WANTED - Jag rear ventilated discs

[PCC]

Les,

I'm with you to a point.

I have jag vents on the front and solid jags on the back.

Breaking at speed on the straight, I might as well forget the rear brakes as all breaking power feels as though it comes from the front - its the only time my front end goes down (still too low at the back)

Yet into a corner is a different story...........

You can feel the backend braking, nearly as much as the front and if your not careful its very easy (at speed) to loose everything and become an olympic floor gymnast!

I have a problem with the inboards on these cars (No 15 on the to do list). I think there is too much heat around the diff caused by breaking and coupled to the rear suspension design (DRB's only) it just does not make the back end perform as it should - may be just me, but may be for once I have a valid point.

When I get to No. 15 on my list, I will seriously consider changing the back end to a more traditional setup with an outboard brake system with twin shocks and coils.

[Rebel1]

Yep...I know what your getting at Pete.

The RMC's seem strange with regard to what happens with the back end during braking and it is that vagueness/inconsistancy (?) which is somewhat disconcerting.

Maybe it is just the heat that is generated by braking combined with the heat being channelled down the tunnel which leads to this "vagueness"

Anyways...whats this floor gymnast thingy.... I'm way past carpet burns and horizontal gymnastics .. leave that to you young fellas.

My story and I'm stickin with it.

[REPTYL]

I had a good look today at trying to get some cool air to the rears.
It's very tight and the only place I can see to pick up cool air from is very close to the lowest point on the car.
Problem with this is, stones dust and water making its way from the road up the tube and on to the brakes.
The only other way I could see would be to run the ducts up the inside of the fake side pipe to the front of the car (that would work - but too much work for me).
Also, you can't get a tube any where near the inside of the ventilated disc, so I'm guess feeding the cold air on to the callipers would be the second best option?

Thoughts???

[BMK]

Jason



Not having a jag rear end ( Live axle 9" Ford ) I'm wondering if you could add a big arc 90 degree sheet just under each seat rear floor area at the very back, that turned up into the area behind the seat back and bring air over your diff centre and the brakes that way?

Basically an air scoop upside down with air escaping upwards onto the diff centre each side.

The sheet would only need to be about 15 - 20 mm below the floor if it was wide - say the width of the floor below each seat.

It would drag a lot of air up from under the car. Don't think it would cause any lift!! The floor below the fuel tank would cause more uplift!!



Make sense?

Bernie

[Rebel1]

Jason ... I've been searching for that pic of a cobra with rear brake ducting .... cant find it ... Yet.

It looked very simple ... Essentially it was a sheet metal rectangular affair which looked at first glance just like a rectangular exhaust pipe exiting in front of the back wheel. About where the side pipes turn outward but from under the car.

It was only shallow.....looked about 50mm deep but was about 300mm horizontally and was cut at an angle facing forward and it partly protruded from the side of the car a little.

What it was shaped like under the car is anybodies guess but I imagine it just channeled cool air to maybe some flex pipes which then fed air around the center of the rotors.

It looked just like an inverted scoop which drew cool air partly from the side but also from under the car.

The owner of the car only fitted them when he was competing. He removed them for street work so I guess some easy fixing like Mikes nutserts would be handy.

The owner did write that they made a huge difference to the rear braking of the car.

Feeding air to the caliper is not what you want. Remember the heat is generated at the pad/caliper interface and you wont get any air there. The rotor is a huge heat sink which converts kinetic energy to heat and it is the rotors job to dissipate that heat to the atmosphere. Thats why vented calipers were designed.

Have a look at those glowing rotors on F1 cars. Thats where all the heat is and where you'll get most improvement.

I'll keep looking for that pic.

Cheers

[Rebel1]

Hey Al,

Yep..I agree with you about the front doing all the work ... but

And here comes the debate

Let me first say that I'm by no means an expert and I guess this subject has a lot to do with driving styles.

But I rather like a little back brake before the front come on. Just a little mind you and certainly nowhere near causing a rear lockup before the front. Just a little so if you tap the brakes the rear will come on a nanosecond before the front brakes and hopefully help pull the car into line before the fronts come on strong.

A little like towing a van/ or a big rig ..if things get loose and messy get the trailer brakes on first and hopefully pull the rig into balance.

Mind you..and I did admit that I am no expert, but I have spent more than my fair share of time in the weeds so this principle may be totally wrong.

Now...about that itchy head.... Just drop into a chemist, they've got all the stuff to fix the little beasts.

Cheers

[NASSTY]

G'day Les,

I know what you mean by feeling the back come in first. On newer cars with ABS you can feel the backs working a lot harder when you start to brake compared to non ABS cars. The ABS car will squat on all fours rather than dive, especially on some european cars that I've driven with 4 channel ABS. But most cobras don't have the advantage of electronics maxing the rear braking effort. I'm hoping my jag front end with anti-dive geometry will help too.
I even understand that trailer braking thingy you're talking about

As for scratching one's head - I'm sure you can relate to how frustrating it is when the Mrs goes to all that trouble grooming ya and she still misses some of the critters especially when ya stayed still and offered her some of your banana!

