Write-Up: F-Body Brake Mod

just a word,you dont have to use spacers or taps or anything for the brackets.just use the firebird bracket bolts themselves.they will go thru the alu knuckles thread right into the caliper bracket
no problem.

The bracket bolts don't thread into the knuckle, they go through the knuckle and thread into the bracket. If you use the F-body bolts, there is slop between the bolts and the holes in the knuckle. This is because the OEM Buick bolts are larger diameter. Unless your car came with F-Body knuckles from the factory, you'll have some serious caliper alignment issues.

You mentioned in your strut thread you're hearing a popping noise from the front end. Bet you a fruit roll-up it's your loose caliper banging around on the knuckle.

This is why we drill and tap the F-body bracket to accept the OEM bolts.

AA wrote:

The bracket bolts don't thread into the knuckle, they go through the knuckle and thread into the bracket. If you use the F-body bolts, there is slop between the bolts and the holes in the knuckle. This is because the OEM Buick bolts are larger diameter. Unless your car came with F-Body knuckles from the factory, you'll have some serious caliper alignment issues.

You mentioned in your strut thread you're hearing a popping noise from the front end. Bet you a fruit roll-up it's your loose caliper banging around on the knuckle.

This is why we drill and tap the F-body bracket to accept the OEM bolts.

Ok.I had to edit my thread.the bolts go thru the knuckles and into the bracket.i got that right.that is how i set it up.i just forgot all about the spacer thing.
I see your point tho.problem is..i cant find the damn Oem bolts!

Ok.now that I think about it.running a tap into a cast iron bracket is completly the wrong way to go about this.the correct way to prepare the bracket is to drill the bracket out so as to accept a HELI-COIL insert,and then insert the bolt.
just tapping the bracket will weaken the bolts holding power .I would rather clunk around until I find a dedicated shoulder bolt
14mm dia shoulder x 12mm 1.75 thread.thats the way.
No arguing AA

Not arguing, just stating the facts:

So far over 4 years and 100k miles on my drilled & tapped cast iron brackets. This includes running track pads for autocross runs and over 75 high-speed road course laps, repetitive decels from 110-115 mph to 40 mph in 2-3 secs, brake caliper temps between 400-500 Fº, possibly higher. This is HIGH STRESS braking activity. The brackets have also been removed from the car and reinstalled probably a half dozen times. Threads are in perfect condition.

If we were talking about tapping very fine threads, I might be concerned, but the OEM bolts have super coarse threads. Also, I had a professional machinist do the work. If you DIY, just know what you're doing and use the proper tools. For anyone interesting in how to properly drill and tap into cast iron, here are a few links:

http://www.bt3central.com/showthread.php?t=36541

http://www.doityourself.com/forum/welding-metalworking/182917-tapping-hole.html

http://www.practicalmachinist.com/vb/general-archive/drilling-tapping-hand-cast-iron-78642/

http://www.chaski.com/homemachinist/viewtopic.php?f=4&t=8139

Ok. but the only proper way to do this is to heli-coil the bracket.anything else is wrong.thats a fact.
your professional machinist should have known this.Not putting you down,just going by the rules.
Wether you tap into a course threaded hole or fine,running a tap over exisitng threads will allmost certainly eliminate at least some of the threads in the process weakening the threads.I dont care how many miles into the bracket anyone has.its the WRONG WAY!
ask a "Professional" machinist which way is the RIGHT way! he'll tell ya

btw,in the links you posted,a predominante word word comes in,' "DRILL AND TAP" if youve ever heli-coiled anything ,you would know that you have to "Drill" out the hole "FIRST" efectively eliminating old threads, then run Heli-coil tap provided with the inserts AND then the new tap. voila

if youre redressing a stripped hole,you can get away with running the same size tap and restoring a thread.But on a braking system why take a chance?

In every instance in this thread I've used the term "drilled & tapped", because the holes are in fact drilled to 12 mm first, then tapped to the M14x2 thread spec. There is no running the tap over existing threads, because they get drilled out. The F-body caliper screw is a smaller diameter, so drilling it out gives you a smooth surface to tap.

I got the specs from an online vendor who sold modified F-Body brackets to the W-body community.

Get it?

AA wrote:

In every instance in this thread I've used the term "drilled & tapped", because the holes are in fact drilled to 12 mm first, then tapped to the M14x2 thread spec. There is no running the tap over existing threads, because they get drilled out. The F-body caliper screw is a smaller diameter, so drilling it out gives you a smooth surface to tap.

I got the specs from an online vendor who sold modified F-Body brackets to the W-body community.

Get it?

whatever.if youre not drilling and inserting a heli-coil youre giving the wrong advise.
get it?

