Brake Bias Valve

[Mitch]

isnt that what i said on the first reply, lol

 

Mitch

[Guest Alan_builder]

isnt that what i said on the first reply, lol

 

Mitch

 

Mitch you are 100% correct.

Its the posts which follow yours that need correcting as per my reply to Steve.

[ibrooks]

I think that a big part of the problem we are seeing here is that all our cars are different and you simply cannot assume that two Robin Hoods with exactly the same brake setup will see the same results (and as we've seen here two with the same brake setup is a rarity). For any given car you might be OK with no bias valve or you might need some way of setting it - there is simply no easy answer.

 

The simple fact here is that too much rear braking is bad. If the rear wheels lock before the fronts then the handling characteristics are dangerous. So long as the fronts and rears provide enough effort for the purposes of the test it's the balance that matters - anything else is personal preference and can be sorted later as you start to drive the car and get a feel for what you want.

 

My 2B failed its first SVA on about 4 items and one was too much rear braking effort. They calculate this by measuring braking force on the rollers, weighing each axle and then crunching the numbers back in the office. They work out the front/rear weight split and from this they can theorise whether the front or rear wheels will lock first. I had the Sierra bias valve in place and as people have said it won't work on the rollers as there's no inertia. I was under the impression that if an inertia valve was fitted the tester had to take it out on the car-park, stand on the brakes and observe which wheels lock first. Tester said "no" (which I still think was wrong but I didn't want to wind him up) so i took it away and when sorting the other problems I fitted a Rover Metro pressure limiting valve. On the re-test this had done the job.

 

Under IVA you basically aren't allowed any form of adjustable bias (SVA allowed them so long as they were locked off with something like a roll-pin). IVA has done away with this and although there are provisions for adjustable setups you need to disable them by welding which isn't really do-able at the test centre previously you could have fitted an adjustable valve and tweaked it at the test to set the bias correctly and then locked it off.

 

This is one of the bigger changes between SVA and IVA and one that I can see presenting a real problem as we don't generally have a way to check the brake balance before we go for a test.

 

Iain

[megadodo]

ARRRGGHHHH! The day befor this thread started, because of other threads i had read on this forum, I spent a good couple of hours removing the rear pipe from the master cylinder, rebending the pipe, making and fitting a bracket for the inertia bias valve, cleaned and sprayed the valve and its holder, fixing that on to the bracket and making a new pipe to connect that to the master cylinder only for you smart alecs to tell me I don't need it!

[Guest mower man]

Check before making comments ! the orig enq was about brake locking and further posts mentioned rears Iposted an opinon based on experience with MY car and not a little involvement with race, rally and fast road cars over the last 40 years Idon't take any offense but stand by my statements in that post.I replaced the orig 1 pot sierra calipers because in my opinion they were unsatisfactory ,the front set up cost me under 300quid so where you 400 + figure comes from I understand not ,lets say we have our own opinions and agree to differ regards and best wishes mower man

[megadodo]

So, is there a consensus then, that for a 2B with rear disks you DONT need a limiting valve for both the IVA and normal road use? Or am I still missing something? Any one want a shiny stainless steel valve bracket? Previous comment, by the way, was made with tounge in cheek, couldn't find the smiley for that and I'm always greatful for everyone's comments!

[codo]

Just as this was blowing over, what about on the Zero?

 

Planning to run 4-pot Wilwoods at the front and standard drums at the back. Will I need a valve?

 

Cheers,

 

Dan

[Guest Christine]

I love this site more entertaining than Eastenders!

[Guest Alan_builder]

I think that a big part of the problem we are seeing here is that all our cars are different and you simply cannot assume that two Robin Hoods with exactly the same brake setup will see the same results (and as we've seen here two with the same brake setup is a rarity). For any given car you might be OK with no bias valve or you might need some way of setting it - there is simply no easy answer.

 

The simple fact here is that too much rear braking is bad. If the rear wheels lock before the fronts then the handling characteristics are dangerous. So long as the fronts and rears provide enough effort for the purposes of the test it's the balance that matters - anything else is personal preference and can be sorted later as you start to drive the car and get a feel for what you want.

 

My 2B failed its first SVA on about 4 items and one was too much rear braking effort. They calculate this by measuring braking force on the rollers, weighing each axle and then crunching the numbers back in the office. They work out the front/rear weight split and from this they can theorise whether the front or rear wheels will lock first. I had the Sierra bias valve in place and as people have said it won't work on the rollers as there's no inertia. I was under the impression that if an inertia valve was fitted the tester had to take it out on the car-park, stand on the brakes and observe which wheels lock first. Tester said "no" (which I still think was wrong but I didn't want to wind him up) so i took it away and when sorting the other problems I fitted a Rover Metro pressure limiting valve. On the re-test this had done the job.

