CrossedFlags77
Active member
- Joined
- May 13, 2008
- Messages
- 34
I was wondering the same thing. What are the advantages of dual pin?
I just got a full set of hawk blues for 99 cents
- Thread starter Yellow73SB
- Start date
I was wondering the same thing. What are the advantages of dual pin?
Cherry
DREAD NAUGHT
I know nothing about Hawk products, I have on my 1976 in the front, brand new Blue brake pads,, are these hawk blue brake pads,, if so, Is that some kind of really good pad?
redvetracr
Well-known member
It`s not the dual pin caliper it`s the "L" shaped pads that are the big deal, they don`t flex and originals used Inconel backing plates. The pic Chris (yellow 73) posted is of a flat Mintex pad, as they come from Mintex they do not fit a Corvette caliper, obviously these are modified...but they do have a thicker backing plate and thicker material and thats why these guys use them, they also have then "bed in" on a machine before they get them. The J-56 dual pin calipers also came with pistons that had insulators on them. I believe the insulators were made from a toxic material thats no longer used in the USA.
redvetracr
TheSkunkWorks
Well-known member
Looked around for an image of an L-shaped pad to give guys who haven't seen one a better understanding, but this shot from Duntov was the best I could come up with...
The "L" at the top of and perpendicular to the backing plate is what makes these significantly stiffer than the single pin stock pads.
BTW, I thought those PoS spacers had been outlawed for competition use by just about every rule book on the planet by now. How does that get thru tech?
The "L" at the top of and perpendicular to the backing plate is what makes these significantly stiffer than the single pin stock pads.
BTW, I thought those PoS spacers had been outlawed for competition use by just about every rule book on the planet by now. How does that get thru tech?
turtlevette
The Turdle
ok here goes.
Why does a brake pad need to be stiff? A caliper needs to be, but i don't see any advantage to a pad backing plate being stiff other than it will prevent the friction material from cracking and crumbling.
TheSkunkWorks
Well-known member
Anything that causes/allows uneven pressure of the pad material against the rotor is detrimental to maximum braking capability. That would include caliper bracket flex, FOD and/or gas buildup between friction surfaces, uneven piston pressures, and backing plate warpage.
turtlevette
The Turdle
i've never heard of backing plate warpage being a problem. NEVER.
TheSkunkWorks
Well-known member
Warpage might not have been the best word for it. Call it flexing, distortion or whatever, apparently the factory felt it was a significant enough issue to warrant designing the stiffer L-shaped pad in an attempt to prevent uneven front pad wear under sever competition braking conditions; conditions to which most do not subject their Vette.
The rotor in post 12 appears to be a Coleman/Howe/Sweet stock car rotor. They are 11.75x1.25 and sold in not-directional or side for side slanted slot directional configurations. Stock car bus run them cherry red all day long nad retain brakes easily.
The spacer is/was an old Greenwood road race trick that did the following:
Enabled you to run thicker pads, albeit custom crafted for longer life and less changes in road race trim. They also enabled you to install spacers and insullators between the pads and the pistons. IN their day, the J56's were the hot ticket due to the phenolic insulators. Today, you can go with Titanium or stainles pistons to resist heat soak of the caliper. Putting spacers between the pads and pistons simply provides for more insulation capability.
Re the spacer, If it were precision ground and made from steel, structurally, it would not hurt or affect the caliper. Especially if you replaced the thru bolt with one that would take the heat.
Some would say stainless but that might not be the better thing to use for the bolt. You'd have to select a bolt that would have a high yield point at elevated temps. - it is called hot strength. Actually, some stainless materials are weaker at room temp than carbon or cr-mo bolts. A good fasterner engineer could work up something here.
The main advantage of the spacer is heat reduction/rejection back to the caliper. I bet you wish you had another photo albeit from a different angle to REALLY see what that particular racer is doing with his brake pads/calipers.
Now a question if I may. I get the imprssion that j56/ dual pin calipers are the same as the stock ones albeit with different pistons and the mods for the cotter pin held pads. 'Twood seem that some J56 calipers might be nothing more than milled/drilled stock ones with different pistons. I"ld love to see what's inside the J56's as it should not be that hard to retrofit stockers at a much cheaper cost.
BTW, the above photo is using a top had that is probably not stock offset.
If the car is using stock J56 brackets, they have to redo the hat spacing for the 1/4" spacer in the rotors. Betcha that's why the guy is using a wheel spacer too. First he spaced the calipers to help solve heat problems, then he changed the rotors from stock oem to aftermarket stock car, and then he changed the top hat spacing to use stock car rotors with spaced j56 calipers. Simple wheel spacer to suit your wheel and go racing. PROPERLY done spacers should not affect the integrity of the brakes and could actually help if done properly. Greenwood did that on his vettes and they ran pretty darn well as i recall..
Looking forward to the replies about the J56 vs stock calipers...
Thanks.
