameter of 54mm - so the total area of the pistons is 2 x PI 27*27 (the doubling of the area is due to the sliding caliper design).

Note that the AP racing brakes used on the Trophy SE and TF160 are employed using the same master cylinder as those with the standard 240mm brakes and sliding calipers - so usually master cylinder size is not a problem.

It depends on the design of caliper you are thinking of using - i.e. how many pistons, and what diameter?
Rob Bell

Hi Rob, Diameter it is!

I thought it was 48mm for the MGF (shared with the maestro?)

I was just wondering, with the big brake kits around and everyone swapping their regular setup for APīs, we all forgot the size of the BMC might have changed in the TF160/trophy engined MGF/TFs.

AP has for the (5000) 5040 caliper two piston sizes, Iīm interested in knowing which diamter was fitted to the above.
Are they alli?

David Peters

Looks as though I could have an error in my notes regarding the piston size David - I'd need to check.

As I recall, the AP 4-pot caliper used on the Trophy/TF160 has a total piston area in the same "ball park" as the standard caliper - i.e. the areas were close, but not identical.

I would suggest the same approach for your plans - namely chose a caliper with a similar piston area. This will not only mean that you can retain the standard master cylinder, but it will also maintain the standard brake force distribution between the front and rear axles.
Rob Bell

Oh, I didnīt know the surface calculations when having a sliding caliper design were done in that manner.

So OEM we have 2 pistons/caliper and due to the sliding design these will have to do double effort (pushing the interior pad against inside o/t disc and pulling/"pushing" the caliper and outside pad against the outside o/t disc)

AP (most 4 pots I guess) are fixed type hence, the BMC has to pull of the same effort hydraulicwise. If we īre talking same piston area.

So weīre all safe running the big red ones *LOL* (well I am not-->cup wheels)

Seems logical to me. Never thought about the sliding design. Did a quick google to check what is was,

thanks a lot.

David Peters

No worries David.

What are you planning with regard to brakes? I am also keen to retain Cup wheels that I have. I was wondering about re-mounting the MG AP calipers and using them in conjunction with AP floating rotors on alloy bells...
Rob Bell

This thread was discussed between 10/06/2006 and 13/06/2006

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