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Princess 4 pot calipers

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Does anyone know whether Princess 4 pot calipers fit the TR6?

I have heard that this was a popular modification when there were still Princesses around (usually in breakers yards!) but I'm not sure what mods are required to make them fit.

Any information much appreciated.

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Not sure about Princess calipers (might be hard to source) but there is certainly a Toyota set that fit. Try a search. I think a guy called Steve Darbyshire on here fitted them on his 6. I recall he had issues with pedal travel but may have resolved that since.

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Hi Guys, i have indeed fitted the toyota 4 pot calipers on my 6.

 

My car has silicon brake fluid, fitted prior to my ownership, and i think this accounts for the slightly longer pedal travel.

 

The calipers are easy to fit, they bolt right up and only require trimming of the backplates as the calipers are bigger.

 

The range of pads available is limited, i use mintex 1109 but would ideally like to use 1144 but its not available

 

Would i recommend them?

 

Probably!, i do feel there is better brake control with these calipers, but as the hydraulic ratio is very similar i dont think they greatly improve power

 

The small disk rotor size is the real limiting factor for power, and bening non ventilated limits longevity, ie they fade.

 

The toyota calipers are available cheaply, i can look out the supplier and part numbers if you’d like.

 

Steve

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Does anyone know whether Princess 4 pot calipers fit the TR6?

I have heard that this was a popular modification when there were still Princesses around (usually in breakers yards!) but I'm not sure what mods are required to make them fit.

Any information much appreciated.

Thats the upgrade for TR7, the other type that will fit the 4a/5/6 is Jaguar Series 1 XJ6 and Series 1 1/2 Etype 3 pot calipers.

Stuart.

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I fitted xj6 4 pot calipers to a stag without too much trouble..they were very heavey though!

Similar suspension

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There's no advantage in multipot calipers, unless they can be used to enable wider diameter brake discs, so that the same frictional force acts with a longer lever arm on the tyres. That demands wider wheels etc.etc. which adds to the cost and 'doability'.

 

I say 'no' advantage, because friction is independant of area. It depends solely on the force between the surfaces, which depends on the pressure in the brake system. If that is constant, and you increase the size of the brake pad, the force per unit area squeezing the pads goes down. But you have bigger pads, so they act over a larger area, and the result is exactly as much braking force as with smaller pads! But with multipots the smaller diameter of the pots relative to the master cylinder can lead to a different system pressure and altered effect, so that changing the M/c can be necessary.

 

The OP, Ron, didn't say why he was considering 4-pots. If he finds that his brakes are inadequate in any way, he should consider why, because TR brakes are perfectly good for most road use. You should be able to lock-up all four wheels and if you can't then the brake system needs to be serviced.

 

Brake fade, due to repeated heavy use from driving style, pass storming or competition, needs vented discs and/or a 'hotter' brake material to be considered. 'Hot' pads can be unresponsive when cold, making that first brake out of the garage a bit iffy, but I'm very happy with Mintex 1155 (1144 for road use, 1166 for race only) as a happy medium.

 

John

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I have a set of toyota calipers on the shelf.. bought them cheap when I was in the US a few years back.. I think one of the attractions of the installation for some was that you could fit vented discs (which I also have)... but can't you just fit spacers to the standard calipers on a TR6 and then use vented discs?

Cheers

Tim

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Another thing to consider is the added weight of larger calipers and discs on the suspension set up.

 

To be effective you would have to use ali calipers, bigger vented discs, sticky pads, consider the brake balance between front/rear and possibly fit an adjustable proportioning valve +/- master cylinder. From past experience I've not found "big brake" kits and conversions that much better than OEM other than fade is reduced and they look nice behind the wheels! OEM with better pads is a better option for road use. Just my opinion :)

 

Andy

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Hi guys

Many thanks for your useful replies.

In my (clearly befuddled!) memory, I thought that this mod had been done before hence the post.

I have to come clean and admit that I had found new ones on fleabay which already have spacers fitted. This would, of course, mean I could use vented discs although I wasn't sure which.

The brakes are not bad but I have done quite a bit of continental touring and felt I could do with upgraded brakes for this reason. Perhaps drilled and grooved discs should be my first port of call.

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Toyota 4 x pots on the front and larger cylinders from a Morgan +8 on the back are a good combination and are a definite improvement on stopping distance using the standard 4wd Toyota pads. Mine is a road car not track and have never experienced brake fade.

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My brakes are standard, and I will see how this performs (normal road use intended); if not adequate, I will fit the uprated (double) brake servo, a new one including new brake lines costs just under 300 euros in Holland and it is a straight fit.

In that way you do not change front/rear distribution too.

Waldi

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Interestingly we compared standard green stuff pads with mintex 1144 on some track laps at spa (otherwise standard setup). The greenstuff began to fade on the last of 3 spirited laps and there was a strong smell of burning.. There was no perceptible change in the mintex performance. Interestingly one the cars in our group with new "standard" pads (don't know the make) was driving at the same speed as us and lost his brakes entirely on the last lap... quite scary!

