Out of curiosity I looked up the prices of calipers, disks and pads for a Mazda 6 at Rockauto. This also got me wondering what bolt on upgrade Mazda 6 owners use, it's seems they use MazdaSpeed 6 disks, calipers and pads as a direct bolt on upgrade.
I compared the two out of curiosity. (Keep in mind I looked on internet forums for upgrades and rockauto vender info on their products).
As far as price goes, the re-manufactured calipers with brackets and hardware are about the same price and core charge for both M6 and MS6. The pads are also about the same prices, the MS6 disks are on average 39% more expensive then M6 disks but they are almost 1.5" larger.
If the MS6 set-up is an actual bolt on and fits the F2T it will require the same disk or carrier spacing as the Mazda6 to fit.
Mazda 6 Caliper:
The Mazda Speed 6 caliper has the same piston surface as the 6 caliper and will only deliver the clamping force supplied by the brake booster and master of the vehicle their used on. Perhaps the slider position and caliper design offers slightly better caliper performance. You can definitely see the taller bracket/carrier on the MS6 caliper.
Mazda6 2005 front disk:
Discard Thickness .............23.114
Outer Diameter.................282 mm (11.102")
Discard Thickness ............23.114
Height........................... 47.5 mm
Outer Diameter.................319.7 mm (12.586") (Some labelled as 320mm/12.598")
MS6 are the same part number disks for Mazda speed 3's (MS3 calipers and pads are different), from what I can find 17" rims would be the smallest that can be run with MazdaSpeed 6 brakes, some MS3 owners have managed to clear the brakes with 16" rims but the caliper is a much lower profile.
Based on the height of the two disks the MS6 disk and caliper would sit 1.25mm farther from the strut then the M6 Disk.
Mazda6 2005 front brake pad:
The Factory 626/Mx6 pads are 129.8mm wide, 52.3mm tall.
The MS6 pad shape and height (taking advantage of the larger disk) would be the real difference but looking at the MS6 caliper picture and pad picture the pistons sits against the top of the pad and not the center, I would think the best clamping force would be delivered if the pads where pushed and pulled in the center, the outside pad would wear evenly but the inner pad might wear more on the upper edge, in turn causing the caliper to follow (with whatever play the sliders allow) and wearing the lower edge on the outer pad.
Both the Mazda 6 and MazdaSpeed 6 have many more choices for performance pads then our 88-92 626/mx6 set-ups do.
My personal opinion and experience with brakes, the brake pads are the key to braking, the more aggressive the pads the more they destroy the disks.
The best thing to do is run performance pads with standard factory replacement disks made in Japan or North America and replace the front disks each time you change brake pads.
With the factory F2/F2T brake system the only pads I have not experienced brake fade with over the past 13+years are the EBC red and Yellow pads (which I find expensive), everything else I have run (all kinds of brands, types of compound and performance grades including factory Mazda pads) have faded during spirited drives or a few 5 or 6 high speed accelerations/decelerations.
Both M6 and MS6 larger disks and pad surface should reduce the heat generated during braking, which would reduce the wear and fading due to heat soak.
Mazda6 drivers that do the MS6 upgrade, claim it's the best mod they've done to their car.
Ms6 brakes allow for a minimum wheel size of 17" (perhaps 16" with thick wheel spacers).
This is to compare factory brakes used on a modified Mx6/626 putting out 300+Hpr
The Mazda MX6 weights about 2674 to 2750lbs
The Mazda 6 weighs 3,102 to 3,461 lbs
The Mazdaspeed 6 weighs 3600 lbs
The TR-326 has variable weight with the driver in it. It's a Motor with a seat and a small enclosure around both, as it runs down the track the driver sweats bullets that evaporate and lighten the overall weight. (To be honest I have no Idea if he plans on racing it at the track but the same applies on the street).
Based on vehicle weight it would seem that the brakes from either heavy lump should be adequate to stop an F2T however if you factor in the frequency at which you would make say 100-180km/h (62-111mph)accelerations/decelerations with a modded F2T vs the Mazda 6 and Mazda speed 6.
Mazda 6 2004 4I: 26.9 seconds
Mazda 6 2004 V6: 17.8 seconds
Mazdaspeed 6 :12.8 seconds
Modded stock engine F2T : 8 seconds and less
And to be fair- Modded stock MRZ 2.3l engine in MS6 100-180km/h acceleration: The MS6 drive-train will disintegrate and the flat bed driver will never hit 180km/h, if the drive-train could take the power I wager a stock MRZ 2.3l engine making 400BHP blows before the brakes fade.
Love the fact Mazda brought back the turbo with the MSP, MS6 and MS3 but they didn't leave much room for upgrades on stock internals, also factor in the vehicle weight to power/torque and the fact the F2T pulls hardest in 4th and 5th, It can put the brakes through heat cycles quicker. Based on weight it (with proper proportion and rear brakes) should stop 12.8% to 34.6% faster then the Mazda 6- MS6 if all three vehicles are using the same brakes. (Those percentages also represent the amount of wheel hp needed to match the F2T at that weight so if gearing was equal the MS6 would need 403.8 wheel HP to keep up with an Mx6 at 300whp).
In the time a 2004 M6 I4 runs 100-180-100km/h a modded F2T will run it 3.49 times.
In the time a 2006 MS6 runs 100-180-100km/h a modded F2T will run it 1.94 times.