128 delete of power brakes
- Thread starter carl
- Start date
brakes
if you want to remove the booster, I suggest a bias valve and rear disc brakes. remember that this a front engine car, and the bias is most likely to the rear, unlike a car with the motor in the back.
better yet, disconnect the vacuum to the booster and block the source at the manifold and see how the brakes respond. probably a little twitchy at best and do a panic stop to determine where the major pressure is going.
mikemo
if you want to remove the booster, I suggest a bias valve and rear disc brakes. remember that this a front engine car, and the bias is most likely to the rear, unlike a car with the motor in the back.
better yet, disconnect the vacuum to the booster and block the source at the manifold and see how the brakes respond. probably a little twitchy at best and do a panic stop to determine where the major pressure is going.
mikemo
128kid
Courtney Waters
I haven't converted one myself (always liked the boosted brakes better) but I think if you remove the booster and bracket the master cylinder will bolt up to the firewall/pedal box. Then you'd need a pushrod from a non-boosted car (or modify yours?). I'll take a look at my '73 when I'm at my shop next.
Removing the booster won't affect the bias since nothing is changing in the hydraulics (just more pedal input force is required). I didn't need a brake bias valve when running the rear disc conversion either, until I deleted the rear brake compensator.
Removing the booster won't affect the bias since nothing is changing in the hydraulics (just more pedal input force is required). I didn't need a brake bias valve when running the rear disc conversion either, until I deleted the rear brake compensator.
dragonsgate
True Classic
I would advise that you keep the power brakes. I took the booster of my 128 to see what it was like and had it back on with in 24 hours. I didn't like it at all.
carl
True Classic
Brakes
I was just thinking ahead. The car is not yet on the street. As soon as I sell one of my spiders (soon I hope) I'll be able to get tags and insurance for the wagon.
My previous 128 2-door was built for trackdays and street use. It had WHOA brakes on the front and front spider calipers on the back. I had to add a brake bias valve as the rears would lock up pretty easy. This was a non-boosted system. With the wagon I'm just running stock brakes but I did remove the bias valve as it was shot. I can't remember the last time I had a car with rear drum brakes!
carl
I was just thinking ahead. The car is not yet on the street. As soon as I sell one of my spiders (soon I hope) I'll be able to get tags and insurance for the wagon.
My previous 128 2-door was built for trackdays and street use. It had WHOA brakes on the front and front spider calipers on the back. I had to add a brake bias valve as the rears would lock up pretty easy. This was a non-boosted system. With the wagon I'm just running stock brakes but I did remove the bias valve as it was shot. I can't remember the last time I had a car with rear drum brakes!
carl
128kid
Courtney Waters
Carl,
What issues are you having with the brakes? One of my old '73s with no booster didn't feel great, probably due to rear drum brake adjustment. If the hydraulics are in good shape, the pedal should be firm regardless of booster performance. The pushrod coming out of the booster is adjustable but unless it's been messed with it's probably fine. I'm sure I can dig up a spare booster (probably in the SL stuff you sold me!) if you find yours is dead.
What issues are you having with the brakes? One of my old '73s with no booster didn't feel great, probably due to rear drum brake adjustment. If the hydraulics are in good shape, the pedal should be firm regardless of booster performance. The pushrod coming out of the booster is adjustable but unless it's been messed with it's probably fine. I'm sure I can dig up a spare booster (probably in the SL stuff you sold me!) if you find yours is dead.
carl
True Classic
brakes
Other that forward and back in the driveway, I have not really driven the car but the brake pedal feels less than inspiring. Seems like way too much pedal travel with the motor on. The booster, MC and front calipers are the same as a 124 but the pedal action does not feel anything like my spiders. The rear brakes are totally rebuilt but I really have not driven the car so nothing is bedded in yet. I'll have a better handle on all this once I start driving the car.
I was just wondering if the conversion to non power brakes was easy but you guys seem to think the power setup is the better way to go so I'll keep with it for now.
carl
Other that forward and back in the driveway, I have not really driven the car but the brake pedal feels less than inspiring. Seems like way too much pedal travel with the motor on. The booster, MC and front calipers are the same as a 124 but the pedal action does not feel anything like my spiders. The rear brakes are totally rebuilt but I really have not driven the car so nothing is bedded in yet. I'll have a better handle on all this once I start driving the car.
I was just wondering if the conversion to non power brakes was easy but you guys seem to think the power setup is the better way to go so I'll keep with it for now.
carl
mid79
Youth Revisited
Rear (drum) brake adjustment?
Hi Carl,
The typical rear drum brakes need a lot of adjustment to get the shoes out where the drum surface is.
While I don't have a lot of experience with Fiat drums of this vintage, most of the cars I owned from that era had rear drums. They all required extensive adjustment before they worked well.
