[DeTomaso] NPC - Brake Drum Wear Limits, does Porterfield R4S material eat drums, etc.

Guido deTomaso guido_detomaso at prodigy.net
Thu Dec 17 14:21:30 EST 2015 

 
FWIW I once put new pads against an unturned rotor, it chewed the new pads down to the steel in just a few thousand miles, learned my lesson there.
Also the drums in question in this experiment measured the same ID as they did 20K miles earlier ... do they typically "grow" the ID significantly even if the friction material is not worn down to the steel or rivets?
If the "max diameter" cast into the drum isn't a machining limit, then there is some ambiguity unfortunately thrown in, how much extra iron to leave behind to be worn off by the shoes.  A machining limit would be black and white, no gray area.
While we're in the 'hood, what do they use to glue the friction material to the shoes/pads?  It's obviously not waterproof, I've had several shoes lose their friction material due to, ah, improper storage / the introduction of moisture or penetrating oil.  Wondering if gluing the friction material back on is something I can try at home.
Thanks,
GD


      From: Jeff Cobb <jeffcobb1 at me.com>
 To: jderyke at aol.com 
Cc: Jeff Cobb <jeffcobb1 at me.com>; guido_detomaso at prodigy.net; detomaso at poca.com
 Sent: Monday, December 14, 2015 5:32 PM
 Subject: Re: [DeTomaso] NPC - Brake Drum Wear Limits, does Porterfield R4S material eat drums, etc.
   
You are correct as long as you speak of brake efficiency and not of material concerns. I was writing about the dimension set forth by the manufacture as a safe limit of which braking safety and liability factors are referenced off of. Yes, many of us will set our own dimensional regulations and realities that we feel work best for us. The wear scratches help out in stopping not because of surface area but because of major frictional increases. What ever famous racer said that was not correct.Heck, Enzo said when asked why he did not use the better front disc brakes that Jaguar was using instead of Ferraris front drums and cut out pontoon front fenders on the 63 Testarossa so to remove the massive heat, he said: “my drivers don’t need to use their brakes”, or something like that to justify his crappy brakes.
Brakes have the ability to save your life more so than any other automotive system. So safety is the primary concern.Take care,
Jeff Cobb
Cell 225-907-4514

Jeff Cobb Auto Works
1316 South Acadian Thruway
Baton Rouge
Louisiana, 70806

http://www.liveoakconcours.org/

Work  225-343-7525
Fax     225-343-7550
zumzum at cox.net
jeffcobb1 at me.com    


On Dec 14, 2015, at 3:24 PM, jderyke at aol.com wrote:

Jeff, way back when drum brakes were the norm, one famous racer said he never turned his drums. The wear, scratches etc slightly increased the surface area and once new shoes were mated to rough drums, the system worked fine. 
As far as wear limits, its when the drum bell-mouths and braking efficiencydrops off. So it depends on lots of factors, not just a dimension.
 
 
 
-----Original Message-----
From: JEFFREY COBB <jeffcobb1 at me.com>
To: Guido deTomaso <guido_detomaso at prodigy.net>
Cc: De Tomaso List <detomaso at poca.com>
Sent: Mon, Dec 14, 2015 3:21 am
Subject: Re: [DeTomaso] NPC - Brake Drum Wear Limits, does Porterfield R4S material eat drums, etc.

Your guy is correct and the internet is wrong about safe usable size limits.
Minimum thickness or max diameter cast or stamped unto a brake rotor or drum indicates the safe min thickness or max diameter. Depending on your lathes bit size and feed rate, you can take off as little as .004 as a fresh up.