Cheers

Tim

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I agree with John. If you increase the pad area you should also consider the disc's. Otherwise you can just end up with brake fade.

 

Another popular up-grade on the the TR7 is the 2.8 Capri set-up which uses Fords 16P metric calipers and vented discs.

 

Ford's fitted a spacer to their 16P caliper to allow for the vented discs.

 

The Ford caliper and the Princess caliper have a different spacing on the mounting holes than the type, 16P, used on the TR6/Vitesse/GT6.

 

Dave

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I fitted Hi Spec four pot callipers along with vented disc's and later Classic Developments alloy hub, bigger bearings and stub axle along with Mintex1144 and have never experienced brake fade.

I changed the pads to Hawk HPS last year as less dusty.No brake fade on either and after 25 laps of SPA (not at the same time) just great. Just did the Ballon"D"Alsace with no fade up or down.

Although one of our members on standard did.

Horses for corses, normal driving probably not and the standard set up fine.

My set up gives me confidence every time.

Regards Harry

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My brakes are standard, and I will see how this performs (normal road use intended); if not adequate, I will fit the uprated (double) brake servo, a new one including new brake lines costs just under 300 euros in Holland and it is a straight fit.

In that way you do not change front/rear distribution too.

Waldi

 

What is the uprated brake servo you refer to Waldi?

 

I've fitted an Audi 2V servo vacuum pump to my car with an adjustable switch so I can increase vacuum up to around 20" if I want. I'm starting at 12" of vacuum with Mintex 1144 pads and Morgan rear wheel cylinders and will experiment further from there :)

 

Gavin

Edited by KiwiTR6

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Gavin,

To be honest I do not know which type exactly but think it is from a Volvo.

A guy in Holland sells them, new, including the two brake lines. Not sure how much has to be modified if you buy the Volvo servo yourselves.

Hope someone will come along with the part no.

Waldi

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Be a bit of a challenge chasing down a set of competition pads for an Austin Princess

But the Princess was big in the BTCCC, the British totally crap car championship that is :-)

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My brakes are standard, and I will see how this performs (normal road use intended); if not adequate, I will fit the uprated (double) brake servo, a new one including new brake lines costs just under 300 euros in Holland and it is a straight fit.

In that way you do not change front/rear distribution too.

Waldi

 

Waldi,

How will a brake servo make "inadequate" brakes, adequate? It only multiplies the foot pressure you apply, up to a limit. Anyone with arthritis or other disability may benefit, but the car's braking ability will not.

JOhn

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Hi Waldi,

my 4A has standard brakes but with Freodo FDS167 pads on the front.

 

Whilst in Scotlandshire last week I approached a width restriction on an otherwise reasonable road at apprx 40+mph.

I had to apply the brakes suddenly as the approaching traffic decided to barge through.

The sudden braking allowed the 'blue smoke' to escape from the rubber and skidded a short distance.

The wheels easily locked up (without a servo). I think the road surface had become smooth.

 

Roger

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This is a bit of a techy response rather than anything practical and useful.

 

The braking torque achieved by clamping the rotating disks to the static calipers is what stops the car. In practical terms for our cars the clamping force is a function of brake line pressure and piston area. We can increase brake line pressure by pressing harder on the pedal (maybe using a servo to help press harder), moving the fixing of the master cylinder arm closer to the brake pedal pivot, or reducing the bore of the master cylinder. The alternative is to increase the piston area or move the clamping force nearer the outer edge of the disk, which is where 4 pot calipers fit in. The two smaller cylinders can have a greater area than the larger single cylinder but it could be less as the standard 2.125" diameter as TR6 pistons are a pretty decent size, and the two smaller cylinders can be designed to be moved out to clamp nearer the rim of the disk but I doubt they would be able to move far enough to make an appreciable difference if keeping the standard disk diameter. Before spending good money it might be worth doing some maths to work out what the increase in braking torque will be. It may be more cost effective to overhaul the existing parts.

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Waldi,

How will a brake servo make "inadequate" brakes, adequate? It only multiplies the foot pressure you apply, up to a limit. Anyone with arthritis or other disability may benefit, but the car's braking ability will not.

JOhn

 

 

Hi John,

Ron (the OP) indicated the wish for upgraded brakes in his 2nd post.

The larger (double) servo will require less force for the same decelleration.

Maybe it is due to my lack of understanding/language, but isnt that more adequate?

 

Waldi

Edited by Waldi

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Waldi,

I understand your point, but if the driver cannot press hard enough for "adequate" braking, that is not a fault of thre brake system.

I agree, for anyo who is in that position, a servo can be useful, but it cannot make braking better.'

 

And there is a limit to the servo effect as show below,

 

post-535-0-85226000-1536679216_thumb.jpg

 

John

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