What's the difference between a regular and an HD caliper for '78 Impala?

S

Stationwagonguy

Forum Member
I've been trying to buy up brake parts to fix this '78 Impala I have, but the one thing that drives me nuts is they keep offering me a choice between regular and "HD" front calipers. I've seen some pictures, and they look identical from the outside. I'm wondering if there's something I'm not seeing- do they have bigger pistons or something? Do they mount differently? Because I can't figure it out, and I don't know who to ask.

If there is a difference, I'm sure my car probably doesn't have them.
 
2 possibilities.

1) Like Sean said, rotor diameter, calipers will look quote similar. IF it's rotor diameter, then if your car has 5x4.75 bolt pattern it's not HD. If it has 5x5 it's HD. Wagons and police cars got bigger brakes 77-90. In 91 all b-bodies (bubbles) got the 12 inch rotors.. which are actually 11-7/8 or so.

2) The 91-96 b-bodies had HD brake calipers. They used the same rotor, but the calipers were a bit wider to handle thicker pads. This was done for the cop cars to have longer service intervals on the grippier, but faster wearing brake pad linings.

I think in 78 it was #1..
 
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