Jeff Cobb- I pad
W-225-343-7525
C-225-907-4514

On Dec 13, 2015, at 8:12 PM, Guido deTomaso <guido_detomaso at prodigy.net> wrote:

> Have done a little driving with the Porterfield rear pads installed,
> to match the fronts. While the fronts made a huge difference, not
> really feeling a big difference after changing the rears. Ought to get
> out in the rain though, make sure the fronts are locking up first.
> Is there any downside to this R4S material, other than initial cost?
> Short life? Eats rotors or drums? Otherwise seems too good to be
> true.
> I also installed the four shoes I had relined, drum brake non-Pantera
> application, new drums too since the shoes cost so much, not really
> seeing yet the huge improvement like I saw on the Pantera.
> The old drums have a max diameter shown as 9.114 inches, mine are at
> 9.095 . Thought I'd get them turned, swap them back on someday, but my
> guy says 9.114 is the wear limit, not the machining limit, so he can't
> take anything off. Internet research seems to support both positions,
> both you can and cannot machine/turn to the max diameter cast into the
> drum. Any thoughts/experience?
> Also what's the minimum a brake lathe can take off typically? If .010
> on the diameter, that would put me at 9.105 with .009 leftover.
> Same ideas would apply to rotors ... Pantera rotors too ... is the
> minimum thickness a "machine to" number, or a "wear to" number?
> Thanks,
> GD
> _______________________________________________
> 
> Detomaso Forum Managed by POCA
> Posted emails must not exceed 1.5 Megabytes
> DeTomaso mailing list
> DeTomaso at poca.com
> http://poca.com/mailman/listinfo/detomaso_poca.com
> 
> To manage your subscription (change email address, unsubscribe, etc.) use the links above.

_______________________________________________

Detomaso Forum Managed by POCA
Posted emails must not exceed 1.5 Megabytes
DeTomaso mailing list
DeTomaso at poca.com
http://poca.com/mailman/listinfo/detomaso_poca.com

To manage your subscription (change email address, unsubscribe, etc.) use the links above.




  
-------------- next part --------------

   FWIW I once put new pads against an unturned rotor, it chewed the new
   pads down to the steel in just a few thousand miles, learned my lesson
   there.
   Also the drums in question in this experiment measured the same ID as
   they did 20K miles earlier ... do they typically "grow" the ID
   significantly even if the friction material is not worn down to the
   steel or rivets?
   If the "max diameter" cast into the drum isn't a machining limit, then
   there is some ambiguity unfortunately thrown in, how much extra iron to
   leave behind to be worn off by the shoes.  A machining limit would be
   black and white, no gray area.
   While we're in the 'hood, what do they use to glue the friction
   material to the shoes/pads?  It's obviously not waterproof, I've had
   several shoes lose their friction material due to, ah, improper storage
   / the introduction of moisture or penetrating oil.  Wondering if gluing
   the friction material back on is something I can try at home.
   Thanks,
   GD
     __________________________________________________________________

   From: Jeff Cobb <jeffcobb1 at me.com>
   To: jderyke at aol.com
   Cc: Jeff Cobb <jeffcobb1 at me.com>; guido_detomaso at prodigy.net;
   detomaso at poca.com
   Sent: Monday, December 14, 2015 5:32 PM
   Subject: Re: [DeTomaso] NPC - Brake Drum Wear Limits, does Porterfield
   R4S material eat drums, etc.
   You are correct as long as you speak of brake efficiency and not of
   material concerns.
   I was writing about the dimension set forth by the manufacture as a
   safe limit
   of which braking safety and liability factors are referenced off of.
   Yes, many of us will set our own dimensional regulations and realities
   that we feel work best for us.
   The wear scratches help out in stopping not because of surface area but
   because of major frictional increases.
   What ever famous racer said that was not correct.
   Heck, Enzo said when asked why he did not use the better front disc
   brakes that Jaguar was using instead of Ferraris
   front drums and cut out pontoon front fenders on the 63 Testarossa so
   to remove the massive heat,
   he said: amy drivers donat need to use their brakesa, or something like
   that to justify his crappy brakes.
   Brakes have the ability to save your life more so than any other
   automotive system.
   So safety is the primary concern.
   Take care,
   Jeff Cobb
   Cell 225-907-4514
   Jeff Cobb Auto Works
   1316 South Acadian Thruway
   Baton Rouge
   Louisiana, 70806
   [1]http://www.liveoakconcours.org/
   Work  225-343-7525
   Fax     225-343-7550
   zumzum at cox.net
   jeffcobb1 at me.com
   On Dec 14, 2015, at 3:24 PM, [2]jderyke at aol.com wrote:

     Jeff, way back when drum brakes were the norm, one famous racer said
     he never turned his drums. The wear, scratches etc slightly
     increased the surface area and once new shoes were mated to rough
     drums, the system worked fine.
     As far as wear limits, its when the drum bell-mouths and braking
     efficiencydrops off. So it depends on lots of factors, not just a
     dimension.

