Bigger rear brakes

[GT6 M]

Some of you will racall, I bunged some rear discs on me GT.
well it were a first, and so really a ratch int dark  as much as a learning curve.

the discs were of the MX5, and the calipers of a Saxo VTS, tinkered wid to fit / work.

the saxo discs were  alott bigger than the mx ones by about an inch.
So what was happening was the pads were running as much on inner disc as on the outer bit.
hand brake was not as good as hoped for,  and rear brakes were down on what drums were.

So just had to tinker agen and sort it once and for all.

here a pic of old disc, showing where it were running at, notice the inner ring.


and 10 inch wide


New disc, 11 inches


old and new discs



re drilling PCD using a spare rear hub as template


had to make new brackets up,  note eng blue aroond wol,


this is what that was for, to show where to drill fixin hole, feindishly simple  solution to find a blind hole..


And whilst at it, this side roto was just starting to go, so changed it, using the Markus MK 1 spring tool









old roto, just starting to go, cracks only visable , and this shot had it levered weel owa to show cracks up


have not used it yet ont road, but by trying to turn wheels wid a bigg lever, the hand brake is alott lott better, and just the slightest touch of the brake pedal, has got the rears working much better than before.
so extra aif inch of disc a side has made a bigg difference.

will let ye all no what its like , as I be oot in it the morrow,

rgds M

[Sheepy]

Nice piece of engineering on the tool there Marcus! Allways the simple ideas that are the best.  ;)

The new discs look better!

[rotoflex]

Marcus, how did the MX5 handbrake work?
The handbrake on the rear discs of my Neon is the separate little drum brake on top of the disc, called a "Drum in Hat" design or something like that.
It seems that handbrakes on discs have always required fudgy solutions to come up with something positive.
We need to have a "Show us your spring lifting tool" thread somewhere.

[That Man]

Nice work there Markus, are you saying your brake balance was too far forward before, hence the reason for the bigger dia discs? Many people use mgtf parts, but i believe they only uses 9 1/2" dia discs

It's handy having a pit in the garage, no?  One of my best mates has one in his garage, it comes in very useful, not that I'm saying that's why he's one of my best mates of course ;)

[GT6 M]

Bill the hand brake works by shifting a cam with a slotted rod, its all built into the caliper.
I needed to put the innards of the left one,into the right one,and vice versa, to get the lever at the top,and pulling inwards like original set up.

the discs I thought were too small as the calipers were off a car with 11 inch discs, not the 10 inchers off the MX 5.  its just the discs that are MX5, as they are a perfect fit for a straight adaptor.

As for the brake balance, yes i did think it too far forad,
12 inch discs up front wid 4 pots and sticky pads.
I dont think that the MGF discs will be dooing much at all, either hand brake or foot brak, they are so small, the clamping will be towards the center, not the out side. so less leverage .

will work ok on an MG designed for them, but not with the OE master cylinder as is whats on.
its a 75 one, and its really not bigg enough,as pedal has about an inch free play, beofre it brakes.
bit like a modern servoed car. but a quick pump, and its a solid pedal

will try a RPV of 2 PSI first, to see if that takes the free play up with the much bigger piston area i got noo,
failing that, I think a .850 or bigger MC will suffice, its no like im pushing for England wid me brake fut
with a .75 MC, { late GT }
As I only have to feather the brakes for them to bite hard and bring car to a very quick stop

Any one,whats the biggest OE type MC there is, or what size is the twin cyliner MC, as fitted to later spittys.

been oot the day, they much much better, can feel the rear sitting a bit now, where as before it was all dive.
braked hard round some corners on a wide empty damp / wet  road at 60 ish, and no tail end drift, so balance is aboot reet i think. and hand brake is much better too, as its biteing further oot, so moer leverage.

So im a happy boyo again.


Ohh Bill says=
We need to have a "Show us your spring lifting tool" thread somewhere.

you fust then ole Boy, show us what ye use. :)
I think there could weel be a vast array of diff things,
as I just used to use a bigg bit of flat bar, clamped onto spring. lifting tool much less fiddlee

M

[thescrapman]

0.813 is available in a girling look-a-like.

1 inch available from Wilwood

http://www.rallydesign.co.uk/product_info.php?cPath=562_582_981&products_id=8064

Cheers

[NC]

Markus did you replace the roto's with the QH type? how long do you find they last?

[That Man]

Maybe a duel master cylinder setup would be the way to go ? is there room for two mc's side by side ?

[GT6 M]

5776 wrote:

Markus did you replace the roto's with the QH type? how long do you find they last?

Sorry for late respondo,  Yes they are QH, these two were put on about  2.5 - 3 years ago,ish.
one that was took off was showing craks, but the other, even wid a lever when its on,
shows nowt at all.
the one I took off still would have given some service, as I seen some thats hardly any bonding left, and still going . :o

the previous QH ones I had on, both lasted about 8 years.
and both showed same amount of wear. So mus,nt grumble at that.

Years ago, I got two pukka items frae JK,s along with bolts, I got 2 years or so out of them.

Talking to the Tech Dept at Trelleborg, they say that they have a shelf life of 5 years,
stored under ideal conditions.
So, some pukka items may well be brand new, but are well past their shelf life.
There was a new batch made last year,so I was told, so they still got a 4 year life left.
any thing else, steer clear,if ye no want to change em often.

Hence why I think this ones go soon, and other is perfect.
bought at diff times frae diff places.

