Free play in power brake systems.

[Kern Dog]

The pushrod in the booster stayed in place. I pulled on it and it remains there. I then just unscrewed the extension nubs to adjust them.
The older boosters I have on the shelf have loosened up enough that the sealing puck and the pushrods come right out. These new ones are securely seated to where I hesitate to pull them out.

 

[Kern Dog]

Every one of the original “seasoned” boosters I have here have pushrods that pull right out.

I'm guessing that the rubber seals inside have shrunken a bit, allowing the pushrods to just slip out. Maybe under vacuum, they tighten up?
Not sure. I don't know enough about this to speak with confidence.
I'm basing my comments on my basic understanding of these old cars.
It seems to me that the newer components fit together tighter and seal better so the pushrod is sort of squeezed into position. Whatever components are inside could be damaged if I tried to pry the pushrod out. It could be like brain surgery to see if a brain is in place...and damaging the brain in the process. Even if this were mine to risk, I would leave it and make adjustments elsewhere.
I was trying to get the car to feel and stop in a manner consistent with other models of the same era. I know that there are some things that we can do to the older cars to improve upon and I strongly support that...Better tires, better Steering components, (Borgeson, for one) Overdrive transmissions, aftermarket A/C systems all can make our old cars feel and perform better than they did in 1968. Some things can be hard to improve upon without reinventing the wheel.

 

[68 Sport Satellite]

For a long time I've been wondering why I can't make my braking system stop AND feel as good as the brakes in my 2019 honda. I know it's a sum of the parts, but it doesn't seem like it should be that difficult - but it is.

 

[Kern Dog]

Just look at the differences in design. The factory power steering versus the Borgeson is one example. Similar concept but different parts and machining to fit in a similar application but a more precise feel.

 

[MWbirdLOVER70]

Every one of the original “seasoned” boosters I have here have pushrods that pull right out. View attachment 1557721View attachment 1557720

View attachment 1557725


I'm guessing that the rubber seals inside have shrunken a bit, allowing the pushrods to just slip out. Maybe under vacuum, they tighten up?
Not sure. I don't know enough about this to speak with confidence.
I'm basing my comments on my basic understanding of these old cars.
It seems to me that the newer components fit together tighter and seal better so the pushrod is sort of squeezed into position. Whatever components are inside could be damaged if I tried to pry the pushrod out. It could be like brain surgery to see if a brain is in place...and damaging the brain in the process. Even if this were mine to risk, I would leave it and make adjustments elsewhere.
I was trying to get the car to feel and stop in a manner consistent with other models of the same era. I know that there are some things that we can do to the older cars to improve upon and I strongly support that...Better tires, better Steering components, (Borgeson, for one) Overdrive transmissions, aftermarket A/C systems all can make our old cars feel and perform better than they did in 1968. Some things can be hard to improve upon without reinventing the wheel.

Bravo brother

 

[Kern Dog]

The MC was unbolted again and the pushrod extension was adjusted IN to rest at approximately where the original one was sitting. Hard to know for sure. I looked but couldn’t find that fancy gauge the owner bought for this very thing.
Now the pedal does have some free play again but it seems like there is less of it. The initial movement of the pedal isn’t a free swing, it has resistance so it isn’t like we all have experienced with the overboosted loose power steering these cars seemed to have.
Less travel but enough to allow the booster to function. It feels great to me. Maybe newer cars have some resistance built into the system that eliminates the dead zone? All cars seem to have some amount of pedal movement before the brakes react.
Without discussing this with a new car engineer, I’ll never know.
I agree that if we can get these old cars to perform like new ones (in terms of braking and handling) that is great. Sometimes you are limited by the constraints of the old design.

 

[66 Sat]

For a long time I've been wondering why I can't make my braking system stop AND feel as good as the brakes in my 2019 honda. I know it's a sum of the parts, but it doesn't seem like it should be that difficult - but it is.

Probably because Honda have a team of brake experts, trained engineers, thousands of hours of testing, the best technology for analysing the performance, specific design tolerances etc whereas we are mostly backyard mechanics who work different jobs in the day and play around with stuff in the evenings or weekends, using over-the-counter parts, cobbled together to make something work ok.
I often wonder if I dropped my car off to a team of Formula 1 engineers or a company like McLaren and left it with them for 6 months what improvements they could make but still using the original design intent. Imagine the same basic car but all the suspension components made of aluminium, carbon fibre body panels, titanium exhaust etc. Like what Singer do with the classic Porsche 911.

 

[Kern Dog]

When I see these custom Restomod builds of these cars, I wonder if they perform as well as they look. I’ve seen 4 wheel disc cars with an aluminum polished master cylinder with an UNboosted system and wonder if the car is ever driven hard enough to find the limits of the brakes.
The coil over front ends surely take a back seat to the longevity and durability of an upgraded torsion bar arrangement.
I’ve considered EFI but dismissed it based on many things including value. I don’t see the benefit when compared to a well sorted carbureted car unless it is driven in varying altitudes and weather conditions. The fact that most aftermarket EFI systems have had widely known failures sure isn’t swaying me toward them.

 

[Ron H]

Maybe not your hassle, and something you’ve already checked; but with my conversion, had to do quite a bit of adjusting the pedal rod – rod to the booster. My case was converting manual to power involving a variance with pedal ratio. Sure you know a bit of free play is necessary to ensure that the pedal ‘home’ position isn’t binding against the brake light switch and on the other end, pre-loading the booster. In my case, initially the pedal was so high I could reach it better with my hand than my foot. Longer story. Ended up machining a new (better grade than in the kit) link on the pedal rod. From there it involved finding the sweet-spot for pedal travel and setting the height where I wanted it.

 

[66 Sat]

Remember too that the actual pad pressing on the disc, or shoe on the drum is only one part of the brake feel.

The "feel" is going to influenced by the tires you have (probably a lot more sidewall than your Honda), the suspension (probably a lot softer than your Honda), the weight transfer, the squishier seats in your classic and so on. It's not a fair comparison in most cases.