   -----Original Message-----
   From: JEFFREY COBB <[3]jeffcobb1 at me.com>
   To: Guido deTomaso <[4]guido_detomaso at prodigy.net>
   Cc: De Tomaso List <[5]detomaso at poca.com>
   Sent: Mon, Dec 14, 2015 3:21 am
   Subject: Re: [DeTomaso] NPC - Brake Drum Wear Limits, does Porterfield
   R4S material eat drums, etc.
   Your guy is correct and the internet is wrong about safe usable size
   limits.
   Minimum thickness or max diameter cast or stamped unto a brake rotor or
   drum indicates the safe min thickness or max diameter. Depending on
   your lathes bit size and feed rate, you can take off as little as .004
   as a fresh up.
   Jeff Cobb- I pad
   W-225-343-7525
   C-225-907-4514
   On Dec 13, 2015, at 8:12 PM, Guido deTomaso
   <[6]guido_detomaso at prodigy.net> wrote:
   > Have done a little driving with the Porterfield rear pads installed,
   > to match the fronts. While the fronts made a huge difference, not
   > really feeling a big difference after changing the rears. Ought to
   get
   > out in the rain though, make sure the fronts are locking up first.
   > Is there any downside to this R4S material, other than initial cost?
   > Short life? Eats rotors or drums? Otherwise seems too good to be
   > true.
   > I also installed the four shoes I had relined, drum brake non-Pantera
   > application, new drums too since the shoes cost so much, not really
   > seeing yet the huge improvement like I saw on the Pantera.
   > The old drums have a max diameter shown as 9.114 inches, mine are at
   > 9.095 . Thought I'd get them turned, swap them back on someday, but
   my
   > guy says 9.114 is the wear limit, not the machining limit, so he
   can't
   > take anything off. Internet research seems to support both positions,
   > both you can and cannot machine/turn to the max diameter cast into
   the
   > drum. Any thoughts/experience?
   > Also what's the minimum a brake lathe can take off typically? If .010
   > on the diameter, that would put me at 9.105 with .009 leftover.
   > Same ideas would apply to rotors ... Pantera rotors too ... is the
   > minimum thickness a "machine to" number, or a "wear to" number?
   > Thanks,
   > GD
   > _______________________________________________
   >
   > Detomaso Forum Managed by POCA
   > Posted emails must not exceed 1.5 Megabytes
   > DeTomaso mailing list
   > [7]DeTomaso at poca.com
   > [8]http://poca.com/mailman/listinfo/detomaso_poca.com
   >
   > To manage your subscription (change email address, unsubscribe, etc.)
   use the links above.
   _______________________________________________
   Detomaso Forum Managed by POCA
   Posted emails must not exceed 1.5 Megabytes
   DeTomaso mailing list
   [9]DeTomaso at poca.com
   [10]http://poca.com/mailman/listinfo/detomaso_poca.com
   To manage your subscription (change email address, unsubscribe, etc.)
   use the links above.

References

   1. http://www.liveoakconcours.org/
   2. mailto:jderyke at aol.com
   3. mailto:jeffcobb1 at me.com
   4. mailto:guido_detomaso at prodigy.net
   5. mailto:detomaso at poca.com
   6. mailto:guido_detomaso at prodigy.net
   7. mailto:DeTomaso at poca.com
   8. http://poca.com/mailman/listinfo/detomaso_poca.com
   9. mailto:DeTomaso at poca.com
  10. http://poca.com/mailman/listinfo/detomaso_poca.com

More information about the DeTomaso mailing list