you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

Now we all know that the 73-87 front crossmember and suspension components can be swapped into the 60-72 trucks. The 73-80 Chevrolet C10 pickups used a 1.28 rotor. Then in 81-86 GM switched to a 1" rotor. I did a bit more digging and found that the calipers are different for the 1" rotor but use a common bolt pattern with 73-80 so, it looks as if the 91 Camaro rotor will work on the 73-86 spindles if the 81-86 calipers are used as well. Also the flexible brake line will need to be changed if you have the 73-80 caliper as one of the calipers uses American standard thread and the other uses a metric thread. The parts house could not tell me which one used what thread but that they were different. I will figure that out when I purchase the parts. I have not done this yet but it does look like it will work. fones1966 a member here PMed me telling me about this possibility and I want to thank him for that. I just thought I would post this information in case there were others that could use it. Olympic Brake here in Washington is who provided this information. One note I want to point out is the specs that I have all show the same bearings on all three rotors. I was told by fones1966 that the 73-80 1.28 rotor used a A-5 inner bearing so that bearing would have to be replaced when switching to the Camaro rotor but, what I found was the 73-80 heavy duty 1.28 rotor used the A-5 inner bearing and the 81-87 light duty rotor used the A-6 as shown in the specs I have provided. I hope this information is helpful. Here are the specs on both the truck and Camaro rotors:

73-80 Truck rotor specs are:

Height 4.88
Diameter 11.85
Min. Thickness 1.220
Hub 3.06
Outer bearing A-3
Inner bearing A-5
Seal Part # 8871
Bolt Circle 5X5

81-86 Truck rotor specs are:

Height 4.63
Diameter 11.86
Min. Thickness .96
Hub 3.20
Outer bearing A-3
Inner bearing A-6
Seal Part # 8871
Bolt Circle 5X5

91 Camaro 1LE Performance Package rotor specs are:

Height 4.65
Diameter 11.85
Min. Thickness .97
Hub 2.78
Outer bearing A-3
Inner bearing A-6
Seal Part # 8871
Bolt Circle 5X4.75

Re: Do you want to change you 5X5 bolt patern on 73-87 front disc to 5X4.75
 

The Camaro rotor will work on the '81-up 1" spindle. It will not work AFAIK on the 1.25" early spindle...

Re: Do you want to change you 5X5 bolt patern on 73-87 front disc to 5X4.75
 

Well after much research and comparisons this is what I have come up with. I would like to thank gringoloco he helped me out here. The 73-87 2-1/2 drop spindle from CPP uses the A-5 inner bearing that has a 1-3/8" bore. This spindle uses the 1-1/4 rotor with the 5X5 bolt circle. This is the same size spindle as the OEM as well. Belltech has a 3" drop spindle that uses the A-6 inner bearing that has a 1-1/4" bore. This spindle uses a 1" rotor and there for can either be used with the light duty truck 1" 5X5 bolt circle rotor or the Camaro 1" 5X4.75 bolt circle rotor. There it is. This is the only way that I found to switch from the 5X5 bolt circle to the 5X4.75 bolt circle using the OEM rotors. Hope this helps

Re: Do you want to change you 5X5 bolt patern on 73-87 front disc to 5X4.75
 

good to know

Re: Do you want to change you 5X5 bolt patern on 73-87 front disc to 5X4.75
 

why would you want smaller brakes and smaller bolt pattern?
just curious.....

Re: Do you want to change you 5X5 bolt patern on 73-87 front disc to 5X4.75
 

There is no advantage with the smaller bolt circle, there is an advantage with the Camaro brakes. Even though they are a 1" thick rotor, they can be had in a much larger diameter as well as bigger calipers.

