Manual Brakes brake pedal?

[Jicaju]

Switching to manual brakes. Instruction say to use upper hole or drill another hole one inch above existing hole on pedal which any one that has pulled a pedal out of a GN knows it uses a pin. I guess my question is if I remove the pin in pedal and bushing it to desired diameter will the powermaster pedal give me the correct ratio of 6:1 or be close enough.

Thanks Michael

 

[northerngn]

I tried that and the pedal effort was too much for my liking...I.drilled a 3/8 hole 1/2in above the (center to center) and really decreased pedal effort and am happy with the feel as well
-Dan

 

[ttypewhite]

Which Master cylinder are you guys using? and do you have disc brakes on all four corners. I just picked up my new Mopar (part#39476) unit at the dealer through my buddy for $57 that works there. I am going to run S10's up front and Wilwoods out the back. What bore diameter are you guys using?

 

[Slow91z]

Those instrutions are for a regular vacuum brake pedal...the pm pedal is already correct.

 

[RmvBfrFlght]

Switching to manual brakes. Instruction say to use upper hole or drill another hole one inch above existing hole on pedal which any one that has pulled a pedal out of a GN knows it uses a pin. I guess my question is if I remove the pin in pedal and bushing it to desired diameter will the powermaster pedal give me the correct ratio of 6:1 or be close enough.

Thanks Michael

The PM pedal has the pivot point about halfway between vacuum and manual pivot points. I ended up using a vacuum pedal and doing what you described. Drilled & sleeved the manual hole (it was tapered) in the pedal arm to take a 3/8" bolt. Used a heim end as the pivot to a piece of cut down & shaped grade 8 bolt for the push rod.

Found a picture of the pedals. Vacuum/manual on the left, PM on the right.




ttypewhite: used a 7/8" bore Mopar M/C with '98 - '02 Camaro/Firebird (LS1) brakes all around.

RemoveBeforeFlight

 

[sackracing]

I used a vacuum pedal, drilled and tapped a 3/8 bolt above the hole that's already there so it would be on a straighter line, and it's like pushing on a brick wall. So, using the manual hole is better? It was angled down really far.

I'm using aerospace brakes up front and drum brakes on the rear, Mopar 13/16 master cylinder.

I'd really like to reduce the effort. I've got 1 inch of pedal travel.

 

[WHITE T]

Sack,
I would measure your ratio. It will be measured from the top pinpoint of the pedal to where the pushrod meets the pedal divided by the top pinpoint of the pedal to where your foot pushes the pedal. Typically on a manual brake you will want to see around 6.25 to 1 ratio. I am assuming your high pedal effort is due to less than desired ratio (since your MC bore is pretty small bore size).

HTH!

 

[sackracing]

I just went out and measured a pm pedal, I came up with 4.9 for ratio. By my calculations the centerlines should be 2 inches from pivot point to pivot point to get 6.75.

 

[sackracing]

And my MC might be 1 1/8. Can't remember.

 

[jevans]

I purchased a manual brake kit from travis at dragracebrakes when I converted over to manual brakes. The kit came with an billet aluminum firewall adapter, Wilwood master cylinder #260-4893(1-1/16" bore) and pushrod. The instructions tell you to drill an 3/8" hole between the pin and upper hole on the pedal for correct ratio.

I used the factory pushrod that mounted to the pin and converted it to the Wilwwod master cylinder. I'm running Wilwood 4 wheel disc brakes and using the factory proportioning valve. I have a full, firm pedal and have plenty of brakes. I street drive my car as well as race it at the track.

John

 

[northerngn]

Looks like mine I got locally... my master is from Strange

 

[sackracing]

Being the dumbass that I am, I mounted the heims joint below the manual hole. From what I can measure, the manual hole should be perfect. And that's where I had it before. I'd rather have a cheese grater run across my bare ass than pull that pedal out again.

One problem I ran into with the manual hole was that the shaft / heims joint is a little short and the pedal didn't come all the way back to the switches. I'll figure something out. I might modify the PM pedal to work.

I really need to do some research or READ THE MANUAL THAT CAME WITH THE AEROSPACE BRAKES that had instructions on how to calculate ratio.

 

[northerngn]

Being the dumbass that I am, I mounted the heims joint below the manual hole. From what I can measure, the manual hole should be perfect. And that's where I had it before. I'd rather have a cheese grater run across my bare ass than pull that pedal out again.

One problem I ran into with the manual hole was that the shaft / heims joint is a little short and the pedal didn't come all the way back to the switches. I'll figure something out. I might modify the PM pedal to work.

I really need to do some research or READ THE MANUAL THAT CAME WITH THE AEROSPACE BRAKES that had instructions on how to calculate ratio.

I had the same issue...i did this and it worked...your welcome!!!

• View topic - Installed my TNT manual brake kit.... **PROBLEM SOLVED**

-Dan

 

[sackracing]

That is a good idea, did you drill above the manual hole?

 

[Jicaju]

Which Master cylinder are you guys using? and do you have disc brakes on all four corners. I just picked up my new Mopar (part#39476) unit at the dealer for $57 through my buddy that works there. I am going to run S10's up front and Wilwoods out the back. What bore diameter are you guys using?

I have a mopar master cylinder I got from TRZ 1.032 bore diameter.

Michael

 

[RmvBfrFlght]

That is a good idea, did you drill above the manual hole?

Shouldn't do this as there isn't enough travel at the M/C. What happens when one circuit fails is that the other circuit can't be pressurized. So all braking is lost.

I found that the M/C springs weren't quite enough to fully depress the brake/TCC switch, ended up using a return spring to assist. Note that this is common and GM even used return springs on many of the manual brake pedal systems.

When using a manual set up pad selection is important. Need to run good pads with a high coefficient of friction.

RemoveBeforeFlight

 

[sackracing]

I can tweak the bracket down so the switches make, no bid deal.

I was wondering if drilling and tapping a hole above the manual hole would be cool for mounting the heims joint.

 

[RmvBfrFlght]

I can tweak the bracket down so the switches make, no bid deal.

I was wondering if drilling and tapping a hole above the manual hole would be cool for mounting the heims joint.

It wasn't that the pedal arm didn't reach the switches. It was that the switch spring was stronger then the M/C spring. The M/C springs being fully extended didn't have enough ompf left to reliably depress the brake/TCC switch.

Don't really want to bend the switch bracket closer to the pedal arm either. This will reduce the available travel, which is needed with manual brakes. The higher pedal ratio already reduces the available travel, no need to reduce it further.

Which is also what happens when using a location on the pedal arm that is above the stock manual pivot point. The push rod travel at the M/C is greatly reduced. Which means in the event that one system develops a leak, you lose both systems. As there isn't enough travel to collapse the leaking circuit enough to engage the piston in the M/C for the non-leaking circuit.

The brake pedal will be on the floor with no means to stop the car.

RemoveBeforeFlight

 

[sackracing]

Mine isn't a matter of spring pressure, the rod is too short. I installed it all new with no fluid in it. When I drilled and tapped the hole I'm using now, I put it a little closer to the firewall and that solved the problem.

I am below the manual hole now, and I have about 1 inch of travel. They seem to work ok as far as stopping the car, but it is a stiff pedal with very little travel. By the calculations, The mc rod pivot point should be a little over 2 inches from the pedal pivot point to get the desired ratio.

 

[sackracing]

cut the pin off the PM pedal and drilled and tapped a hole 2 1/8 from center of the pivot point. I know have a full pedal stroke.