Front brakes lock up poll

[ward00]

Have you performed a brake servo bypass/delete?

Have your front brakes ever locked up? If yes, was it with or without the brake servo bypass delete?

Answers to these question will help me determine how critical it is to do the delete and/or master cylinder upgrade.

I have read that most brake lockups occur when driving in the rain, which I don't plan on doing. On the other hand, your answers to my questions may sway me to do the delete.

 

[Ron Avery]

The PO I purchased my 1976 Montecarlo from, deleted the booster. And upgraded the the discs to Prima front brakes, with braided brake lines. I have not had any lockup problems.

 

[NigelProdrive]

I looped a Scorpion with the booster installed. Very low speed and didn’t hit anything but was like WTF? May have been getting on power but the brake pressure from the booster hadn't released front brakes timely. Or open rear differential. 30 years ago and was leaving a pub. Removing 10 feet of brake line back to booster and 10 feet back to front brake T connection is more direct brakes and less things to fail.

Two local owners to me, Brian OLooney and John Ovington doinked their Scorpions from lockups. Others who wreaked theirs probably aren't checking this forum because they no longer have a Scorpicarlo.

 

[Pete Whitstone]

Have you performed a brake servo bypass/delete?

Have your front brakes ever locked up? If yes, was it with or without the brake servo bypass delete?

Answers to these question will help me determine how critical it is to do the delete and/or master cylinder upgrade.

I have read that most brake lockups occur when driving in the rain, which I don't plan on doing. On the other hand, your answers to my questions may sway me to do the delete.

I did on my car because it was locking the front brakes with the engine running and no foot on the gas. Very strange, could roll the car around with the engine off, but it locked the front brakes as soon as the engine turned on. Anyhow, got rid of all that mess, and then it was basically the same system with the same feel as an X1/9. No real problem with X1/9 brake systems, and I didn't experience any problems with the booster delete. Not sure if I ever locked the front brakes after that, but the car was modified in other ways that would affect that - bigger wheels for instance.

I would not hesitate to do another booster delete on a Scorpion.

 

[BEEK]

The 2 scorpions I drove daily for a few years many years ago never suffered from front brake lock ups.

 

[johnph]

I did on my car because it was locking the front brakes with the engine running and no foot on the gas. Very strange, could roll the car around with the engine off, but it locked the front brakes as soon as the engine turned on. Anyhow, got rid of all that mess, and then it was basically the same system with the same feel as an X1/9. No real problem with X1/9 brake systems, and I didn't experience any problems with the booster delete. Not sure if I ever locked the front brakes after that, but the car was modified in other ways that would affect that - bigger wheels for instance.

I would not hesitate to do another booster delete on a Scorpion.

WOW! We are talking about two completely separate problems here!
1) Car rolls fine with engine off, but front brakes lock up when engine is started. <this is a malfunction of the OE system>

2) With stock wheels and tires, perfectly maintained, under heavy straight line braking on a clean paved surface, the front tires start to slide (lockup) first. Compare this to -all four tires slide simultaneously(rare on production street cars) or rear tires lock up first(like an unladen pickup truck in the 60s-70s before anti lock brakes). The X 1/20, as delivered with no modifications may have a tendency to slide the fronts first. This is a designed in <to some drivers annoying> 'flaw'. Discussion above shows how to modify the car.

If your car has symptom #1, you need to fix what is malfunctioning.
If you do not drive your car on the track or near the cornering or braking limit on the road, there may be no need to modify your car from stock.

 

[NigelProdrive]

Symptom 1 is malfunctioning booster creating brake pressure without brakes being applied.

If there wasn’t an issue driving the series 1 in stock form then they wouldn’t have gone through such great lengths (dual circuit, larger rotors, larger wheels for the rotors, ...) for the series 2. It was the reason production ceased between the 2 models.

The front is too lightweight for the boosted brakes. Just like stomping on the throttle on a pickup truck in wet with no weight in back, there is no grip.

And the system 1 malfunction can be present is lesser degree allowing vehicle to drive with brakes dragging and releasing as booster fails causing dangerous situations no matter what type of driving.

The solution for all is: ditch 20 feet of brake lines and problematic booster and upgrade front brakes to compensate.

The poll was voted on by the Lancia engineers who redesigned the system to what they gave you in a series 2.

 

[ward00]

So perhaps the question I should have asked is have your brakes ever locked up with a car that has had the servo deleted? In other words, is that enough on its own?

