[DeTomaso] Trying to diagnose weak brakes

Will Kooiman will.kooiman at gmail.com
Sat Feb 17 14:04:59 EST 2018 

My experience:

The brakes on my car were terrible when I bought the car.  It had sat for
14 years.

The fronts had not been bled properly.  I bled them when I got the car,
but at the time didn¹t know about the bottom bleed.  When I bled the
bottom screws, a lot of orange fluid came out.

They still weren¹t that good, though, so I changed to Porterfield R4S
pads.  Very big difference.

Then I changed to stainless flex lines, which firmed up the pedal a lot.

In this configuration, my car would stop faster than my wife¹s Boxster-S,
which had the big red 911 Brembos.  Very impressive.

I drove it like this for quite a while, until the booster started leaking
air.  Rather than rebuilding the booster (or probably just replacing a
leaking valve), I switched to Wilwood masters, which stopped just as good,
but required more pedal pressure, since I didn¹t have vacuum assist
anymore.

I have wilwood calipers on it now, but I haven¹t driven it enough to
comment.


On 2/17/18, 12:44 PM, "detomaso-bounces at server.detomasolist.com on behalf
of jtaphorn at kingwoodcable.com" <detomaso-bounces at server.detomasolist.com
on behalf of jtaphorn at kingwoodcable.com> wrote:

