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Brake Bias adjusting in the Pedal box of your Butler
Hi Fellow Butler owners.
Have you found it to be difficult or is it a problem to adjust the brake bias on your Butler for perfect brake balance? Seems to me that you would want an easier way to dial in the correct brake bias setting. I'm thinking of installing a Wilwood, or similar, Bias adjuster with remote adjusting cable. This modification will make adjusting very easy, just turn the knob as you drive and test the result as you use the brakes. I've "heard" that for optimum street driving and track performance, bias settings may need to be different. What are your thoughts on this? Has anyone done this modification? Would love to know the details. Thanks, Arthur |
No takers???
I thought this would be a good discussion on F to R balancing.. SAFE BRAKING tips would be great? Arthur |
Ralph
I have my brake bias set at about 60/40 front to rear using the balance bar. This setting gives good balance for the street. At the track you might want to fine tune for track conditions and temps, not difficult but cannot be done on the fly without a balance valve. There are a lot of variables to contend with at the track running at 8 to 10 tenths. This is where, in my opinion, a balance valve proves it's value. I don't track my car and find my settings (60/40 prox) to work fine for me. It looks like you are making a lot of progress with your build. Leo |
According to what I've read and put in practice the balance should be really close from hydraulic sizing. Worst case you get a little too much from the rears and valve it down on them till you get a good balance. You can set up remotely adjustable valves or make it an under the car adjustment. I would only use a remote for a track car. If you shoot me an e-mail address I'll send an Excel sheet I made up that will get you real close on brake sizes with your values.
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Seems to me that it would require a lot of stop start driving. Then either jacking up the car or removing the pedal box cover, loosening the lock-nuts on the Bias-Bar, making the adjustments locking up the lock nuts, then driving and testing brakes then adjust again. I would like to adapt/use Tilton remote adjustable cable http://www.pegasusautoracing.com/pro...asp?RecID=1090 or similar Wilwood or CNC on the 1/2" 20tpi threaded rod that is in the Butler pedal box. But this will take a few modifications with the way Ron engineered it. It may require removing the 1/2" hemi-joint that is attached to the bottom of Ron's pedal and replace it by welding a sleeve to the pedal that will then accept the Tilton http://www.pegasusautoracing.com/pro...asp?RecID=6531 Bias bar. Then a 90 degree http://www.pegasusautoracing.com/pro...asp?RecID=3442 connector with remote adjusting cable should do the trick. Hoping to hear from more Butler drivers on the subject. Thanks, Arthur |
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I have tandem master cylinders 3/4" front and 7/8" rear with an adjustable balance bar. I believe I've got the hydraulic sizing correct but would like to see your Excel sheet. email me: mitchy.usa@att.net My front calipers are Wilwood four piston and the rear are Jaguar XKE. Even if the masters I have iinstalled are are appropriate, I think that the mechanical balance bar would still be of help in tuning in the brakes. I do not know how to use valves for balancing the brakes when using two master cylinders. Can you direct me to where I may read about how to do the plumbing and what types for proportioning valves to use. This option may be easier than modifying the mechanical balance bar. Why do you advise against using remote adjustment for street cars? Seems like if the car were used occasionally on the track the remote adjusting would be beneficial? Thanks, Arthur |
My apologies Arthur, I responded to you as Ralph.
When I set my balance bar it was far from scientific. I moved the sleeve to what I felt (eye balled) was 60/40 prox., with 60 being biased toward the front. Mickmate is referring to a hydraulic pressure adjusting valve that would be placed in the hydraulic line itself. This would require the brake line from the rear master cylinder to be routed to the valve, placed somewhere easily accessible in the cockpit. Another brake line would be routed from the adjusting valve to the rear calipers. Not particularly difficult to do and would result in better control. On the track where you must manage tire wear, and brake wear, (improper bias will result in "using up" your tires / brakes) along with a myriad of other things. The valve would give you some advantages in managing these things. On the street, because you are not pushing to the limits of the car or driver, it would not be as necessary. Leo |
Good information to read on brakes at the following link.
http://www.stoptech.com/tech_info/wp...g_valves.shtml So is it possible to have two master cylinders front and rear as the Butler has with the balance bar, and install a brake proportioning valve like the Wilwood #260-8419 http://www.wilwood.com/products/006-...1-PV/index.asp on the rear master cylinder? Will this valve add to the adjustability of brake bias control? Or is this valve designed to operate on a single master cylinder setup that operates all four brakes. Arthur My Cobra build link: http://apps.facebook.com/wildfire/fb...oid=1023096501 |
Hey Arthur that is the valve I was looking at there are some smaller and more discreet valves available also. I have set cars up with valves like this but my preference is to make an adjustment and take the car out and try it. I've had drivers out playing with adjustments like that on track and it's hard to get a controlled adjustment and good feedback from most guys in the heat of the moment. Some like the Tilton have 7 positions to click into.
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So what you're saying is that for an ideal setup you can put one of these valves in series with the rear brake line when you're using two master cylinders and a mechanical Bias Bar like I have. Correct? If that's the case it seems like that would be perfect. Adjust the mechanical bias bar for an "optimum" street machine and tweak it on the track with the valve. Sounds like a good plan. Arthur |
You got it, set it up as close as you can with hydraulic cylinder sizes and tweak it with the rear control from there.
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Thanks, Arthur |
After doing a bunch of research I've decided to stick with the Butler balance bar unit. I did have some issues with the main heim joint that is attached to the bottom of the brake pedal. It's the one that carries the balance bar. It was not fully tightened and it flopped around. So the ball of the joint was not doing what it was intended for. The heim was actually pivoting on it's thread instead of the ball moving. So I aligned it and tightened it. Then I pinned it with a roll pin so it would not move out of alignment. I also changed the adjusting nuts on the balance bar with nylock nuts installed backwards. The narrowed portion of the nylock nut is against the ball. This I thought provided for maximum travel without binding on the points of the hex nuts.
I still intend to place a proportioning valve to reduce pressure to the back brake in the event that adjust is ever needed when driven aggressively under track conditions. http://www.clubcobra.com/forums/pict...pictureid=2610 |
A good starting point with a balance bar is to have all 4 wheels off the ground, then have someone gently push your brake pedal. When you can no longer turn the front wheels by hand, have them hold the pedal steady, and turn the rear wheels. You should still be able to easily turn them. This is just a starting point for adjustment.
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