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Duel MC bias bar on haynes geometry
mcg - 7/4/12 at 08:28 PM

Hi again, having a few brake issues:

• I built a Haynes spec pedal box, but instead of the single master cylinder, I used two master cylinders with adjustable balance bar.
• I located the MC at the same point as the Haynes has for single MC.
• 0.62, and 0.7 girling MC
• M16 ford calipers on front
• Sierra calipers on rear
• Bled brakes through a number of times with and cleared the air. (used easy bleed)
• Can get the brakes to lock up (tested at speed on a track), and fronts lock before the rears, but there is a lot of pedal travel.
• 90% of the noticeable stopping force comes in after the pedal has travelled almost 50% of the way.
• Doesn’t bottom out on bulk head when fully depressed, and wheels are well and truly locked.
• When testing on the track, the brakes did the job in terms of stopping the car, but I didn’t like the feel of them, and would have expected them to be sharper, and more effective early in the depression.
• Another symptom is the brake light switch is only switching the lights on half way through the depression. (Which is dangerous I know)

We wondered if the geometry of the Haynes box needs adjusting to suit twin MC and balance bar set up? Thinking that moving the MC up would give a shorter pedel throw to activate? Really don’t want to have to do that as it will be a fairly big re-work. Also wondered if larger MC would give a more positive brake feel.

Has anyone else had a similar issue? Any help would be massively appreciated!

Thanks in advance.

Matt

avagolen - 7/4/12 at 08:39 PM

I have put a twin MC on my fury, and after the initial bleed, the pedal felt like the explanation of yours.

I had used a one man bleed kit - semi profesional with an electricp pump putting the oil into the system.

After getting my wife to press the brake pedal and I bled the brakes, the pedal has a lot less travel
and even though I have not yet driven the car, it feels very firm, even hard to get much movement at all.

So give it a go and bleed them the old fashioned way.

Len.

Ben_Copeland - 7/4/12 at 09:05 PM

With regard to the brake light switch, Check that its facing down so air cant get trapped at the sensor. Also if its fitted in the rear brake line its never going to work well. Needs to be fitted in the front lines.

mcg - 8/4/12 at 10:03 AM

Hi - thanks for the thoughts.

The brake light switch is mounted on its side, which I had previously read was the best for potential trapped air issues. So facing down is better than side mounted?

I will get the missus to help me do some old school brake bleeding. Really hope it helps! Dont fancy having to pull the brake box out etc, but needs must eh!

Thanks again

Ben_Copeland - 8/4/12 at 11:30 AM

quote:
Originally posted by mcg
Hi - thanks for the thoughts.

The brake light switch is mounted on its side, which I had previously read was the best for potential trapped air issues. So facing down is better than side mounted?

I will get the missus to help me do some old school brake bleeding. Really hope it helps! Dont fancy having to pull the brake box out etc, but needs must eh!

Thanks again


Side probably just as good, as long as its slightly downhill and not uphill so the air can move away.

Is the brake switch on the front circuit?

mcg - 8/4/12 at 12:22 PM

Yep.switch is.on front circuit. I could probably.tweak.its.position.to.run.slightly downhill as well.

FuryRebuild - 8/4/12 at 12:59 PM

I have a set of cosworth brakes on the rear of mine, and the mounting kit means the calipers sit very low down. In order to bleed it, I have to take the caliper off so I have the bleed nipple off and sitting vertical. Then I put a brake disk in there to give it something to clamp against. otherwise air would get trapped in the caliper due to the shape of the chambers.

It's never easy to get this perfect with the slight compromises involved in a kit. and yes, I would the wife was the best tool to do the job properly.

mcg - 8/4/12 at 04:36 PM

Interesting. We re-bled yesterday, and by opening the rear bleed nipples quickly and wide open, it pushed quite a bit of air out that had previously not been seen. I think to be sure, it will be worth doing as you say, and removing the caliper prior to bleeding.

Has anyone else experienced slightly sloppy pedal feel with the 'easy bleed' type approach? Is it possible that traditional bleeding technique allows you to build up a higher pressure in the system?




quote:
Originally posted by FuryRebuild
I have a set of cosworth brakes on the rear of mine, and the mounting kit means the calipers sit very low down. In order to bleed it, I have to take the caliper off so I have the bleed nipple off and sitting vertical. Then I put a brake disk in there to give it something to clamp against. otherwise air would get trapped in the caliper due to the shape of the chambers.

It's never easy to get this perfect with the slight compromises involved in a kit. and yes, I would the wife was the best tool to do the job properly.