Is there some consensus to what size (OD) to go for? Is there anything else that needs to be done for some applications?

Seems like looking at some of the threads and instructions out there I find 5.95", then one place listed something much smaller but then ended up going 5.85" with a little step cut into the face (no dimensions listed). I think I've seen 5.65" somewhere but I cant seem to find where. I'd like to leave as much meat around the bolt circle as possible, but don't want to run into picking up some replacement rotors last minute on the road or something and finding that they have a slightly smaller ID and won't fit my hubs.

I also know that the 96 and up f-bodies, and I believe all the C4 and up corvettes used a smaller pilot hub diameter than the earlier RWD GM's did, so I'm wondering if the later rotors that people are converting to have a large enough bore diameter to fit over the 3rd gen pilot hub diameter or if the need to be cut to fit, and in that case does it make sense to turn down the pilot hub surface on the 3rd gen rotor?

 

Mine ended up being smaller than the numbers I found posted. I think I ended up at 5.8, but I didn't document it....

I had the rotors on hand, and it didn't occur to me that others might be a different size :-/

I kept the fit kinda tight, which may bite me in the @ss when I try to remove them in the future.

I didn't have any problem with the pilot hub.

 

I had mine machined down at the point where the rotor "meets" the hub, for my LS1 brake swap.

I guess this should work fine.

If the rotor is or is not a tight fit, I don't think it matters too much.

I could be wrong, though.

 

In my personal experience, on most cars the rotor fits the hub pretty closely.

 

yeah I imagine the less that is machined off the hub, the tighter the fit will be, and the tighter the better (one would think).

 

My aluminum hubs are 5 15/16". If that is enough meat for aluminum it is certainly enough for steel.

Old school GM hub diameter is 70.3mm. The new stuff is 67mm. I'm not sure if there is enough meat on the oem hub to turn it down to 67mm. I don't have one sitting in front of me right now.

 

I am guessing that the way I had mine machined down, the fit will be pretty tight and definitely tight enough to be solid.

I don't think it will be too big to fit the rotors on, but I do worry about this, since I've never done the LS1 brake swap before.

I just had the rotor machined off and kept the hub diameter untouched, at the point where the rotor part "meets" the hub part. I sure hope it fits, since I had the hubs powdercoated, plus I already packed the new bearings and assembled all the parts onto the spindles and everything.

It would suck if the LS1 rotors did not fit onto the hubs. I would be displeased, to say the least.

 

Hard to say. The LS1 hats are 162mm wide according to Autozone. That looks like it will be pretty tight.

 

162 is 6.378", I'm pretty sure that my stock rotors hubs were right around there or slightly bigger, so I'm betting it will be a very tight fit if it fits at all.

So I'm guessing there is no consensus on the OD, and that no one is machining the pilot hub??? C4 and LS1 rotors fit over the stock pilot hub or are you guys machining them to match?

 

I have not seen anyone machine the pilot hub. I do know for a fact that the C4 rotors fit on our hubs.

 

Buy the rotors & take your 3rd gen rotors to the machine shop together. "Machine these down to fit in these." Then they'll fit good. Just tell them how "tight" or "loose" you want them. Anybody got a 4th gen to measure the stock hubs of, to see how the stock ones fit?

 

Mine were with the blackenedbird method. Cut em down til they fit in the rotors! Mine are a close fit, but dont touch.

 

I have a set of aftermarket slotted LS1 rotors, and they fit over the pilot no problem.

No consensus on hub OD though it seems. I would shoot for .03-.05 clearance if I were to do mine again.

 

I messed up on mine darn it. For LS1 rotors, they need to be down to at least 5.87 inches. The front/top edge also needs to be beveled a bit to clear the inside of the rotor hat.

To my dismay, I found out yesterday that the LS1 rotors will not fit over the hub if it is taken down only at the point where the rotor meets the hub.

Crap....back to machine shop they went. Should be done tomorrow.

 

What rotors were you using/ I turned down a set of stockers and only needed to take a little off the edge of the hub to clear the rotor hat, the hubcentric part is just fine, it's a tight fit..no problems at all. I checked it with C5 rotors and baer eradispeed 2 pc rotors. They all fit just fine. Same as the J55 C4 Corvette HD (13") rotors.

 

I bought a set of 2000 Camaro rotors. I figured these were "LS1" rotors and figured I needed these rotors to match the LS1 calipers.

