To Bias Bar Or Not To Bias Bar

[Guest mcramsay]

I scrapped the gbsc pedals and standard brake master cylinder for a twin bias pedal box... With iva looming and the host of additional work needed to get the car through Iva with the bias bar system fitted, it's a big headache...

 

 

With two things outstanding- not being able to get a decent clutch/ clutch cable set up due to the pedal box, and the issues with getting the pedal box through IVA.

 

Would you stick with what you have built and present the car to Iva with the pedal box. Or remove the pedal box, fill up the holes in the floor, and redo the brake lines and fit the standard gbsc pedals and clutch cable, it is probably a day or 2 work... I know this is what I should do! I just need another experienced opinion! Opinions please!

[Guest mcramsay]

Problems being-

Leg room in the footwell

Setting up the brake bias and locking prior to Iva

I can't find a clutch cable that is the correct length

 

To swap back the old system would require new brake lines being made up, and a tiny bit of wiring,

[speedtripledan]

Can you not get a cable made? I used cable tec Mansfield to get a bespoke throttle cable made, they may be able to help on the clutch front

[Guest mcramsay]

Ive thought about having one made, but I think it would cost more than I would be willing to pay just for a cable!

[Guest Alan_builder]

Leg room in the foot well

 

I can't find a clutch cable that is the correct length

 

 

Don't understand the problem.

 

The IVA tester won't be the same size as you so no problem with clutch position

 

The Cosworth clutch cable is so long it will go to the nose cone and back, so it is long enough. Is the problem the length of wire inner poking out each end?

[Guest mcramsay]

I need a really short cable, longer cables leave me no adjustment at all, And what I mean for leg room is because the pedals are further forward than the standard top mounted pedals if you have long legs your knees will hit the steering wheel, I get away with it as I'm short and dumpy!

 

After thinking about it, the easiest and less stressful way of doing things is reverting to the original set up and putting the bias bar set up back in at a later date, I have all the bits to revert do it shouldn't take so long, it just means taking off a few panels. To run the new lines. I know I sound like I'm panicking but, the standard set up has been proven to pass Iva ( once the pads have been bedded in) where as the set up I have currently is to be honest frowned upon by iva.

[knights_templar]

Hi again

 

a lot of work I know, but if assembled "correctly" it will suffice.

 

at the risk of upsetting many, for road use on a Zero a bias system is of no use. (note I said ZERO and ROAD)

 

Why?

 

the brake system is balanced about spot on for road conditions, given that the weight distribution varies, (driver, driver passenger, tool box in boot, etc)

road conditions vary (man hole covers, white lines, diesel (being a biker, people who allow their vehicle to spill diesel should be hung drawn and quartered), road surface)

 

And, in particular you need to fully understand what you are doing and its effect on the vehicle, get it wrong and you could be facing backward very quickly, whilst on a track that is anticipated by other drivers, there are run off areas to make it less hazardous, and someone will come and help when its bent, on the road?

 

For serious track use? thats another thing all together. but note I said serious, the odd track day doesn't count.

 

Regards

[Guest mcramsay]

The car will be used on the road mostly. I fitted it because I don't really know why to be honest. The bias system is getting stripped out this morning and the new lines run. Once a few bits arrive tomorrow or Friday it should be done by the weekend. Ive got plenty of time.

[Guest Alan_builder]

So why won't a longer clutch cable do? You just need to support it along it's length.

 

For IVA you must have the fronts lock prior to the rear!

 

Newer drivers, (post front wheel drive) tend to brake in bends, having the rears lock up first sets up the spin. If you had a car with rod brakes, skinny cross ply tires, you braked prior to the bend. The Citroen Saxo Ford KA and Pug 206 have about 20% rear breaking efficiency to sop cars spinning.

The best braking is when all wheels lock at the same time and their road speed and the true road speed is 5% different. If you are short circuit racing like stock car you can tell how fast you are going round by the time difference between all 4 smoking as you brake and the rears lighting up when you accelerate out of the bend.

 

The Zero, If it uses the standard Ford discs and calipers all round the front cylinders are 30% larger than the rears. The 2B at IVA weighs in at almost dead on 50:50, the Zero will be a little lighter at the rear but not that much.

 

So If you use a common master cylinder and standard Sierra discs all round you will fly through the IVA, as you will with the read drums. No proportioning valve is needed as it can only reduce the rear breaking further.

 

I don't see the road issues in quite the same light. That standard road car following will have either flown off the bend prior to the Zero loosing it or will have slowed down sufficient to stop if you do spin. Your problem is surviving the carnage if the comes into contact, but the other bloke is liable for the damage.

 

The servo tends to over press the braking system and lock the front wheels (2B with standard Sierra breaking system and no bias valve). Reducing the servos force amplification or removing it totally can help stop locking up and give a better feel.

 

So twin master cylinders with a 30% size difference can aid breaking.

 

PS, % calculation not defined the base, 70 rear 100 front is 43% or 30% if the base is 70 or 100 respectively.

[Guest The Modfather]

I use a Ka master cylinder (no servo) with original sierra front and rear brakes, and it is excellent. There is in my opinion, no need to over brake the car as this will cause problems for you. Use braided lines and ditch the rubber ones for a better pedal feel.

[Guest sandy77uk]

i used an escort master cylinder as it has 4 outlets as opposed to 3 on the sierra and the brakes are superb (the braking efficiency was commented on at IVA with them saying how good it was)

[Guest mcramsay]

thanks for the advice guys, i have obviously decided to revert to the braking system that GBSC had in mind for the car, 2 hours in the garage this morning and the pedal box has been removed, and the welded in support bar cut out, and the front brake lines have been removed. this afternoon i will remove the rear brake line and then cut a new drivers side foot well panel and pedal box top cover out of some sheet aluminum i have in the garage. and then hopefully tomorrow my new sierra master cylinder and 3/16" brake line should turn up in the post tomorrow.....now where did i put the old pedals. fingers crossed it should be all back together by early next week. then the major things for IVA are emmissions, headlight positioning, and getting the acewell speedo to read correctly.