4 piston callipers & 15” wheels

Just curious what people have used.
I picked up a set of Porsche 996 callipers which are Brembo Mono-block callipers however I seem to have run into a stumbling block when it comes to fitting a disc in them. They use a 61mm deep pad on the front, consequently I have been unable to find a 2 piece rotor that takes a pad of this depth that is small enough in diameter.

Ie looking for some discs ~11.75” / 300mm OD
Inner diameter of swept area 7” / 178mm ID
Bolt face 6.3” / 160mm PCD ?

Either that or find an alternative calliper?
I see that the Superformance uses something very similar to the Billet Narrow Superlight 4 calliper.This has a pad depth of 1.77” / 45mm. (someone posted a photo and part of the part number was visible on the calliper, so I may be wrong here)
Do they use the same calliper front and rear? The Porsche Brembo set up uses different sized pistons front and rear however the rear pads are smaller so this may equal it out some more.I can see some more time crunching numbers coming my way.

http://www.wilwood.com/Calipers/CaliperProd.aspx?itemno=120-8071-L

Regards Ryan
 
Hi Ryan,
Not entirely sure the issue - can you not find thick enough rotors that are small enough diameter?

If so best might be to source some rotors of the correct thickness and have them machined down to reduce the diameter. We've also tacked material on the backing plates of the pads before to increase thickness, but this is far from ideal. Better to have the higher thermal mass of the thicker rotor.
 
I am gathering the pad hits the hub of the disk.

you can cut the 996 pad down as long as you dont have piston hanging over your pad.

Caliper kits for the brembos might be worth more than a wilwood caliper.

Im on 15" and I use a 296mm disk 30 wide I think ,VE com.
To be honest I use the VE caliper as well and project MU pads and it stops like a bastard lap after lap.
It pulls 1.3 G on the meter ,It can stop harder but its not the best way to drive it so I dont brake any harder than that.

You can use the same front and rear you just have to balance off with bias or master size.

As Duncan stated shims are fine. my disks are correct for my caliper and as i get pad wear I shim anywhere up to 6-8mm.

Jim
 
Thanks Gents.

have to start somewhere at some time i guess.

the problem is........I stuffed up.

Disc ~300mm (150mm radius)
Pad depth 61mm
hub face od 155mm (77.5mm radius)

150 - 61 - 77.5 = 11.5mm spare space in the radius in which to get the disc hat to turn down, head down the side of the hub and then bolt the rotor onto.

not going to happen as a 2 piece rotor
maybe if your lucky you might be able to find something OEM somewhere which you can then re-drill to suit.

basically, its would be a lot easier to get it to work if the pad depth were shallower at 45mm like the Wilwood calipers mentioned. Looks like a lot of effort for minimal gain using the Porsche Calliper on the front.

the matching Porsche calliper for the rear only uses a 49mm deep pad.
so
150mm - 49mm - 77.5 = 23.5mm.
that may be enough but then you have the added problems of getting the handbrake mechanism in there. ie the inner drum for a hand brake can be no bigger than 77.5mm + 23.5mm = 101mm radius.

So that would be workable if i could find a disc. I think BMW had two different hand brake sizes, 180mm up to the E46 generation and 185mm for the E9x generations onward. I think this is also similar to the VT Commodore.

That's it for me tonight. time to re group and work on it from a different angle.

PS, anyone in Melbourne got a VT on-wards Commodore rear end they want to donate to a GT40 project?

Ryan
 
You need to measure the inner barrel on your rim.
When I did the 206 its a 13" rim.
Wilwood had a caliper that in the spec sheet listed the OD fitted to a 275mm disk.
I had the barrel size so it was a good start, I ended up with 2mm clearance.
I would think wilwood would have similar specs on other model calipers.


Maybe able to help more if you gave some specs on suspension
What upright are you using and what wheel, is the inner barrel straight or stepped up on the rim.
Road or race or track days ?

I always use DBA or RDA catalogs to select disks.

Jim
 
Last edited:
Re: 4 piston callipers & 15†wheels

not sure im going to be able to answer those questions Jim.

wheels are 15" three piece wheels, the barelas are steel and are fairly far gone, so i may have to replace them, not sure if i can get steel replacements, or alloy ones. not sure if they will be able to bend the alloy to the same radius as the steel so they might be junk.

wheels are a 5 x 114.3mm stud pattern, so i was trying to find a rear rotor/disc that i could get to work under the Porsche calliper, and then work out what the matching hand brake mechanism for that rotor/disc was going to be, so that i could then go about sourcing that and designing that into an upright.

at this stage some stuff from Mercedes was looking promising (google found the image, its not mine)


as well as a few options from BMW
ECS - 1165563XSGMTLRA - Rear Cross Drilled & Slotted Brake Rotors - Pair (294x19)

or the Monaro version from the VZ Commodore
Access Denied

i think the BMW one will fit on the Commodore hub as they share the same stud pattern and i think the hand brake drum is the same size as well (I'm probably wrong is commodore 180mm as well?)

The original Porsche disc has a center bore of 98mm so that would leave a fairly large section of the inside of the wheel face unsupported and only 2.5mm wall thickness on the inside of the stud if running a M12x1.5 thread that's typical.

I think in the long run it will be easier if i get a Commodore hub as that has drive shaft advantages as well. I will work out something with the wheels later. either re-drill the commodore hubs or get some other wheels. these ones are near identical (±1mm) to the Vintage Wheels in dimensions.

