celbii

iTrader: (2)

Hello All,
I have an 88 NA fc, which im hoping to reach around 170WHP at the end of the day with streetport and supporting mods. That said I have a base 4 lug model, with the smaller brakes all the way around. I was recently told that it would be a waste to upgrade to the 5 lug and larger stock brakes upfront, and just unneeded weight, since at my power levels I wouldn't out use the single brakes. Any thoughts on this matter? Track running wouldn't be anything serious just high speed touring at Hallett Motor Racing Circuit and maybe some autox days.

Thanks

eage8

iTrader: (9)

The larger brakes have aluminum front calipers and are probably lighter than your current front brakes...

I would do it. They're pretty nice for stock brakes and will probably be pretty cheap to do.

LargeOrangeFont

iTrader: (7)

I would do it. The larger rotors will be less prone to brake fade. Lots more cheap wheel choices too (sn95 mustang wheels).

If you get the correct hubs you can get all new brake calipers, rotors and pads for around $400.

DeaconBlue

iTrader: (31)

Not to mention that there are more pad fiction options for the 5-lug 4-piston calipers setup.

apsolus

iTrader: (2)

just throwing this out there, i just got rid of my 87 base 4 lug and now have an 89 convertable with the 5 lug and the brakes are not any better as far as street driving. even getting on the brakes hard, the vert doesnt stop better compared to the old coupe. but if your serious about taking it on the track at all im sure the bigger brakes will be worthwile

j9fd3s

iTrader: (3)

one of the fastest IT cars i've seen was a 4 lug car. @170hp there is no reason to switch, and wheel selection is probably better with the 4 lug.

also the base brakes were used on the 1st gen too, so pad selection is about the same

nofords

iTrader: (9)

What I've found is that there are better pads out there for the FC/FD front brakes and as far as a track day car is concerned, the 4 piston setup is more ideal from a serviceability/reliability stand point.


There are many reasons why this would be. Something as simple as changing to an economy pad over OE will make this true.

DeaconBlue

iTrader: (31)

The one thing that is very often over looked when swapping from 4-lug to 5-lug brakes in the FC is the m/c size and booster. The GXL, convertible and GTUs came with the same 5-lug brakes as the T2, but they had to make do with the smaller m/c and single diaphragm booster from the base 4-lug setup. This means a longer pedal travel and "lazy" initial action. That is why the 929 m/c and booster swap is so popular (even on T2 cars). Also the FC is known to have a lot of firewall flex which adds to this “lazy” pedal feel. A master cylinder brace is highly recommended in a FC that sees any track time.

The two biggest impacts on brake performance is coefficient of friction (cF) of the pad material selection and tires. For example I run Hawk HPS pads on the street and Hawk Blue pads on the track. There is a big difference in cF rating as well as cold and hot bite with those two pad materials. Not to mention the switch from street tire to DOT R tires as far as grip is concerned.

Large brake rotors do increase the amount of torque generated per pedal pressure applied because of their larger diameter. They also have a greater thermal capacity due to increased fire path mass. The greater width also increases the vent width and cooling surface area. Both of these greatly reduce fade.

But larger brakes tend to add to the un-sprung weight at each corner. Now 2-pcs aftermarket rotors with aluminum hats can help offset any weight gain compared to the same diameter OEM 1-pcs rotors. Since I don't have the actual weights of all the 4-lug and 5-lug components in front of me, I am not sure which setup is lighter or heavier or by how much. !5” rims fit over both factory setups, so you are not adding more weight by having to switch to a 16” or larger wheel/tire combo which can be the case with other brake upgrades or on other cars.

Multi-piston fixed calipers tend to keep a more evenly applied pressure across the pad to rotor interface (differential bore pistons sized calipers help even more) compared to single piston floating calipers. They also tend to be a much more durable setup than the single piston floating calipers

The key is if you car is light enough and with lower power, you may be fine with the 4-lug brakes on a say smaller road course. But if you have a major braking zone or two on a longer or larger road course or the brakes begin to fade after only a few laps into the secession, then you need to either upgrade the pads and / or the hardware to the 5-lug setup. Luckily if you have a base coupe and need to make the 5-lug upgrade it is fairly easy and cheap with readily available parts.

DeaconBlue

iTrader: (31)

You may want to double check on that. I recently received a notice from RockAuto where several brake companies were discontinuing their pad/caliper offerings for the 4-lug applications. That doesn't mean that you still can't buy decent street or race pads or even rebuilt calipers for the 4-lug step-up, but I also noticed that there were not any 5-lug applications noted in the soon to-be-discontinued parts listing this time around. The FC is 23-28 years and the SA/FB is older. The aftermarket parts movement is getting fairly slow across the board for these cars, so parts availability gets a bit scarcer every year now. Since RX7 were so heavily raced in their day, track worthy pads should continue to be available for some time.

nofords

iTrader: (9)

Another thing to with this comment is Wilwood makes a direct bolt on 1 1/16 mc to T2 booster which is larger than the 929 mc and easier to come by.

eage8

iTrader: (9)

Really? what's the part number? 1 1/16 might be bordering on too big...

DeaconBlue

iTrader: (31)

I had heard that a few folks have used a Subura Legecy 1-1/16" master cylinder, but I did not know that Wilwood had one that would bolt-on to the T2 booster. That could come in handy for those using aftermarket multi-piston calipers

nofords

iTrader: (9)

Wilwood Aluminum Master Cylinders 260-4893

I believe that is it. It has 3.2" c-c bolt holes.

To install this on the T2 booster, thread the head of the pushrod between the booster and mc all the way in (not the end that connects to the brake pedal).

I used this on my race car: FC 4 pots up front and wilwood 4pots out back with a wilwood proportioning valve. Medium-Hard pedal but that's something I like!

DeaconBlue

iTrader: (31)

Here is the print for the Wilwood m/c #260-4893

nofords

iTrader: (9)

Ignore the piston in that diagram. That part# is shipped without one and if you buy the one that has it included (260-4894) you won't use it anyway.

Carl

iTrader: (2)

Slight shift of the thread. Are the 5-lug calipers (4 piston) a direct bolt-up replacement for the 4-lug calipers (single piston)?

DeaconBlue

iTrader: (31)

IIRC, someone (maybe CorkSport) used to sell a kit with brackets, but you had to have the '84-85 GSL-SE hubs/spindles - or something like that.

nofords

iTrader: (9)

if you are referring to FC then yes, once the hubs are changed then the 4piston calipers bolt to the spindles

DeaconBlue

iTrader: (31)

This was assuming you were referring to install the FC 4-piston on an FB.

DeaconBlue

iTrader: (31)

Here is how to install the 4-piston FC setup onto a 4-lug FC and keep your 4-lug wheels.

How To Install 4 Piston Brakes On A 4 Lug FC RX-7