What sucks is the hubs are powdercoated now

 

no, you need to machine stock hubs for LS conversions and 1LE hubs for the corvette 13"HD J55 setup because of the offset on the 1LE hubs (they allow thicker brackets, otherwise you will end up with a stepped bracket or a very thin one) So, want ls? turn down stock rotor. Drill the spindle w/ a 10mm drill, use an M12 coarse machine tap to tap the holes with a drill and persto done. I did a set of spindles yesterday in 15 minutes, it's that easy. Use 12.9 grade M12 on the spindle and M14 on the caliper abutments

 

What's the M12 for? To hold the caliper adaptor brackets or something else? if yes I'm trying to figure out why you really need to thread them for a different bolt, why not just use the stock size?

In my case I want to use the C4 12" brakes with a set of rear C4 12" rotors so I have room for thicker brackets. I'd love to go with something bigger like LS1 brakes but I don't think anything bigger will work with the wheels I want to run.

 

Can someone tell me if I have all the parts I need for my LS1 brakes?

I have the full assembled calipers with that metal bracket thingy in the middle of each of them, a new set of pads that came with shims, the rotors, and the lines.

Do I need some other weird parts to make the pads fit in the calipers properly?

I don't want anymore surprises when I go to put my front end back together.

Thanks to anyone who answers me!!

 

M12 is to bolt the caliper brackets to the spindle. Depending on what abutments you have the calipers use M12 or M14, most use M14..I think only mustangs used M12 abutments on the C4 corvette type PBR calipers. LS calipers use M14 bolts.

What wheels do you want to run? 13" C4 HD conversion (grand sport, Zr1, baer track1) works behind a 16" iroc wheel and all 17" wheels. No need to go for 12'.. The 12' JL9 C4 rotors are very thin and frankly they suck. The only worthwhile conversion is the J55 caliper and thë 1.1 wide 13" rotor. The adapter brackets are the same. The difference between 12 and 13" is in the bolt hole locations in the abutment. Only prob is, you can not use the 12" corvette abutments because the abutment is straight in the middle, it will hit the rotor hub. You will need 1LE abutments to run 12s but those abutments and brackets are stupid expensive. the J55 13" stuff is cheaper in total because of that....another reason to go that route.


Cut down spindles, 1LE hubs and adapter brackets

 

You need the calipers, the anti rattle clips, the pads and the abutments. the abutment is the bracket that bolts to the spindle, the caliper floats in it.
Furthermore you need the lines, the rotors, a set of turned down stock hubs..NOT 1LE hubs, a set of modified spindles and adapter brackets for C5 calipers. Same bracket for all sizes (if you use C6 abutments with 13.5 Z51 rotors it will simply bolt on)

stock rotor machined into a hub w/ arp studs, bracket on modifed spindle


caliper w/ abutment installed


backside, same rotor & bracket but w/ z06 calipers (needs larger rotors)


comparison, C5 13x1.25 rotor left, stock late pbr caliper 11.5x.81 rear rotor middle and C4 J55 13x1.1 rotor on the right

 

A little info I copied from my own forum tech article

C4 Corvette Caliper Pictorial

Below are some pics and descriptions that show some of the differences between the later ('88-'96) C4 calipers.


Pics of the JL9 (12") caliper:










Pics of the J55 (13" Non-GS) caliper:










Pics of the GS (13") caliper:







Noted differences between JL9 (12") and J55 (13") Caliper:

 

As you can see below, the major difference between the J55/GS and the JL9 caliper is the width of the throat where the rotor resides. The J55/GS caliper is the one on the left and is about .5" wider than the JL9.



Noted differences between J55 and GS Caliper:



It's very hard to tell in this pic but you may notice that the rib running between the piston cylinders is deeper on the J55 caliper then the GS caliper however the GS calipers rib is a bit wider.



There are a couple of differences noticeable in this pic. First, the ribs on the top of the calipers. The J55 has more ribs but they are thinner than the ribs on the GS. Second, notice that the triangle shaped leg on the J55 caliper is not present on the GS.



Main difference here is that the GS caliper is smoothed with the "CORVETTE" logo unlike the plain, ribbed J55 caliper.



Another view of the top of the calipers showing the difference in ribs.

This is a Camaro 1LE caliper 7 abutment bracket (and adapter bracket + modified spindle, just like stock 1LE). The 1LE uses a 1.1" wide 12" rotor, it's the same caliper as the J55. The abutment bracket is different though, it uses the smaller mounting hole distance like in my 1st pic of the GS calipers.



The abutment bracket itself is also what makes the difference between a 12" and 13" setup, the bolt holes are simply in a different location.

This is the abutment bracket like used on Corvettes. See how it's got the bolt holes spaced wider? The 1.1 sized abutment bracket also has a wider clearance slot for the rotors and is wider overall. On a 12" bracket the 2 bolt holes will be drilled closer to the caliper.


