1st Design Calipers: Advantages and Disadvantages

[Joe C.]

My '65 was restored using second design calipers with stainless sleeves, which I rebuilt 16 years ago using new pistons. The right front is just now starting to leak. I used lip seals and DOT 5 fluid.

I have acquired a full set of properly dated first design calipers, which have been sitting in my attic for about ten years. They are unmolested and have the phenolic piston guides in place. I understand that they can now be rebuilt using the guides.

Should I rebuild the second design calipers, which would be much easier and cheaper, or should I have the first design ones rebuilt. I'd only use the second option if there are CLEAR advantages to the guides.

Thank you.

[Joe L.]

Re: 1st Design Calipers: Advantages and Disadvantages

My '65 was restored using second design calipers with stainless sleeves, which I rebuilt 16 years ago using new pistons. The right front is just now starting to leak. I used lip seals and DOT 5 fluid.

I have acquired a full set of properly dated first design calipers, which have been sitting in my attic for about ten years. They are unmolested and have the phenolic piston guides in place. I understand that they can now be rebuilt using the guides.

Should I rebuild the second design calipers, which would be much easier and cheaper, or should I have the first design ones rebuilt. I'd only use the second option if there are CLEAR advantages to the guides.

Thank you.

Joe-----


The piston guides in the calipers are not phenolic. They are just a feature of the casting which is machined when the calipers are machined.

There is no real clear benefit to the 1st design, guided calipers. Supposedly, they are better for off-road racing applications but for street applications, they are more prone to the "air pumping" phenomenon. I think that either of those claims are marginal, at best. I think the main benefit of the 1st design calipers is the phenolic INSULATORS on the pistons (in fact, this may be where the claim that the 1st design are better for racing is rooted). The 2nd design calipers do not, of course, use insulators on the pistons except for the 2nd design J-56. Those insulated pistons are now available in reproduction from Lonestar Caliper. So, if one wanted the benefit of the insulated pistons, simply use these. In fact, the 2nd design insulators are better than the 1st design as they are much thicker.

[Joe C.]

Re: 1st Design Calipers: Advantages and Disadvantages

Joe-----


The piston guides in the calipers are not phenolic. They are just a feature of the casting which is machined when the calipers are machined.

There is no real clear benefit to the 1st design, guided calipers. Supposedly, they are better for off-road racing applications but for street applications, they are more prone to the "air pumping" phenomenon. I think that either of those claims are marginal, at best. I think the main benefit of the 1st design calipers is the phenolic INSULATORS on the pistons (in fact, this may be where the claim that the 1st design are better for racing is rooted). The 2nd design calipers do not, of course, use insulators on the pistons except for the 2nd design J-56. Those insulated pistons are now available in reproduction from Lonestar Caliper. So, if one wanted the benefit of the insulated pistons, simply use these. In fact, the 2nd design insulators are better than the 1st design as they are much thicker.

Thanks Joe.

I'm using DOT 5 which has a higher BP, so it's possible that insulators would be redundant. Thoughts? If my pistons are servicable, I'll re-use them, otherwise I'll use the J56 pistons when I buy the rebuild kits from LoneStar.

[Joe L.]

Re: 1st Design Calipers: Advantages and Disadvantages

Thanks Joe.

I'm using DOT 5 which has a higher BP, so it's possible that insulators would be redundant. Thoughts? If my pistons are servicable, I'll re-use them, otherwise I'll use the J56 pistons when I buy the rebuild kits from LoneStar.

Joe------



Yes, the DOT 5 silicone fluid would ameliorate a lot of the justification for the insulated pistons. I really like the idea of the insulated pistons, though. Yes, for a street car it's probably way overkill but the only downside is cost.

With respect to re-using existing pistons, you need to examine them carefully. If there is any wear-through of the hard anodize at the major diameter, I do not recommend re-using the pistons. Rarely will you find pistons that have been in long service that do not show some wear-through. Wear-through of the hard anodize at the major diameter means that further wear will occur much faster.

[Joe C.]

Re: 1st Design Calipers: Advantages and Disadvantages

Joe------



Yes, the DOT 5 silicone fluid would ameliorate a lot of the justification for the insulated pistons. I really like the idea of the insulated pistons, though. Yes, for a street car it's probably way overkill but the only downside is cost.

With respect to re-using existing pistons, you need to examine them carefully. If there is any wear-through of the hard anodize at the major diameter, I do not recommend re-using the pistons. Rarely will you find pistons that have been in long service that do not show some wear-through. Wear-through of the hard anodize at the major diameter means that further wear will occur much faster.

Haven't taken them apart yet, but bought 2 front seal kits yesterday from VetteBrakes, who had the best price by 40%. Asked if made in USA and got positive answer.

FYI: The insulated pistons are 50, yes, 50 bucks each while the standard pistons are 5 bucks each!