Servo vs booster

ward00

ward00

True Classic
I am trying to understand what it is that the "servo" does. I thought that it was the vacuum booster that provides braking assistance. If so, how is it that the servo provides braking assistance? I presume the reason that it can be deleted is that any assistance it provide is minimal compared to the vacuum booster. Is that correct?

Correction? So after looking at a diagram of the brake system, it appears what I call the vacuum brake booster is called the servo and has nothing to do with vacuum; is that correct. The diagram also shows the master cylinder, but it appears it is not actuated by the vacuum booster like in a Fiat. If so, what is the thing that hangs off the servo in my photo)?

The further I go down this rabbit hole, the more clear it is that I am clueless. I am trying to correlate the Fiat brake system to the Lancia and it is only confusing me. Does one actually remove the brake servo (the vacuum booster looking thing) on the early Montecarlos? If I were to do this on my Fiat, I am sure I would not be happy with the braking force needed.
 

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Brake servo and brake booster are the same thing. Italians refer to it as servo.

The brake plumbing in your Scorpion is different from the X1/9, and in particular, the X1/9 does not have a brake booster.

The first generation Scorpion / Montecarlo had a remote brake booster for the front brakes only; the rears were not boosted. The car had a reputation for locking up the fronts prematurely, particularly in the wet. The second generation Scorpion did not have a brake booster, and many owners have chosen to remove the booster from their first generation cars as well.

The diagram in your post shows the hydraulic lines only. What is not shown is the vacuum hose going to the brake booster; visible in your photo:

20211115_094028.jpg
 
ward00 said:
The further I go down this rabbit hole, the more clear it is that I am clueless. I am trying to correlate the Fiat brake system to the Lancia and it is only confusing me. Does one actually remove the brake servo (the vacuum booster looking thing) on the early Montecarlos? If I were to do this on my Fiat, I am sure I would not be happy with the braking force needed.
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In a "normal" car, the brake booster is sandwiched between the pedal assembly and the master cylinder, and it boosts the front and rear brakes equally. In this case, it is hard to see a good reason to remove the booster.
 
S1 Montecarlo had front brakes boosted which presented lockup issues. To rectify the issue S2 removed the booster and opted for larger rotors (which is why they increased wheel diameter) and dual circuit master cylinder and plumbing.

Adding the dual circuit system to your S1 would be labor intensive and replacing master cylinder is PITA project.

What S1 owners do is bypass and remove the booster and improve front brakes with at least performance pads or preferably installing larger rotors. You already have larger wheels capable of using larger rotors.

A great option available in US that will have manufacture support easier than finding Lancia bits is using the Wilwood calipers in conjunction with rotors and braided hoses available here:

Whoa!Brakes

If you go this route also consider their wheel stud conversion to install all together. And check your car for wheel spacers. If it still has the factory cast iron spacers they have aluminum replacements in different thicknesses.
 
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NigelProdrive said:
S1 Montecarlo had front brakes boosted which presented lockup issues. To rectify the issue S2 removed the booster and opted for larger rotors (which is why they increased wheel diameter) and dual circuit master cylinder and plumbing.

Adding the dual circuit system to your S1 would be labor intensive and replacing master cylinder is PITA project.

What S1 owners do is bypass and remove the booster and improve front brakes with at least performance pads or preferably installing larger rotors. You already have larger wheels capable of using larger rotors.

A great option available in US that will have manufacture support easier than finding Lancia bits is using the Wilwood calipers in conjunction with rotors and braided hoses available here:

Whoa!Brakes

If you go this route also consider their wheel stud conversion to install all together. And check your car for wheel spacers. If it still has the factory cast iron spacers they have aluminum replacements in different thicknesses.
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Yes, will definitely be going with the caliper rotor upgrade. After I do an informal poll on in a separate post I'll decide how much other stuff I will do.
 
One automotive journalist from back in the day wrote that by the time the brake pressure went from pedal all the way back to booster in engine compartment behind passenger and then back to the front brakes you were already past what you were braking for.

I doubt there is brake lag but still see his point as valid.
 
kmead said:
As brake fluid is nearly incompressible I find the delay concept as rather specious.
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If this is the case, which I believe to be so, rather than delete the servo from the front brake circuit, why not modify the servo plumbing to include the rear brakes? Anyone tried that?
 
I'm sure there are some Italian automotive eggheads that actually know what the Lancia folks were thinking with the brake setup on the Montecarlo/Scorpions. I can only assume that someone in sales/marketing said that the brake pressure needed from the driver was too high for the "class" of the Montecarlo - it was quite a bit more $$$ than the somewhat similar X1/9, but interestingly only around 150 to 250 lbs heavier. That's like driving with your large uncle in the car!

@ward00 - I assume you're building this car for your enjoyment, so it certainly feels like removing the booster as other Monte owners have done will be a great solution (also, put on great rotors and pads and keep everything nice and fresh).

