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#Post#: 89150--------------------------------------------------
Re: Brakes, question for,
DIR By: prof-pat-pending
Date: June 7, 2014, 1:42 pm
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most of our trailers (hgv) are still on the drum brakes
:rolleye0012:
yes they can suffer from brake fade - but overall they stop you
just the same as disk braked trailers :-?
it is a matter of driving within the limits of your equipment
:rolleye0012:
have you noticed that wagons give a bigger gap in front of them
and slow down using their gears more etc :-?
read the road ahead better and you wont need to brake as hard or
as long - keeps your brakes cooler from when you really need
them :smilewide:
- - its an opinion :toothless:
#Post#: 89152--------------------------------------------------
Re: Brakes, question for,
DIR By: Wooden
Date: June 7, 2014, 2:51 pm
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^^^ Wise words.
#Post#: 89153--------------------------------------------------
Re: Brakes, question for,
DIR By: Roveerman
Date: June 7, 2014, 2:55 pm
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I'm with you guys!, I DO have disc brakes and, shock horror, no
servo, I do drive leaving PLENTY of space, I slow down using
engine braking before needing to apply the foot brake and guess
what no trail of dead bodies behind me, but as stated in the
other thread I'm some kind of cunt (his words not mine).
I don't mind being called this if I've done something wrong on
purpose, we all make mistakes, but my questions are posted to
help me understand and not just take it as gospel just because
it posted on the internet.
The setup is from Zeus and so far I've never (touch wood) got
into trouble, Zeus was consulted about the use on my landrover.
It all comes down to the tyre and the road at some point, grip
is king and when the tyre lets go, game over (unless you have
abs).
So far I've never locked the wheels (not that I've tried) so the
tyres have never broken grip from the road and therefore I've
never skidded, BUT AND ITS A BIG BUT if I can get the brakes to
a point where I could lock them (if I can't at the moment) and
use the proper modulation of the pedal to control the brakes so
they don't and keep the balance between front and rear then I'm
up for the work to get there.
First question how do we measure the performance?
Next how did mg get away with out one in the MGB?
Do I need twin line for a disc drum setup?
Finally is it the master cylinder or is it the proportion valve
that regulates the pressure to the rear brakes to stop rear
lockup occurring?
Just question to help me understand
#Post#: 89165--------------------------------------------------
Re: Brakes, question for,
DIR By: fuckwit
Date: June 7, 2014, 4:39 pm
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Jesus. Christ. Almighty.
There si more need for my brake thread than I ever realised.
Gentelmen, please FFS leave that thread alone. Instead go back
to the start of it and see how it covers most of the principles
of brakes, Clearly most of you to be asking msot of these
questions don't undertand how brakes actaully work.
My thread shoots down the myths and misconceptions. It started
with a bias towards discs, largely because I'd assumed you all
understood how brakes operrate. And I'd also assumed soem would
come in with the drum info so that I would not need to do that
bit. It now appears as it gains momentum, other are doing jsut
that. bit. I was going for the development end of brakes, but I
can that frazzle your brains.
This ain't Particle Physics, this is school-boy stuff.
[Looks skywards]
#Post#: 89168--------------------------------------------------
Re: Brakes, question for,
DIR By: Wild
Date: June 7, 2014, 4:47 pm
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On a twin line set-up the master cylinder should give correct
for'd / aft proportion, however in my testing this does not
prove to be exact enough (the same master cylinders is often
used on many model variants, so that says it all). Other devices
fitted to further reduce pressure in the rear brake line are
there to do the final proportioning.
Some thoughts form me that may be of use/interest:
You do not necessarily have to have twin lines to achieve
correct proportioning in your described setup .
I don't know much about MGBs but i'm sure many were fitted with
a remote in line servo, this could be fitted where you have
space in a series 1.
So i would have thought in your case if you want to retain the
original MC and single line system you could fit a remote servo
(approx 2:1 ratio should be enough) and then to prevent the rear
brakes locking dangerously fit a pressure limiter or g valve in
the line going to the rear brakes. This should give you powerful
and balanced brakes.
One other potential problem you may come across with the
original MC is that it has some residual pressure, this is
intended to keep the shoes close to the drums in a drum set-up,
but can cause binding, accelerated wear and excess heating in a
disk set-up.
#Post#: 89226--------------------------------------------------
Re: Brakes, question for,
DIR By: Sunny Jim
Date: June 8, 2014, 6:27 pm
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--- Quote ---
> No it doesn't, it comes down to grip between the tyres and the
road - when you reach the limit of that, you can have as big
brakes as you want, it will do no more
--- End Quote ---
Actually it comes down to controlling the dynamic friction
between the brake lining and the disc/drum - the best
retardation is achieved by keeping the dynamic friction of the
linings just below the break point for the tyres. The advantage
of discs is that you can control this far better than with
drums, that is why the stopping is superior to that of drums. So
why people endlessly repeat the notion that because they can
lock up their 10" drum this somehow indicates that there can be
no improvement by moving say to discs?
