Fixed the excessive pedal pressure on the brakes

[Jim Stabe]

I built the car with double master cylinders and a balance bar and designed it to have about 100 lbs of pedal pressure to get a maximum G stop. After driving it for a while I found that to be too much so I replaced the 3/4" masters with 5/8" and it now has the feel I was after. It is not power brakes but I don't have to use both feet to get a full G stop anymore. The car has awesome stopping power now - stops on a dime and gives you 9 cents change.

[BlownMGB-V8]

That's excellent Jim.
My thought is that you should use all your pedal travel, leaving about 20% as a reserve, especially if you have gone to rear disks as we have, in which case you could get by with even less reserve. That way you use the smallest cylinders possible for the lowest pedal pressure. But as you drive it and adjust the balance bar you may notice optimal braking at a point significantly off center which tells you that you can decrease one of the MC's to get a more centered balance point. With my inside adjustment knob I frequently made a minor adjustment going from dry roads to wet, as I balanced it for the rears to begin to lock just a bare fraction befor the front, and with a wet road that balance shifts a bit. This time around I think I'll put a dot on the adjuster knob so I can see it it has been moved.

Jim

[Jim Stabe]

I run it very slightly biased toward the front master. I experimented moving it around and this seems to work the best. With the 3/4" masters the pedal was very high and now it comes out just above the throttle - perfect for heel and toe. I can always adjust the height of the brake pedal but it feels just about right now. The balance bar stays straight (not cocked) with pressure on the pedal so I think the master sizes are correct for the caliper sizes.  I have to push really hard to get it to lock up but the deceleration before that point is quite impressive and very linear with pedal pressure. I'll probably have to tweak it again once I get some new rubber on the car.

[BlownMGB-V8]

Sounds about right. I hope mine is that close this time around.

Jim

[Charles]

Jim S. I always like spare change in my pocket. I installed the balance bar set-up in my VTECMini then forgot to tighten the locknut. What a surprize.
charles

[tr8todd]

Jim, what did you use for brakes front and rear(piston sizes) and where did you find the brake pressure calculator.  I used to use one that was on the factory five website, but now I can't find it.  Just picked up a set of Wilwood reverse hung pedals and want to find appropriate masters for the TR8 I'm putting together.

[Jim Stabe]

Todd

I have the same Wilwood balance bar pedal assembly as you do with the shorter 5.1:1 ratio pedals instead of the 6:1 . I have the C4 J55 optional brakes with 13" rotors in front. All the parameters for the car are entered in the spreadsheet calculator. PM me your email and I'll send it to you then you can enter your own values.

[tr8todd]

Thanks for the offer but the guys over at GRM came thru with a good calculator.  Here is a link to it.  http://www.tceperformanceproducts.com/dual-bias-calc/