TheSamba.com :: View topic - Need suggetions from brake pros on sand rail

Wed Jul 20, 2005 7:48 am

Need some advice on setting up my brakes on my sand rail. I have setup brakes before on other cars but the laws of braking typically follow the rule that most of the braking is done by the front brakes. With rails is this rule the reverse since most of the weight is in the back?

My rail is setup with discs all around. I am going to install this wilwood dual circuit master cylinder:

http://wilwood.com/Products/006-MasterCylinders/008-CRTMC/index.asp

I am also going to install 2psi residual pressure valves on the front and rear line since the master is lower then the calipers.

My main question is will I need a proportioning valve to help balance the brakes and if so do I install it in the front or rear line? I would assume like other cars that since the front brakes do most of the work I would isntall the prop valve in the rear line to control the rear discs from lock up, but if braking works different in rails due to weight etc should I install the prop valve in the front line if I even need it.?

Thanks in advance for the help.

Wed Jul 20, 2005 9:32 am

Hey...

Where the weight sits when the vehicle is static is not relevant here...what matters is that the front of the vehicle (when the vehicle is moving forward) will always take the bulk of the load when braking. (So that's why they put the larger wheel cylinders on the front of the vehicle...I almost swapped mine, but didn't after I did this research...)

I'm not certain on the prop valve question, but I've talked to several folks about this and they confirm that the weight distribution doesn't matter here.

...but maybe they're full of it. Not sure...:)

Wed Jul 20, 2005 10:32 am

I am assuming that since most of the weight transfers to the front when braking and the front brakes do all the work I would install the prop valve on the rear line so I can adjust pressure to the rear discs so they do not lock up before the front.

Does this sound logical?

Wed Jul 20, 2005 11:21 am

I would rather the rear lock up before the front offroad. when the fronts lock up first you lose most of your steering. and when cornering rear skid helps in the turns while the fronts are stilll rolling and turning. just my $.02.

Thu Jul 21, 2005 10:05 am

If it is a true "sandrail" and only use the car in the sand, front brakes are really not that necessary. It just adds extra weight and more parts to get full of sand. My buggy had only rear brakes with cutting brakes to help in tight turns. You will need a residual valve if using discs, otherwise you'll loose adjustment everytime you let off the brake pedal.

Thu Jul 21, 2005 10:11 am

Oops, I just realized that you don't have many sand dunes where you are... :oops: Nevermind. However, you will want to proportion the brakes to lean a little to the front. Most of your braking power will be there. The harder you brake, the harder the front will work. I agree with Baja5 about wanting your rear to lock first in the dirt though.
It will really depend on what you plan to do with the car. If you spend more time on pavement, you'll want more braking in the front.

Fri Jul 22, 2005 10:36 pm

Thanks JPS. Yes the sand rail is setup for street and the only sand it will see is ehen I drive it to the beach. Thanks for the tips on the brakes. I already have ordered the parts

2# residual pressure valves for front and rear lines

Wilwood dual circuit master

Prop valve for rear line

Hopefully if all goes to plan it should feel just about right.