lee
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| posted on 8/1/08 at 07:16 PM |
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does size matter ?
Does the bore of a master cylinder make a lot of difference?
My brake system uses a .625 (5/8) bore master cyl and no servo.
question is, if I uprate cyl to .750 (3/4) will it improve braking effort?
My logic is that the same pedal movement would move more fluid. Therefore I think pedal would feel "firmer", but would the brakes feel
better?
I need to improve the brakes, but have no room for a servo.
As the Hubs are Triumph Herald there is a limit to what can be fitted. But may have to get some engineering done.
Any thoughts are welcomed
Lee
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russbost
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| posted on 8/1/08 at 07:22 PM |
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If you go to a bigger bore cylinder you will get less pedal movement, but will require greater pedal pressure to get the same braking force. I suspect
you are trying to do the opposite?
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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lee
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| posted on 8/1/08 at 07:29 PM |
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size
I am trying to improve braking.
Because of the unusual hubs it is difficult to fit alternative discs/calipers, so thought about master cyl.
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twybrow
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| posted on 8/1/08 at 07:30 PM |
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Better brakes how...? Better feel? Overall stopping power? Fade resistance?
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lee
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| posted on 8/1/08 at 07:34 PM |
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size
I am having probs with engine, so may well change/upgrade the 1500 spitfire engine. As the brakes are only "adequate" at the mo, I will
need to make sure I can stop it if I carry on with the upgrade. So the plan is to improve the overall braking efficiency.
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rusty nuts
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| posted on 8/1/08 at 07:35 PM |
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I built a Marcos a few years ago that used Triumph front suspension.. Marcos supplied vented discs and four pot calipers so uprated brakes are
available
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lee
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| posted on 8/1/08 at 07:41 PM |
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size
Do you have any idea who supplied the discs etc? I have been unable to find anyone offering more pads.
The engine by the way, will almost certainly be 1600 8v cavalier with Type 9 'box. So not not "fast" but the car is VERY light and
would suicidal with a 'decent' engine fitted.
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matt_claydon
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| posted on 8/1/08 at 08:03 PM |
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You need a smaller dia m/c to get more braking effort for the same pedal force.
Line pressure is dependent on cylinder AREA, so for the same pedal effort the increase in braking you will get is equal to (old dia/new dia)^2.
Eg if you went from 5/8" dia to 1/2" dia you would get:
[ (5/8) / (1/2) ]^2 = 1.5625 more braking force.
You would of course get longer pedal travel though.
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rusty nuts
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| posted on 8/1/08 at 08:20 PM |
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The discs were supplied by Marcos as part of the brake upgrade kit. The only fly in the ointment is that the car used Ford P.C.D. hubs. The caliper
was mounted on a small bracket mounted to the upright. Have you looked at any of the Triumph specialists for upgrades?
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lee
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| posted on 8/1/08 at 08:29 PM |
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size
Have tried various Triumph specialsits with no real results.
Thanks for info dia= force formula, I know a guy who can sleeve down a cyl for me. As I have a few spares of dubious quality I will try and see what
happens.
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caber
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| posted on 8/1/08 at 08:31 PM |
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You can get remote servos that can be placed at a distance from the master cylinder so you should be able to find somewhere to put it.I think they are
for MGBs check in Practical Classics they are advertised by a couple of suppliers.
Regards
Caber
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smart51
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| posted on 8/1/08 at 10:20 PM |
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If you are pushing the brake pedal, pulling on the steering wheel and gritting your teeth tying to slow the car down, you need a smaller diameter
master cylinder, at the expense of having to push it further.
If you tickle the pedal and lock all the wheels but the pedal moves down a lot, you need a bigger master cylinder.
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RazMan
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| posted on 8/1/08 at 11:11 PM |
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You could try increasing the pedal ratio by decreasing the pivot/mc pushrod distance. This will give the same effect as a smaller mc bore but still
using the same components.
I had a similar problem on my brakes - changed the mc bores to the smallest I could find, changed the caliper pistons to the largest I could find -
finally realised my pedal ratio needed inceasing and presto!
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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Nick Skidmore
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| posted on 9/1/08 at 08:35 AM |
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I have done some work on Marcos brakes. It was for a 2.8l essex v6 engined car but the brake discs were of an older Peugeot (will have to find out
which one, possibly 505). I reduced the outer dia by 5mm and opened up the bore that fitted over the wheel mounting spigot on the hub by 40 thou and
drilled the hub mounting face for ford pcd.
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lee
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| posted on 9/1/08 at 07:20 PM |
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size
Thanks for all the suggestions guys, they have really given me something to think about. Many thanks.
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