Alternate brakes for track use?

G

Guy Engelsman

New Member
I fully admit that the standard brakes on a P6 are perfectly adequate for everyday road use. But on a track under repeated heavy braking the smell, and glowing, and flames, and the screaming, and the fire extinguishers gets a little tiresome! :twisted: I am looking to upgrade the brakes on Pooh and am curious to find out if anyone else is mad and has done a useful upgrade?

I have found on the AP Racing website a great looking set of brakes and wonder if they will work. They are 4 pot calipers with 41.3mm bores, and a solid back but blank mounting lugs. They also take a 300mm diameter 28mm thick grooved and vented disc, but still look almost standard. I am unable to get the link to work completely (due to a complete lack of ability in this area) but the website is at http://www.apracing/calipers/products just look under the Historic range. The disc (with suitable bobbin) is also on the cards (just needs to be measured up). They should fit under the 15 inch Superlite wheels as well (I think :? ) I may have to accept a smaller disc, but the standard discs are 280mm (ish) and they fit under 14 inch steel wheels fine. I will most likely need a brake balance system to be fitted but I am also looking at how I can stuff twin master cylinders into the pedal box. Time will tell...........

What do you all think? :wink:

Photos included.

Cheers

GUY :D
 

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Hello Guy

I agree with you that an upgrade to vented discs at the front is a good idea for track use. Equally as important is the ability to use a suitable pad. I'd actually start at the pad end of the discussion. The standard caliper has EBC GreenStuff and RedStuff pads available because it is common to a variety of Jaguars. GreenStuff might be adequate, RedStuff certainly will be, but the red will need significant warming up so will be pretty poor for road use. Both red and green need grooved discs/rotors to work properly as they gas under load and the grooves are needed to allow the gas to escape and prevent the pads floating on the discs. I'm personally very anti drilling on the grounds that, however carefully the holes are chamfered into the disc, they act as crack propogation sites. You therefore expect to have to change the discs at regular intervals. Unless required by the regulations, I'd also fight shy of going dual circuit. It's very difficult to achieve the same feel with a twin circuit set up as a single circuit one.

I'm also not convinced that moving to a four pot caliper is strictly necessary. Once you abandon the standard bore sizes in any of the brake components you will inevitably upset the system balance and a balance valve only really corrects this for one particular application pressure - in the cae of a racing set up, a full aplication! So you will generate something that is very difficult on the road.

My start point would therefore be to split the existing caliper and insert a spacer block and use a more readily available vented disc that can then be grooved. This is the Alan Ramsbottom solution from Classeparts and I'd want to be convinced it isn't adequate before getting involved in the hassle of completely redesigning the whole system around a new caliper. It will be a lot cheaper too! I'm sure Alan could post you just the spacer blocks and the discs to save on postage bulk. Alan uses a readily available (in the UK) Ford disc re machined to suit the P6 hub dimensions. Maybe there is an Australian equivalent - you're looking for the correct stud pattern and then you can machine the hub face to suit the caliper position on the P6.

I'd be equally as concerned as to what to do with the rear brakes. Alan has produced some options for this including using Sierra Cosworth calipers and Audi calipers so as to permit a vented disc. I'm not convinced by these options for the reasons given earlier about changing the front calipers. Something does need to be done though, as there are no pad upgrades available for the standard Girling calipers. My start point would therefore be to see if I could source a pre '66 Dunlop set up for the rear. This is common with contemporary E Type and so has decent pads available for it. I intend to do this to Lucky in due course, so have such a set up in my garage waiting for the Girlings to expire! I can send you a photograph if you pm me your email address. My plan has been to use this set up on a standard solid disc suitably microgrooved. My experience with a variety of road cars is that simply micro grooving a solid disc and using with GreenStuff pads is very adequate - so I'd be inclined to try the same with RedStuff for your racing use.

I think upgrading the rear to match the front is important even for racing. Leaving the rear standard would effectively give you a car with no braking at the rear at all, and I'm sure that isn't a good idea for stability under braking.

So my conclusion is that your proposed AP racing set up is rather over the top. More importantly you are storing up a lot of development aggro getting all the bore sizes of master cylinder, servo and wheel cylinders to work together. I'd strongly counsel starting out by using factory cylinder sizes through using the standard front calipers and the factory Dunlop rears. There's no reason for that to limit you on disc and pad specs.

Only after you've prooved that that isn't adeqaute for what you want would I embark on the development time to generate a compatible new set up.

Hope that helps

Chris
 
Thanks for all the feedback so far.

I am also looking to replace the standard diff with a Jag (possibly with LSD if I can get away with it). This means that we will be putting a new set of calipers on the back end as well. In terms of development of a new brake setup, I am a compulsive tinkerer and this avenue holds no terrors for me, in fact I love a challenge!!!!!!!!! I am a bit wary of splitting the existing calipers, and the new ones will be monoblocks, so much stronger with less chances of a leak. I have used greenstuff in the past on my fast early Dunlop braked 2000, and it was great, but for the 3500 I really need more pad area, and better cooling noting that the new engine spins happily to 6800rpm giving me a (theoretical) 160mph. The standard discs can warp under a high duty cycle (as in racing) as they dont disipate heat too well, hence going to vented discs. For the interim period while setting up suspension and new engine etc I will be on Red stuff for race/ track and Green stuff for any road work that may come along on the standard (but grooved) discs (and taking it a bit easy :wink: ).

The biggest advantage to using a complete new setup is that I can tailor the bore sizes (different master cylinder bores for front and back) to generate the balance that I need. However this is most likely still 12 months off at the moment as I (still) need to get the new engine and gearbox into Pooh (photos tomorrow I hope). I like to get working on major upgrades like this early so that I can work thorough the many (many :roll: ) issues that will result from major engineering work. Work is also limiting the amount of time I have to mess about with old cars (one morning a week due to study, exams etc) hence the long lead time between starting and finishing anything at the moment :oops:

Over the top is not always a bad thing Chris.......... :twisted:

Cheers

GUY :D
 
In that case, I'd say go for it and have the AP calipers! The arrangement for the brake master sounds like it may be a bit of a challenge! I do approve of the idea of using seperate circuits for front and back (rather than a more conventional split) though.

Another approach might be to find out what early E Type people use for racing - as they have the same calipers as the V8 as standard. Presumeably this will give you a clue as to what might be compatible with the existing struts.

Don't forget to re-read Simon Owen's thread on fitting the Jag diff!

Chris
 
Hi Guy

I'm watching this with interest as I've had a few hair raising moments myself in mine when needing to slow down rapidly from high speed. The car pulls up straight, but it's the distance. This is after every like pads, discs, fluid, etc has been checked.

There's a guy called "DBA steve" that used to post on a few forums, he's pretty cluey at brake conversions too if you get in contact with DBA.
 
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