Brembo Disk Bell Ring-Hub bolt Failure

[Wess-RA]

Jim-cost wise you definitely lucked out on the RA brakes. I had no issues with them. They really held up well.
Kevin makes a valid point with the heavier initial braking loads due to the HP advantage on the GTS's. Kel you are running higher HP's and soon to increase again. What brakes/rotors are, or will you be, running?
I am going through all the hardware replacements now. It wasn't the hat hardware that failed though; it was the 5 bolts which pass through the adapter into the hub. They appear to be just 5/16 hardened socket head cap screws. (My previous comment about stripping aluminum threads was crap. Disregard it. The adapter is aluminum but the bolts thread into the steel hub) A previous time when I was at the track I saw a Cobra shear off his (I am estimating by eye) 5/16 hub bolts; I think he had 8 of them. He had huge meats on the rear so in passing, I wondered if he just overstressed the entire hub assembly. Now here I am with a similar situation.
I believe Brian G. has commented in previous threads that he also has a similar replacement schedule. Definitely critical!

[panozracing]

CRITICAL!!!! Change the spindles, 4 bars, hubs, most hardware (especially what connects the wheels to the frame), etc.

I even had to have the rear end housing sent to panoz to have all the bracketry replaced. Over time they had twisted and cracked from the heat and then the nut that holds the rear hubs on skipped a thread..... There is nothing on the car that shouldnt be replaced. My car is almost 10 years old. Thats a lot of abuse!

Just think of it this way...ever part you take off becomes a perfect backup for the trailer. After a while you will have backups to everything and track repairs are easier. I even keep the used bolts.

[Wess-RA]

Points well made! It does get spendy, but thats what we all signed up for.

[NZGTRA17]

Originally Posted by Wess-RA

Jim-cost wise you definitely lucked out on the RA brakes. I had no issues with them. They really held up well.
Kevin makes a valid point with the heavier initial braking loads due to the HP advantage on the GTS's. Kel you are running higher HP's and soon to increase again. What brakes/rotors are, or will you be, running?
I am going through all the hardware replacements now. It wasn't the hat hardware that failed though; it was the 5 bolts which pass through the adapter into the hub. They appear to be just 5/16 hardened socket head cap screws. (My previous comment about stripping aluminum threads was crap. Disregard it. The adapter is aluminum but the bolts thread into the steel hub) A previous time when I was at the track I saw a Cobra shear off his (I am estimating by eye) 5/16 hub bolts; I think he had 8 of them. He had huge meats on the rear so in passing, I wondered if he just overstressed the entire hub assembly. Now here I am with a similar situation.
I believe Brian G. has commented in previous threads that he also has a similar replacement schedule. Definitely critical!

Uwe, my RA had the standard rotors/pads/calipers on it when I got it. I have changed to rotors locally CNC'ed from blanks cast in Italy (half the price of using PFC rotors). I am also running Carbotech endurance compound pads.

I think that the additional load generated in a GTS is probably related as much or more to the torque compound of the pad being used. Remember that the RA comes with PFC 97's which are a low torque pad. Similarly the endurance pads I run are not as high torque as what you will run in a GTS for sprint type racing. I note a couple of comments about RA brakes being lower spec. The only major differences are the pads/lack of bias adjuster/larger rear master cylinder, all other components are essentially the same as the GTS as far as I am aware.

On the design side though Uwe I point out with interest that the RA brakes use 8 aircraft grade bolts to attach the disc hub to the wheel hub. There are 8 floater bobbins and bolts between the disc and disc hub. I see that the newer brakes use only 5 bolts between the disc and the disc hub/hat. The reduction from 8 to 5 bolts will mean that there is a less efficient clamp between the parts requiring a larger dia bolt and a higher torque loading to prevent fatigue. What dia are the 5 bolts and what is the torque loading on them?

Personally I am happier with the 8 bolt arrangement and will not be going out of my way to change this anytime soon !! (especially given your experiences).

[Cobra4B]

For the record the PFC97s feel great once you get some speed in the car and can get them up to temp. Traqmate shows that the GTRA is hitting 141 on VIR's main straights now. Brakes are my favorite part of the car.

[NZGTRA17]

Originally Posted by Cobra4B

For the record the PFC97s feel great once you get some speed in the car and can get them up to temp. Traqmate shows that the GTRA is hitting 141 on VIR's main straights now. Brakes are my favorite part of the car.

If you like them now Brian, then you will absolutely love them with a higher torque compound pad fitted. The 97's are a great all round and long lasting pad, but compared to some of the more recent high torque compounds they would not cut the mustard in sprint racing (i.e 6 - 8 lap events).

Kel.

[Gatorac]

The performance and stress on the brakes is also directly proportional to the grip of the tire. If you can lock up your tires, no need for more agressive pads.

[Panoz26]

Originally Posted by Gatorac

The performance and stress on the brakes is also directly proportional to the grip of the tire. If you can lock up your tires, no need for more agressive pads.

what a true statement.

[NZGTRA17]

Originally Posted by Gatorac

The performance and stress on the brakes is also directly proportional to the grip of the tire. If you can lock up your tires, no need for more agressive pads.

Agree Jim. Are you easily able to lock the brakes in your car with good DOT's or used slicks on? To really get the best out of an RA braking wise I have found that you really need to change the rear master cylinder down in size and put a balance adjuster in (both of which the GTS and GTWC have). Without these mods the car will lock front brakes a lot more easily, particularly on DOT's.