White racing sells the correct bracket
http://www.whiteracingproducts.com/i...ex&cPath=6_170

The 1LE abutment brackets won't work, they also have that bowed center, that was done to clear the hub on the 12" rotors (a 1pc rotor/hub), if you see that hump, you know they are the wrong brackets

 

I keep reading that the factory 16" TA wheels will not clear anything bigger, not even the LS1 brakes. I believe that I can actually run 15" firebird rims with the c4 12" brakes, but no others, but those are not a make or break for me.

huh, that doesn't seem to match some of the other stuff that I've seen on here, I haven't heard anyone else mention the 1LE stuff with the 12" brakes, at least not if you're using the rear rotors.

Not sure I care, since I'm probably going to end up using some modified racecraft spindles (very long story), and it looks like they're just a straight bracket to use them with the 12" c4's (I wish i could confirm, don't have all the parts and don't particularly want to buy everything till I know what will work and I can't seem to get info from racecraft, or flyinbye who makes the brake brackets for the racecraft spindles).

I keep meaning to ask what paint u used on those, I thought they were white in other pictures but here they look grey...

 

Thanks!

The anti rattle clips are those clips that snap into the center of the calipers, right? If so, I have those. I also have all the other stuff I need, and I am hoping the third gen lines will work with the LS1 calipers. I am pretty sure they will.

I am very familiar with the abutments...I had to practically break one of the guide pins out of one of the abutments because it was rusted in there. Then I took a .44 caliber bore brush and some WD40 and cleaned the heck out of the hole in the abutment so the new guide pin would slide in and out of there properly. It worked like a charm.

I screwed up on the machining of my stock hubs, though. I took them back and had them taken down to 5.87" and also to get that beveled edge on the front face. Sucks because I already got them powdercoated and packed and installed the bearings and put them on the spindles. Darn it!!

It's always something.

I am also wondering what I should do about steering stops. I cut the lower ears off the spindles when I modded them for the new brackets. I know I can cut the stops shorter on the A-arms, so the banjo bolts won't hit them, but then what will prevent the wheels from rubbing inside the wells when fully turned?

 

The stock lines will work just fine. That is what I am running until I can afford braided lines.

I didn't modify my steering stop at all and the ears are cut off my spindles. I had no issues with banjo bolt interference.

 

Cool. So do the tires rub inside the fender wells? Is the steering weird without any stops?

 

With some trimming and a small spacer shim a 12.5 set of rotors and LS calipers with some grinding done will clear the lace wheels.

The C4 J55 calipers are a lot more forgiving when it comes to wheels because of the larger rotor offset and the use of 1le hubs allowing more clearance to the caliper. They will not fit a lace wheel however


I was only discussing the fronts. For the rear you can upgrade the 11.5?? rear rotor to 12" C4 rear rotor and use new brackets.

The 12" V4 stuff bolts to exactly the same bracket as the 13". The difference is in the abutment bracket, the holes are drilled lower. The 12" has a nartrower caliper and abutment but you can get a wide caliper and abutment and then use a 12x1.1 custom rotor or an eradispeed or whatever and use that. It will bolt to the std. C4 adapter bracket.

Check the pic of my baer calipers w the gold abutments. Now imagine the holes 1/2" up towards the caliper and the ears cut off. I have a set of those abutments lying around. The only problem is, it will NOT fit a normal brake hub because of clearance issues. That's why the 1LE abutment has the curved center, to clear the rotor hat.

 

I think you've managed to confuse yourself and to be honest, I don't know that I'm following what you posted:
- I'm planning on running LT1 rears, they will clear everything I want and I have some sitting around
- currently planning on running 12" C4 fronts with C4 rear rotors, the rear rotors have a different offset that is supposed to give more room for a bracket.
- other links on this site seem to document that you can't just use the same bracket

I'd love better suggestions for what else will work, but I'm not sure I'm following. Here is my brake suggestions thread, but noone said anything about the fronts there:
https://www.thirdgen.org/forums/brak...e-options.html

 

I'm not confused at all, LT1 rears are the same as the late 3rd gen rears apart from the parking brake bracket and the vibration dampers on them (late 91/92 have those too) so thats 11.5 rear discs. I was mentioning the 12" rear C4 corvette rotors and adapter brackets, you can use those with the same calipers as the vette rotor is also .81 wide

If you use C4 stuff in the front the stock front rotors will work fine if you use 1LE hubs, if you sue regular hubs your bracket will be paper thin, even with C4 rear rotors. The offset difference is minimal.

The only reason you can not use the same bracket for the 12" fronts is because of the rotor hub not clearing a normal 12" abutment bracket. That's the reaason for the funky 1LE bracket with the arch in the middle and the different mounting position.