If I recall correctly, the typical rear drum brakes were finely adjusted by going in reverse down the street and tapping the brakes several times. That would cause the adjustment mechanism to move the shoes to the proper position. Have you been able to do this adjustment maneuver in the driveway?
Hi Carl,
The typical rear drum brakes need a lot of adjustment to get the shoes out where the drum surface is.
While I don't have a lot of experience with Fiat drums of this vintage, most of the cars I owned from that era had rear drums. They all required extensive adjustment before they worked well.
If I recall correctly, the typical rear drum brakes were finely adjusted by going in reverse down the street and tapping the brakes several times. That would cause the adjustment mechanism to move the shoes to the proper position. Have you been able to do this adjustment maneuver in the driveway?
turbofiat124
True Classic
I tried that once on a Brava and the car was hard as hell to stop. It was so bad I was afraid to take it out of my garage as soon as I put my foot on the brake.
For whatever reason if the brake booster is in place but there is no vacuum present, it seems to magnify the breaking effort 10 fold.
It doesn't look like it would be too hard to fabricate a spacer using a piece of pipe and two flanges. One that bolts to the firewall and one that bolts to the master cylinder and a piece of pipe between the two. And make everything the same thickness as the brake booster. Then you would need a longer rod.
Just assuming...
turbofiat124
True Classic
Every Fiat I've owned including my Yugo, the brake pedal goes almost to the floor (like about 1" of hitting the floor). I've always just dealt with it.
The only two cars I've ever owned that was not like that was my X 1/9 and my Brava. Those car only had about 1" of pedal travel.
I could possibly get rid of some of this travel by adjusting the acorn nut on the end of the rod but every time I think about doing this I remember your story about your brakes locking up on the interstate after you messed with that adjustment nut.
Did you ever figure out what happened?
Looks to me like if you left enough clearance (like 1/8") between the acorn nut and the end of the master cylinder, it should have made up for any heat expansion that might have occured.
carl
True Classic
brakes
I messed with the acorn adjustment nut on two spiders and both times the brakes locked up so I don't do that anymore.
On the 128 I found the emergency brake cable adjustment is critical. It's amazing what a difference it makes on pedal travel. It was way off to begin with with 10 clicks or more. Reduced it to the factory 6 clicks and pedal travel was greatly reduced. Tried 4 clicks yesterday but I'm afraid of self energizing the rear brakes as I can hear the driver side rear just barely ticking when I spin the wheel.
By the way, proper adjustment of the emergency brake cable has the same effect on other Fiats with rear discs. If for some reason you want to remove or disconnect the emergency brake cable then you should put front calipers on the rear or you will end up with too much pedal travel.
I messed with the acorn adjustment nut on two spiders and both times the brakes locked up so I don't do that anymore.
On the 128 I found the emergency brake cable adjustment is critical. It's amazing what a difference it makes on pedal travel. It was way off to begin with with 10 clicks or more. Reduced it to the factory 6 clicks and pedal travel was greatly reduced. Tried 4 clicks yesterday but I'm afraid of self energizing the rear brakes as I can hear the driver side rear just barely ticking when I spin the wheel.
By the way, proper adjustment of the emergency brake cable has the same effect on other Fiats with rear discs. If for some reason you want to remove or disconnect the emergency brake cable then you should put front calipers on the rear or you will end up with too much pedal travel.
128kid
Courtney Waters
Pushrod adjustment
FYI, I was just flipping through my Haynes manual and in the supplement it says that the pushrod stickout dimension was changed twice. That's news to me!
They show the dimension of the face of booster (master cylinder mounting face) to tip of pushrod (pushrod protruding) as:
to-1973: 1.26 to 1.85 mm (.049 to .073 in) **this is probably euro Rally only, US sedans were not boosted;
1974: 1.05 to 1.25 mm (.041 to .049 in);
1975-77: 0.825 to 1.025 mm (.0325 to .0404 in).
FYI, I was just flipping through my Haynes manual and in the supplement it says that the pushrod stickout dimension was changed twice. That's news to me!
They show the dimension of the face of booster (master cylinder mounting face) to tip of pushrod (pushrod protruding) as:
to-1973: 1.26 to 1.85 mm (.049 to .073 in) **this is probably euro Rally only, US sedans were not boosted;
1974: 1.05 to 1.25 mm (.041 to .049 in);
1975-77: 0.825 to 1.025 mm (.0325 to .0404 in).
carl
True Classic
adjustments
I'm gun shy of adjusting that nut. Did it twice on 124 spiders and twice I had the car grind to a stop when the brakes self energized....one of them a few weeks after adjustment.
In my situation it appears that e-brake adjustment has a tremendous effect on brake pedal free play and I have it where I want it now.
carl
I'm gun shy of adjusting that nut. Did it twice on 124 spiders and twice I had the car grind to a stop when the brakes self energized....one of them a few weeks after adjustment.
In my situation it appears that e-brake adjustment has a tremendous effect on brake pedal free play and I have it where I want it now.
carl