 

[NigelProdrive]

Posted by Bernice on another thread.

"As for the brakes on the series one Scorpiacarlo, that front vacuum brake booster was a really bad idea. The amount of power boost to the front brakes is dependent on engine vacuum, how much the brakes are used, how many pedal cycles the brakes are actuated and a long list of related factors. This is one of the prime reasons why bypassing that front brake booster is a good thing to do. This is what was done on the series two MonteCarlo and they increased the front rotor diameter to ~250mm made possible by applying 14" wheels. Regardless, know the system remains front brake lock up prone and intended as designed. Difference being, once the front vacuum brake booster is bypassed-deleted the point of front brake lock up is more predictable similar to an exxe or similar vintage cars without ABS."

 

[ward00]

So perhaps the question I should have asked is have your brakes ever locked up with a car that has had the servo deleted? In other words, is that enough on its own?

Well, I think this answers my question. Seems like the "delete" is an unreliable placebo that should not be relied upon.

Front brake booster deletion...

In dealing with the huge disaster that is my pedal assembly (frozen nuts=twisted lines etc.), I think now is the time to delete the front brake booster. Am I correct in that I can simply run a new line from the front circuit pedal assembly bulkhead union directly to the front tee? This would...

xwebforums.com

 

[NigelProdrive]

Well, I think this answers my question. Seems like the "delete" is an unreliable placebo that should not be relied upon.

Front brake booster deletion...

In dealing with the huge disaster that is my pedal assembly (frozen nuts=twisted lines etc.), I think now is the time to delete the front brake booster. Am I correct in that I can simply run a new line from the front circuit pedal assembly bulkhead union directly to the front tee? This would...

xwebforums.com

That is John Ovington. For best results you have to do it all. Like he said, may have been prevented with weight up front. I transferred weight from rear to front with the fuel cell and fuel systems up front. Going to carry a spare and don’t have the rear tray for it, see what fits up front.

He was on 13s and likely considering current availability very outdated ones. You already have a larger contact patch and are hundreds pounds lighter without Scorpion bumpers, emissions or AC. Use soft compound grippy tires.

 

[ward00]

That is John Ovington. For best results you have to do it all. Like he said, may have been prevented with weight up front. I transferred weight from rear to front with the fuel cell and fuel systems up front. Going to carry a spare and don’t have the rear tray for it, see what fits up front.

He was on 13s and likely considering current availability very outdated ones. You already have a larger contact patch and are hundreds pounds lighter without Scorpion bumpers, emissions or AC. Use soft compound grippy tires.
View attachment 55057

From what I understand, my naturally reduced weight does not help the issue. Along with the delete, bigger tires and improved brakes, can it be assumed the more weight added to the frunk the better (200pds?)

 

[NigelProdrive]

Your naturally reduced weight helps avoid the issue. Being lighter is less weight to stop. Look at gokart brakes and they still stop being lightweight. Not having AC, emissions or US bumpers likely hardly changed the front to rear weight ratio because there is weight being removed from both ends. Would avoid adding weight anywhere just to add weight. Lighter is better. Transferring weight up front helps two fold lighten butt and increasing front but only options are fuel cell or spare tire. Not carrying a spare at all is better than having it in engine compartment. Depending the offset of your rims and if the wheel spacers are still installed, there may be space to widen the track (aluminum spacers lighten sprung weight compared to cast iron spacers it came with) which helps with stability.

 

[ward00]

Your naturally reduced weight helps avoid the issue. Being lighter is less weight to stop. Look at gokart brakes and they still stop being lightweight. Not having AC, emissions or US bumpers likely hardly changed the front to rear weight ratio because there is weight being removed from both ends. Would avoid adding weight anywhere just to add weight. Lighter is better. Transferring weight up front helps two fold lighten butt and increasing front but only options are fuel cell or spare tire. Not carrying a spare at all is better than having it in engine compartment. Depending the offset of your rims and if the wheel spacers are still installed, there may be space to widen the track (aluminum spacers lighten sprung weight compared to cast iron spacers it came with) which helps with stability.

I think we know what we need to do now. Thanks for all the info.

 

[johnph]

More ideas on moving weight around. Remember that early (1971 for instance) Porsche 911 had a lead weight in the center of the front bumper and others had 2 six volt batteries in compartments low under and behind the headlights.