Drill and tap with a .332 bit and tap 3/8" - 24.
Or... 13/32 bit and tap 12mm x 1.75.
?

 

I pick up a .332 drill bit and 3/8" - 24. tap yesterday i was planing to do these this morning but i was just fallowing up and reading once more before i drilled and taped i read others used the 12mm x 1.75 tap. Im having a set of brackets cut using luke's DWG file. I printed off the PDF file i looked at the templates for the holes they look almost like a 1/2". id assume it wouldn't matter if i went 3/8" or 12mm.

 

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12mm = 0.47"

3/8 = .375"

So you tell me.....Do you think .475" is close enough to .375" for it? What size are the bolts that are going to be used? If your matching the bolt sizes to whatever you tap it to, I'd go with maximum strength.

 

I was just wondering what is the best to use. This what i mean.





then on here he says.

4) Now two of the three holes where the dust shield was mounted must be drilled out and taped for a larger bolt. The stock bolt size in the spindle used to hold the dust shield on is far too small and would be too weak to hold a spindle bracket. The holes need to be drilled with a 27/32 drill bit. Make sure you use a brand new drill bit for this, you want the holes to be a straight and clean cut as possible. I highly recommend using a drill press, an angle (tilting) vice, and a small bubble level to make a perpendicular hole. The hole must be almost exactly perpendicular to the mounting surface, if it is not the bolt will be at an angle against the spindle bracket and could cause fastener failure. You should also drill both holes all the way through the spindle.



5) Tap the newly drilled holes with a 12mm x 1.75 mm tap. Make sure you use thread cutting oil to insure clean cut threads. Another tip when taping the holes is after every full turn back the tap out one half turn to help clear the metal filings. I also coated the spindle with Por-15 to prevent rust.



If you go with a bigger bolt you'll decrees the amount of material around the spindles but increase share force. 3/8" or 12mm its what about a 1/8th difference? is it going to really matter what i drill and tap with?

 

OEM LS brakes (on 4th gens) are 12mm x 1.75.
I used 12mm on my conversion. Grade 10.9

 

I just got done reading the 12 page post on the ls1 and I believe ebmiller ended up using 1/2" on the top and 7/16 on the bottom

 

Those were the sizes of hardware included with the conversion plates I purchased from Ed Miller. I chose to use the 12mm as it matches the OEM caliper to spindle bolts (which now bolt to the plate). 4 x 12mm 10.9 per side.

 

To keep it simple I normally use a 7/16"-20 on the upper bolt and a M10 x 1.5 button head Allen on the lower spindle bolt. The button head allows the caliper abutment to clear the bolt head, it's very tight in that area. You don't need to go to the larger M12 but that's up to you. Using slightly smaller bolts leaves more spindle material for you.

Ed

 

Thanks for all the info guys

 

Can you use M10 x 1.5 button heads on the upper and lowers? or is there a reason why you cant? are they both (upper/lower) by 30mm in Length?

 

Provided you use the correct grade bolt, there should be nothing wrong with using button head bolts in both locations. IIRC, 30mm was just slightly too long by a couple of threads. I used an SAE style washer under the bolt head and trimmed off a couple of threads as well.
Interesting in that I had sufficient room to use a regular hex head bolt whereas others haven't been able to. All of my hardware is 12mm grade 10.9.

 

I think all be going with 12.9 grade M10x1.5x30mm and some M10 washers for both upper and lowers then.

 

Be careful with your selection of bolt grade. It's not necessarily a good thing to "upgrade" to a higher grade bolt because you can. From my understanding, a higher grade bolt (12.9 vs 10.9) MAY prove to be too brittle for the application. The tendency would be to break under shear loads as opposed to flexing or bending a little before failure.
I selected a 10.9 grade M12 bolt because the 4th gen caliper carrier OEM bolts are 10.9.
Something to consider.

 

Are are people using to bolt the caliper carrier down to the LS1 caliper bracket? all have to see if i can find some 10.9 button heads then i guess.

 

IIRC Ed Miller sent along 10.9 grade button head screws so as to provide clearence between the adaptor bracket and the modified spindle. In my case (for whatever reason) I didn't need the extra clearence. When I scooped the 4th gen carriers from the scrapyard I also grabbed the 12mm bolts that attached the caliper to the spindle. OEM is 12mm grade 10.9. Plenty of selection at the local auto parts outlet.

 

Do you know the length of the carrier bolts?

 

I used 30mm for everything. Adaptors to spindle bolts were where cut to fit the drilled and tapped blind holes. I cut off about 3 threads. Same with the carrier to adaptor bolts. I cut them to provide clearence with the rotor as the holes are open. I thought it was best to use as much thread in the carrier as was available.