Im no to bothered aboot em going, as I can change one in aboot an hour.
so not a real biggee jobby for me.

Also, if the rear is running lots of neg camber,or they are left jacked and hanging for a while, the strain on em is alott moer than as they sitting normally.

when ye think aboot it, how long did they think folk would be owning their GT or Vit, 1300 / 1500 FWD cars,  3-5 years, and the rotos still ok,  the most owners {original } would no even be thinking of a roto change.
Mam had 2 1300s and I can never recall them being done, as she got rid of it after 4 years or so.
so never experianced the problemo.
Its only us lot woe have had them for ages that fins these things oot.

So, get so QH ones for 23£ and get maybe 8 years or so if brand new when put on
or go Trelleborg, and pay 100£ for aboot the same  time if brand new { as is now }
or get 2-4 years if old stock.
Can only say what ive found out owa the aeons of time
may be of some help to ye

M

[GT6 M]

That_Man wrote:

Maybe a duel master cylinder setup would be the way to go ? is there room for two mc's side by side ?

I dont think there will be with oot moving the supports .
Ive taken the HB levers up a wee bit, and its helped a bit.

Im thinking if I get the .813 rubbers,{ they sell em as spares } and boer out a spare MC  to 813, to see if it makes a diff to pedal travel,
there 4 mm of meat left either side when taken oot to 813

failing that its a RPV set up.

I think most folk would say its OK, as most moderns have got alott of mushy pedal travel.
just im used to having a solid pedal.

M

[NC]

Thanks Markus, Quinton Hazellnuts it is.

[rotoflex]

Very good report of rubber coupling research & use, Marcus!  Thank you for doing the lab work!

[drofgum]

Markus,
If you do rebore a master cylinder to 0.813" keep close watch on it as you may find it wears rapidly. I think the original bores are hard anodised to give them a better surface  for the piston seals to slide against. Boring will remove that hard skin.
                                                                                      Regards,
                                                                                      Paul

[GT6 M]

Thanks Bill.
Paul, good call, niva thought of that.
a few options,
1, doo nowt, as its not to bad
2, bigger aftermarket MC, Butt, they are not the same as the GT ones.
the fluid bit is at a diff angle, thats why  3
3, use original, and bore oot,  now with a SS liner in it.
4, fit a dual MC, with either same as original, or with a remote, so will no have to worry aboot the angle.

M

[drofgum]

Markus,
You might be able to combine 2 with 4 by getting a large bore aftermarket master cylinder with remote reservoir(s).
                                                                                        Regards,
                                                                                        Paul

[GT6 M]

Got the brakes a solid pedal now, not with out  some cussing first.
fitted the RPV the way it said , arrow to brakes,re bled all brakes, and wheels were locked solid. :-/ :o

took it off, blew it thru, re fitted, still the same,
decided it may have been assembled either back to front, or their info was wrang.
So fitted it back to front, arrow to MC and it worked

made up an adaptor, 3/8th UNF to 10 x 1.0 MM  and put RPV direct onto MC





M

[rotoflex]

What does that thing do?

[smithy]

I believe it's a reactor pressure vessel containing Markus's small thorium fuel cell, to provide his nuclear braking.

[uksnatcher]

;D ;D ;D ;D ;D

RESIDUAL PRESSURE VALVES:
These in-line pressure valves retain a minimum brake line pressure to help eliminate excessive pedal travel in both disc and drum brake systems.

The two pound valve is used in disc brake applications where the master cylinder is mounted below the horizontal plane of the calipers and fluid drain back occurs from gravity and vibration, thereby causing excessive caliper piston retraction and a longer brake pedal stroke. The minimal two pound residual pressure prevents fluid from flowing back without causing the brakes to drag. With drum brakes, a ten pound valve is used to compensate for return spring tension in the drums.

http://www.speedflowshop.co.uk/wilwood-residual-pressure-valve-569-rpv-1181-p.asp

[GT6 M]

rotoflex wrote:

What does that thing do?

Bill, its a sort of one way valve, keeps a wee amount of pressure in the line,
this so the pistons dont go too far back, so need moer peadl movement to re apply.

all these for discs have a 2 psi, and drums have a 10 psi, as springs are stiffer than rubber alone.

reason I need this is that the rears have 30 MM pistons, the original ones about 15 mm i think.

so double the fluid displacement.= moer peadl travel

Alot of cars already have em built into the MC, but alass, no the Girling ones.
any wiser noo  ;)


EDIT, Gaz Snatcher has beaten me to it, :-/ ;)

M

[uksnatcher]

796 wrote:

EDIT, Gaz Snatcher has beaten me to it, :-/ ;)

M

Sorry mate.. :B....i was also wondering what it did too.. ;)

[tiggrr1]

That's an interesting little gadget Marcus  :)

[GT6 M]

Need one Steeve,!!!

I think it will actually be of benefit to the vast majority of  folk on here.
as the rear drums on most will be worn away, so moer pedal travel.

this will take up most of that lost travel.
also could eliminate pad nock back too a wee bit.

M

[Spider]

Where did you get yours from Marcus? I think my current GT6 could do with one and possibly my MK1 2000.

[GT6 M]

http://www.mcgillmotorsports.co.uk/index.php?page=1&act=viewCat&catId=14
http://www.ebay.co.uk/itm/Brake-Residual-Pressure-Valve-2-PSI-Black-Brisca-F2-Superstox-Kit-Car-Rally-2PSI-/380473035882?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item5895f5cc6a

Ask for Billy,

M