[ZR1] Heads UP - ZR1 Carbon Ceramic Rear Caliper Fastener Failure
08-01-2013, 04:29 PM
#1
Melting Slicks
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Heads UP - ZR1 Carbon Ceramic Rear Caliper Fastener Failure
Gentlemen,
About two years ago I became the first C5 Corvette owner to install the C6 ZR1 ceramic brakes on my 2002 Z06.
The brakes work fabulously! ! !
About one month ago I attempted to remove the front and rear calipers so I could inspect the brake pads. The front calipers came off without a hitch. Unfortunately, I could not remove the lower bolt that attaches the right rear caliper to the knuckle assembly.
So, today I took my Z06 over to D.J. Racing in Ortonville, Michigan. Dan Kellermeyer and I put the Z up on jack stands and with much effort we got the offending bolt assembly out of the caliper. What we found should be of concern to all Corvette owners who have these brakes.
First let me show you a picture of the rear caliper before I installed it on my Z:
Please note the two large attaching holes. In the bottom-view please note the line on both attaching ears. That line represents where a serrated steel insert is pressed into the aluminum caliper.
Next is a picture of the serrated insert:
Note how shallow and short the serrations are.
The next picture shows what we found when we were finally able to remove the lower bolt assembly:
The serrations have been completely stripped out of the inside of the bolt hole.
The next picture shows the upper attaching hole after we removed its serrated insert:
Notice how shallow the serrations are in the bolt boss and how they do not reach fully into the boss.
We repaired the stripped hole by applying J.B. Weld to the mating surfaces on the nut and to the interior of the attachment boss.
The front calipers do not use a serrated steel nut. They are threaded completely through the aluminum casting.
We decided to chase all the threads on the four calipers and we gently wire brushed the treads on all eight bolt assemblies. We found much blue thread sealant debris in each hole and on the bolts' threads.
We surmise that the blue thread sealant's strength was greater than the serrations ability to keep the nut from spinning.
In the future, we are going to apply a light coat of assembly lube to the bolt's threads and limit the assembly torque to 60 lb.-ft.
-
About two years ago I became the first C5 Corvette owner to install the C6 ZR1 ceramic brakes on my 2002 Z06.
The brakes work fabulously! ! !
About one month ago I attempted to remove the front and rear calipers so I could inspect the brake pads. The front calipers came off without a hitch. Unfortunately, I could not remove the lower bolt that attaches the right rear caliper to the knuckle assembly.
So, today I took my Z06 over to D.J. Racing in Ortonville, Michigan. Dan Kellermeyer and I put the Z up on jack stands and with much effort we got the offending bolt assembly out of the caliper. What we found should be of concern to all Corvette owners who have these brakes.
First let me show you a picture of the rear caliper before I installed it on my Z:
Please note the two large attaching holes. In the bottom-view please note the line on both attaching ears. That line represents where a serrated steel insert is pressed into the aluminum caliper.
Next is a picture of the serrated insert:
Note how shallow and short the serrations are.
The next picture shows what we found when we were finally able to remove the lower bolt assembly:
The serrations have been completely stripped out of the inside of the bolt hole.
The next picture shows the upper attaching hole after we removed its serrated insert:
Notice how shallow the serrations are in the bolt boss and how they do not reach fully into the boss.
We repaired the stripped hole by applying J.B. Weld to the mating surfaces on the nut and to the interior of the attachment boss.
The front calipers do not use a serrated steel nut. They are threaded completely through the aluminum casting.
We decided to chase all the threads on the four calipers and we gently wire brushed the treads on all eight bolt assemblies. We found much blue thread sealant debris in each hole and on the bolts' threads.
We surmise that the blue thread sealant's strength was greater than the serrations ability to keep the nut from spinning.
In the future, we are going to apply a light coat of assembly lube to the bolt's threads and limit the assembly torque to 60 lb.-ft.
-
08-01-2013, 10:30 PM
#3
Burning Brakes
Here is a picture I recently pulled off the net regarding the ZR1 brakes.
Based on this picture it appears that there is no threaded insert, only a threaded housing.
Is it possible that the parts you used were not new and the prior owner installed the thread inserts?
Based on this picture it appears that there is no threaded insert, only a threaded housing.
Is it possible that the parts you used were not new and the prior owner installed the thread inserts?
08-02-2013, 08:25 AM
#4
Melting Slicks
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Byron,
No. I purchased the parts directly from a Chevy dealer.
What you are not seeing in the photo you provided is shown in the bottom rotor of the following picture:
Notice in the bottom-view picture above there is a parting line between the attaching bolt boss itself and where the serrated insert is pressed into the boss.
08-02-2013, 12:30 PM
#5
Burning Brakes
I think I found a better picture:
It definitely shows the insert outline. Seems that instead of using a threaded insert which could be locked to the caliper body they chose to use a simple press in.
Cost or production raises its' ugly head again instead of parts longevity.
It definitely shows the insert outline. Seems that instead of using a threaded insert which could be locked to the caliper body they chose to use a simple press in.