To prove it I will take a pic of a 12" bracket tomorrow next to a 13 bracket, its the same abutment with the ears cut off and the hole in a different spot.

Still, C4 corvette JL9 front brakes are junk, a waste of money. A buddy of mine is running 12.5 front rotors w/ C5 calipers and he used a small sapcer to clear the wheel. The C5 caliper is much larger. If you were able to find a 12.5x1.1 rotor that would be a much better option. You'd need a custom bracket for it though with the holes relocated .25"

 

I didn't read the whole thread carefully, but the 2000 camaro front rotors I bought last week measured 5.905" inside. I had the "hubs" turned to 5.900"ish for clearance since the center pilot was pretty much size to size with the rotor.

 

I would have to agree. Those brake are worthless. I would just stick with stock and save your money. Your best bet would be to find a thick (1.25") 12" rotor in you must use 15" wheels. Something like what Ed uses on his 12.2" Wilwood FSL kit to fit cross lace wheels.

 

I am pretty busy now but I have to take apart some of my front right suspension of my 2000 to check out a clunk. I will try to see if I can get an ok measurement of he hub. Factory size, seems like a good number to base what ls1 calipers go on right?

 

I don't have the option of sticking with stock, I'm using spindles that don't have the stock mounting holes but have the dust sheild mounting holes that are used to mount the aftermarket conversion brakes.

Honestly, the standard duty c4 brakes are larger in diameter which is the only thing that should affect stopping power. the thinner rotors shouldn't, it just might make them less durable in heavy use, but honestly, even though this car will be setup much like a road race car, it will probably see mostly (in order of total amount):

1. street
2. dragstrip
3. autox
4. maybe RR

use... That being the case, the 12" c4 brakes seem like a great choice, they're larger OD which should give me more stopping power, will fit under all the wheels that I might want to run, the lightest of the bunch (I believe that the whole conversion will totally being lighter than the stock brakes, and something like 25# lighter unsprung than say an LS1 conversion...


If there is another set of brakes that can be had for close to that price that will work better and still work with most of those wheels I'm all ears, but i don't believe there is. I'm not beyond making custom brackets to use mismatched parts to get a more optimum setup, but:

• I don't have easy access to a lot of parts to mock this up so i'd probably need pretty close to a list of parts to buy that will work, I also don't have room in the garage for it, so it really can't sit disassembled in my driveway for more than a day or 2 before my HOA will get on my case.(I hate being spoon fed but that's pretty close to what I'd need here).
• I'd want them to be all stock, off the shelf parts (maybe with the exception of the adapter brackets which are not wear items), nothing that would need to be ordered in case I needed a replacement. this is a street car that I drive to work regularly (at least its not my DD)
• I'd want them to at the very least fit under factory pontiac 16" rims, which appear to be tighter than the camaro 16" rims, and 15" drag skinnies

 

Yeah in your case, considering you can't easily or cheaply use the OEM setup, maybe the C4 brakes are the right choice.

 

You can argue all day long but the fact is, JL9 brakes suck! I have 2 C4s and have had otehrs and those brakes are always junk, they fade very quickly because the rotor runs a lot hotter than the J55 one due to the significant mass difference, they are not a worthwhile upgrade if you ask me.

What you could do is get a J55 rotor and turn down the OD, the stock caliper only swipes the outer part of the rotor anyway, there's enough meat there from the looks of it to move the caliper down on a turned down diameter.

Or you could get a 7.5x12 bolt circle C4 corvette hat from Baer and then buy a set of 1.1 thick 12" rotors for that bolt pattern..or the same from any other manuf.

 

Saving this post for later.

 

A bit of experience: I made hubs from cheap rotors that I got for free, but when I pressed the new (longer) wheel studs into them the hubs cracked from the stud hole out to the edge in one or two stud positions on each hub. I threw both hubs in the trash. I guess I need to buy Wagner or another name brand rotor to start.

 

Same thing happened to me when I upgraded to LS1 brakes. I haven't seen this anywhere but apparently GM used two different diameter studs over the run on these cars. One studs shoulder is 0.501 and the other is 0.509 and thats enough difference to crack the hub/rotor. I think the newer 91/92 cars use the bigger stud because mine is a '88. I cracked one of the hubs that me and my Dad turned down in his lathe so I went to the j/y to get another one(came off a '91) and they went in fine. The other one from my car we ended up reaming out some(dorman recommends a 0.024" press fit if I remember right) so they'd fit without cracking the hub. As for the hub diameter we just turned it down till the rotor slipped over it and for the hole that goes over the dust cap it fits just fine. I got some cheapie slotted/drilled zinc plated rotors and powerstop pads from ebay for $88 shipped, been on the car since January this year and haven't had a single problem.