Breaking this down as simply as possible:

F-body caliper brackets use M12x1.75 internal thread spec. The factory drilled the original holes using a 10.2mm bit, then tapped the M12x1.75 threads. The major dia for an M12x1.75 internal threads is 12 mm.

Our Buick caliper screws are M14x2 ext thread spec. This is 2 mm larger than the M12x1.75 F-body screws.

When you drill out the F-body brackets with a 12 mm bit, the old threads are gone. It becomes a smooth bore.

Now tap the new 12 mm holes to M14x2 internal threads. 12 mm is your minor dia, 14 mm is your new major dia. The result is a clean thread, looks like this:



The problem with using heli-coil inserts in this case, you'd need to tap a new thread anyway to install the insert, because you don't want to install heli-coils in smooth bores. So, why not just tap clean holes to accept the caliper screws? A much simpler and easier process, and it's not wrong. GM didn't need to install inserts, and neither should you.

well why didnt you just put all these specs down in the first place? what did you do?run out to the garage and disasemble your brakes to prove a point!? why do i allways have to Dope it out ?
you are a very confusing man AA

I did provide the specs, on page 19 of this thread:

https://rivperformance.editboard.com/t2310p270-write-up-f-body-brake-mod#73750

(you also PM'd me about this last year and I provided you the info)

The photo was from someone else's write-up. Search F-body bracket mod and you'll find dozens of pictures showing similarly modified brackets.

I don't think it's that confusing. It's a hole with threads, not rocket science. I said "drilled & tapped" like 5 times, and you're telling me I need to drill first and use heli-coils. WTF?

boy,yer such a grouch

Robo, you just posted a bunch of misinformation about something you didn't know enough about. Don't take it personally. I just don't want somebody killing themselves from putting their brakes on the wrong way, because you said it works. Now, go and fix your brakes before something bad happens.

Just throwing this out there. "Drill and tap" is not exclusive to do with heli coils. The drill part is setting the hole to the taps inner dimensions, and then you run a tap into it to make the outter. You need two marked points to cut a thread, the inner DIA and outter DIA of the thread pitch. (A heli coil has much the same process to put in because its basically a tap thread around a tap thread for use with different metals.)

AA wrote:

Robo, you just posted a bunch of misinformation about something you didn't know enough about. Don't take it personally. I just don't want somebody killing themselves from putting their brakes on the wrong way, because you said it works. Now, go and fix your brakes before something bad happens.

Ok.first off.my info is correct too.I did not get read enough into your write up,that does not mean that inserting a heli-coil is wrong.It can be done that way too.Even tho 2mm might be enough to give the bolt enough purchase,I would venture to say that a heli-coil would give more.
as for your theory of the "Clunk" I.ve examined my caliper and bracket and find no evidence that the caliper has moved At All.up or down along the knuckle. so before you jump out there with "Theories" re examine that one. and let me not bring up your jacked up stainless brake hose debacle.
So dont go jumping all over my ass with "people killing themselves" comments.Drama queen

Never said the helicoil was wrong, just completely unnecessary.

If you're using 12mm f-body screws securing the caliper through 14mm holes in the knuckle, you have a disaster waiting to happen. It's not a matter of if but when. That's the part you're wrong about.

SS braided line failures were ZZP's faulty product. They fixed the issue and sent me replacements. It's all in the thread.

AA wrote:

Never said the helicoil was wrong, just completely unnecessary.

If you're using 12mm f-body screws securing the caliper through 14mm holes in the knuckle, you have a disaster waiting to happen. It's not a matter of if but when. That's the part you're wrong about.

SS braided line failures were ZZP's faulty product. They fixed the issue and sent me replacements. It's all in the thread.

ok here is the part that you failed to get,I will be replacing the 12mm f-body bolts with a 14mm shanked 12mm threaded bolt.Im not wrong about anything.
the SS braided lines in your thread were too short.I would have spotted that in an instant.

robotennis wrote:

just a word,you dont have to use spacers or taps or anything for the brackets.just use the firebird bracket bolts themselves.they will go thru the alu knuckles thread right into the caliper bracket no problem.

This is wrong. This is dangerous advice, stated after Robo improperly installed his brakes.

robotennis wrote:

now that I think about it.running a tap into a cast iron bracket is completly the wrong way to go about this.the correct way to prepare the bracket is to drill the bracket out so as to accept a HELI-COIL insert,and then insert the bolt. just tapping the bracket will weaken the bolts holding power .I would rather clunk around until I find a dedicated shoulder bolt 14mm dia shoulder x 12mm 1.75 thread.thats the way. No arguing AA

This is also wrong. Drilling & tapping the cast iron brackets has been done many times. It works, and has been road proven. It's the way GM manufactured these parts in the first place. Heli-coil inserts are not necessary. Correctly modified brackets are included in brake kits from ZZP and W-Body Store. Other venders sell these modded brackets. They don't use Heli-coils nor odd-sized fasteners to short-cut.

