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The mkiv Supra Owners Club

Rear Brake line bypass Valve


THOR Racing
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Has anyone thought of fitting a valve in the brake line to disconnect the rears during drag racing so the foot on the brake pedal only holds the fronts on? Could this be an electrically operated solenoid? Fails safe to always open, hence normal operation?

 

It would help heat up my rears prior to launch and save my autobox torque converter.

 

Also set it to disengage after the front wheels start moving thus giving you your braking back at the end of the run.

 

Pete

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Guest Mycroft

I should think CW has all the bits to hand they are common enough on racing cars and just the electronic control would be 'your thing' but the 'average pressures range from 800psi to 1400psi.

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***THIS POST COULD BE A RIGHT PILE OF SHITE***

 

is there not a bias valve between the front and rear brakes, if there is wouldnt it b easier to use this to shut off the backs.

 

i think i can remember reading about a bias valve somewhere, not sure though. thought it would b worth a mention.

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Guest Mycroft

There is, but i think it cant be set to shut off the rear without some serious work and certainly not whilst going 'balls out' on a the drag strip, but it IS worth having another look, and this I will do.

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Just dug out my elderly Rally Design catalogue (1999) and it has the correct device listed - it's called a "Hydra-Lock", the picture shows a label with "Jamar" written on it so that might be the maker although it's listed with Wilwood parts.

 

"A simple device to hydraulically hold brakes locked

Use with your existing brake system - supplied with metric fittings

Press once to lock un-driven wheels, press again to unlock

Gives that dragster style start"

 

£59.50, does exactly what it says on the tin!  What do you need all the electronic stuff for?

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>What do you need all the electronic stuff for?

 

cos I like controlling stuff with electronics! Haven't you worked that out? ;-)

 

But for £60 this device will do the job.  So what/where can you find more details?

Worth a web search under Hydra-Lock I guess.......

 

Pete

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I think it's this.....

 

http://www.jamarperformance.com/products/brakes.htm

http://www.bcbroncos.com/brakes1.html

http://www.bugsandbuggies.com/Parts.asp?CN=506&SN=5&GN=7

 

PARK_LOK

 

A hydraulic lock that uses the line pressure of the system to hold your brakes locked, no electrical or special linkage required. Just step on the foot brake , push the Park-Lok down, let off the foot brake, and it's locked. Step on the foot brake again, and it opens automatically. Holds any vehicle with hydraulic brakes where you put it. With the Park-Lok set, the brake removes all pounding on ring and pinion gears when trailering a vehicle.

 

PRICING

Brake Line Lock $32.00

 

Cheap. So where would this be fitted? Would the brake hoses have to be extended into the cabin area???

 

Pete

 

 

 

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No idea about a website for the part I mentioned.  I can dig out Rally Designs part number and contact details when I get home, but both will be three years out of date . . . worth a shot though!

 

And yes, you will need to route the rear brake line to the device, which needs to be mounted where you can press the knob on it.

 

One advantage of an electronic device would be that you could put the device in the lines and you'd only need to route some wires into the cabin.  Plus it would be an excuse for Pete to put some more flashing light type stuff in his car?

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Well, all modern brake system are "dual circuit".  There are two totally independant brake lines which are pressurised by the cylinder, one for the front brakes, one for the rear.  this is a safety feature so that if one of the brake lines bursts you still have brakes on one axle.

 

So, you only plumb the line lock into the brake line which feeds the rear wheels.  Hit the pedal, all brake lines are pressurised, lock the rears on, release the pedal and the fronts are no longer pressurised but the rears are still locked on.

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