?PO removed brake bias regulator - good or bad?

3852 Views 13 Replies 7 Participants Last post by shiny_car, Apr 12, 2011

shiny_car

Discussion Starter · Apr 2, 2011 (Edited)

Hey guys

I just bought a 1990 Oz-spec 3.0 L-Jetronic 75 non-ABS as a project car.

It looks like the brake bias regulator has been removed (I haven't searched for an adjuster knob but there wasn't an obvious one). The front/rear brakes are standard AFAIK (I haven't checked pad brand/model yet). My plan is to add the RS Racing 'Budget Performance Brake' upgrade, which relocates the front calipers on brackets to fit 305mm discs.

I've only driven the car in the dry, gently, and the brakes feel ok to me.

What's the lack of bias regulator mean for the car? More or less rear brake bias?

The car will be used purely on the street, but upgraded to a 'fast street' vehicle (ie: RS Racing coilovers, polybushes, brake upgrade, exhaust; retain the 12V 3.0). I don't want the risk of locking up the rears in the wet, to catch me out in traffic around a corner.

If you advise I should have a bias regulator refitted, no probs, I can do that. I've also read that Alfetta GTV(6) ones may have more/better rear bias compared with the standard 75/Milano one?

TIA

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Duk

· #2 · Apr 2, 2011

It's probably more of a plus than a negative, not having the factory bias valve.

I did read on GTV6.com that there was at least 1 guy who much preferred the car without the factory bias valve. The rear brakes always seem to be under performing any way (at least they did on my 2 Alfa's).
If you are really concerned, then fit a proper adjustable 1 like a Wilwood.
As for locking up the rears in the wet, there is less over all traction available, so the car can better use rear bias because there is less weight transfer onto the front wheels and off the rear wheels.

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slyalfa

· #3 · Apr 2, 2011

The ABS fitted cars with non-working ABS (fuse pulled or bad sender) but working pump etc. seem to lock up the back first. And there is a valve in the ABS system. So with none I would think the back would be coming around on almost every stop. But the best test is to break until something skids and see which ends locks up first. Might need the help of a friend. If you lock it just before stopping you can tell by the skid marks as to which tires they belong to.

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shiny_car

Discussion Starter · #4 · Apr 2, 2011

Thanks guys.

So I figure my car probably has excessive rear brake bias. Test-skids down my street?

Good idea; I have some pretty-vacant back roads where I live, so it's suitable for testing.

Thoughts on Milano vs Alfetta GTV regulator? And what about when I upgrade the brakes? I suppose there's a chance it would even out, and a bias regulator may be unnecessary?

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Kristian p

· #5 · Apr 2, 2011

Cant help.

But just want to say, Congrats with 75

.

Im sure it is going to look good, once your done. having seen, how your 155 project turned out.

/Kristian.p aka kristian155.

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AR4me

· #6 · Apr 2, 2011

slyalfa said:
The ABS fitted cars with non-working ABS (fuse pulled or bad sender) but working pump etc. seem to lock up the back first.

I think that would be too big a liability for a car manufacturer. Usually, the ABS systems are designed to revert to a safe operation mode when the ABS malfunctions. Reverting to a mode where the rear locks up before the front is dangerous! I ran my Milano race car with ABS system but "fuse pulled" to get the better feel of the ABS brakes (but without ABS functionality), and in my case the front would always lock up before the rear.
Jes

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slyalfa

· #7 · Apr 2, 2011

Both mine lock the back first. And when I had a bad bush before I added a uni-ball the back would dart out on any hard break. I just got used to it. it even saved me one time on 101 in a panic I went sideways and just made the room for the car in back of me.
but after the uni-ball even when the back locks up the car goes straight now.

And for the gold (the one I added ABS too) it now locks the front first with the 205's in the front and the 245's in the back.

but I bet you could change the balance on the ABS with just different pads etc, it is very close. maybe even different tire PSI

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slyalfa

· #8 · Apr 2, 2011

BTW if you are going to be changing things like "And what about when I upgrade the brakes?" if that is changing disk sizes etc you might as well get a adjustable one now.

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shiny_car

Discussion Starter · #9 · Apr 3, 2011

Kristian p said:
But just want to say, Congrats with 75.

Im sure it is going to look good, once your done. having seen, how your 155 project turned out.

/Kristian.p aka kristian155.

Thanks Kristian! Good to see you here.

slyalfa said:
BTW if you are going to be changing things like "And what about when I upgrade the brakes?" if that is changing disk sizes etc you might as well get a adjustable one now.

Sounds like a plan. I'll try and assess lock-up on local roads 'before' then 'after' the front brake upgrade, then go from there.

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Mound Dawg

· #10 · Apr 8, 2011

I want to get rid of the stupid standard valve in my car, the previous one I had fitted was limiting the front brakes too, they were only 45% efficient on the test which failed the annual safety test (surprise!)

I put a new standard one in to get it through the test but when it comes off the road for the gearbox rebuild it'll get new rear calipers and all new brakes lines. I'll take the opportunity to delete the standard limiter and instal one of these-

Screw Type Brake Proportioning Valve | Classic Alfa Romeo spare parts and accessories

I suspect that the standard limiter is one of the reasons for the long brake pedal that the 75 suffers with but I'm not sure about the idea of running with no limiter. My car's got Ferodo DS3000 pads in the front which stop it like an Act of God but I can still flick the tail slightly if the car isn't going completely straight and I brake hard. I should imagine that it'll be worse with no limiter and otherwise standard front brakes.

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shiny_car

Discussion Starter · #11 · Apr 8, 2011

Yeah, I think an adjustable valve is ideal. However, in Australia and the State I live in, I suspect they are not 'roadworthy' and thus technically not allowed (would be ok for a track car). I will have to research this first. So, for me, if disallowed, I'll have to fit either a standard 75 version or a GTV6 one.

Interestingly, my brake pedal has great feel and pretty short travel to execute braking. It surprised me how good it felt, but it is probably explained by the lack of the proportioning valve!

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la_strega_nera

· #12 · Apr 8, 2011

Might also be a 164 master fitted - they're a bolt in but a bigger cylinder - results in a big improvement in feel.
as for the bias valve - they can only ping you for it if they can see it

- I think the way around it is locate it somewhere not too obvious, and once it's adjusted where you want it, remove the knob.

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shiny_car

Discussion Starter · #13 · Apr 8, 2011

Hey mate; good to hear from you here.

'Hiding' it is an option, for sure. Nice idea. I might also try and see the part number on the master cylinder when I have a chance, and cross reference it.

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shiny_car

Discussion Starter · #14 · Apr 12, 2011

I drove the car today on some damp roads for testing. Indeed, the rears lock up first (didn't get the fronts to lock up), so it's not ideal.

But I will wait until I've done the front brake upgrade before testing again. If the rears continue to lock first, I'll have a regulator/proportioner fitted at the same time I have braided brake lines fitted.

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