I have only had wheel locking occur (fronts regularly) when I had a shock absorber problem, no balance bar and the large rear master cylinder (which puts more bias to the front brakes). When I had this issue I rebuilt the front shocks and added the balance adjuster and smaller rear master cylinder. The car was then able to be bench set up (balance bar) as per the GTS manual. This balance setup was then so close to what I need to run at my local track I now leave it alone. In my car in its current configuration, I believe that I would benefit from a higher torque pad for sprint racing than say the PFC 97 or the Carbotech 9 compound that I currently have.

I guess this is also very dependent on the track surface you race on. Whether it is true or not I am unsure, but I have been told that many of your Stateside tracks are a bit slicker than the asphalt surfaces we generally race on over here. This could be due to lower ambient temps over here as much as anything though.

Kel.

[Wess-RA]

" The reduction from 8 to 5 bolts will mean that there is a less efficient clamp between the parts requiring a larger dia bolt and a higher torque loading to prevent fatigue. What dia are the 5 bolts and what is the torque loading on them?"-
Personally I am happier with the 8 bolt arrangement and will not be going out of my way to change this anytime soon !! (especially given your experiences). [/quote]I blew the quote format, you guys get the idea.

Kel, based on my recent experience I was thinking the same thing. The 5 sheared bolts are 5/16 hardened and black oxided socket head cap screws (Adapter to hub). I have 10 bolts attaching the adapter to the rotor using the hats. I don't have my RA anymore so I cant do a visual on the differences. I believe you are saying that you have 8 hub to adapter bolts. as well as 8 adapter to the rotor bolts?

So the manual states:
Rotor Disk to Rotor hat 60 in. #'s 10/wheel
Rotor Hat to Hub 25 ft #'s 20 total

So it appears on the GTS's, even the older style had only 5 bolts/wheel

I did like my PF brakes with the exception of occasional front lockup which as you stated the balance bar and cylinder change would correct. I never had to worry about this type of failure.

[Gatorac]

I believe you are saying that you have 8 hub to adapter bolts. as well as 8 adapter to the rotor bolts?

Yes that is correct. At least on my RA.

[Wess-RA]

I went ahead and replaced the new hat and hardware on the right wheel which broke. I also disassembled the left hub/rotor assembly to inspect the hat to hub bolts and out of these 5 bolts, I found one loose and 2 snapped off completely; which left only 2 bolts holding this rotor in place. Clearly this rotor was just waiting to let go.

Here is a pic of the broken bolts.

My hand was a bit shaky, but clearly these bolts have been snapped for a while now, judging by the rust at the break points.

So here is the brand new hat which Panoz is now outsourcing to someone other than Brembo. The new non-Brembo parts are now gold anodized. The color is the clear distinction whereas the Brembo hat is black anodized and actually has the Brembo P/N laser engraved on it.


Without getting to much into the dimensions, the new hats are .010 thicker at the mounting flange than the Brembo hats. As we all know the bushing (bobbins in the manual) have a fixed length which determines the float of the rotors. The Panoz engineer stated that they would like to see a min. of .014 clearance (float). I inspected all my bushings and I see a .004 overall length variance over all 10 bushings. The tolerance stack up between the hat flange and the rotor flange creates a problem. My clearance with the new hat calc.s out at only .004 clearance (due to the thicker hat). With the out of plane condition of the rotor I end up with no float when pulling/pushing the rotor by hand. When I turn the individual bushing/bolt sub-assemblies I can get them to move from flat to flat (stop to stop). Panoz stated that they have sold many of the new gold hats and have not had reports of problems. This is mainly an FYI, but it could be an important one. I have 3 track days on the car since assembly and haven't noticed any difference in performance. My understanding is that the float is to allow heat dissipation by letting the rotors find a neutral position between the pads. Can anyone confirm that this is the main purpose of the float?
I was under the gun when I found the left side broken the evening before I had to leave to the track. I had no time to order a new Hub to replace the one which had the 2 broken bolts inside the treaded holes. I very slowly and carefully (carbide) drilled out the hardened bolts to the minor thread diameter and then counter-bored the hubs from the backside and was able to drive the remaining thread (which now looked more like a helicoil) out through the other side of the hub. So I couldn't help but wonder why some of you are replacing the hubs. This part is so beefy that I don't think it would ever fail. Why aren't you guys just driving out the bearing races (at bearing replacement time) and reusing the hubs? Has anyone ever had a hub actually fail?

[panozracing]

I have had front spindles shear off. I have not had the rear hubs fail and I agree they are beefy. We do drive the bearing races out and reuse them but all parts fatique. And if you are truely pushing a car to its limits ALL parts will fail and the $100 hub is not worth a big failure at speed. Every part needs to be replaced and whatever schedule you use depends on how hard you drive. We drive HARD and parts break. I wish we drove the same tracks to really understand... 1.58 @ Daytona, 2.13 Sebring, 1.27 homestead w/ banks 3/4, 1.29 without banks, 1.30 Barber, 1.28 Mid-O, 1.33 RA or better (have not been with current mods) to name a few....and those are all repeatable times.

[Wess-RA]

No doubt you push harder than I ever will. I am trying to figure out the correct balance of economies for my level. I'm definitely not a slouch though. I've been doing pretty well.

[panozracing]

I wasnt comparing skill levels more just helping determine the levels. We all have room to grow. We determined what we thought was a good replacement routine based on racing hours of use. The routine was developed by failed components. It took years to figure it out. We have owned 2 GTS for 5 years. We didnt replace anything the first year or so and so alot of failures so we then changed everything and got a baseline and went from there.