Make it handle

[hotrod1]

Originally Posted by robnolimit

Brakes more specifically, the delivery system. That being the pedal, booster and master. If you have ever read about "the pogo incident" from my younger days, you know I have spent some time on brakes. The goal, for me anyway, is to create 1000 to 1250 psi of line pressure at the top end with the type of pedal feel that you want to match you intended driving style.
I have a great three car comparison. Three that are currently in my garage.
1. My trusty sled, 1946 ford convert. Has a 5.5-1 pedal ratio, hydro-boost and a 1 1/8" master. (4wd, oem type 11"ft, 11"rr) This car weighs in at 3400 lbs, and stops on a freekin dime with three cents to spare. I once put a set of really agreesive pads on it, and with Falken tires it stopped from 60-0 in 92 feet, out braking a Porsche! The pedal is very soft and smooth, BUT, in a track setting, or the roads up to Big Bear, the pedal feel is so light its hard to feel the pad contact.
2. The Bullit, 55 F-100, has big 14" 6 piston Baer brakes, the pedal is 6-1, and uses an 8" dual diapham booset and 1" master. This is a standard street/perf set-up. The motor makes good vacuum and it is very comfortable to drive. Stop and go is no problem. Pedal feel is great. It does take a bit more effort than my '46, but much less than a stocker old p/u. I like it. When the Bullit was fresh build, I had got a hold of a bad master right from the start, the fading master cost me three points at the first Truckin Throwdown. Had it not failed, I would have won by two points. Aaargh!!!, but, its an easy fix and now works perfect every time.
3. HellBoy. My goal was to eliminate anything that could fail, and to have lots of adjustment for tuning. I used a Wilwood hanging pedal at 6.5-1 with tandem masters. The front is a 3/4"bore, and the rear is 13/16". The diffenerce in bore size puts a lille more pressure to the front brakes. The balance bar assembly allows adjustment to the front and rear brake without a proportioning valve. It's a pain to bleed. It looks really cool. Yes, it works very well, and the pedal feel on the track is consistant. It is easy to feel the brakes, and modulate pedal input. But, it takes a firm push to stop it, so on the street you have to be used to it. Most of us are not used to manual brakes any more. It takes some getting used to.
I'll put together some info on this for you.

Hey Rob:

Looking forward to more information on the brakes.

I just took a look on the internet for your truck "Hellboy" and found some pics. WOW, that thing makes my heart race. Where can I find more and more pictures? Hey, where is the radiator? In back? Tell us more about that as well. How well does it cool? I imagine that you dont drive this anywhere except for autocross.

[gringoloco]

Originally Posted by MrBlue

Rob,
First thanks for all the information. I know that I read this somewhere between page 1 and this last page, BUT What shocks do you recommend. I am going to lower with springs, this is a street driver, not a racer. Thinking of 3-inch front and 4-5-inch in the rear
Thanks,
Victor

Start at post 1302...

[jlsanborn]

Originally Posted by MrBlue

Rob,
First thanks for all the information. I know that I read this somewhere between page 1 and this last page, BUT What shocks do you recommend. I am going to lower with springs, this is a street driver, not a racer. Thinking of 3-inch front and 4-5-inch in the rear
Thanks,
Victor

Victor,
I'm in the same boat and got some feedback a page or two back. I'm going with the Monroe shocks. Rob is in the process of developing some that are specific to our trucks but I'm not sure when he'll ha e those available or what the price point will be. He has the Monroe's on his site but ok not sure how to pick the right shock. There has to be a formula that he uses to determine the proper dimensions (extended length and collapsed length).
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[69gmcc10]

Found this thread half way down page 2 and I started feeling sad, so I am bumping it back to where it belongs!

Mr. Rob, do we have any more great info on brake systems?

[GMC Canuck]

Found this thread half way down page 2 and I started feeling sad, so I am bumping it back to where it belongs!

should be a sticky.

[AJohn6]

Rob,

I have a question about Sway Bars. I am certain it has been covered but sifting through 56 pages to find it is proving to be more difficult than I had imagined.

The truck is a '71 C-10 Stepper and I have your Fatbar 4-link w/ 6.9" single adjustable Shockwaves attached to a F@$d 9" and a 4x2 custom back half. I am looking at buying the Speedway Engineering swar bar but I'm not sure what bar I should get. Should I get a solid/hollow bar and what thickness should I get?

The front end is the Porterbuilt mild dropmember with their sway bar and RS-7 bags

Thanks in advance,

Adam

[robnolimit]

I'd go with a 1" splined bar and arms. I tried a 1 1/4", and even at .065" wall, it's a little stiff. Once you're set up with the 1" bar, you can change bars easy. I'd start with a 1" solid.

