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LIBRA BRAKES 
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GTM on order

Joined: Fri Aug 18, 2017 8:37 pm
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Post LIBRA BRAKES
Hi everyone,
last year I purchased a Libra coupe (yellow, Honda B18C VTEC, 20K miles).
Since then I have only done approx. 250 miles as we have spent a lot of time trying to cure various problems,
especially a poor gear change and an annoying rattle. The rattle was thought to be loose baffles in the fuel
tank, new tank fitted but not sure that it has cured it. The car has had all new brake discs and pads (Pagid), but
the brakes feel very wooden as if there is no servo assistance. Taking the pipe off of servo reveals suction and a
loud hiss suggesting that the servo is receiving vacuum and holding it. Holding pressure on the brake pedal with
engine stopped, it then drops slightly when the engine is started. The brakes are MGF Trophy 4 pot front calipers,
large discs and rear calipers.
Has anyone had a similar problem, any suggestions or is this the way that they all are?
I would have thought that a small lightweight car with big brakes would be much better. Perhaps the large brakes
are not matched to the small servo or master cylinder or the front pads are too hard.
Thanks in advance for any help.

Jeremy


Sun Feb 18, 2018 5:54 pm
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Joined: Sat Mar 12, 2016 7:05 pm
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Post Re: LIBRA BRAKES
Jeremy I have AP racing 4 pots on the front of a libra V6 and the feel of the pedal is awful you think it is not going to stop then stand on the pedal and it does stop but very difficult to lock the wheels up not that you want that. I think the lack of feel is down to the servo and am considering firstly a change of pads ( a friend who races an Elise swears by Pagid so that is not your problem ) then twin remote servo if I can find somewhere to fit it. I also have a TVR Tuscan with 4 pots and ford Ka servo and these don't feel much better
Ian


Sun Feb 18, 2018 8:48 pm
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Post Re: LIBRA BRAKES
You shouldn't have any problems stopping the car with AP brakes!

The problem with the brakes on a Libra is leverage. The pedal ratio is something around 4:1 rather than 5/6:1 which is more common.

I found better feel with a standard pad rather than a more performance hard pad.


Sun Feb 18, 2018 9:15 pm
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Joined: Sun Oct 19, 2014 10:10 pm
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Location: Bristol
GTM: Spyder
Post Re: LIBRA BRAKES
Interesting to read as I have "standard" front calipers - Rover 600 I think, single pot sliding caliper design but I have some AP 4 pots from a TF160 with bigger discs waiting to go on. The standard ones work pretty well, I've done quite a few track days now and they don't fade, I can lock the fronts, even with warm semi slicks, but I have to really stand on the pedal to do so. I was kind of thinking that the 4 pots would need less pedal pressure and maybe more travel with more piston area facing the fluid but this thread so far (and others I've read) suggest maybe not.

I'm kind of thinking I should stay with what I have - if it aint broke... and also I've three sets of wheels and only one set will fit over the 4 pots.

But, on the other hand, I've got these AP 4 pots sitting there saying "fit me, fit me"!!!

It would be good to hear some more opinions.


Sun Feb 18, 2018 9:54 pm
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Joined: Sat Mar 12, 2016 7:05 pm
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Post Re: LIBRA BRAKES
They do stop but do not inspire confidence and you have to stand on them but I was expecting it to stop on a sixpence (showing my age now) being a light car
Ian


Mon Feb 19, 2018 8:39 am
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Joined: Wed Apr 15, 2015 4:52 pm
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Location: Devon
GTM: Libra
Post Re: LIBRA BRAKES
I concur with standard pads.
They are designed to work well from cold i.e.on the road
'Better' pads may be fine for the track when up to temperature but rubbish on the road and cold.
I would even think that with the weight of the GTM it is very unlikely to cook standard pads on the track


Tue Feb 20, 2018 4:25 pm
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Post Re: LIBRA BRAKES
I have to say Malcolm had reverted to the std. caliper but I put the 4 pots back as the std calipers frightened me to death
Ian


Tue Feb 20, 2018 7:49 pm
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Post Re: LIBRA BRAKES
Has anyone ever tried to improve the pedal ratio or maybe change the master cylinder size?


Tue Feb 20, 2018 9:02 pm
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Post Re: LIBRA BRAKES
I have seen an article on this but cannot remember where now may have been on team GTM
Ian


Wed Feb 21, 2018 8:34 am
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Post Re: LIBRA BRAKES
I know a couple of people fitted adjustable floor mounted pedal boxes with dual cylinders. No link though I'm afraid.


Wed Feb 21, 2018 6:33 pm
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Post Re: LIBRA BRAKES
All i can say is glad i never had a Metro
Ian


Wed Feb 21, 2018 6:34 pm
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Post Re: LIBRA BRAKES
Why? The brakes in a Metro are a better pedal ratio with better feel!


Wed Feb 21, 2018 7:44 pm
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Joined: Mon Jul 13, 2015 6:32 pm
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Post Re: LIBRA BRAKES
Is there nothing can be done to increase the pedal ratio to something approaching 5/6 to 1. Or is a smaller bore master cylinder (if you can get one) an option.

Is it just a case that you need to push a bit harder than you’d expect or are the brakes limited by the pedal ratio / master cylinder? I’ve not had to stand on the brakes in a Libra yet but expect I’ll find out this summer when mine hits the road.


Wed Feb 21, 2018 9:32 pm
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Post Re: LIBRA BRAKES
I did use the term "stand on the brakes" in my earlier post but that may have been a slight exaggeration! They do need a fairly hard push, kind of like an unservo'd system in a normal car (if anyone can remember them!). I guess we've all become used to light brakes in our daily drivers so the difference is what is noticeable. After the first couple of prods I get used to it and then find that they are actually pretty powerful and progressive enough to know the difference between locking up or not. I guess having to press hard is quite a good thing with a light front end as otherwise it would be too easy to lock up, especially with no ABS. I'm running standard pads and I find they don't fade, even on track days, and there is enough stopping power to lock up the fronts even on hot A048's if you really want to. That is on rover 600 (or are they 800?) single pot sliding calipers.

I'm still agonising about whether to change to the four pots. I think I'll stick with what's on for this year...


Thu Feb 22, 2018 8:40 am
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Joined: Wed Aug 11, 2010 9:27 am
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Location: Sheffield
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Post Re: LIBRA BRAKES
I went from std 240 disc plus calipers to the red AP 4 pot with 304 discs and found it a massive improvement in power and 'feel', I have EBC black pads. Rear calipers are OE 200/400.

Don't forget that tyres and suspension have a lot of influence over how well brakes work and feel.

SAS

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2000 GTM Libra 1.8VVC 145BHP


Thu Feb 22, 2018 7:04 pm
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