Bypassing the Brake Compensator?

[KalamazooJohnny]

Has anyone done this, and are there any opinions on if one should or should not do this?

[TulsaSpider]

I did it. Used Mark's bypass hose. No issues. I am sure there are some previous threads on here!

[baltobernie]

I think the Spider needs some sort of external proportioning between the front and rear brake circuits. If you have the same amount of pressure F/R, the rears will lock up first due to weight transfer. The effect would be particularly pronounced in the wet. Even if you are skillful enough to modulate the pedal, the braking distance would be much longer.

When I redid my brakes, I used a Wilwood proportioning valve, installed near the M/C. I calibrated it to my car and tires on wet and dry roads. There's a "W" and a "D" paint mark on the wheel; the default setting is "D". If I have to put the top up, I try and remember to pop the hood and turn the dial to "W".

[manoa matt]

The valve is there for a reason or the engineers would not have put it there. Besides a new valve is cheaper than the by-pass hose.

[boogiedude]

So is smog equipment, but we all get rid of that too..

[kmead]

So is smog equipment, but we all get rid of that too..

The difference here is that locking rear brakes can and will cause the car to skid on wet low friction surfaces. What harm does it do to keep it?

On a front engined car the rear wheels do less than 20% of the braking, if they lock up early and you need to modulate then your stopping distances will be longer.

Removing your likely ineffective 30 year old smog equipment only nukes the gay unborn baby whales so it really has little effect.


I would turn it around and ask: What is the benefit of removing the rear brake pressure compensator? Does someone have documented performance data of the same car with the same tires on the same roadway surface to show the efficacy of making the change?

[124ADDHE]

It will stop a bit better (unless setup perfectly (lots of trials)) in a straight line with the compensator removed, however, if going down a hill or when braking late into a corner, there is a certain risk of losing traction of the rear tires and loss of control - compensator is a great device!

[maytag]

....

[manoa matt]

"some of us LIVE for that!!!! "

And some of you will DIE for that! The Fiat is not a good/safe car to wreck, you head is VERY close to the windshield. Been there several times at 16 years old with my first spider, 6 more inches to the left and there would be a tiny cross next to a telephone pole in Kentucky.

[maytag]

.....

[Kent124]

The valve is there for a reason or the engineers would not have put it there. Besides a new valve is cheaper than the by-pass hose.

+1.

[TronDD]

When I redid my brakes, I used a Wilwood proportioning valve, installed near the M/C. I calibrated it to my car and tires on wet and dry roads. There's a "W" and a "D" paint mark on the wheel; the default setting is "D". If I have to put the top up, I try and remember to pop the hood and turn the dial to "W".

A prop valve that has to be adjusted based on the weather?

Tim.

[So Cal Mark]

if your car has been lowered and you didn't modify the compensator linkage, it's never going to work. It's very common to find those compensators completely seized, not allowing any rear braking. I've yet to hear one complaint about anyone bypassing the compensator and experiencing rear lockup.

[maytag]

....

[kmead]

if your car has been lowered and you didn't modify the compensator linkage, it's never going to work. It's very common to find those compensators completely seized, not allowing any rear braking. I've yet to hear one complaint about anyone bypassing the compensator and experiencing rear lockup.

Says the man in sunny, it rarely rains in southern California...well most years

Mark's point is correct, if you have lowered your car it does need to be readjusted to work in the manner intended.

Completely seized speaks to lack of maintenance which should be performed. I'll stand by my statement: prove removal improves performance. If its better in the driving conditions you use the car in then go for it.

I work with engineers all the time and work at a company where we look very carefully at the cost of our products. I can assure you that if it wasn't really needed, it would not be there. I doubt Fiat was much different then or now.

Personally I don't hold the engineers as the divinity of sacred anything, I also am a very hard driver and have utilized the compensator on tracks, autocrosses and on my daily trek to work on all of my favorite turns. I know what can happen when you get rear lockup be it just lengthening my stopping distances or causing some interesting wagging back and forth.

Nearly all cars have some form of pressure reduction system for the rear brakes, on modern cars the ABS system performs this function.