Front brakes

[John Addy]

I have some Princess 4 pot calipers which whilst the fit the front hubs, they foul the inside of the wheels. The only other calipers I have come form the early Vitesse (with the 9 inch discs) and consequently won't fit either. Are there other ways to uprate the brakes with calipers and discs from other cars. The reason I'm uprating is the car is fitted with the 2.5PI engine. Cheers from NZ John

[nang]

John,
FWIW I fitted Princess calipers to my 2500 TC many years ago, they're still on there, but I honestly don't think they improved the brakes. I also have a 2500 S with standard brakes and they seem the same as the other car.
Tony.

[Clive]

If I remember correctly (dubious!) you need to use some washers to centralise the calliper to the disc.

And also use GT6 brake discs. This was the setup that came with my previous spitfire, all very satisfactory and a decent improvement over the spitfire brakes.

[thescrapman]

Princess claipers only fit inside steel wheels I think. They also only fit Spitfire uprights.

Or you have to use a combination of wheel spacers and a grinder on the caliper body.

[John Addy]

Cheers Colin and yes a little work with the angle grinder might be the answer. However, I may revert to buying some proper GT6 calipers and selling the 4 pots - there should be a good market for them??  Also, are the Spitfire uprights/hubs the same as the Mk3 GT6?

[Clive]

Gt6 uprights/hubs/stub axle etc all different to spitfire.

Thinking back, my old spit had std spit 1500 wheels initially, but also some MGF 15" alloys at one point and later 5 1/2J steel wheels.

[Nick Moore]

Clive's right, the GT6 and Vitesse uprights are different to Spitfire and Herald uprights, as are the hubs, stub axles, bearings, discs and type 16 calipers. If you can find them though, they're a good upgrade. The wheel bearings are larger and so theoretically more robust.

Then, if you still want more stopping power, there are various further front brake upgrades, such as Canley Classics big disc and AP calipers.

I fitted the complete GT6 front and rear brake setup to my Herald, and yeah, it has enough brakes. My GT6 has the Canley setup as I've also fitted a 2.5 injected motor. If they're not enough I will look at parachutes or boat anchors.

[JohnD]

Here's another with Princess 4pots.  I fitted them to my original Old Blue Vitesse racer, but the brake mod that made the difference was Capri 3L vented discs.  The entire assembly has been handed down unto the third generation, SofS.   Venteds entirely prevent fade, even under race conditions as long as I use Minted 1155 pads.  

In fitting 4pots you need to consider the physics and operation of brake systems.   Yes, they can mount bigger pads, but area does not figure in the Friction Equation, only pressure.   And the braining effort from the foot is spread out over that greater area so the pressure per unit area is less.  The result is the same braking effect whatever the pad size.
And as you have twice as many, only slightly smaller,  pistons, the master cylinder must be slightly bigger.  But a bigger M/c will need more foot pressure for the same braking effort.
By themselves, 4pots have no effect on braking ability.

Originally, these were part of a split braking system, for safety,  and so had separate bleed screws.   The one on the back of the caliper fouls the wheel, but as installed on a Triumph is not needed.  It may be screwed down hard with thread sealer and ground off.

John

[GT6 M]

any chance that 14/15 inch wheels can be fitted
low profile+ same,ish rolling radius

MGF types,plenty aboot, {over in NZ ?? }

then the discs can be upped frae 247mm OE{9.7 in }

to owt frae 280-310 with just a either a skim to hubs, or to inner
hole ont disc, aboot 25thou
just need to re drill  PCD to suit

then citroen /peugeot  vented discs can be fitted, as they are the correct off set like the OE disc,
So nee fartn aboot wid spacers, then ye can use yer own calipers,wid a widening strip fitted {v easy } and some  good pads.
this way, ye still have a good foot pedal, but a bigger disc area an vented.

bigger discs 310mm, best mod  i ever did, much much better pedal feel/ controll
and v v little effort to stop



M

[Gt6s]

I too used the big Citroen discs with stock Gt6 callipers widened. Under 15 in wheels. Scrub an awful lot of speed very quickly.

Laurence

[JohnD]

Marcus is quite right - wider discs provide a greater lever moment to increase braking effort.
BUT, unless you make other mods, wider wheels need narrower ratio  tyres, to achieve the same rolling radius and/or to fit in the wheel arches.
Low ratio tyres have stiffer walls, that will not tolerate the wide range of camber change that the swing axle, and swing spring, impose, as thye will lift the tread off the road sooner than a 80-70% ratio tyre.

It's the usual situation in suspension mods - you change one thing for the better, to find it makes another factor worse.


Limiting camber change, without going for a completely different suspension, is usually done by going for much stiffer springs, shockers and antiroll.
Which will make the ride very hard (see above!)
John

[Jonny-Jimbo]

A popular mod is Capri 2.8i discs (may be the same as 3L) and 16P calipers. That's what I have on my Vitesse, and has seen racing and track use with the previous owner too. I have never been short of brakes with there, even when driven hard. For cost effectiveness, it's hard to beat.

