Technical Do I need a brake pedal stop

Hi

Do I need a stop at the bottom of the brake pedal travel to keep the piston from hitting the back off the cylinder too hard or is it OK to let pistons bottom of travel be the stop.

Phil

 

Nope. You don’t need a stop. When you add fluid, the piston will only be touching the fluid.

 

You do mean the piston retainer and not bottoming out right?

 

I think he means bottoming out in the master cylinder. Just make sure that if/when your pedal bottoms out that the plunger in the master cylinder is also at the end of it's stroke.

 

You could put one in that you calculated to do what you are asking but I don't really see a viable reason why you would need one.

 

If you can get the piston to travel that far down the bore of the master cylinder, something is wrong with your brakes.

 

I understand that when everything is working normally the piston should never get close to bottoming out. When bleeding the system if there's no stop it will happen. In a OEM system the pedal hits the floor in a system failure. I just wondered if that was important to happen before the piston completely bottomed out.

Phil

 

Listen to Gimpy, even with a failure in one side of the system the pedal still shouldn’t hit the floor.


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I always build the brake system so the pedal hits the floor just before the piston bottoms out. Put a stop in if it makes you feel better, but I don't think it is needed. Just don't hammer it when bleeding the brakes.

 

I had to put a pedal stop in my old pro street Morris Minor so the pedal wouldn't hit the front tire in case of brake failure and I was turning. That's the only reason I can think of. There's only so much room in those little cars.

 

Thanks everyone, I'll try to set it up so it hits the toe board at almost the bottom of travel.

Phil

 

I put a stop on mine, but it was for the opposite direction, to keep the pedal from coming too far up.

 

I wouldn't want anything to stop my brake pedal except for the brakes.
Remember that if one portion of the system fails with a duel master cylinder, the pedal will sometimes travel almost to the floor before the brakes will work.

If you want something to stop the brake pedal besides the brakes, you could just throw a bottle of water on the floor. It'll roll under the brake pedal eventually. Just making a point LOL.
Good luck!

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In fact, set it up with that in mind.

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Having the pedal hit the floor is terrible advice if you want the safety portion of a dual master cylinder to actually function...

Have a look at OEM stuff, let us know how many brake pedal stops you find.


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When bleeding ,put your toe under the pedal to keep it bottoming out , that's what I was taught 60 years ago...

 

Dual (tandem) master cylinders should always be able to full stroke before the pedal hits the floor, to allow the safety advantage of a dual master. That's what should happen in any OEM vehicle with a dual master.
A single system master is not as critical because any major hydraulic failure will result in total brake loss anyway. The (residual) check valve located at the end of the cylinder could be damaged during a hard full stroke, something I'm not sure of.
I'm not sure because I never did any single system master cylinder testing. Mine started in '71, 5 years after dual masters became mandatory.

 

the cylinder should stroke to the bottom of its bore.

Depending on your exact build and set up, you may want or need a pedal stop just after the the cylinder bottoms.

And for goodness sake allow adequate clearance for carpet and padding to be in the way and still allow full stroke after it’s all put together.

 

If its a new brake master cylinder, say a gm c3 corvette style and you have set it up so you cannot fully stroke it, especially if you have a brake booster, you have to bench bleed it...….
before you fit it to the car, clamp it in a vice.
using the two brake fittings you have and the pipe bender you have just bought, make some pipes that
come from the unions and enter into the fluid receptacle and touch the bottom.
using a blunt bar with a domed end - not a screw driver, I said NOT a screwdriver! fully stroke the cylinder, marvel at the amount of air coming out
what you are doing is getting the air pocket from the end of the cylinder out, which you would leave there IF the master didn't plunge all the way, compress and have spongy brakes
this is also true of hydraulic clutch master cylinders