rear bias adjustment

[jimnielsen]

I have adjusted the rear brake bias the way it says to in the manual with the 5Kg weight suspended from the small hole at the end of the lever arm. As you can see from the 'clean' pieces of metal this has resulted in an adjustment that looks to me to be at the end of the travel of the system anyway.

Does moving the arm in the direction that I have moved it provide more braking force for the rears (all else being equal) or less????

jimn~

[WhizzMan]

if I'm not mistaken, the harder the car pushes down on the rear wheels, the harder it pulls on the spring. Since you've tightened the spring, it should have put much more power on the rear now.

[wrinx]

If it's at the end of travel you could change the spring as it is weak.

But yes, tight spring means more braking....fitting an uprated (stronger) spring will improve braking again.

Someone from 155.org used their trolley jack spring :lol:

wrinx

[jimnielsen]

before I adjusted it the spring was just "flopping around" as you can see from the pic.. maybe i'd better get a new one?

[AlfaJack]

When I enquired the spring was about ?25, and the normal 155 spring is only about ?4!!

When you did the adjustment to the bias, were the rear wheels on the ground as I believe they should be for this.

[jimnielsen]

yep, I did it with the car still on the trailer!

jimn~

[WhizzMan]

In my opinion, changing the spring will change the characteristics of the "progression" of breaking depending on how much force is on the rear. You could use this for adjusting it to your preference of course. However, I would say it may be wiser to shorten the length of the spring a bit, so you can pre-load it properly with the weight without changing any of the progressive characteristics. If it's not progressive enough to your taste, you can always swap it out for a heavier one later on. I am quite certain the people at Alfa Romeo played around with this and found this would be a good spring-rate. Of course, your car is modified, you use it for track use, but why change it out before you know if the stock setting is actually to your liking?

Is the mounting-point for the spring on the rear ARB still in place? If I remember correctly, these are clamp on and it might have moved or come loose even, that would prohibit the regulator from working correctly.

[jimnielsen]

Yes the mounting point is still in place, but I think I'd better do as you have suggested and shorten the spring just a little so that there is some tension on it before I do the adjusting. It appears that there has been not tension on it at all in the past.

Jimn~

[Steve Webb]

The spring for the rear bias valve is attached to the rear ARB with a clamp, so it may well have slipped and become lose.

If you change the rear ride height you will need to reset the spring mounting on the ARB otherwise you will have rear brake bias valve permanently set as if the rear of the car is loaded up. The result being too much rear bias in the brakes.

[WhizzMan]

The spring for the rear bias valve is attached to the rear ARB with a clamp, so it may well have slipped and become lose.

Ah I remembered correctly, the plot thickens. Anyone remember what the correct position of the clamp shoud be with the car on the ground? (only way to set up/adjust the balance is with the car on all 4 wheels) Now I come to think of it, Jim, you *did* adjust this with the wheels properly on the ground?

[Brul(tm)]

Jim, you *did* adjust this with the wheels properly on the ground?

Whizz, AlfaJack already mentioned this. Jim has also given the anwser :biggrin:

:funnypost:

Greetings,
Marc

[cuore_sportivo_155]

with regards to shortening the spring: this will change the progression of the adjuster as well, since the characteristic of the spring will change... the spring characteristics are defined by it's length, diameter of the wire and diameter of the windings...

move the clamp up and redo the adjusting with the weight. add a few kg to the weight if you want more brake action in the back still...

[WhizzMan]

with regards to shortening the spring: this will change the progression of the adjuster as well, since the characteristic of the spring will change... the spring characteristics are defined by it's length, diameter of the wire and diameter of the windings...


If you don't cut into the windings but in the "straight" part of the spring it shouldn't make a difference. there's a relatively long straight on one side end which you can shorten a few millimeters without changing the characteristics. Given all this, it should have the correct length if the clamp is set correctly. If it's too long it's probably worn and you might want to replace it because it's too weak.