Upright is in CAD at present and looks like a GT40 rear. I will get it a bit closer yet.

Ryan
 
Ryan, you are correct on the Superformance caliper model. SPF uses them front and rear. With narrow Wilwood pads they do fit 1.25" thick rotors. The discs are 11.75" diameter with a separate hat. The Wilwood rotors are:
Wilwood Disc Brakes - Rotor No: 160-13499
Wilwood makes hats to fit that disc in certain bolt patterns, but will not sell the SPF hat direct to buyers.
 
Last edited:

Fran Hall RCR

Moderator
GT40s Sponsor
We use a 2 piece 11.75 x 1.25 rotor..our own hat, 6 piston front and four piston rear calipers with no clearance issues at all on 15 inch wheels.
wildwood calipers front and rear..
no problem supplying you our parts but not sure of your bearing and offset etc obviously
 
Last edited:

Dave Bilyk

Dave Bilyk
Ryan, fronts I used 310mm discs with universal alloy bells (machine depth to suit) and got my own caliper mounts made to suit granada uprights and Wilwood Superlites. Rear I used alloy bells again but with HiSpec calipers and a Wilwood disc. I have a thread for front and rear if you care to look in user id statistics. Dave
 
Ryan
Reading your post I gather you are scratch building.

If you are going to do this properly you make it fit the wheel you have.
If you are thinking the wheels are scrap then you need to sort your wheel issue first.
Whitehourse ind make spun alloy rim halfs.

You start with the wheel, the offset that suits the look you are chasing.
Make the upright and brakes fit into the wheel.
Place the wheel on the ground and build arms the correct length.

My 2c worth.

Jim




Jim
 
Last edited:
Re: 4 piston callipers & 15†wheels

I am using the Wilwood GN 6 piston calipers with Coleman 12.19" floating rotors on my Pantera with 15" wheels . The GN caliper uses a much larger pad than the usual Wilwood offering .
Wilwood Disc Brakes - Grand Calipers National GN6R

Ron

Thanks Ron,

I have almost made my mind up about it at present, but for others following along in the future ill chasse it down.

Is this the grand national calliper your talking about.
http://www.wilwood.com/Calipers/CaliperProd.aspx?itemno=120-13947
pad shape = 7520


I think the Porsche pad is still likely to be a bit bigger


the 12.19” disc might be possible with the Porsche calliper, as that would leave 0.64” of space between the inner edge of the pad and the outside edge of the hub based on the previous assumption for hub diameter.
I will have to look up the disc tonight.

Ryan
 
Ryan, fronts I used 310mm discs with universal alloy bells (machine depth to suit) and got my own caliper mounts made to suit granada uprights and Wilwood Superlites. Rear I used alloy bells again but with HiSpec calipers and a Wilwood disc. I have a thread for front and rear if you care to look in user id statistics. Dave
Dave,
Can you get a pad 61mm deep on the front disc, and where did you get it from?

Ryan
 
Ryan
Reading your post I gather you are scratch building.

If you are going to do this properly you make it fit the wheel you have.
If you are thinking the wheels are scrap then you need to sort your wheel issue first.
Whitehourse ind make spun alloy rim halfs.

You start with the wheel, the offset that suits the look you are chasing.
Make the upright and brakes fit into the wheel.
Place the wheel on the ground and build arms the correct length.

My 2c worth.

Jim




Jim
Jim, yes a scratch build.

tires, wheels, brakes, uprights/knuckles, suspension geometry, chassis is probably the easiest way to go.

however, I think that suspension geometry/tires probably come together and are equally important. Probably no right way to do it. Just need to do something every day.

Ryan
 
No your spot on the money Jim get a wheel first and work from there, ive done it backwards before, and ran into all sorts of bother because even though its a 15" rim doesn't mean poop, it all depend where the bell opens up from on the inner section, as to what size rotor combo your going to fit with out spacers, or worse surgery to caliper.
cheers John
 

Dave Bilyk

Dave Bilyk
Ryan, I will check, I assume by 61mm depth you mean pad thickness including backing? I remember that I had options for different disc thickness with the same caliper, in which case the spacer in between the two caliper halves changes thickness, so that the same pad fits any case. i.e pad thickness x 2 +disc thickness = gap between caliper halves. So the spacer thickness changes to accommodate a different thickness disc and the pad stays the same. Does that make sense ?
Dave
 
Dave, the measurement that has caught me out is the minimum radius that the pad requires. if I put the top of the braking material in line with the outer diameter of a 300mm disc, the inner diameter of the braking surface on the disc would need to be 300mm - 61mm - 61mm = 178mm diameter at a maximum

if one was to use a pad that had friction material that only came down from the outer edge by 45mm then the equation would be
300mm disc diameter - 45mm - 45mm = 210mm diameter of the inner edge.

Ryan
 
Ryan, re rear / hand brake
I started out using the Willwood small puck caliper and changed because getting leverage and brake effort was just tooo much hassle. I have changed to a willwood 4 pot integral hand brake mechanism caliper which is available in NZ but strangely not listed on Willwood sites. These are available from Cardwell Racing here in Auckland. It also saves mounting a seperate caliper.
The part number is on the box and I am running 15inch rims and a Holden ss Commador rear disc on custom uprights.
Hope this helps.
Cheers
 

Attachments

Top