Robo made these comments after installing his brakes the wrong way, claiming he knows better than our write-up. Don't buy into it. He doesn't have a clear understanding of how these brakes go onto the car. It may seem I'm making a big issue about something as simple as the screws holding the brakes to the car, but there is no good reason for Robo to challenge the knowledge we've collected in this thread, other than to throw a wrench into the gears.

To be clear, I dont want to discourage folks from trying new things, just be sure when you make a claim, have some kind of evidence to back your idea, other than "I am right and others are wrong, just because..." Take photos, list specs, test your method, and be prepared to defend your idea with some real data and experience, not what you might do or will do, or what you assume. It does not help to argue your case while you're stuck in the middle of a problem. Solve it first, test it, THEN show us your findings. Never be afraid to ask questions if you need help.

Best, AA

Ok.On top of the massive fabrication I've undertook in the past few weeks,forgetting all about the bushing sleeves is an easy thing to overlook.Pointing this out to me had me go"gee.I forgot that" but not until afterwards did I say"a Heli-coil would be better.You say its an unnecesary step.Thats your opinion.Dont ram your shit down my throat
.When I originaly installed the Caliper,I used the Firebird bolts and I said"Man! they work!" not realizing that the knuckle bolt bore is 14mm Id and the bolt is 12mm OD.everything went on nice and tight.You say this could cause a clunking.OK.I get it.I looked at the caliper and the bracket and found no signs that the caliper has moved at all despite the 12mm bolt.Even if the smaller bolt were to stay there I dont see it causing any catastrophic failure at all.
The bracket is held good and tight to the knuckle.This does not mean that I'm going to be a yahoo and leave it there.Of course reminding me that its the wrong bolt size is the right thing to do.thanks.I told you what I would do.Instal a shoulder bolt! thats the way to do it.A fully threaded bolt will dig into that alu knuckle and gauge it all to shit.No need to tap or drill,Simple solution.14mm shoulder bolt,20mm shank x 12mm x1.75 thread.OK.
So dont go out there and pretend to be Riv perfformance's modification savior.YOU installed the wrong brake lines in your car.Had you not noticed this or had it gone on for a little longer and another member followed your advice and bought the same lines ,you would be typing a different tune. so dont come to me with all this dramatic ,Oh God,Robo is going to kill my club members bullshit,! I'll take a clunking anyday.The clunking I found out,is the alu control arm bracket.I made it 1/4' too wide.simple fix.remove CA bracket,cut ,weld,reinstal.clunking gone.
Once again AA.yer not a bad guy but youre a typical drama queen.you will say anything to win an argument. disect that

Hey Robo, it appears to me that Aaron is just concerned about the chance that you might kill yourself because of a brake job gone bad. Don't actually know if he is correct or not because brake jobs are the one thing I won't touch. I have a problem messing with something that can kill me if I screw up. But I suspect that anyone who depends on his brakes to bring him down from 100 MPH regularly has a point worth listening to.
So listen, dammit! This site would be kinda dull without you.

Robo, you asked me for help multiple times through PM. I tried to explain to you again and again how they go on. You clearly didn't understand how the F-Body calipers were attached when you installed them. You didn't bother to read this write-up, and you didn't bother to order a pre-fab upgrade kit. If you had done either, you'd be using drilled and tapped brackets, no Heli-Coils, and no odd-ball screws.

Robo, you and I do things in extremely different ways. You assume the methods in this thread are "my way", but actually everything here is a group effort. Guys like Mr. Riviera, Oldsman, turtle, ewolfe laid the foundation for what would become an acceptable and effective way to put 2-piston calipers on the Riviera. So when you put down the way we modify the brackets, you're actually saying you know more than half a dozen Riv owners who've done this mod and tested it for years. I wasn't actually the one to discover that spacers with F-Body screws were a bad idea - I followed advice from 99prixgt, who posted this info:

"As far as the drill and tap vs. sleeved...There has been way too many instances to list where the bolts backed out with the sleeve method, bolts loosen the caliper and leaning into the wheel, leading to an extensive amount of wheel damage and wheel lockup. Basically the f-body caliper bolts are smaller on the LS1's, with your riviera and my grand prix the bolts are larger, some may argue but the correct way to do your brake swap is to drill and tap your f-body calipers to match the bolts for your stock caliper brackets. Im not sure what size caliper bracket bolts you use but you can take them and your f-body caliper brackets to any local machine to get them tapped to the correct size, for me i spent $10 on the bit, and $20 for him to do the labor, a small price to pay for safety."