>Mike
>
>The brake issue you describe may also be caused by a stuck piston in one
>of your calipers. 
>
>JT
>---- Stephen Nelson <steve at snclocks.com> wrote:
>
>=============
>Having gone the Wildwood route - hey, maybe it is overkill for a road car
>-
>but it is good overkill.  Can one have too good of brakes?
>
> 
>
>I am very happy with the brakes on 5332 - went with a kit from Pantera
>Performance - and kept the original back caliper for the emergency brake.
>
> 
>
>Thought I'd throw in a shot of our car, pulled the a/c compressor, dryer
>and
>expansion valve last weekend, will be flushing the system and bolting it
>all
>back together this week.  And putting on the 10 inch rims I found here
>locally.  Then we will be READY FOR SUMMER!
>
> 
>
>And yes, I know it is crap picture, but I think it just plain looks cool -
>like it is flying!
>
> 
>
>Hey Mike - drive on down - we'll put it up on the other rack and sort out
>those brakes.
>
> 
>
>Stephen - 5332
>
> 
>
>-----Original Message-----
>From: DeTomaso [mailto:detomaso-bounces at server.detomasolist.com] On Behalf
>Of Mike & Elizabeth Thomas
>Sent: Saturday, February 17, 2018 8:45 AM
>To: 'Julian Kift' <julian_kift at hotmail.com>; 'Joseph F. Byrd, Jr.'
><byrdjf at embarqmail.com>; 'List DeTomaso Forum'
><detomaso at server.detomasolist.com>
>Cc: 'List DeTomaso Forum' <detomaso at server.detomasolist.com>
>Subject: Re: [DeTomaso] Trying to diagnose weak brakes
>
> 
>
>Thanks all.  I am planning a full-on restoration of the car in a year or
>two, and running of fresh brake lines, master, etc. even if I do retain
>the
>original Girling brakes, will be on the list.  I will try a proper
>bleeding,
>and it may not be a bad idea to upgrade to whatever master I intend to use
>after the restoration.  I may consider going the full Willwood route, but
>as
>I never intend to track the car, that may be overkill.  If I stay with the
>Girling calipers, I'll certainly have them properly rebuilt.
>
> 
>
> 
>
>Mike Thomas
>
> 
>
> 
>
>From: Julian Kift [ <mailto:julian_kift at hotmail.com>
>mailto:julian_kift at hotmail.com]
>
>Sent: Saturday, February 17, 2018 8:20 AM
>
>To: Joseph F. Byrd, Jr. < <mailto:byrdjf at embarqmail.com>
>byrdjf at embarqmail.com>; 'Mike & Elizabeth Thomas'
>
>< <mailto:mbefthomas at comcast.net> mbefthomas at comcast.net>; 'List DeTomaso
>Forum'
>
>< <mailto:detomaso at server.detomasolist.com>
>detomaso at server.detomasolist.com>
>
>Cc: 'List DeTomaso Forum' < <mailto:detomaso at server.detomasolist.com>
>detomaso at server.detomasolist.com>
>
>Subject: Re: [DeTomaso] Trying to diagnose weak brakes
>
> 
>
> 
>
>Your diagram refers to the shuttle valve, the proportioning valve is the
>hunk of metal in front trunk also but plumbed purely to the front brakes
>limiting output pressure by about 20% of input. It does much the same as a
>stepped master cylinder in compensating for woefully undersized rear
>calipers. It was installed based on tires of the day etc. but modern
>rubber
>especially 335 on the rear significantly alters brake balance and wheel
>lockup front to rear.
>
> 
>
> 
>
>Although referring to the wrong valve your postulation that air is trapped
>in it might be a very valid one, that or it's probably the master cylinder
>going bad. I have a Motive pressure bleeder and it makes the task an easy
>and one man operation, with no fear of running the reservoir dry during
>bleeding (yes we've all done it!).
>
> 
>
> 
>
>As a general note removing or gutting the proportioning valve should be
>evaluated along with any brake component upgrade (note Mike said he has an
>aftermarket master cylinder). It is hard to get all the components matched
>perfectly right to ensure the front brakes lock up just before the rears,
>hence installation of a more modern adjustable brake proportioning valve
>can
>provide the fine tuning to ensure that. I would strongly recommend
>everyone
>test their brakes for lockup periodically on a very quiet and wide stretch
>of asphalt, not only is that a basic safety test it also provides you a
>measure of what pedal force locks up the brakes, if only under the road
>conditions prevailing at the time
>
> 
>
> 
>
>Julian
>
> 
>
>  _____  
>
> 
>
>From: DeTomaso <detomaso-bounces at server.detomasolist.com
>
>< <mailto:detomaso-bounces at server.detomasolist.com>
>mailto:detomaso-bounces at server.detomasolist.com> > on behalf of Joseph F.
>
>Byrd, Jr. < 
><mailto:byrdjf at embarqmail.com%20%3cmailto:byrdjf at embarqmail.com>
>byrdjf at embarqmail.com <mailto:byrdjf at embarqmail.com> >
>
>Sent: Saturday, February 17, 2018 8:06 AM
>
>To: 'Mike & Elizabeth Thomas'
>
>Cc: 'List DeTomaso Forum'
>
>Subject: Re: [DeTomaso] Trying to diagnose weak brakes
>
> 
>
> 
>
>Forgive me, but after having to participate in several "Fault Tree"
>
>evaluations where we thought of ridiculous scenarios that could be
>possible.
>
>Given;
>
>~3 inches of travel before braking
>
>Rear doing the most braking
>
>The proportional valve is gutted
>
>Assume;
>
>Air is trapped in the proportional.  This would cause the first master
>cylinder piston to travel while not establishing front caliper pressure to
>
>move the second piston.   After 3" of pedal travel, the first piston makes
>
>contact with the second and now the rear caliper pressure is devolved with
>majority rear braking.
>
>However, one would expect the differential valve to give failure lamp.
>
> 
>
>-----Original Message-----
>
>From: DeTomaso [ <mailto:detomaso-bounces at server.detomasolist.com>
>mailto:detomaso-bounces at server.detomasolist.com] On Behalf Of Mike &
>Elizabeth Thomas
>
>Sent: Saturday, February 17, 2018 10:37 AM
>
>To: 'Mike Drew'; 'List DeTomaso Forum'
>
>Subject: Re: [DeTomaso] Trying to diagnose weak brakes
>
> 
>
>Thanks, certainly the cheapest and least invasive approach.
>
> 
>
>-----Original Message-----
>
>From: Mike Drew [ <mailto:MikeLDrew at aol.com> mailto:MikeLDrew at aol.com]
>
>Sent: Friday, February 16, 2018 9:04 PM
>
>To: Mike & Elizabeth Thomas <
><mailto:mbefthomas at comcast.net%20%3cmailto:mbefthomas at comcast.net>
>mbefthomas at comcast.net <mailto:mbefthomas at comcast.net> >
>
>Cc: List DeTomaso Forum <