The spacer is/was an old Greenwood road race trick that did the following:
Enabled you to run thicker pads, albeit custom crafted for longer life and less changes in road race trim. They also enabled you to install spacers and insullators between the pads and the pistons. IN their day, the J56's were the hot ticket due to the phenolic insulators. Today, you can go with Titanium or stainles pistons to resist heat soak of the caliper. Putting spacers between the pads and pistons simply provides for more insulation capability.
Re the spacer, If it were precision ground and made from steel, structurally, it would not hurt or affect the caliper. Especially if you replaced the thru bolt with one that would take the heat.
Some would say stainless but that might not be the better thing to use for the bolt. You'd have to select a bolt that would have a high yield point at elevated temps. - it is called hot strength. Actually, some stainless materials are weaker at room temp than carbon or cr-mo bolts. A good fasterner engineer could work up something here.
The main advantage of the spacer is heat reduction/rejection back to the caliper. I bet you wish you had another photo albeit from a different angle to REALLY see what that particular racer is doing with his brake pads/calipers.
Now a question if I may. I get the imprssion that j56/ dual pin calipers are the same as the stock ones albeit with different pistons and the mods for the cotter pin held pads. 'Twood seem that some J56 calipers might be nothing more than milled/drilled stock ones with different pistons. I"ld love to see what's inside the J56's as it should not be that hard to retrofit stockers at a much cheaper cost.
BTW, the above photo is using a top had that is probably not stock offset.
If the car is using stock J56 brackets, they have to redo the hat spacing for the 1/4" spacer in the rotors. Betcha that's why the guy is using a wheel spacer too. First he spaced the calipers to help solve heat problems, then he changed the rotors from stock oem to aftermarket stock car, and then he changed the top hat spacing to use stock car rotors with spaced j56 calipers. Simple wheel spacer to suit your wheel and go racing. PROPERLY done spacers should not affect the integrity of the brakes and could actually help if done properly. Greenwood did that on his vettes and they ran pretty darn well as i recall..
Looking forward to the replies about the J56 vs stock calipers...
Thanks.
Kid Vette
Master-Baiter
I'm really enjoying your posts NC Cams. Welcome to the forum. :drink:
You have a lot of knowledge and experience. Care to share some of your background?
You have a lot of knowledge and experience. Care to share some of your background?
big2bird
Charter Member, Founder Bird-Run, Cruise-In Bird-R
redvetracr
Well-known member
I know the guy who built the car attached to that brake pic above as well as the owner. I am pretty sure those are directional vane rotors with a welded Mintex brand pad as the flat pad used with a Wilwood GN caliper is about .250 shorter than a Corvette pad but the correct thickness, they also use SSBC stainless non insulated pistons. J-56 calipers are a modified stock caliper (see J-56 piston pics below). The Guldstrand endurance kit consists of four aluminum blocks, longer bolts and two spacers that move the hub out 1/2 the distance of the spacer block making those "hats" standard offset, I run the split caliper on my racer with factory J-56 pistons but elected to use a custom thickness "L" shaped pad. On the car attached to the above brake pic the builder (who happens to be a former Nissan GTP engineer) built a (fabricated) stiffening bracket, if you notice the calipers are mounted to the rear of the spindle opposed to the stock mounting, I also have rear mounted calipers (as do most vintage racers) but don`t use any stiffening brackets. Also keep in mind when comparing what was used almost 40 years ago to what is available today...today we have SRF fluid, Carbon-Kevlar pads and two piece HD rotors w/hats, none of that stuff was available way back when, it is also doubtful in my opinion if a split caliper and two piece non stock rotors were even "legal" in SCCA production racing.
redvetracr
Kid Vette
Master-Baiter
John Greenwood in his VIP article said, "For continuous, fast lap racing applications, generating sustained high temparature operation, I recommend you install the GM pistons and insulator assemblies from the old GM J56 brake option (front insulator #5463822. rear #546699593). This will help insulate the rotor heat from the brake fluid. For continuous heavy duty use I further recommend installation of the GM front caliper support brace for the J56 heavy duty brake package which bolts to the steering arm and caliper.
When selecting high speed racing pads, pay particular attention to how the lining material is a fixed to the backing plate. Riveting is not adequate. The pad material must be bonded through holes in the backing plate. Also, pads come with both single and double pin backing plates. I recommend the double pin, L-shaped backing plates for hard use. If you are going to autocross regularly or you have 450 HP or more, you should definitely consider using double pin brake pads. Straight single pin backing plates can flex up to .020 under hard brake application. To modify your calipers to allow the L-shaped backing plate to fit properly, cut the single pin mount off both sides with a hack saw and file smooth. Then using the double pin pad as a template, mark the new holes and drill with a 3/16" size drill. Also, when buying the double pin L-shaped pads, be sure to get the pads with original GM backing plates made of Inconel steel. Some remanulacturers are making their own backing plates and I don'I think they are as good." :quote:
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