Cost or production raises its' ugly head again instead of parts longevity.
08-02-2013, 01:18 PM
#6
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A threaded insert would be pointless as it would essentially be the same as attaching the mounting bolt directly to the caliper body ( steel to aluminum either way). While these parts are all chevy approved parts I would hesitate to pass judgement on the quality or fitness of this particular application as it is not a stock factory engineered application.
As to JB Weld, my experience is that while the epoxy itself is quite hard I would doubt it's integrity in this use as it is very likely to fail where it adheres to the mating surfaces. It is very brittle and flexing/vibration may cause it to lose adhesion to the mating surfaces.
Is it possible to capture the bolt head with a bend tab type of washer or safety wire?
You might go back and check the fiche for possible missing washers present in the ZR1 but left out of your installation.
My 2 cents.
Fretka
As to JB Weld, my experience is that while the epoxy itself is quite hard I would doubt it's integrity in this use as it is very likely to fail where it adheres to the mating surfaces. It is very brittle and flexing/vibration may cause it to lose adhesion to the mating surfaces.
Is it possible to capture the bolt head with a bend tab type of washer or safety wire?
You might go back and check the fiche for possible missing washers present in the ZR1 but left out of your installation.
My 2 cents.
Fretka
08-02-2013, 02:03 PM
#7
Melting Slicks
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A threaded insert would be pointless as it would essentially be the same as attaching the mounting bolt directly to the caliper body (steel to aluminum either way).
While these parts are all Chevy approved parts, I would hesitate to pass judgement on the quality or fitness of this particular application as it is not a stock factory engineered application. - Not so. All the parts and fasteners used in this installation are genuine GM parts, which are used exactly as they were designed.
As to JB Weld, my experience is that while the epoxy itself is quite hard I would doubt it's integrity in this use as it is very likely to fail where it adheres to the mating surfaces. It is very brittle and flexing/vibration may cause it to lose adhesion to the mating surfaces. - I have personally witnesses J.B. Weld being used to hold a pulley to the shaft of a dry-sump pump when the attaching fastener failed. The pump and pulley functioned without loosing the integrity of the joint for two seasons of Corvette road racing.
Is it possible to capture the bolt head with a bend tab type of washer or safety wire?
You might go back and check the microfiche for possible missing washers present in the ZR1 but left out of your installation. - There are no missing parts.
My 2 cents.
Fretka
While these parts are all Chevy approved parts, I would hesitate to pass judgement on the quality or fitness of this particular application as it is not a stock factory engineered application. - Not so. All the parts and fasteners used in this installation are genuine GM parts, which are used exactly as they were designed.
As to JB Weld, my experience is that while the epoxy itself is quite hard I would doubt it's integrity in this use as it is very likely to fail where it adheres to the mating surfaces. It is very brittle and flexing/vibration may cause it to lose adhesion to the mating surfaces. - I have personally witnesses J.B. Weld being used to hold a pulley to the shaft of a dry-sump pump when the attaching fastener failed. The pump and pulley functioned without loosing the integrity of the joint for two seasons of Corvette road racing.
Is it possible to capture the bolt head with a bend tab type of washer or safety wire?
You might go back and check the microfiche for possible missing washers present in the ZR1 but left out of your installation. - There are no missing parts.
My 2 cents.
Fretka
08-02-2013, 02:13 PM
#8
Burning Brakes
Per the service manual the calipers simply mount with the 2 bolts torqued to 129 lb.ft..
A possible reason for wanting a steel insert would be to resist crushing the caliper mounting ear since the torque is so high, at least that would be my thought on it. Red or green Locktite to secure the insert would prevent it from coming loose. Steel tends to resist wear better where parts are removed and installed multiple times.
A possible reason for wanting a steel insert would be to resist crushing the caliper mounting ear since the torque is so high, at least that would be my thought on it. Red or green Locktite to secure the insert would prevent it from coming loose. Steel tends to resist wear better where parts are removed and installed multiple times.
08-02-2013, 06:00 PM
#9
Definitely not the best way to achieve steel threads in an aluminum casting. However, I can't say relying on JB Weld is the safest thing to do for performance car brakes!
I would suggest looking up the sizes for Time-Serts to see if there is an oversize repair insert (and a fairly short one) that can be installed. If not, look into Rosan or other ring-lock inserts. They are the best (for aerospace and helicopter use), yet are rather expensive and require expertise to install. Either way, you can get back to using the full tightening torque, which is necessary.
Serrated inserts, while cost-effective, were a not too good an idea long, long ago. Heli-coils are only slightly better, but should still be avoided unless in an absolute pinch.
Chris
I would suggest looking up the sizes for Time-Serts to see if there is an oversize repair insert (and a fairly short one) that can be installed. If not, look into Rosan or other ring-lock inserts. They are the best (for aerospace and helicopter use), yet are rather expensive and require expertise to install. Either way, you can get back to using the full tightening torque, which is necessary.
Serrated inserts, while cost-effective, were a not too good an idea long, long ago. Heli-coils are only slightly better, but should still be avoided unless in an absolute pinch.
Chris