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Big rear drums for racecars


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Hi Michael,

It may have been used on TR2 or 3 but with disc brakes on the front which is where most work is done and the weight transfer from back to front under braking a more effective rear brake is not normally found to contribute much in my opinion, leading to rear wheel lock up. I have used a Tilton brake valve and increased the the rear wheel cylinders allowing the balance between front and rear braking to be varied which I found useful in the wet where I would apportion more effort to the rear to reduce front brake lock up. I've also completed a number of laps when a split oil seal dosed the rear brake shoes with oil...and found no difference in my lap times, giving credence to the fairly minimal effect the rears made to braking although I could feel a difference in the cars "attitude" with the oil soaked brakes. 

Mick Richards

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Yes though for road work, I have 10" Alfins (originals not repro) on the back of my solid axle 4a, with 3/4" cylinders, I do have original asbestos linings and brake pads and Ive found it to brake perfectly and very controlled and will actually when pushed to extremis lock all four together . I do have very hard suspension though.

Stuart.

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Wonderful, i have been trying to gather information, and certainly some of the race drivers have worked towards having more rear braking using balance bars, as I only have the usual Triumph style split system that doesn't enable a bias in front to back braking a 10" rear drum should increase rear brake effectiveness.

Of course it is possible to fit Triumph 2000 rear brakes to a 4A-6 rear end: I have that on my 4A but as it is a road car now (was used for Road Rallys) it never gets really tested

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32 minutes ago, MichaelH said:

Wonderful, i have been trying to gather information, and certainly some of the race drivers have worked towards having more rear braking using balance bars, as I only have the usual Triumph style split system that doesn't enable a bias in front to back braking a 10" rear drum should increase rear brake effectiveness.

Of course it is possible to fit Triumph 2000 rear brakes to a 4A-6 rear end: I have that on my 4A but as it is a road car now (was used for Road Rallys) it never gets really tested

You could go for a twin master setup which will alter the balance depending on how set. http://www.racetorations.co.uk/triumph-c56/tr4-c6/tr4-brakes-c33/racetorations-dual-brake-master-cylinder-kit-tr4-4a-p362

Stuart

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46 minutes ago, stuart said:

You could go for a twin master setup which will alter the balance depending on how set. http://www.racetorations.co.uk/triumph-c56/tr4-c6/tr4-brakes-c33/racetorations-dual-brake-master-cylinder-kit-tr4-4a-p362

Stuart

I presume they are split front to Back ?

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10 minutes ago, stuart said:

Correct.

Stuart

Thanks 

they are dear aren’t they

 

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Just now, Hamish said:

Thanks 

they are dear aren’t they

 

True but well made. I have fitted them before.

Stuart.

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Hi Stuart

That is whatI already have: it is not easily adjustable! I am trying to work out how to create the equivalent of a Tilton set up with the screw bias adjustment using the TR 4 pedals and a new master cylinder(s) bracket 

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Mike

At least two of the four works TR4 rally cars have 10 inch rear brakes and I use these on BST82B and have done for many years, all with steel drums and very good brake linings. 3VC and BST82B have the Revington TR Twin circuit system or similar. 5VC will also. All are basically road rally cars but have done circuit work as part of that as you know.

In my experience the 10 inch rears work very well on BST82B in particular and I experimented over a long period with settings on the manual balance bar in front of the 0.75 inch cylinders to get the proportion front to rear right. I’m assuming you could do the same with a cable winder onto that adjuster bar.

I also have a cable / hydraulic handbrake set up (which affects only the rears obviously) and can be used to progressively pull on the rear brakes as I need - this works either via the (upgraded) cable and pulley set up or the hydraulic circuit which is tapped into the rear brake line and which I can lock off and remove if necessary for regulations. 

In my case using the handbrake allows me to balance the car better really in poor conditions (ie very wet, Ice, snow etc) and basically increases the brake load on the rear to flatten the car on braking or turning. I run the car with soft springs and stiff dampers with only a front ARB, so the car is more twitchy than a circuit car. If you run a rear ARB you will doubtlessly control the roll side to side better and maybe flatten the attitude of the car for better tyre contact to the tarmac, but for me this made the car tramline and understeer too much, with no grip to deal with that and in poor conditions you can’t load on the power. Probably an element to add individually as see if you can tune it to your satisfaction and worth doing stand alone after the brakes are sorted out ? Also points at dry vs wet set ups, so worth talking to other TR4 racers about what they do.

regards

Tony 

 

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  • 2 months later...

Hi back again with brake ideas: managed to put a balance bar break combination together, while I was at it I changed the ratio of the break pedal: (ratio of the length below the fulcrum= pedal to the length above the fulcrum to the balance bar now 5:1 where as the standard TR is 4:1 this should make the brakes softer and more gradual.

The system was made by inserting 1.5" into the standard TR4 brake set up and doing some work on the pedals to fit in the balance bar

We will see if it helps next month

Regards

Michael

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Edited by MichaelH
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