From a vacuum boost perspective, I think boosting the entire system makes a lot of sense. In effect you're just adding some assistant to the "push" of the brake pedal, much like hydraulic power steering systems help in pushing the same way you're already pushing. Adds complexity, weight etc. If you do modify your system to boost everything then you probably need to recalibrate everything to include the extra boost the rear will get, or at least I think that makes sense. I'd try no boost first and spend your initial money on really excellent brake bits.
 
Disks and calipers have been ordered. I'm just trying to learn more about lancias (I have a 124 spider and coupe).

So how about this idea. Why not just disconnect vacuum to the servo instead of doing the bypass/delete?
 
Just a thought. Why not initially upgrade the rears only to the S2 larger 251mm discs and larger 38mm piston calipers and very high friction pads. Delivering more braking on the rear, and keep the boosted fronts and see how it goes. I did that rear upgrade on my track X1/9, still with the unboosted 227mm front discs and standard caliper.
 
ward00 said:
If this is the case, which I believe to be so, rather than delete the servo from the front brake circuit, why not modify the servo plumbing to include the rear brakes? Anyone tried that?
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You would need a second servo based on the design. One could consider the Alfa remote servo which could serve both front and rear. I suspect you would still need to adjust bias to keep a more reasonable front lockup strategy.

Personally I would go down Darin’s approach which is to optimize a system without any booster. My right foot can deal with the pressure needed and given the X and Scorpacarlo are nearly the same weight pressure needed would be similar.
 
The Lancia 037 Road version had two remote servos. I only know that from looking at the literature online. Some one in England tried two remote electric servos. I don’t think they were successful.

my old Scorpion had 4 big discs all the same size (284mm Euro Fiat) and wilwood brakes made by TCE brakes. Car also had the old Monte hospital modified pedal assembly like John O. Plus a 2lb residual valve. Car stopped great, but never drove it in the rain. The only problem which I hated was I had to run 15” wheels and the car felt like a truck with those 15*7 wheels.
 
lanciahf said:
The Lancia 037 Road version had two remote servos. I only know that from looking at the literature online. Some one in England tried two remote electric servos. I don’t think they were successful.

my old Scorpion had 4 big discs all the same size (284mm Euro Fiat) and wilwood brakes made by TCE brakes. Car also had the old Monte hospital modified pedal assembly like John O. Plus a 2lb residual valve. Car stopped great, but never drove it in the rain. The only problem which I hated was I had to run 15” wheels and the car felt like a truck with those 15*7 wheels.
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Just another newbie question, after Lancia did their fixes, did they physically remove the servo from their cars?
 
So another question. I am reading the Lancia book "Italian Inspiration" and am seeing a reference to "Out went the brake servo, to be replaced by pressure sensing brake limiter that progressively fed more braking effort to the rear brakes as brake pressure increased" To me this sounds like the critical piece needed to eliminate brake lock up. What exactly is this part and where does one get one?
 
Poorly written prose there.

Basically they added a valve which limits the pressure to the front wheels to move the brake bias rearward.

One can acquire adjustable valves proportioning valves from Wilwood. Getting the right balance requires testing and then ensuring the valve can’t drift to another setting.

Wilwood Disc Brakes - Porportioning Valves & Pressure Valves

Wilwood makes a wide assortment of small, lightweight master cylinders that are suitable for high performance street and racing applications and they are available in a variety of bore sizes. This page displays Porportioning Valves & Pressure Valves
www.wilwood.com www.wilwood.com

Montehospital doesn’t list the OE part this person appears to be referencing. Looking at the parts list for the later cars would tell you what the part looks like and its part number so maybe you could track down the OE parts.

VW used to use small add on fixed proportioning valves on the master cylinder itself on the A1 bodied Golf and its derivatives, I don’t know the percentage they used but they were a nice bit tech in a small package.
 
kmead said:
Poorly written prose there.

Basically they added a valve which limits the pressure to the front wheels to move the brake bias rearward.

One can acquire adjustable valves proportioning valves from Wilwood. Getting the right balance requires testing and then ensuring the valve can’t drift to another setting.

Wilwood Disc Brakes - Porportioning Valves & Pressure Valves

Wilwood makes a wide assortment of small, lightweight master cylinders that are suitable for high performance street and racing applications and they are available in a variety of bore sizes. This page displays Porportioning Valves & Pressure Valves
www.wilwood.com www.wilwood.com

Montehospital doesn’t list the OE part this person appears to be referencing. Looking at the parts list for the later cars would tell you what the part looks like and its part number so maybe you could track down the OE parts.

VW used to use small add on fixed proportioning valves on the master cylinder itself on the A1 bodied Golf and its derivatives, I don’t know the percentage they used but they were a nice bit tech in a small package.
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To me it looks like a valve that is designed for the Scorpion and that does not need user adjustment/experimentation . Is there an online parts list resource for different year Lancia's?
 
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