ae86, ra40, ra60 front hubs.

[bunki86]

hey,

do these all share the same brake disc pcd ?

ive never checked ae86 ones, but i hear they are 87mm ?
i have ra40 ones and i checked them and they seem to be 97mm. i have ra60 ones on my car but arnt able to check them as the car is in a shop at the mo
do ra 60 share the same brake disc pcd as ra40 ?

cheers.

[LittleRedSpirit]

You can look this up on various brake manufacturers catalogues.

[LittleRedSpirit]

I think the bearing is smaller on ae86 hubs compared to either of these two options, so swappability is limited. Also the hub thickness varies a lot from one to another, with the ra40 rotor being quite flat and the hubs being quite thick, whereas the ra hubs from memory are thinner and the rotor has more of a hat to it to make up the distance.

[bunki86]

hey man thanx for reply.


i havnt yet seen any brake suppliers say what pcd they are, they all say either 4 hole or 5 hole. typical specs are diam-thickness-height-bore size and amount of holes.

yeh i know the hubs are all different, and the bearings on ae86 a smaller. i just wanted to know if the brake pcd is the same, thats all.

i need to order some customs disc's, and looks like im going to have to wait to get my car out of the paint shop, to check my hub brake side pcd, as they are *a6* hubs.

cheers.

[Javal]

AE86 isn't listed in the DBA online catalogue but a very quick google puts them at 87mm. RA40 listed at 4x97mm and RA60 at 4x100mm.

[bunki86]

thanx heaps javal.
dunno why i couldnt find it on the dba site. i think my scriptsafe was blocking the catalogue.

cheers.

[LittleRedSpirit]

If you are looking around for an upgrade then you will find the rotor pcd is the easiest thing to change as most brake shops can redrill the rotors, as long as there is enough meat on the rotor where it counts and it began as a 4 stud or could be ordered undrilled. I've got ra40 struts so the thing I'm looking at is a hub that attached the rotor at a more outboard point to allow thicker vented rotors. I figure the rt142, st141, ma61 and the like will all put the rim mating surface in a reasonably similar place but the thing that changes is the rotor height that each hub suits as ra are thin solids. The ra40 hubs have a big offset to the rear with only a 16mm total height rotor. The ma/ra brakes have more hat height on the vented rotor which I think was around 26mm, with some swappable Toyota hubs having as much as 50mm rotor height according to the catalogues. I've been looking for something that gives maximum separation to the calliper/spoke clearance and allows the thickest vented rotor possible. I could care less about finding a bolt on calliper bracket and rotor combo as the ra40 calliper has these really wide spaced mounting bolts that are bigger than the standards often used of 3.5 or 5.5 inches. I will just find the appropriate wilwood callipers to use to suit my rotor and hydraulic needs and make a bracket to suit once Im happy with the rotor and hub placement.

Its easy to work out the correct multi piston callipers you need to replace the single piston calipers, you just work out your piston area that the fluid acts on, so ra40 is 55mm diameter and works out to be 3.67 square inches. When comparing to multipiston calipers the way you do it is to consider one side of the calipers piston areas, so for example if the calliper I'm looking at using has 4 x 35mm pistons, with 2 and 2 opposing one another, I consider 2 pistons on one side of the thing, then I add the areas of both these smaller pistons together and I compare to the stock hydraulic systems piston area, if the area of the calliper pistons varies by 10 percent or more, you might need an MC change.

So to finish the example, 2x35mm pistons have an area of 2.99 square inches. Variation from stock is 19 percent smaller, meaning the existing MC would need to be corrected to a different size, more than likely smaller. Stock MC is 13/16 of an inch so 0.81 inches. which works out as 0.52 square inches.

So if you need 19 percent less fluid, you need 19 percent less area of the piston for the same pedal travel. Therefore the piston area should be 0.42 sq inches. A 3/4 inch master gives a piston area of 0.44 inches so that's as near as makes no difference to perfect.

So if you are wondering how the new callipers you want to use will function with your existing mc, then you can do this maths and know 100 percent the result without needing to do the swap to feel the pedal and find out the hard way.



So hydraulically, the new brake calliper might need a smaller MC to regulate its pressures properly.

[Hen may possibly be a nut]

While you may have sorted this out, another possibility which could open up more options is to mount the disc from the front. Slide it over the wheel studs, instead of bolting it to the back of the hub. I've heard of people that have had to take a mm or two off the OD of the hub, but should give you plenty more compatible discs.

Hen

[LittleRedSpirit]

While that potentially works, I'm trying not to have extra kgs of steel there unsprung on each strut. The centre hats that clear the hubs weigh a tonne, and if I could get a big rotor without that I would be much much happier. Why undermine the lightweight nature of the parts to begin with? Also it acts as a spacer and it pushes your wheels out further reducing clearance at the arches and again necessitating longer heavier wheel studs and more unsprung weight. If I had better braking at the expense of the steering and suspension performance what's the point?

[bunki86]

i ended up using mini 294mm discs, on the back of ra60/ga61 hubs. with fd calipers (tho i havnt made the bracket yet) (been bizy)

i used to run the same hubs with, slip over z32 rotors and calipers, but using that setup meant i had to run 16" wheels.
with the fd mini combo i can run 15" wheels.

tho, all im waiting on, is me getting the caliper bracket machined up. it all seems to be on track to working well. ill just keep using my r32 m/c. i was using with the z32 setup.


this is the diff between ra60(ga61) hubs, compared to ra 40 hubs.

http://www.ae86drivingclub.com.au/dcimages/1/6/8/7/7/560718.jpg



cheers.

[LittleRedSpirit]

Thanks for the photo, as I was suspecting the hubs have a bit more room for the thicker rotor behind. I think the mini or the peugeot rotor would be good with this setup depending on which calipers you want to run. It also pushes your wheels out which could aide spoke clearance with the multi piston calipers.