wcsinx

Just curious

I've heard other people say they can't no matter how much work they do on them. Seems to me that I should be able to though. I just got through making my custom booster pushrod extension, reinstalling the booster, bench bleeding the MC, reinstalling the MC, and bleeding all 4 corners (yes in the right order).

And now my pedal is hard as hell. I don't get that lovely 5" of travel before getting any resistance anymore thanks to my pushrod extension. But I never have and still can't lock the wheels up no matter how hard I push. I know my booster is good. It's not that. I can get the wheels to just squeal/howl slighty, but they won't lock up. Is this normal?

norvalwilhelm

I have hydraboost and if is easy to lock all 4 corners, even at 80 mph you can make all 4 wheels squeal without pushing too hard. Did it my accident a few weeks ago.
The vacuum booster can not begin to compare with the power of a hydraboost.

Steve Straus

Norval, I didn't know you had an accident! Were you hurt? How is the car?

I did a search and didn't find anything, so link me to the post , if there is one, so you don't have to go over it all again.

zwede

I think Norval just did a typo. He meant to say he locked the brakes BY accident.

zwede

I don't have any problem locking up the brakes. My system is stock with the following changes:

Braided hoses.
Raybestos brute stop pads
High-perf synthetic fluid (DOT3/4).
Springs removed from rear calipers.

Using a new (not rebuilt) booster and MC. I had all sorts of problems with rebuilt boosters. I could NOT lock the wheels with any of the 3 rebuilds I tried. On 2 of them the pedal would slowly go to the floor (dunno how a bad booster can cause that, but it did). The 3rd one had no assist at all. Paid the $200 for a new booster from GM and problem gone.

wcsinx

Yeah, I read on the Hydraboost website where they describe the stock boost system as being "inadequate" to take advantage of the C3s big azzed rotors and calipers. I can certainly attest to that! I'm just wondering ...

1. Am I performing as well as be expected with a stock setup?

2. Has anyone made any modifications to extract more braking power out of the vacuum brake system?

wcsinx

You're the second person today I've heard say that. I'm befuddled. How can a bad booster cause you to lose pressure at the calipers? Shouldn't you be able to brake as well without vacuum assist by just putting more pressure on the pedal? The booster doesn't affect the operation of the MC?!?!

norvalwilhelm

Sorry Steve I didn't have an accident. I did it BY accident. My original post was miss typed. I was running about 80 mph and I thought an animal/dog was comming out of the ditch and I paniced and hit the brakes too hard and the car just locked up all 4.
NO ACCIDENT. SORRY

gkull

Your tire diameter and how sticky your tires are has a big effect. Pad type has some effect as to the temp range where they work the best.

Hydra boost is the real way to go.

From day one with my 79 I have been able to lock tires. Now in the sub 70 mph range a Norval stomp panic stop will send out big clouds of smoke off my rear tires and big long black marks 315 in width. with smaller diameter fronts they lock.

I use synthetic dot 4, all new HD stainless steel O-ringed calipers, with PF pads from autoZone.

Buffalo Dude

I can now

In theory, yes, loss of vacuum should still allow you to push on the pedal to stop the car, but you'd probably be standing on it. But, mine was acting funny. It seems like whatever mechanical linkage backup is in the booster wasn't working, it's like the booster wasn't pushing on the piston in the mc hard enough. I don't know how to explain it, maybe some else can?

zwede

Re: Booster: I'm as baffled as you as to why the bad booster would let the pedal go to the floor. I thought the booster had a mechanical connection between in and out. But alas, sitting at a light with my foot on the pedal I could feel it slowly sink until it hit the floor. Even weirder was that the brakes felt normal during light braking. It definetely had assist until the halfway point.

wcsinx

And I'm assuming you replaced the booster independently of the MC? When I had my booster out, I could grab the MC rod and the pedal rod and push one against the other. It felt like they were touching end to end i.e. a solid link all the way through the booster with the MC rod being attached to the bladder. I just can't understand how a booster could fail like that. Does anyone have a tear down diagram of these boosters?

mayberg

All this time I thought it was a big-block thing. I drove a 79 and could lock the fronts on demand. But the '74/454 (that used to be pictured below - I'll get that working one day) slows just fine, but I don't seem to ever lock them up.

I rebuilt the brake system during the winter of 2002/2003 - sleeved calipers, springs removed, DOT 3/4 fluid, new organic pads, new front rotors. The brakes are great, but I'm not locking up.

zwede

Yep. Same MC the whole time. I replaced the MC first with a new unit from NAPA. The MC has been fine and I'm still using it today.

wcsinx

SB, BB - same brakes I believe, but now you're the second guy with a '79 who claims he could lock them up on demand. I know the MC and booster design was changed in '77. Was the newer design that much better I wonder?

That's exactly how I feel with my '76. Don't get me wrong, it comes to neck snapping halt, but the wheels will not lock. It feels like I'm braking right at the limit of my tires traction because I just barely hear them start to howl. Maybe this is kind of a good thing because it'll always take longer to stop via sliding. *shrugs*

I am not alone

mandm1200

I know it's hard to lock mine up; however, a couple of months ago some ahole was in the left lane to make a left turn and decided to go straight and cut into the right lane. I naturally hit the brakes and the screeching began. The next day I notice 30' of rubber marks. That my have been the only time I locked them up.

Mike

tom.keyes

My stock 1968 can do it. I had to do just that last week. Now I will also say I used both feet on break to do it!

FeedVaal

Stock '77. Locks up all four on demand.

tshort

I can lock mine up with no problem. Everything is stock except braided lines.

ram82fire

ZTI o ring pistons , hydroboost , braided lines , hawk pads = brakes as they should be on a vette ! And yes as Norval said lockup is no problem ,,,,,,,,,,,,


G