J65 Sintered Metallic Brakes

[Sam D.]

J65 style Sintered Metallic Brakes shoes, How much better stopping abiltiy do they provide then the regular brake shoes. And are they worth spending the extra money for?

Thanks,

Sam

[Duke W.]

Re: J65 Sintered Metallic Brakes

Back in the day they were the best brake setup available for serious road performance and light racing, but they do have their drawbacks.

The friction material Cf characteristic is not constant, but increases with temperature, so the first couple of stops in the morning require a lot of pedal effort.

On a racetrack they become very sensitive when hot - almost like power brakes, so one has to learn good pedal modulation techniques, but they never faded when I hot-lapped racetracks with my SWC back in the sixties. (BTW ,I would not recommend PB with J-65. J-50 could be combined with J-65, but I expect that the brakes would become unmanageable on a racetrack.)

They are extremely long-lived, but by the time the shoes are worn, the drums are likely worn to near the wear limit - but that's typically well over 100K of normal road driving.

Given the typical mild service that most vintage Corvettes see nowadays the base OE linings or equivalent aftermarket linings will likely be fine because the C2 drum system is essentially the same as on full sized Chevrolets, which weighed up to 1000 pounds more than a Corvette. If you drive in a sporting manner or are thinking about running "track day" events there are modern lining materials that offer many of the positive features without the drawbacks. See:

www.carbotecheng.com

If you have an original J-65 car there is no way to verify it through the normal judging process since nothing can be seen without removing a wheel and drum. NOS J-65 replacement shoe sets occasionally show up for sale, but they are usually very expensive. J-65 also incorporated return springs with a higher heat treat, which can handle much higher temperatures. The front drums have a slightly thicker web and the drums are honed to a 20 microinch finish.

You should do an archive search as there have been previous discussions of J-65 over the years.

Duke

[Stuart F.]

Re: J65 Sintered Metallic Brakes

As mentioned in previous discussions, I replaced the Sintered Metallic linings on my 63 with Matrix Ceramic shoes/kits from Praise Dyno Brakes in Texas. My pads on the original linings were breaking loose and floating. My first attempt with the new linings, I used replacement drums as I was told after 40k miles with the SM linings my drums would be shot (not so). As it turned out, I could not get the repro drums to work well as it seemed the shoes would not line up correctly in the drums (position of the braking surface in relation to the hub). I had my originals trued up with a minimal cut and have been very happy with them. Performance characteristics for normal driving seems very similar or equal when hot, better when cold. I use a standard MC with an SS sleeve, which is correctly dated for my car (my original was stolen).

Stu Fox

[Clem Z.]

Re: J65 Sintered Metallic Brakes

stopping power of drum brakes has a lot to do with the fit of the lining to the inside diameter of the drum. to get good results without waiting for the shoes to "bed" in you need to radius grind the lining to the same radius as the inside of the drum so you have full contact right away. mrs clem could not stop my vettes with the SM lining at the stop sign at the end of our street,good thing that cross street had very little traffic.

[Stuart F.]

Re: J65 Sintered Metallic Brakes

Clem;

Bravo to her for trying, specially the second time. What used to get me was when they were warm, a good hard application would bring every thing from the rear into the passenger foot well as the seat back would come flying forward. Thems when you knew you had brakes!

Stu Fox

[Clem Z.]

Re: J65 Sintered Metallic Brakes

Clem;

Bravo to her for trying, specially the second time. What used to get me was when they were warm, a good hard application would bring every thing from the rear into the passenger foot well as the seat back would come flying forward. Thems when you knew you had brakes!

Stu Fox

i told her to ride with her left foot on the brake pedal to warm them up but she kept forgetting.

[Loren L.]

Re: J65 Sintered Metallic Brakes

Unless you're autocrossing or otherwise abusing the car, the answer is NO.

[Clem Z.]

Re: J65 Sintered Metallic Brakes

Unless you're autocrossing or otherwise abusing the car, the answer is NO.

back in the 60s we were doing "track days" at places like "nelson ledges" with no roll bars. i also remember some 100 MPH hill climbs and autocrosses back then. there were not as many lawyers looking for work back then.

[Bill M.]

Re: J65 Sintered Metallic Brakes

back in the 60s we were doing "track days" at places like "nelson ledges" with no roll bars. i also remember some 100 MPH hill climbs and autocrosses back then. there were not as many lawyers looking for work back then.

Hi Clem:

We're still doing them! I tried a track day with a "big brake" '92 (Z07) and the stock brakes were very unhappy...never did a track day again. I got up to about 100 mph on the longest straight.

(There are pads that fix the problem, but I wanted to keep the brakes dead stock.)

We do an autocross on the same track and get up to 100, but because there is a cooling off time between the runs, the Z07 brakes are happy.

[Stuart F.]

Re: J65 Sintered Metallic Brakes

It's amazing so many of us survived the things we used to do "back in the day". I only put seat belts in my first car to keep me behind the steering wheel. Figured I could always drive my way out of anything so long as I had my hands on the wheel and my feet near the pedals.

Stu fox

[Clem Z.]

Re: J65 Sintered Metallic Brakes

Hi Clem:

We're still doing them! I tried a track day with a "big brake" '92 (Z07) and the stock brakes were very unhappy...never did a track day again. I got up to about 100 mph on the longest straight.

(There are pads that fix the problem, but I wanted to keep the brakes dead stock.)

We do an autocross on the same track and get up to 100, but because there is a cooling off time between the runs, the Z07 brakes are happy.

at my age,74, the number of track days i do are very few as my 2008 corvette is a lot quicker than my reflexes.

[Jerry G.]

Re: J65 Sintered Metallic Brakes

Is radius grinding a difficult task? Is it something a brake shop could do today or is this going to be a machine shop problem?

[Stuart F.]

Re: J65 Sintered Metallic Brakes

Jerry;

Radius grinding used to be a common practice, or as we used to call it; fitting the shoes to the drums. When I replaced my SM linings with Matrix Ceramic, and decided to cut and reuse my old drums, I checked with the vendor about doing that and they told me it was not necessary, specially with the small amount of resizing mine required. I was told it is not done or required by the new material linings. There are many, myself included, who are old school skeptics, but my brakes are working very well w/o.

Stu Fox

[Duke W.]

Re: J65 Sintered Metallic Brakes

Is radius grinding a difficult task? Is it something a brake shop could do today or is this going to be a machine shop problem?

It was also referred as "arcing in the linings". I still think it's a good idea, but a lot of shops may not have the equipment, nowadays.

Duke

[John H.]

Re: J65 Sintered Metallic Brakes

When I restored my '57 twelve years ago, I took my drums and new linings to an old-time local brake shop; they had an AMMCO lining grinder that "arced" my linings to exactly match the I.D. of my drums. When I assembled the brakes, I made one minor adjustment after about 50 miles, and never had to touch them again for five years and about 5,000 miles.

Probably not a lot of shops that still have an "arc" grinder - the EPA and OSHA got involved as well due to the asbestos dust issue if old linings were "arced".