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

ahhh, I see :thumbs:

Re: Do you want to change you 5X5 bolt patern on 73-87 front disc to 5X4.75
 

If you notice in the first post the Camaro rotor is almost identical as both the 1" & 1.25 truck rotors. The advantage is the 5X4.75 bolt circle in my case. I have a new set of 18X8X4.5 with the 5X4.75 bolt circle Billet Specialties wheels that I want to use on the front of my truck and because you like pictures Joe....:lol:

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

good info,i ran into the same problem, bought some nice cheap 20s and adapters but they wouldnt tuck, so i took my rotors to a machine shop and they knocked the studs out and redrilled the rotors to 5x 4.75 and put my stock studs back in for $100 for the front, and if i ever wanted or needed to go back to 5x5 all i gotta do is knock the studs out and put them back in the factory holes, i took my axles and drums and had them done too for $100

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

I researched this route(in my case it would have been 25.00 per rotor plus studes) but was afraid the redrilling could compromise the integrity of the rotor as part of the webbing on the back of the rotor hub has to be removed in order to redrill. Not to mention the hassle of replacement parts. This way all replacement parts are OEM and available at your local parts store.

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

The rotors on my 74 were re-drilled to car pattern & the snout of the hub was turned down to car pattern as well (they were stock Raybestos GM 1/2 ton 1.25" 5x5 rotors). They've seen daily use since '02 w/no issues (been turned one time).

The use of 1LE rotors on LT duty truck spindles would work for a limited use application. But one of the first upgrades made to F-bodies is bigger/better brakes (rotors) that don't warp as easily as the stockers would/could.

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

Can you explain on the upgrade? I had a 87' SWB and the warping was an issue. Maybe I would be better off redrilling the 1.25 5X5 rotors?

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

The thicker surface area of the 5x5/1.25" thick style rotor is less prone to warping vs. the thinner 5x5/1.00" Lt.Duty rotors. The warping is usually evident in heavier vehicles or those that see harder than normal use (think performance vs. basic passenger transportation).

It also has a lot to do w/factory rotors vs. an aftermarket supplier as not all parts are created equal.

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

Most F-body guys upgrade to the 1LE brakes. There are kits out there to upgrade to a '98-'02 F-body front brake(12x1.25 -basically the same as your truck brakes) or C5/6 brakes which are 13x1.25. There are upgrades from there to Z06 or Z51 brakes but the parts get spendy...

I've been researching this a little. It looks like the aftermarket C5 upgrade brackets might work on the light duty spindles. That is, if the dust shield/backing plates interchange between big car/light truck, then a bracket may already exist to adapt the 'Vette stuff.

More to come when I get some time...

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

Ahhhh . . .... Not a bad idea. Get ride of the problem rotor & keep the spindles w/the appropriate bearing dimensions.

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

Keep us posted on this.

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

So ALL '73-'80 half ton 2wd trucks have the 1.25" rotor?

Thanks!!

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

Yes. '71-'80 actually. Around '81 was the start of the light duty brakes.

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

And you should be aware that not all '81 up 1/2 tons have the light duty brakes. My 87 1/2 ton has the bigger brakes because it's a diesel (and thus very nose heavy).

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

I was just wondering because the '73-'80 trucks are much more common in my area and I'd rather have the heavier-duty rotor anyway.

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

OK, how do I get the 4 3/4" pattern for my rear disc brakes and camaro calipers with Glock's brackets? I haven't been having a lot of luck with this one.

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

Re-drill rotors/axles is a no brainer. Maybe cross-reference the F-body 1LE rear rotors & see if they'll swap.

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

Yeah that's what I was finding I was gonna have to do.
The rear f-body hats aren't tall enough. I was hoping someone might have tried some different front options. Maybe s-10 or van or something. I'll keep looking and measuring.

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

Hhmm.... The S-10 would be my first choice. I might have an S10 rear rotor in my possesion (I had a rear disc set-up for my G-body/pro-tour ride). What measurement would you need?

Re: you want to change your 5X5 bolt pattern on 73-87 disc to 5X4.75
 

If I remember correctly, :rolleyes: The measurement is from the wheel contact surface to the back of the disc, basically furthest outside point to furthest inside point.
'94-'96 Impala - 2.335" (the brackets are specifically made to work with these but they have the 5x5 bolt pattern)
'89-'92 Camaro rear- 1.97"
'93-'97 Camaro rear- 1.81"
mid '90s S10 I think front - 2.87"
The calipers are from a '97 Camaro because they have the e-brake built in and, of course, work with the brackets.
I can probably use spacers to make some of these work, I'm just not sure how much spacing I want to do and how much is safe.