Took my spare spindles to a machine shop to have them drill and tap the 12mm x 1.75 hole for the 1LE brackets, which follows the instructions from that How-To PDF I got from here. Got them back, and the guy told me he wouldn't use them, as it doesn't appear to be much meat left (edge distance) on the spindle after modifying one of the holes. And to me, he's right. Check out the pics. The holes are perfect size for the bolts from the brackets, I checked. And they were drilled on the centerline of the original holes.

What am I missing here? Anyone have pics of their modified spindles with a good clear head-on shot of the hole? The how-to file only had angled pics and I couldn't tell.

 

Looks fine to me.

 

I just happened to spot this issue when jerking spindles for my conversion at the yard. GM made two different spindles that I found in the yard for F-body cars. One had very little "meat" by the upper bracket hole (the ones you show) and the other had much more material around the upper bolt hole (like the lower hole). I pulled three spindles before I figured out that there is a letter that designates the differences between the two without pulling it all apart. On the upper portion of the original caliper ear there is a letter "B" cast into your type of spindle. The ones with the meat have a letter "A" cast into them. I could not tell which ones can be found on which years. I found letter "A" spindles on a 91 and 92 RS camaro and letter "B" spindle on a 85 firebird. I dont know what my 83 has yet cause I havent tore the factory stuff off yet. I can take a clairification picture when I get home tonight.

 

AndyZ28, one of the first 1LE gurus, details the change in spindles:

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.

The drills holes can be seen in the following link (and the OP's look fine):

http://web.archive.org/web/200605221.../1LEbrake.html

JamesC

 

I bought this car with a truck bed full of spare parts, and these spindles are most likely from a pre-'89 car, as most of the other parts I got were from that year group as well. The car itself is a '92, so I'm going to compare the spindles I got machined to the ones on the car and see what's up.

Thanks for all the replies.

 

Looks fine to me as well. Please note, depending on which 1LE brackets you use, you don't have to go that big with bolt size. I normally just use a 7/16" bolt as that's plenty big for this. Obviously if you use GM brackets you need to use the larger M12 size.

Ed

 

Id like to see the exact differences between the post and pre spindles. i might already have that answer though i just have to dig out several sets of spindles iv acquired over the years. At any rate if someone got some comparison pics post them up.

 

I took a set of '92 spindles I have and compared them to the ones I had modified and there is a noticeable (small, but noticeable) difference in edge distance around the holes that are to be modified. I have that set at the shop now getting drilled, so I'll post up some pics when I get them back to compare.

I also have a set of unmodified pre-'89 spindles that I will take pics of to compare to the modified ones. I didn't take pics of the '92 spindles before mods.

 

Here's some pictures for future reference of early spindles vs. later (I assume '90-'92) spindles. The late spindles were off my '92 car. Both sets have been drilled and tapped to the 12mm x 1.75 thread to match the factory bolt that comes with the brackets. You can see a clear difference in them.

I'm not a structural engineer, so I can't say the early spindles would fail, but just judging by what I can see, I'll be using the '92 spindles.

I will add, however, had the early spindles been made differently where the hole wasn't so close to the edge, I might be less prone to saving them for backups. Even on the '92 spindles, you can see that the holes aren't dead center of the built up area around them. Unfortunately that's not something you can control, as they were made 20 years ago Oh well.