Braided brake lines from FFR

[J R Jones]

NAZ we agree on the potential mismatch of brake applicating parts. Having a half stroke also make bleeding more arduous.
jim

[NAZ]

Jim, I agree that a limited stroke on the M/C will make bleeding very difficult and suspect this is the cause of bleeding issues for so many.

Over the last several years I've read on this forum of folks that have installed their pedal assemblies in a way that limits the full stroke of the M/C. Usually they are installing the Wilwood balance bar system and are having trouble bleeding their brakes. Some have also come to the conclusion that if they loose either the front or rear brakes the other end will not provide any braking. My first thought is that the root cause of their bleeding and lack of redundant braking is installation error.

As you know, the M/C piston area is significantly smaller than the total piston area of the calipers connected to that M/C. On my car the ratio is 26.3:1 -- the total area of the caliper pistons is 26.3 times larger than the M/C piston area. So it takes a lot of M/C stroke to equal the displacement of even a small stroke of the caliper pistons. If my caliper pistons all move .010" it takes more than a 1/4" of M/C stroke to equal that displacement and at 6.25:1 pedal ratio, the pedal travels more than 1 5/8". So when I release the pedal and the caliper piston seals pull the pistons back maybe .010" it takes ~2" of pedal travel (including my free play) before pressure builds in the front braking system. I'm not sure most realize this relationship when setting up their brake system otherwise there would be more emphasis on ensuring the M/C pistons have full stroke.

[Brave Salmon]

MY THOUGHTS EXACTLY. From full up on pedal to firewall only extends the booster pin that ~.8" clearance between the pin and the M/C bushing is maybe .020. I cannot move the pedal higher because it hits the steering shaft.

[NAZ]

It looks like you've found the source of your braking issue when you discovered the short stroke on the M/C. Is there a way that you can see to reduce the pedal ratio from the 7:1 on the current set-up? That'll give you more M/C stroke and I think I read one post where Jim has already calculated the optimum pedal ratio for your current set-up.

With limited space in these little cars it may be difficult but you need to have a pedal assembly that gives you full travel of the M/C. You may have to get creative with your corrective action and think of what modifications that would facilitate full travel. Even if that means cutting out the diagonal brace at the firewall to get an extra inch of pedal travel. I eliminated that brace on my car and pushed the firewall out ~4" to get more leg room by fabricating a blister.

Don't give up, your brake issue can be resolved.

[Brave Salmon]

Hi Naz, Jim, and everyone else..
"The pedal pad travels 8" and stops at the firewall." THAT'S INCORRECT. The pedal is actually hitting one of the bolts (left side) that anchor the steering column to the firewall. I pulled the bolt, shaved half the head off and re-installed it from rite to left. I also relieved the pedal an 1/8th to gain a bit more travel. However, with the pedal now as far down as possible, I'm only getting 1.60 - .77=0.83" of stroke at the booster pin. The 1.6 is measured from booster cavity with pedal down.. .77 measured with pedal up. I busted my arse to gain a lousy 10th of an inch. Pic is of the pedal as recvd from Whitby. Marks on table show my calcs of pedal ratio. I cannot move the arm down to the hole because it will hit the steering bracket big time. I wonder if I can cut off the left side bracket? I'm convinced that the ratio is AFU but Jeff at Whitby swears he has hundreds of theses working just fine. I've never heard from anyone who is using this setup so maybe a separate post is in order. That's all for today, SF getting beat by Seattle, my car is down, back hurts and beer is on the menu. Thank God I have a cardio appt in the AM! Thanks gents...

[J R Jones]

Brave Salmon, This is getting more odd. Your ratio of 8 inches pedal travel to 0.83 actuator rod travel is close to 10:1.
I see you are seeking Whitby experience. Good.

If you find time it would be interesting to know two more dimensions:

Length pedal pivot center to pedal pad center.
Length pedal pivot center to brake actuator rod pivot.
This gives us the mechanical ratio of the lever.

With a side photo of your brake pedal lever (complete) we might access if the rod pivot point can be lowered without the rod binding.
With 8 inches pedal travel you need about 6:1 ratio.
jim

[Brave Salmon]

Brave Salmon, This is getting more odd. Your ratio of 8 inches pedal travel to 0.83 actuator rod travel is close to 10:1.
I see you are seeking Whitby experience. Good.

If you find time it would be interesting to know two more dimensions:

Length pedal pivot center to pedal pad center.
Length pedal pivot center to brake actuator rod pivot.
This gives us the mechanical ratio of the lever.

With a side photo of your brake pedal lever (complete) we might access if the rod pivot point can be lowered without the rod binding.
With 8 inches pedal travel you need about 6:1 ratio.
jim

Sorry, I meant to include a picture 20211003_085659.jpg

[Brave Salmon]

Brave Salmon, This is getting more odd. Your ratio of 8 inches pedal travel to 0.83 actuator rod travel is close to 10:1.
I see you are seeking Whitby experience. Good.

If you find time it would be interesting to know two more dimensions:

Length pedal pivot center to pedal pad center.
Length pedal pivot center to brake actuator rod pivot.
This gives us the mechanical ratio of the lever.

With a side photo of your brake pedal lever (complete) we might access if the rod pivot point can be lowered without the rod binding.
With 8 inches pedal travel you need about 6:1 ratio.
jim

Sorry, I meant to include a picture 20211003_085659.jpg

That 8" is with the pedal raised to an uncomfortable level in the footbox. I'd rather see it down around 6" so it's more similar to gas pedal. Thanks again.

[J R Jones]

Brave Salmon, Your problems have been so unusual, I am almost reluctant to advise and add to the frustration.

The 4:1 option looks promising and with the six inch pedal travel you mention, you should get 1.5 inches of rod and M/cyl piston travel.

The potential interference is if the 4:1 hole puts the rod at an angle that comes in contact with some other part.
A test fit and bleeding attempt is in order. With no interference it appears to be a viable alternative.

If the clevis pin is welded to the lever, you might want a new lever with the pin in the "C" hole.
You could test with a bolt/nut in the "C" hole but that is not appropriate or safe for street use.

One picture and dimensions are a huge contribution to the solution.
One test is worth a thousand opinions.
jim

[NAZ]

You can also lower the ratio by shortening (cutting) the pedal arm and welding a pad back on it. If that does not interfere with the steering column or something else under there AND if the pedal height change is acceptable. That's if there are no optional pedals available or moving the M/C push rod to the lower hole is not a better option.

There's almost always a way to overcome a problem, just some fixes are more work or cost than others. Just keep brainstorming ideas, you'll come up with an answer.

[J R Jones]

Brave Salmon,
I will PM you later. I do not know how deep your fabrication skills are. With tools, skill and determination the original clevis pin can be removed and re-welded to the "C" hole.
If that is not possible "in house" someone can. A new lever might be cost effective.
The photo is not terrific, but my perception is the pin weld looks like a bird turd.
jim