Now THAT'S good info! I listened up and did things the right way. And I never took credit for this, because I know that sometimes others know more than I do, and I soon learned that EVERYONE in the 3800 community was doing it this way, and that was 4 years ago! 99prixgt did his homework and shared with us some critical info for those who were willing to listen. I notice YOU - Robo - are not willing to listen to things that make sense. Is it because you think you have all the answers? To add insult to injury, you have the balls to come in here the day after you incorrectly installed your brakes, to tell US that YOU KNOW MORE THAN US?!!! Are you friggin' kidding? GIVE IT A REST! If you think I or anyone else is going to dismantle our F-Body set-ups just because some self-proclaimed prima dona says we're wrong, you're wrong. I'll tell you where you can put those Heli-coils, Robo!

As for the SS brake lines you keep bringing up, they were only ones available for Riviera/Bonneville at the time for the F-Body mod. It was a new idea for ZZP, and they made a mistake. Other Riviera guys were running them, too. When I saw what was happening, ZZP was already on top of it, and they sent me a longer set, which also had an improved strain relief. You can blame me if you want to Robo, but I will say this - I still buy products from ZZP, partly because of their great customer service. At least ZPP knows when to admit when they're wrong.

1) I did ask you multiple times thru pm,to explain the bits that go into the dril & tap method.I even orderd the tap from Mcmaster.I do know how the calipers are attached.I just overlooked the bolt bit.Still,no harm done and no clunking.what your point? again,you just have to win a little argument in your little office.

2) I am not saying that I know more than anyone else.those are your words.I'm saying that a Heli-Coil would be my way.Wether just tapping into a drilled out hole or not.I like Heli-coils.Theyre good and sharp stainless steel. whats wrong with that? And,i have so much on my plate that going over the F-body thread over and over again is alot of time I dont have and I cant remember everything.

3) you just cant concede can you? Now it's insults to get youre point across "I'll tell you where you can put those Heli-coils, Robo!"
nice.real grown up. And what the fuck do you mean by "Prima Donna"? where in the fuck did you get that?I dont shove my views down anyones throat.I dont say my way is the absolute way.I dont put my mods out there(and they are tried and true) and demand that everyone adapt them.what the fuck are you on about?

4) As soon as I would have recieved brake lines 3 to 4 inches too short I would have imediatelly sent them back,not ignorantly put them on only to have them fail.Duh.Dont you know how to measure? Could you not see that the lines were binding and taut?I guess not.

5) I.m not going to give anything a rest just because you say to.I'm in the right just as you are.my calipers dont move AT ALL. So this is all just an ego stroking,oh look how I can go into the archives and pull up every little sentence proving my point thing, right? So no.I will continue to respond to your logic with my own.

I give up then. Robo will never get it until his calipers fall off the car. For everyone else who tries this mod: NEVER use the F-body caliper bolts to secure your 2-piston calipers to your Buick Riviera knuckles, like Robo did. It doesn't matter if you think the calipers won't move, can't budge them by hand, or if you can't see any evidence they've moved. Don't assume there's no harm done. Fact is, when you secure calipers with 12mm bolts through 14mm holes, they're going to move every time you switch from reverse to drive. Each time they budge, the calipers get looser, and looser, and the bolts will wear against the knuckles. It does happen, has happened, and will happen given time. F-Body brakes are a great mod, easy to do, VERY RELIABLE, but ONLY IF YOU DO THINGS CORRECTLY. The brakes are one of the most important systems on the car. Don't be that guy who should have known better. Be smart. Read the threads. Listen to people who have used these brakes for years, and have info from experience that will save you time, and figuring things out the hard way.

GOOD LORD AA. Did I not just say that I will replace the damn bolts?
Did I not concede for everyone to see ,that I realize that I put the wrong bolt in?The fact that I do not discern movement in my bracket dont mean it cant occur.I give you that.Did i not give the dimensions of my new shoulder bolt.Posted in my previous comments? Did I not?I did.
Holy smokes! The wrong bolt is in my bracket! I see that.I dont see that my method of dealing with the problem is that big of an issue as is the issue YOU have of admiting that I admited to the wrong bolt!

I sed "Ok.I had to edit my thread.the bolts go thru the knuckles and into the bracket.i got that right.that is how i set it up.i just forgot all about the spacer thing. I see your point tho.problem is..i cant find the damn Oem bolts!" I know that my OEM bolts wont work.I get it.Advise from F-body modders wont go unheaded.I just got carried away with my other mods and lost track of it all.

I think its clear to anyone following this thread,God knows,all the good boys and girls have gone to bed allready,that I see your point.I'm not arguing that.I just like a good fucking Heli-Coil! whats wrong with that?

I also sed "I would rather clunk around until I find a dedicated shoulder bolt
14mm dia shoulder x 12mm 1.75 thread.thats the way.No arguing AA" no more Beast Ice on saturdays for you AA.You become too argumentative.

That you mentioned on numerous times that you wrote for all to read "DRILL AND TAP"well..like I sed,I cant remember everything