Thread: poor brakes

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Hey Guys I'm having issues with my brakes on my 40 Ford p/u. I have wilwood disc on all four, 7" brake booster with 6-1 ratio brake pedal. Vaccum measures 14 inches with my gauge< not sure how accurate it is.
My brakes seem like they have no power to them, I'm thinking not enough vacuum. would putting a vac "CAN" do any good or would that just be the same. master cyl has a 1 inch bore. I know I can go to a 7/8 but that cost and will create a longer pedal push.
Any body use a electric powered vac pump ?
thoughts ?

A vacuum can could help. But 14 inches should be plenty. so maybe figure out a way to really measure the vacuum. Which calipers are you using? Wilwood Dyna-lite? Also, is your master higher than the calipers? If not did you use residual valves?

Originally Posted by 34_40

A vacuum can could help. But 14 inches should be plenty. so maybe figure out a way to really measure the vacuum. Which calipers are you using? Wilwood Dyna-lite? Also, is your master higher than the calipers? If not did you use residual valves?

can't remember the calipers, it all came as a kit from Wilwood. I do have 2lbs residual valves installed. Good firm brake just no stopping power.
I just read a note from a Wilwood post saying 8" booster is the smallest booster that should be used. I have a 7" don't have room for bigger one.

Are you using the double diaphragm booster or the single? The double 7" will give will give more total area than a single 8". This comes at the expense of a longer booster while keeping the diameter approximately the same.

Originally Posted by Hotrod46

Are you using the double diaphragm booster or the single? The double 7" will give will give more total area than a single 8". This comes at the expense of a longer booster while keeping the diameter approximately the same.

yes its a double , thanks for that info .

MPB recommends a minimum of 16" of vacuum, so 14 is borderline. A pump might help, but I think your best bet is change the MC or pedal ratio. Both of those will increase pedal travel, as you know.

You could also change pad compound. The pads that came on my Baer setup, which is very similar to Wilwood, don't seem to have the high initial bite that stock factory cars have, but also don't have much fade when hot. There are probably pad compounds that have higher friction coefficient than the pads you have.

Not easy to do, but rigging a pressure gauge on the brake line would give you a good idea what is actually going on. You're going to need 800 PSI minimum with 4 wheel discs. 1000 would be better. Of course, that pressure is entirely dependent on the braking situation. There may and probably will be times when 300 PSI will be enough, but for maximum braking and panic stops, you will need that high pressure available.

And I was going to offer the same opinion on the pads. Over this summer, I replaced my Master Cylinder as I was feeling the same as you. Just no "grippiness" , I was chatting with Wilwood Tech and we went over the list of components, I settled on going to the next smaller ID master. I had a corvette 1" and changed to a 7/8" Wilwood. I've had the car since 2000, and all the brake components are original to then, so I broke it all down, replaced the caliper rubber parts, cleaned and washed all the interior parts. After re-assembly and on a test drive I forced the pads to "bed" and that probably improved the whole package as much as changing the master! The procedure is on their website and I'd suggest you follow it if you've never done it before. It really helped mine.

Mike/34_40 mentioned bedding the pads. I wondered about pad material. Some of the sintered metal pads are so hard they almost seem to lose gripping ability. You might chat with Wildwood about your kit & application.

I'd be curious (as Mike mentioned) to know what the actual brake line pressure is at the calipers. Once you know this pressure it may be easier to decide what to do to improve stopping power.

Originally Posted by Dave Severson

I'd be curious (as Mike mentioned) to know what the actual brake line pressure is at the calipers. Once you know this pressure it may be easier to decide what to do to improve stopping power.

I have a line gauge somewhere, I just have to fine the time . A happy Thanksgiving to ALL !!!

Originally Posted by Navy7797

I have a line gauge somewhere, I just have to fine the time . A happy Thanksgiving to ALL !!!

And a Happy Thanksgiving to you and yours as well!

I am running Wilwood Brakes as well, also with a 7" dual diaphragm booster.
I also have a vacuum problem, so I went with a Hella UP32 vacuum pump (it has a 1200 hour life expectancy)-it is a vane pump used on electric cars, and I also wired in a vacuum switch to regulate the pump-
Everything was new, and I was quite unimpressed at first-here is what I learned:
-first off, I had a hard time getting a firm pedal-using a power bleeder solved that, but it took awhile.
-secondly, I have a Wilwood adjustable proportioning valve-adjusting that really helped, but I still wasnt satisfied-
-it took about 2-300 miles of variable driving to bed in the pads (which seemed like forever), but now it stops really well-
Doing it again I think I would add a 8" booster, but, like you, I'm out of room-
Drive it-a lot, and cycle the brakes-