The thing that concerns me about the mods to fix Jag brake bias is that they all seem to revolve around reducing the performance of the front calipers so the rears can keep up. Either a proportioning valve in the front or smaller pistons in the front calipers. A better solution in my opinion would be to put a better caliper on the rear to improve it's performance so it'll keep up with the front. The main problem I see with this is the hand brake is part of the Jag rear caliper design.

Fortunately there are alternatives now. Hi Spec are making a caliper with a built in seperate hand brake mechanism. They also supply a mechanical handbrake caliper if you want to use an AP or other caliper for the rear that has no hand brake setup. Hi Spec handbrake caliper

http://www.hispecbrake.co.uk/Picture...alipers-72.gif

Just another option.

Cheers

LB you are indeed correct in your assumption that the fronts are doing all the work.

Firstly, some time back ( couple of years maybe) there was a story in the snaketales mag which detailed the efforts of some-one to correct the RMC jag brake imbalance. Should some-one find it and post a link would be appreciated and will show the extent that person went to.

Without detailing all the efforts past owners have invested (and money), the overall thinking is that the front brakes are wayyyyyyyyy to big and powerful. They were after-all designed to stop a 4000lbs sports saloon from high speeds that car was capable of. We are half the weight.

General consensus is to use a smaller front caliper. Nissan 4 spot calipers are light and proven to correct much of the problem.

I have also been told (albeit by an Englishman) that use of the earlier jag caliper (2 piston, bolt right in) is much better than using the later 4 spot series 11 onward for our cobras.

I should also advise once you get the balance sorted and the back doing more work, then you will have to attend to the rear solid rotor getting too hot and going away.

A vented rear rotor conversion is available to assist in addressing that problem.

Cheers

I suppose I will find out soon enough if it's a good idea or not. :eek:

Wot ya mean Uncle Craig? :) what you doin to that gorgeous RMC ya got? :rolleyes:

Just fitting those knock-off wheels I have. :D

Proportioning Valve
 

Please don't quote me on this but to proportion the front by limiting the pressure is illegal.

You are only permitted to limit the pressure in the rear system. Mike has the right idea of matching the rear brake performance with an upgrade.

Phil

So does anyone know if I can get aluminiun calipers to fit ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????

Wasnt there some suggestions regarding Willwodd stuff in the states at the start of this thread?

The Wilwood Dynalites fit and adaptors are easy to find.

The Skyline calipers are a squeeze but do fit and there are people who do Jag kits, just can't find there names.

You might also be able to fit the PBR 2 piston caliper in there.

And I think Mike also said the Hispecs can fit the jag front too, near the start of this thread!!

But Mike, what weight difference is there bewteen the std front 4 pot calipers on a S2 jag and the equivalent Hispecs.? Cause the initial question has my interest too.

Steve

The Hi Specs weigh 2.2KG each. Probably 2.4KG when you add the brackets.

A Jag caliper weighs enough that you'll really regret it if you drop one on your toe.

Cheers

You just need to make sure you can get them in there. From what I have seen it looks fairly hard to fit larger calipers to the standard jag discs. Just looking at clearance to rest of the suspension. Running larger rotors etc would make things a lot easier.

Mike runs custom hubs, with custom offset and that's the way I have gone as well.

I agree that this is the best solution, however I have recieved a neverending stream of advice from people telling me that the 4 pot jag stoppers are 'too much' and telling me to get something else (most often the 3 piston front brakes)

Personally I find the notion that the brakes are too powerful a bit odd (particularly when reading about various braking upgrades) and would prefer to upgrade the rears however I'd like to see how much difference dialling in more balance makes.

So I reckon that if so many people are happy to put less powerful brakes on the front then why not just limit pressure for much less cost.

I dont see why putting a proportioning valve on a brake line is different to adjusting a balance bar between two master cylinders (not talking about the legalities here). It seems to be a more accepted 'racer style' approach but I'm not quite ready to revamp my whole braking system to this point without first trying out some intermediate steps.

Maybe I'm throwing good money after bad trying to the maximum value out of my jag brakes but I'm yet to hear a compelling arguement to convince me of that - would appreciate one.

Weight savings alone aren't doing it for me - maybe the heat shedding properties of aluminium or the need for bigger brakes will when I get to a point where I actually start decreasing my lap times (!?)

LoBelly

So after all that I quess the answer to my question is, no, no one knows what will fit.

Hi Spec used to list a complete kit for the Jag front end. They will probably be able to supply everything: Calipers, brackets even disc if you need them. Give them a call.

There's plenty of dimensional drawings of calipers on their web page and AP and Wilwood have the same sort of drawings on their web pages. You should be able to wave a tape measure round in your front end and quickly determine what will fit.

Cheers

Paul, have you been reading the posts.

Wilwood definitely fit jag front-ends.

Skyline definitely fit jag front-ends.

Both can be found and sourced with bolt-on adaptors if you look hard enough.

Hi-Spec look good, but are a lot more expensive than the options above. But sounds like they fit as well.

With wheels, I don't think you are going to have any problems with wheel centre clearance due to the jag hub -> rotor face offset.

Just make sure you don't have any issues with clearance due to specific front setup on your Cobra, I wouldn't expect so.

Okies, Today I contacted a brake conversion company here in Brisbane.

They are VERY familiar with Jag brakes and of the opinion that the excessive front brake is caused mainly by a mismatch of componentry.

When asked what the RMC brake system comprised I answered with:

Mitsubishi servo
Ford Master cylinder
series 11 4 spot front calipers and Jag 2 spot rear calipers.

His response was immediate. The ford master cylinder incorporates a proportioning valve. The Jaguar did not incorporate a proportioning valve as such. It used a dual servo to apply a different assist for each end of the car.

He feels the problem can be overcome by using a master cylinder with no proportioning valve but then also play with different cylinder sizes to get the bias correct.

Does this make sense to any-one?

Thanks for the help guys I think I will go with the AP's , I have heard bad things about wilwood, cracking etc.
Again thanks very much

You can't go wrong with AP. Fantastic quality and design.

Cheers