 

you would use the 12mm by 175 im doing this now and that is what is spelled out when u get your brackets also these are the rite thread and pitch for attaching the caliper to the bracket the bollts you can get at the hardware store or you could bag them at the yards on fourth gens with rear discs hope this helps some ted

 

That would be by using lukes brackets... What about Ed millers since his using
7/16"-20 on the upper bolt and a M10 x 1.5 button head Allen on the lower spindle bolt... The bracket would have 7/16/m10 sized holes ?

 

I found that Ed's (flynbye) spindle to caliper adaptors had holes large enough to accomodate a 12mm bolt.

 

I had my spindles tapped for a 3/8" x 24. I am wondering what bolts to get for it. I found some alloy button head bolts but cant find a rating or PSI rating for them. I found some heat treated hex bolts with 140,000 psi rating, and some grade 9 hex bolts with 180,000 psi rating.

If I go with hex bolts do I need to put a washer under them, and will the button head bolts work and be strong enough?

 

I would think that 3/8s is somewhat undersized. There's a reason why GM would use a 12mm grade 10.9 bolt.
The equivalent in imperial would be grade 8. If what you've purchased have no markings, chances are they are minimum grade and won't be suitable.
I like to use washers wherever it's practical. If you have the room, then yes, I would use washers. Button heads will be fine provided they are of the correct size and strength.

 

3/8" works for Baer brakes on their setup and it uses nearly identical components to the LS1 setup. I dont see why there would be a strength issue with the size, I mean if there was why would Baer of all companies use an inferior bolt size on their brake system?

I had a friend do it at a machine shop and I heard there was clearance issues with the M12 stuff. If it is a big deal I will see if he can do it again or I will just try and chuck it up in my press and do it on that and bring it out to a bigger size.

 

An LS1 brake swap would be sweet! I have size 15 aftermarket wheels though so Ive heard they wont fit Once my new tires wear down Im going to look into some new rims.

 

I am just piecing the kit together right now as I still have 15's with 2 brand new tires. I picked up a set of gold GTA wheels but I need new tires for the rims so it will be a little while before I actually get the brakes on the car.

 

I'm not familiar with Bears components in this application but I thinks it's safe to say (as you've suggested) that if it works for them, it should work for you.
Like I said though, GM uses 12mm. Flynebye (Ed Miller) actually uses two sizes when they ship the caliper adaptors (spindle to caliper carrier). From memory I believe it was 7/16th's for one and 10mm for the other.

The LS1 front brakes will definitely not fit the 15" aluminum Camaro rims. I can't comment on the other 15" rims available.

For the record, I picked up the caliper carriers and calipers from the scrap yard (2001 Camaro). Refurbished the carriers and used the old calipers as cores. Saved a bit of dough over buying a complete package. There are excellent articles out there regarding the spindle mods needed to make it all fit.

 

I am not saying you are wrong, but I dont know if I am right, so if I am wrong, or if the 3/8 bolts is questionable I will drill and tap to a larger suggested size. Thanks for you input.

 

Question is, how do we find out?

 

I am sure EBmiller or one of the other brake guys can chime in and let me know if I am off track or offer a better bolt size.

 

I ended up looking this up after not being able to find any 10.9.

Class
Proof Load (MPa)
Min. Yield Strength (MPa)
Min. Tensile Strength (MPa)

10.9
830
940
1040

Class
Proof Load (MPa)
Min. Yield Strength (MPa)
Min. Tensile Strength (MPa)

12.9
970
1100
1220

Tensile Strength: The maximum load in tension (pulling apart) which a material can withstand before breaking or fracturing.
Yield Strength: The maximum load at which a material exhibits a specific permanent deformation
Proof Load: An axial tensile load which the product must withstand without evidence of any permanent set.
1MPa = 1N/mm2 = 145 pounds/inch2

 

I plan on taping the spindles for M10 (upper and lower) I had opened up lukes LS1 bracket CAD file i see the bolt hole diameter is 0.5000" which is 12.7mm on all four of the holes since im going to be doing M10 bolts i would want to edit the spindles holes to 0.4212" / about 10.7mm to add clearance so the bolt fits the hole pretty sung correct?

 

Sounds a about right. I have decided to drill and tap my holes to a larger size. After looking at stuff I feel a 3/8" bolts is too small. So now I am debating on a 7/16" bolt or 1/2" bolts. I have taps and drills for both of those so it is a no brainer for me.

What thickness bracket are you using? I had a buddy plasma me some out of 3/8" plate but I read that with my late (90) spindles 5/16" works better. Who knows the answer to that?