I have a disc/drum set up a la 1980s Santana 88" and this
balances quite will with just an ordinary LWB single circuit
master cylinder and a standard Series 3 servo and no fancy
pressure reducing valves. In reality, to increase the servo
boost, you would need to reduce the pressure to the rear. To Mr
Fuckwit, in answer to what you asked elsewhere, this setup works
fine and compared well with my Astra at the time I did it (14
years ago). My latest Astra has disc/disc with ABS so seems to
have a much higher boost and makes the Land Rover setup seem a
little heavy by comparison, but no different from going from a
year 2000 Astra to a current model! The brakes 'dig in' nicely
from speed, they just take a little more effort than a modern
car. I have no intention of upgrading further at the current
time.
Over the years I have had a variety of tyres, starting with Avon
Traction Mileage which would be 'entertaining' by today's
standards. I have been through Michelin X, Goodyear Wrangler
Radial and now Wrangler AT/S. There is no doubt that good
branded tyres make a lot of difference on the road, and both
models of Wrangler have been good off road or in snow etc.
Sunny Jim
#Post#: 89256--------------------------------------------------
Re: Brakes, question for,
DIR By: Wooden
Date: June 9, 2014, 1:20 pm
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Hopefully, from these recent brake-related threads, we can one
day have a concise yet comprehensive guide to brake
mods/upgrades, as well as service tips for standard set-ups.
#Post#: 89263--------------------------------------------------
Re: Brakes, question for,
DIR By: fuckwit
Date: June 9, 2014, 1:56 pm
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I'm not at all happy with SJs set-up. It is a long way from the
Santana set-up. The solution could be put in two or three
sentences, but why that is the case would take a detailed
explanation. My actual answer has been moved to the Tap room.
I'm half way thru' brakes and their mods at:
HTML http://ollr.createaforum.com/technical-tips-questions/fuckwits-tips-for-sorting-out-your-brakes-properly/
#Post#: 89305--------------------------------------------------
Re: Brakes, question for,
DIR By: Roveerman
Date: June 10, 2014, 9:31 am
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At the beginning of this thread I asked several questions that I
hope could be answered to help me understand the theory behind
the dynamics of brake systems. I did not get the answers I'd
hoped for and the thread went of into a "my ways better than
yours" direction, this was not my intention.
Brakes are a very important system, if not the most, on any
vehicle and need to be treated with the utmost care and
attention. Discussion is good if it helps people to understand
what is going on and if a statement that is made is factually
incorrect the best way is to explain the facts, show where the
errors are and guide people to the correct answer.
I have read and reread fuckwits thread and have gleaned some
very useful facts, and I have looked for information from
external sites, most from academic sites and some from
commercial companies.
I'm in the middle of writing up, quite long as it turns out,
answer to the first of these questions as I have come to
understand it and I'm asking for a bit of patience to all who
care to read and follow while I compose my findings.
This will not be "use part number such and such" but more on the
theory behind where we want to be when we have finished working
on or modifying our brakes.
One last caveat if you are unsure of what you are doing please
get help.
#Post#: 89307--------------------------------------------------
Re: Brakes, question for,
DIR By: Roveerman
Date: June 10, 2014, 9:34 am
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My first question was "how do we measure the ultimate
performance of our brakes"
The best answer I have found is by a MOT certified test machine.
But there's more to that than a pass or fail and this is were I
will agree and disagree with fuckwit,
First up the pass rate for a single line (mine is and will
probably stay that way) is 50% (if this is the wrong number
would any MOT tester correct me) and is shown here
HTML http://www.motuk.co.uk/manual_3100.htm
Now this is were some maths is needed, to get to this percentage
the following formula is used
Total Brake Effort / Vehicle Weight X 100 = % Efficiency
Total brake effort is the force that the brake exert though the
wheels onto the rollers (or road if you are driving) and is
measured in KgF (kilogram force) and is made from the readings
from the front and rear brakes and added together, prepare for a
bit of agreement/disagreement with fuckwit,
How this total is made does not concern the MOT tester (or at
least the one I spoke to, again any current MOT testers can
shoot me down if that statement in their eyes is wrong or
offensive)
as long as the 50% is reached you pass, so MOTS do tell you
something.
Bunging some numbers into that shows that to have 100% efficient
brakes a series 1 weighing 1254kg will need to generate 1254KgF
1254kgF/1254kgx100=100%
Now all you have to do is find a set of tyres that can give you
that kind of grip.
The part that you really need to take heed of is the balance
between front and rear as well as side to side. As you begin to
apply the brakes the centre of gravity of the vehicle begins to
move forward this results in more weight though the front axle
and less on the rear, if your brakes are biased incorrectly with
more brake effort in the rear than the front , your rear wheels
will lock and the back will break free and start to skid, not a
good situation.
So what you want is more KgF generated by the front brake and
less by the rear and from what the MOT tester showed me it's
about 100 to 200 KgF more by the front that the rear.
This is also dependant on the weight of the vehicle being
tested, so big vehicle big brakes, small vehicle small brakes
(we all kinda knew that anyway).
How we get to this level of braking efficiency is a different
question and I'm still looking into the maths of it all, but
what I am coming to the conclusion is "there's more ways to skin
a cat".
I like numbers, numbers prove things and with fuckwits kind
indulgence in the not to distant future I will hopefully fill in
my blanks.
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