 

Under IVA you basically aren't allowed any form of adjustable bias (SVA allowed them so long as they were locked off with something like a roll-pin). IVA has done away with this and although there are provisions for adjustable setups you need to disable them by welding which isn't really do-able at the test centre previously you could have fitted an adjustable valve and tweaked it at the test to set the bias correctly and then locked it off.

 

This is one of the bigger changes between SVA and IVA and one that I can see presenting a real problem as we don't generally have a way to check the brake balance before we go for a test.

 

Iain

 

Ian, I disagree with your first paragraph but then you are spot.

 

A design problem for car manufacturers is the variable load at the rear end, big boot and 3 seats in back. They put in devices to reduce the rear braking when lightly loaded.

 

Everyone!

The weight distribution of the Sierra & Hood determine the braking forces needed for IVA/MOT front and rear. Hence the calculations. The system was designed for about 70:30 not 50:50 weight distribution. All Hoods are the same, in common with all other 7 type cars using standard Sierra brakes, drum or disc rears and transferred to a 7. The design says you are under braked at the rear! NOT ME, gravity.

 

You all pass IVA, SVA or the MOT without the Ford inertia valve operating as it is a static test.

 

Under dynamic conditions the Ford inertia valve can only reduce this rear braking further and make a HOOD dangerous.

 

In the above condition if you car is not under braked to some extent at the rear then there is an underlying problem which needs fixing. You can't change the laws of gravity!

 

I won't comment on upgrading the front brakes or fitting a pedal bias arrangement, if anyone don't understand the basic principles then further changes need the services of a motor engineer and not a pushy salesman.

 

Oh £400 was questioned

Caliper pricing

Discs

So 2 calipers and 2 discs about £600, you will pay from £250 to £1000 so my £400 is ?

 

Please, please think about your insurance. They consider this post as a warning to remove the Ford inertia valve if fitted if there is an accident.

 

I wish you all happy safe motoring.

 

Alan

 

I my

[Guest smartfazer]

So do we or do we not fit a bias valve? :lol: :lol: :rofl:

 

 

"runs for cover..................."

[Guest Ian & Carole]

Maybe

[Mitch]

depends on personal choice and set up,

 

 

Mitch

 

 

Ps mine HAS but donsnt need it ,

 

[Guest mower man]

Ian, I disagree with your first paragraph but then you are spot.

 

A design problem for car manufacturers is the variable load at the rear end, big boot and 3 seats in back. They put in devices to reduce the rear braking when lightly loaded.

 

Everyone!

The weight distribution of the Sierra & Hood determine the braking forces needed for IVA/MOT front and rear. Hence the calculations. The system was designed for about 70:30 not 50:50 weight distribution. All Hoods are the same, in common with all other 7 type cars using standard Sierra brakes, drum or disc rears and transferred to a 7. The design says you are under braked at the rear! NOT ME, gravity.

 

You all pass IVA, SVA or the MOT without the Ford inertia valve operating as it is a static test.

 

Under dynamic conditions the Ford inertia valve can only reduce this rear braking further and make a HOOD dangerous.

 

In the above condition if you car is not under braked to some extent at the rear then there is an underlying problem which needs fixing. You can't change the laws of gravity!

 

I won't comment on upgrading the front brakes or fitting a pedal bias arrangement, if anyone don't understand the basic principles then further changes need the services of a motor engineer and not a pushy salesman.

 

Oh £400 was questioned

Caliper pricing

Discs

So 2 calipers and 2 discs about £600, you will pay from £250 to £1000 so my £400 is ?

 

Please, please think about your insurance. They consider this post as a warning to remove the Ford inertia valve if fitted if there is an accident.

 

I wish you all happy safe motoring.

 

Alan

 

I my

Your 400quid is 125 quid more than Ipaid,special discounts ,favours etc were not used and it includedVAT and carriage is the spending of afew quid not better than risking life and limb?. Iwill not reply to your comments about pushy sales men etc butwould add that it is very wise to do proper research before modifications /upgrades are carried out you owe it to every body not least your self !! mower man

[speedtripledan]

My disc and drum set up stops on a coin in a straight line so i hardly feel its dangerous unless someone is driving to close when i stop hard

[Guest gdc]

so mayby we get to the end of a thread , i think i know understand all that there is to know about the ball bearing in a can ,

it wiil work on a sierra or a car of the same weight ,

it needs to be angled at exactly the right angle to work as designed in a car of that weight ,

our cars dont weigh the same as a seirra , so unless you can retrofit the ball in a can idea in a car of the same weight .

and at the same angle .then you have to addapt .