 

Yes that would be correct. Just enough clearence to allow the bolt to fit.

I don't believe there is a difference from one year spindle to another. At least not so far as this modification goes. The problem that you may run into is the fitment of the caliper/carrier onto the rotor. With the 3/8ths plate from Flynbye, the caliper was perfectly centered over the rotor. At least with thinner conversion plates, you'll have the option of added a shim washer between the plate and the carrier to restore the alignment if it's an issue.

 

Just an FYI from AndyZ28's 1LE CD:

Spindle Comparison

1982-1989 vs. 1990-1992

"The spindles made for 3rdgen cars from 1982-1989 were essentially identical. Sometime in late 1989 a change was made at the foundry to incorporate several small changes to the spindles. This was done to increase structural integrity (in a very small way) to the existing spindles. Remember that at the same time a change was made to the brake line fitting threads affecting the thread pitch of the combination valve threads.

"The foundry change was a direct result of the advent of 1LE cars, and all of the derivatives. A study of the photos in this section will show the changes were required for the adapter to properly attach to the spindle. I encountered this interference when I did the 1LE upgrade on my 1982 Z28. I used a pair of 1986 spindles, and I could not seem to get the adapter bracket to line up with the upper holes (see problems). The reason was, that the adapter was designed to be used with the later 1990-1992 spindles. Those spindles had been made with an additional amount of metal removed in this area. At the same time metal was added to the area around the bosses that the adapter bracket was to attach to. This can clearly be seen in the photos, below. What I did to overcome this problem was to simply grind away the area of the spindle that was causing the interference. This work very well, and I have done the same thing several times since then. It occurred to me upon examining a set of the later spindles, that the foundry did exactly what I did. Only in reverse, It appears that they took a grinder, and modified the die to fit their needs. This meant removing some metal from the die, to in effect, add metal to the spindle. The thin area at the upper bolt hole has had no detrimental effect on my brakes at all.

"I would not go to all the trouble to hunt down a set of 1990-1992 spindles because they are stronger. The belief that the later spindles are stronger is a myth. But they might be easier to work with. I hope the images are helpful in deciding this for yourself."

http://www.andyz28.com/3rdGen/1leupdate.html

JamesC

 

Thanks James, I knew there was additional metal around the upper bolt hole. I did not know the rest. I guess that makes me feel a little better I have the newer spindles to work with. I think I am going to go with 1/2" bolts for the mounts, at least I can go with a M12 bolts if I want to.

 

Bolt list for two spindles.

M12 x 1.75 x 30. 10.9 hex bolt qty (4) bracket to caliper carrier
M10 x 1.5 x 30. 12.9 Allen head qty (2) bracket to bottom spindle
M10 x 1.5 x 45. 12.9 Allen head qty (2) bracket to upper spindle
Do i need any washers, anything missing?

 

Washers under all bolt heads that have the room.
Don't forget the locktite.
It may help to have some shim washers on hand should you need to align/center the caliper over the rotor.

 

I ended up going with grade 8 7/16" 14 pitch bolts for the spindle bolts. M12 will of course stay with the abudment bracket. Everything fits great. I did have to clearance the bolt heads between the brackets and the abudment bracket. I shaved my brackets and spindles for plenty of clearance between them and the caliper. Now I just have to save up for the rotors and pads, oh and some tires for my GTA rims.

Does anyone know what Flynbye performance does to make their LS1 setup clear GTA rims?

 

I didn't think it was an issue with any 16" OEM rim. The LS1 calipers (with Flynbye's bracket) clear my 16" IROC's.

 

Because of the design of the GTA crosslace rim, the caliper rubs on the back of rim. I was wondering if anyone knew what Ed does to his brakes so they fit the GTA rims. If it is secret please PM me the details and they will stay with me.

If it is just a spacer included with the kit I guess I will get some.

 

I believe in this thread there's pics and it was talked about...

https://www.thirdgen.org/forums/faq-...s1-brakes.html

 

just looked yup, post #279 to #283 .

 

Just make sure you say you will need them and they'll be sent along.

Ed

 

I know this thread says " LS1 " and i know theres something diffrent between te LS1 and C5 conversions. But can i follow this and be ok with C5 brakes? or would there be something i would need to change?

Love the diagram BTW, i think someone should build a how to modify the spindle thread and have it stickied somewhere cause ive searched my butt off and this is the only thread ive found.

 

Anyone?

 

If you haven't already, check out these websites.

http://lukeskaff.com/?page_id=329

There's also Ed at

http://flynbye.com/

Between the two of them you'll have all the part numbers and resources you'll need to assemble whatever you want.

 

Thanks for the info!

Youre Right, thats everything you need to know.