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I ordered the wrong calipers. Please help

spreadmonkey

Full Member
Joined
Dec 15, 2008
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284
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Austin, Tx
A while back I posted a picture of my rear brake calipers, part of the PO's mods. I was told by a few people they were the small GM calipers. I am replacing them to incorporate a parking brake, and went to install my caddy calipers yesterday.

After I pulled them off the truck I realized they are not the small calipers. The spacing from pin-hole to pin-hole is 6 5/8". So not only did I order the wrong calipers and possibly its too late to return them, now I'm back to not knowing what I need to order.

Please help!
http://www.flickr.com/photos/31492820@N07/

The pictures I took yesterday are at the top, and the ones with them still on the truck are towards the bottom of the page.
 
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Apogee

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Nov 26, 2005
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6,033
Could these be the right swap maybe? My rotors are 1 3/16" thick
http://www.tsmmfg.com/3120.htm

Those TSM calipers that you linked to are ~7" center of pin to center of pin but you're saying that yours are 6-5/8...is that center to center or did you measure the shortest distance between them? The ~7+ inch calipers are the standard large GM caliper dimension and were used extensively on the 76-77 Cadillacs, so they are "caddy" calipers as well.
 
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spreadmonkey

spreadmonkey

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I measured them without the pins, so the shortest distance between the two holes. That sounds like it would be about right for the 7" pin-to-pin
 
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spreadmonkey

spreadmonkey

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Well, I looked up the specs on the 76-78 eldorado rotors that were used with the large calipers and they're about the same thickness as mine. So I'm guessing that's what one of the POs used for his conversion.

From what I have read, I shouldn't have any problems using the large calipers, so unless anyone can tell me why they wont work, I'm going to call TSM today and try to exchange the small caddy calipers back for a set of the large ones. Seems like they should fit, but I'm so new to the idea of brake conversions and EBs so I'm trying to make sure I don't pay shipping and restocking fees and then get another set that wont fit.
 

toddz69

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is a conversion with the larger calipers pretty common?

There are some axles (GM 14 bolt, for example) where the larger calipers (76-78 Eldorado) are commonly used for conversions. But they're not common swap pieces for 9" rear ends.

Todd Z.
 

toddz69

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Well, I looked up the specs on the 76-78 eldorado rotors that were used with the large calipers and they're about the same thickness as mine. So I'm guessing that's what one of the POs used for his conversion.

From what I have read, I shouldn't have any problems using the large calipers, so unless anyone can tell me why they wont work, I'm going to call TSM today and try to exchange the small caddy calipers back for a set of the large ones. Seems like they should fit, but I'm so new to the idea of brake conversions and EBs so I'm trying to make sure I don't pay shipping and restocking fees and then get another set that wont fit.

If they'll fit, I'd say go ahead and run them. They're more caliper than you need for the rear end, but they should work OK.

Todd Z.
 

Apogee

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I agree with Todd, however I would seriously consider swapping your front calipers to the larger piston T-bird calipers if you've got Ford front discs, not Chevy. It would help you regain some front bias in the system which would be a good thing considering the short wheelbase of an EB.

Just FYI, the large GM Caddy calipers use a 2.5" diameter piston and the smaller ones are 2.125", so you have about a 40% increase in piston area going from the small to the large calipers.
 
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spreadmonkey

spreadmonkey

Full Member
Joined
Dec 15, 2008
Messages
284
Loc.
Austin, Tx
I agree with Todd, however I would seriously consider swapping your front calipers to the larger piston T-bird calipers if you've got Ford front discs, not Chevy. It would help you regain some front bias in the system which would be a good thing considering the short wheelbase of an EB.

Just FYI, the large GM Caddy calipers use a 2.5" diameter piston and the smaller ones are 2.125", so you have about a 40% increase in piston area going from the small to the large calipers.

I took a second look a little while ago and it turns out I have the large GM calipers up front also. No wonder it stops so well!

Sending the small ones back tomorrow in exchange for the larger ones. Hopefully they come soon I'm anxious to get this done.
 
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