4 pistion caliper write up

[JWP]

What I'm showing here is my 4 piston caliper write up. I know 4 piston calipers may be overkill, but i did them for a few reasons. I had them, Empi makes brackets to work with drum spindles and them, and personally you can never have too much brakes, just not enough tire to stop you.

During mockup I found that out of the box the bracket all but hits the rotor, certainly too close to use. I determined if I could take two brackets, over lap them I could gain the clearance I needed and make everything fit. I next determined that in the pre drilled positions in the bracket (countersunk holes) the caliper interfered with the steering arm or would be in the way of the trailing arms. I found an alignment that aligned one of the 3 spindle bolts, didn't have any interferences and should clear the trailing arms just fine. I drilled two new holes by aligning the spare bracket and marking the center of the necessary holes.

Then I bolted the brackets to each other perfectly aligned and drilled my index holes (yellow circles). These will later be used to attach the trimmed portion of the other bracket for final mockup and welding.

The calipers are 4 piston Aerospace Components calipers and are more or less a copy of Wilwood's Dynalite.

[JWP]

In this picture you can see the bracket is marked where the spindle goes and where the first bracket over laps.
Notice the index holes fall within this area (yellow holes). My next steps are to trim away the area that interferes with the spindle.
Once that is complete i can bolt the two pieces back together, this time with a 5 mm offset. which will clear the rotor with room to spare.
Following that will be test fitting before welding the two pieces together.
Sorry if I've seemed to ramble on, had a few other things going on while doing the write up. More to come as i progress.

[JWP]

I made some more progress the past couple of days. Here you see the two brackets after being cut down.



Here I've bolted them together using the "index holes" I mentioned in the first post. Once I have the other side made the two pieces will be welded together



Here is the assy bolted to the spindle. The arc drawn on the smaller bracket is about where the larger one overlaps.



These last two are the completed assy bolted up.

The caliper was originally for a .81" rotor. Ghia rotors are .375 so I removed the spacer bridge from the caliper making it the perfect fit and gained some space between the caliper and wheel.

[raul arrese]

Good job , i did the same thing on my build , but i used wilwood 4 piston on all 4 corners , i made my own brackets and did a little machining on my spindle to recess the bracket deeper , mine were to close to the rotor i used ... More people should do these kind of mods and not be afraid to modifly there own brakes ... the reason i did it was more for looks and not pay the rediculous prices a certain person ask for his disk brake kits ... only a few do it and they are no big deal... any ways hopefully more people will do them themselves ... thanks for the write up..

[doc]

Nice work! Great project.

doc

[JWP]

Thanks guys. I'm on stand by until I get my other brackets. I don't want to weld this one up until I get the next one made. These will be the template for the passenger side. I was going to use the oe front caliper on the rear. This is going to be a street car too so I wanted an e-brake/parking brake. I ordered the CB rear disc kit for my car with parking brake. When I got the kit, the calipers look very similar to what i had on my Mustang race car from a few years ago(i'm 99% sure they are the same). They stopped that car with ease and it was twice the weight so I've since called off the efforts to increase the rear caliper size.

[Chris V]

I've always interpreted the reason not to run the cheaper aftermarket cailpers on the street was due to there being no seals around the pots to keep-out debris - most OEMs have the dust boots on all moving pieces.

Without dust-boots to protect the pots it makes it wise to remove the pistons at pad-changes to clean their OD's before plunging them back into the calipers across the O-rings.

[whiteboyspooky]

im curious will these fit under a 15 in rim? and would you consider selling those modified brackets? i dont have the fab skill/tools to be able to do that myself.

[JWP]

I've always interpreted the reason not to run the cheaper aftermarket cailpers on the street was due to there being no seals around the pots to keep-out debris - most OEMs have the dust boots on all moving pieces.

Without dust-boots to protect the pots it makes it wise to remove the pistons at pad-changes to clean their OD's before plunging them back into the calipers across the O-rings.

Chris V, I was also taught this, but then I entered the world of amateur motorsports, I ran special calipers on my Mustang because they were reported to be durable and were superior due to having dust seals. 2 track events later, the calipers seem durable enough but the dust seals were on their way down hill, on the 6th event one had burned through due to the heat. I never looked back and never had an issue. Those calipers are still in service today, still have the same burned pieces of dust boot.

Do I think it's important, yes on a street car thats sees more inclement weather. On a sunny day street car and autox/track car not as much but still something to watch for.

im curious will these fit under a 15 in rim? and would you consider selling those modified brackets? i dont have the fab skill/tools to be able to do that myself.

In short yes, I am running 15x5.5" mangels and it was a priority of mine to keep a stock wheel due to the direction I'm taking my car. However that has been modified some so I hope I haven't painted myself into a corner. I wouldn't have a problem making them, however I have no R&D time on these, I couldn't guarantee any level of safety, performance, function etc. If you are still interested send me a PM and we can discuss further what I would need to make a set.

[PhillipM]

I've got 4-pot Hi-Specs on the rear of the rail and despite getting them hot enough to turn the epoxy on them a lovely burnt colour, turning the discs a lovely hue of blue and melting the grease out of the wheel bearings, the piston dust seals are still fine

[JWP]

I've got 4-pot Hi-Specs on the rear of the rail and despite getting them hot enough to turn the epoxy on them a lovely burnt colour, turning the discs a lovely hue of blue and melting the grease out of the wheel bearings, the piston dust seals are still fine

Then you are not using them enough. In road racing it's not uncommon to see glowing rotors going into turns at the end of high speed straights especially with the modern aggressive brake pad compounds available today.

[JWP]

I called my local VW shop on Tuesday and the guy who answered the phone said my brackets were in, I went there Wednesday and they were not. I'm hoping I can get them by tomorrow, if I so think I can get the other side made and be ready to put them on the car for some suspension cycling before the end of the weekend.

[Chris V]

I've got 4-pot Hi-Specs on the rear of the rail and despite getting them hot enough to turn the epoxy on them a lovely burnt colour, turning the discs a lovely hue of blue and melting the grease out of the wheel bearings, the piston dust seals are still fine

Then you are not using them enough. In road racing it's not uncommon to see glowing rotors going into turns at the end of high speed straights especially with the modern aggressive brake pad compounds available today.

In short circle-track racing (where I've cut my teeth) it's not abnormal to see rotors glowing nearly all the way around the track

[PhillipM]

Then you are not using them enough. In road racing it's not uncommon to see glowing rotors going into turns at the end of high speed straights especially with the modern aggressive brake pad compounds available today.

Yes, I've had the rotors glowing, you want heat? Try using the cutting brake while the rotors are glowing and getting on the throttle all the way around a bend - they come out the other side in 'put your welding goggles on' mode. I run carbotech XP10's in the the rear atm, might be stepping up to 12's next year.

Whilst you can radiate massive heat from the disc and pad surface, ceramic-based pads and stainless pistons with ceramic cups deflect a lot of heat from the caliper and seals themselves.

[JWP]

Then you have better dust boots than I did. I was running performance friction z rated pads which are close to an xp 10. Is your car a road course car?