[BiTurbo228]

Quoted from GT6 M

any chance that 14/15 inch wheels can be fitted
low profile+ same,ish rolling radius

MGF types,plenty aboot, {over in NZ ?? }

then the discs can be upped frae 247mm OE{9.7 in }

to owt frae 280-310 with just a either a skim to hubs, or to inner
hole ont disc, aboot 25thou
just need to re drill  PCD to suit

then citroen /peugeot  vented discs can be fitted, as they are the correct off set like the OE disc,
So nee fartn aboot wid spacers, then ye can use yer own calipers,wid a widening strip fitted {v easy } and some  good pads.
this way, ye still have a good foot pedal, but a bigger disc area an vented.

bigger discs 310mm, best mod  i ever did, much much better pedal feel/ controll
and v v little effort to stop

M

Hmmm, that's got me thinking. I've got a set of Canley 4-pots (although the eBay ad said they were leaking fluid past the seals) and a set of vented GT6-type calipers on some sort of vented disc (haven't had a close look at them yet). I've also got a mate with 3 106 GTis so he has quite a large stock of front discs if they're the ones you use (and maybe a spare set of hi-spec 4-pots for those too)

I'll have 15" MGF wheels going on so they should clear bigger discs. What's the setup for the Citroen/Peugeot discs?

[GT6 M]

Jimbo, ev a deek thru eer

select the brake PDF
then look at the  Rover, {triumph is init } and see off set
GT is 27 MM

then go to the Peuogeot, Citroen, bits, and look for the  discs that match the
triumph off set.
will ev,t re drill PCD,  BUTT, if yer going to 5 inch or so ish wheels.
then it maybe better to shave the hub doon, to match the disc, than shave the disc doon to match the hub
its aboot  a cats wisker to come off.

Xsara for discs up to 288
407 Coupe for 300+ discs,

and I think therea Bigg citroen type with same off set.

Butt all are either 4 or 5 stud, so a re drill.
in my mind, much better than the Ford offerings, as they are just same size as OE GT brakes, but vented.

Note, the steering arm can be packed oot a bit, so if ye see another disc, wid diff off set, , but the 407 coupe is what I got on.



http://www.national-auto.co.uk/brake_products/brake_catalogue.aspx

M

[bob dunn]

I am fitting GT6 Discs , callipers , bearings, and rear drums . I have a TR6 master cylinder do I need it to power this bigger brake set up . Being fitted to a 75 mkiv Spit.

[Nick Jones]

The Spitfire will have a 5/8" master cylinder and a GT6 would normally be 0.7".  However, I put a 5/8" one on my Vitesse (same calipers etc as GT6) to reduce the pedal effort and it works fine without excessive pedal travel, so based on that you can probably keep the Spit one.

The TR6 ones are either 0.7 or 0.75" bore dependent on year and will be intended to bolt to a servo so probably won't fit anyway.

Nick

[bob dunn]

Thanks Nick .I got  the master cylinder from Mev spares ,south London ish . It looks the same as a normal one ,he might
have ment its the same bore as a TR6. I was looking for a bigger capacity for a different job that I didn't need in the end .

[uksnatcher]

Here are Citroen saxo vented discs/princess spaced calipers/using spit 5/8 master cyl and spacer fitment for steering arms and caliper aligment.
Fitted on my spit with 15" wheels (fits under 13" steels and lots of other 13" alloy wheels but fouls Sprint alloys) been on for 6 yrs of abuse now with no probs.

Plenty to read using search, heres just one thread:
Sorry , link no longer available

[Nick Jones]

Bit of thread revival here.......

Pondering the vented disc question again.  

I know Capri 2.8 dics is one popular route, but they are not quite right as the centre hole is too large to centre them properly and they also have slightly wrong offset so sit a couple of mm too far inboard.

There is talk in this thread (and on others) about using Citroen discs which have the correct offset and a centre hole which is just a gnats whatsit too small, making it easy to open out to the correct dimension.  The implication is that these are a better fit than the Capri ones.

However, when I look at the various online catalogues, while I can find Citroen discs with the correct offset and centre hole in 262mm diameter, I cannot find any in the correct 247mm diameter.  All the 247mm ones I can find have offset that makes them a couple of mm worse than the Capri ones....

Am I being thick/blind?

Nick

[ferny]

I'm running these with 1155 now. Well, I would be if it hadn't been off the road since October after someone modified the front end with another car... I'll let you know if I still get brake fade between roundabouts in Milton Keynes.

[Nick Jones]

Ah..... that's not what I mean by vented though 🙂

Nick

[Clive]

I went through a similar process with my conversion.
I used the capri discs, and had a bit machined off the hub to improve ball joint clearance.

Do not be tempted to buy the larger "french car" disc and machine it down to the correct diameter. I tried that   (luckily on a gifted pair of discs) only to realise the disc centre (where the vented sections open and no braking surface) is actually rather large, leaving a too narrow braking surface)

[JohnD]

Been using Capri discs for more than ten years on the race car.
With 1155 they totally abolish the brake fade I had before.
I can't drive fast enough to cause it, even on repeated heavy braking.

I also removed the disc shields as there wasn't room for them, and it has left the discs running very close to the track rod ends, as Nick says.      
This caused rapid heat deterioration of the TRE rubbers, until I fitted greasable TREs that don't need rubbers.

ferny's experiment would be of interest, if he will test them on a track day, as road use doesn't compare.   Does 1155 alone abolish fade?

John  

[Nick Jones]

So the Citroen discs myth is just that then...... Pity.

Nick

[Clive]

Not exactly a myth,I think the larger discs are viable under bigger wheels.
And some (Gaz, no idea were he is hiding now) did use Saxo discs IIRC. So it can be done.

You are very welcome to cast your eyes over my setup at CC in April if you are still at the "thinking" stage then