><mailto:detomaso at server.detomasolist.com%20%3cmailto:detomaso at server.detom
>as
>olist.com> detomaso at server.detomasolist.com
><mailto:detomaso at server.detomasolist.com> >
>
>Subject: Re: [DeTomaso] Trying to diagnose weak brakes
>
> 
>
>Mike,
>
> 
>
>Another note. If the Les Schwab people are so dumb that they don't know
>that
>
>DOT4 is just DOT3 with a higher boiling point, I.e. an improved product
>that
>is 100% interchangeable, I wouldn't trust them to do a proper job of
>filling
>and bleeding your brakes.
>
> 
>
>I suspect there is nothing really wrong. Carefully drive to a friend's
>house, one with good mechanical aptitude and an appetite for the beer you
>will bring on the passenger seat, and together just bleed the brakes
>properly using a quality brake fluid. (I like ATE Typ 200, available from
>Tire Rack, Summit and Amazon to I suspect). I have a feeling they will be
>perfect afterwards....
>
> 
>
>Mike
>
> 
>
>Sent from my iPad
>
> 
>
>> On Feb 16, 2018, at 18:50, Mike & Elizabeth Thomas
>
>> <mbefthomas at comcast.net
>
>< <mailto:mbefthomas at comcast.net> mailto:mbefthomas at comcast.net> > wrote:
>
>> 
>
>>   I've been working through trying to figure what seems like a weakness
>
>>   in my brakes on 6328.
>
>> 
>
>> 
>
>>   How do they feel now?  There seems like a fair bit of pedal travel
>
>>   before they start to hook up.  Once they hook, they're fine when I'm
>
>>   just in normal traffic and stop and go.  If I have to stomp down on
>
>>   them, it just doesn't seem like they're biting very well.  If I have
>>to
>
>>   really stomp on them, I can't get any wheel to lock up at all.
>
>> 
>
>> 
>
>>   Current setup:  the brakes are stock Girling, rebuild in 2004. they've
>
>>   been fully bled at Les Schwab 6 months ago with DOT 3 (they wouldn't
>
>>   use DOT 4 as it was not spec).  Yes, they were aware that there were
>
>>   two nipples on the front, the tech that handled me has 2 or 3 Panteras
>
>>   that come in through the year.  The flex lines were replaced with
>
>>   stainless lines in 2004 when all of the calipers were rebuilt.  The
>
>>   vacuum line from the engine to the tube and tube to booster is recent,
>
>>   about 3-4 years ago.  So far as I know, the proportioning valve has
>
>>   been gutted, but not really sure nor know how to be sure.  The master
>
>>   is an early `80's GM/Cadillac replaced about 10 years ago, the same
>>was
>
>>   in the car when I bought it in `04.  I've just replaced the
>>Porterfield
>
>>   R4S pads.  It was rather cold day when I went out to burn them in so
>
>>   first speculation is that they are not fully `seasoned'.  However,
>>they
>
>>   feel about the same as the previous 10-yr old R4S's, and that wouldn't
>
>>   explain the pedal travel.  The booster is original so far as I know.
>
>> 
>
>> 
>
>>   First question, how much pedal travel should there be before the pedal
>
>>   feels resistance the brakes start to take up?
>
>> 
>
>> 
>
>>   So, what else can I check/do out to figure out why my brakes seem so
>
>>   lazy.  I will try to re-season them when the weather gets warmer, but
>
>>   that won't deal with pedal travel.  When brake booster starts to fail,
>
>>   how does that happen?  Gradually or all at once?
>
>> 
>
>> 
>
>>   Your input is appreciated and eagerly awaited.  I'd like to get this
>
>>   figgered before the season starts as everything else is running a well
>
>>   as it ever has.
>
>> 
>
>> 
>
>>   Thanks
>
>> 
>
>>   Mike Thomas
>
>> 
>
>>   Pres., Panteras Northwest
>
>> 
>
>>   206-795-3302
>
>> 
>
>>   Yellow '74 #6328
>
>> 
>
>>   [1] <http://www.panterasnorthwest.com> www.panterasnorthwest.com <
><http://www.panterasnorthwest.com> http://www.panterasnorthwest.com>
>
>> 
>
>> References
>
>> 
>
>>   1.  <http://www.panterasnorthwest.com/>
>http://www.panterasnorthwest.com/
>
>> _______________________________________________
>
>> 
>
>> 
>
>> Detomaso Email List is not managed by POCA Posted emails must not
>
>> exceed 1.5 Megabytes DeTomaso mailing list
>
>>  <mailto:DeTomaso at server.detomasolist.com>
>DeTomaso at server.detomasolist.com
>
>> < <mailto:DeTomaso at server.detomasolist.com>
>mailto:DeTomaso at server.detomasolist.com>
>
> 
>
>>  <http://server.detomasolist.com/mailman/listinfo/detomaso>
>http://server.detomasolist.com/mailman/listinfo/detomaso
>
>> 
>
>> To manage your subscription (change email address, unsubscribe, etc.)
>
>> use
>
>the links above.
>
>> 
>
>> Members who post to this list grant license to the list to forward any
>
>message posted here to all past, current, or future members of the list.
>
>They also grant the list owner permission to maintain an archive or
>approve
>the archiving of list messages.
>
> 
>
> 
>
>_______________________________________________
>
> 
>
> 
>
>Detomaso Email List is not managed by POCA Posted emails must not exceed
>1.5
>Megabytes DeTomaso mailing list  <mailto:DeTomaso at server.detomasolist.com>
>DeTomaso at server.detomasolist.com <
><mailto:DeTomaso at server.detomasolist.com>
>mailto:DeTomaso at server.detomasolist.com>
>
> <http://server.detomasolist.com/mailman/listinfo/detomaso>
>http://server.detomasolist.com/mailman/listinfo/detomaso
>
> 
>
>To manage your subscription (change email address, unsubscribe, etc.) use
>the links above.
>
> 
>
>Members who post to this list grant license to the list to forward any
>message posted here to all past, current, or future members of the list.
>
>They also grant the list owner permission to maintain an archive or
>approve
>the archiving of list messages.
>_______________________________________________
>
>
>Detomaso Email List is not managed by POCA
>Posted emails must not exceed 1.5 Megabytes
>DeTomaso mailing list
>DeTomaso at server.detomasolist.com
>http://server.detomasolist.com/mailman/listinfo/detomaso
>
>To manage your subscription (change email address, unsubscribe, etc.) use
>the links above.
>
>Members who post to this list grant license to the list to forward any
>message posted here to all past, current, or future members of the list.
>They also grant the list owner permission to maintain an archive or
>approve the archiving of list messages.

More information about the DeTomaso mailing list