Cheers

[PCC]

Al,

I'll have you know Les is not a monkey ie banana reference

A baboon may be, but definitely not a monkey

Pretty sure the original Daytona's had double ducts on either side to cure any overheating at the back end.

With regards switching from a jag irs what you guys recommend?

I know the newer DRB's now have the twin shocks, but still use the jag inboard rotors.

One thing good about teh inboards, the rear wheels stay shiny

[NASSTY]

Peter,

What about a Skyline rear as per a Harrison?
Talking to Warrick Harrison when I was up north, they're about $400 and there is a strong supply.

Or there is the Ford AU IRS.

How you'd fit these I wouldn't know

All I do know from experience is that a live end can give a harsh ride.

Cheers

[Rebel1]

Pete..If you would like outboard brakes .. try here

http://www.cobraracing.com/ProductsP...k2000Main.html

There is also another after market Jag suspension mob but they dont use the outboard brakes.

http://www.cwiinc.com

I think that cobraracing mob used to supply Robnel with rear suspension bits and pieces. Don Pillings robnel has that wide alum bottom A-arm

Also of interest is that watts linkage which does away with trailing arms.

Hope this helps

Cheers

[Rebel1]

Ooopsy.. Gawd, you guys are cruel .. no wonder I suffer a giant inferiority complex.

Al, Wots this grooming bit?? Is that wot ya call it?

Nuh...my missus never had to search me for critters .. specially not around the " Banana " as you call it.

I'll have you know I've led a very sheltered childhood so I'll leave that pastime to you more worldly fellas.

Talkin about grooming and Bananas...In my day we used to call that sort of activity as " Living on the fruits of love".

Just don't throw the skins out the window..they choke the ducks.

[NASSTY]

[pneall]

The humor on this site is cracking me up. Hard to type as I am laughing too much. OK back to the real world. Must work hard pay for Cobra stuff

Phil

[REPTYL]

It looked very simple ... Essentially it was a sheet metal rectangular affair which looked at first glance just like a rectangular exhaust pipe exiting in front of the back wheel. About where the side pipes turn outward but from under the car.

The more I think about this option the better it sounds.
Should get plenty of air from the side of the car.
Being just above the side pipe would stop any dirt or small stones entering from the road surface.
Two right angles and a bit of flexi-tube would do the trick.

Cheers Reb'

[Rebel1]

Yep...thats pretty close Jas.

Remember, at track speeds the amount of air being pumped thru even a 50mm flex tube is gonna be a $hitload. Just make the scoop in the airstream as large as ya can

Cheers

[justbetter]

Hey Jason, i might have a solution, " i know" from me...

Back when i was a boy, 18 or so, Gee they were the days.

I was with a gal who's mothers boyfriend was one of the Grafereo Brothers, from the Truck racing Grafereo's and that monstor 4 turbo, v 12, on nitros Bandag bullet, so ended up spending a bit of time with them at the track, mmm maybe thats why that relationship failed .

Anyway, they had a problem of cooling down the drum truck brakes at the end of the straight, ready for the next corner, not much room either for a vent.... so.

They plumbed small brake lines to 2 points to each side, then filled a fire extinguisher with water, plumbed it to the two lines, pressurised the fire extinguisher, cause they have a tire valve filler point, set a opperation switch to a harder pressing point behind the brake, for only opperated at hard braking.

This system may work for you, as you will only really require it on track days, and you could vary the size of the tank, cause you wont need that much water.

A hint might be to add a little oil with the water, for those elimination of close behind cars.

[REPTYL]

Gee... I could do that. but now you've got me thinking.

Back when I was a young boy, we used to race billy carts at brake neck speeds.

and my favorite cart had an excellent braking system that could easily be installed on a Cobra.

Only materials needed are: 1 piece of 2x1 treated pine and one pivot pin (I don't think the 3 inch nail could be adapted to the cobra conversion, you could tap a bolt straight in to the side intrusion bar).

[pneall]

Seem to remember when Jaguar raced the XJC's that they fed air directly onto vented edge through the openings accesible from the boot. The Cobra boot would have same relative position , just have to work out how to get air into boot without looking daggy. I will try to find photo.

Phil

[justbetter]

Hey at last i can give some one a hand being in the timber game.

Let me know the length you need and its done, may even inset some nails into the end for some great sparks effects.

Also suggest to fix to the side intrusion bar so when you open the door it moves out of the way too...

Love it when i can help.

[justbetter]

Now if Jason cut some holes in his roll bar ( entry position ) then some where they come through in the boot ( exit position )

Well aa, proplem solved.... im on a roll today

Any one else got a problem ?