[robnolimit]

On to Master Cylinders It's all about line pressure. And that means numbers. The first thing we all have to agree on is how hard to push on the pedal. The DOT standard is 30 to 40 lbs foot pressure. But we need a standard that everyone can agree on. I like to use 30 lbs on street drivers, and 40 lbs on race/performance builds. If thats OK with everybody, we'll start there. So, for the street, lets say 30 lbs of pressure comes from your foot. This would be multiplied by the pedal ratio. ?? What? I'll work on a picture for this. But for now, lets say you truck has a pedal ratio of 7-to-1. So, 30 lbs from your foot, times 7 from the pedal, = 210 lbs of force pushing into the master cylinder. Now to covert that into P.S.I. (line pressure) we need to know the size of the master cylinder. The area of the piston in the master can be calculated using the formula for the area of a circle. or, Area = 3.14 x R x R ( thats the best way I can type it in.) R being the Radius, or, 1/2 of the diameter. So, a 1" bore master has a 1/2", or .5" radius. 3.14 x .5 x .5 = .785 sq.in. of surface area. To get line pressure, we take the input force (lbs) and divide by the piston area (sq.in.) For our example, 210lbs / .785sq.in. = 267 lbs of line pressure. Not much. This will not stop your truck very well. So, what to do.

[AJohn6]

Originally Posted by robnolimit

I'd go with a 1" splined bar and arms. I tried a 1 1/4", and even at .065" wall, it's a little stiff. Once you're set up with the 1" bar, you can change bars easy. I'd start with a 1" solid.

Thanks Rob, I appreciate the advice.

Adam

[jlsanborn]

Originally Posted by robnolimit

I'd go with a 1" splined bar and arms. I tried a 1 1/4", and even at .065" wall, it's a little stiff. Once you're set up with the 1" bar, you can change bars easy. I'd start with a 1" solid.

He Rob,
I had asked earlier but I think it got blown buy. In regards to the front swaybar, If I were to bone-yard one, which is the best one? I found a 3/4t burban with the optional heavy-duty unit. Keeper? I've got your panhard rod kit and shock relocate. I'll be getting your rear swaybar next week (still in stock?). I'd also like to get the Monroe shocks from you, but I'm not sure what I need with the drop I've got. Still offer 10% to board members?

Thanks!

[gringoloco]

Originally Posted by robnolimit

So, what to do.

Um, add a booster, piston area, and pad friction coefficient? Good info! Timely, too What's the pedal ratio on a 67-72 pedal assy?
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[mongoose]

my square is only 3.5:1.. dunno if the 67-72 is the same.

[robnolimit]

Boosters This is the most common way to gain pressure. A power brake booster is like a stereo amp. It takes the the signal coming in and amplifies it on the output side. Bigger Boosters are like bigger amps, - more power.
The other key item is vacuum. Gotta have some. We use 18" as a test standard. Over the years we have tested a lot of boosters, and of coarse, we gathered all of the info. So, it's kinda like this:
For a givin size of a booster, you can have an approximate multiplier, based on 18" vacuum. This multiplier can be factered into the line pressure calculation.
A 7" single diaphram booster has a 1.7 to 1 multiplier
7" dual diaphram = 1.95 to 1
8" single = 1.9 to 1
8" dual = 2.25 to 1
9" single = 2.15 to 1
11" single = 2.45 to 1
Now these are averages from years of collecting data. **your results may vary**

If we go back to our example, at 267 psi. and add an 8" dual diaphram booster (267 x 2.25) we can expect to get 600 lbs of line pressure, givin 30 lbs of foot pressure on the pedal, and 18" af vacuum.

With this information, you can figure out the results of changing ratio's, boosters, and bore size.

[Mechanic77]

Great information on the vacuum brake boosters Rob, but do you happen to know the approximate multiplier for a hydroboost? Some of us like to run big cams that don't make much vacuum

[robnolimit]

Oh yes, I was gettin to that. Hydro-boost units use the pressure from the power steering, (hydrolic pump) And have a great amplifier advantage. There are many factors here too, such as p/s pump output, hydroboost bore size, and the pressure loading of the acumulator. As a general rule, I would use a multiple of 3.5 to 1 for most hydro units. The downside is a loss in pedal feel, some of this can be gained back by lowering the pedal ratio.

Next up, the good, the bad, and the ugly of all these items.

[NPilot1975]

Rob, I was looking at a manual pedal setup with a 5.75:1 ratio that is floor mount. Do you think this would be safe on the street with some getting used to?
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[robnolimit]

Well now, if we all wanted safety we wouldn't be hanging out here. But, yes, I think this is do-able. If you run a 7/8" master, you will end up with appx 391 lbs of line pressure at 40 lbs from your foot. Then look for an aggressive brake bad. You'll have some brake dust, but she'll stop. If it is a tandem master cyl set up, try a 3/4" bore (front)and a 13/16" bore (rear)

[robnolimit]

Two big events today. GoodGuys @ indy, watch out for Brad Coomer and the Summers and Sons C10 on the Auto-X. It's Brads Birthday, and he wants a Pro class trophy in a bad way. In Ohio, @ the Lingenfelter Performance Nationals, Chris from Smitty's has his fresh C10 build out on track. As of last night Chris was only 2 sec. off the overall leader, and this is his first full day of Auto-X in the new truck. BTW, Chris recieved an invite to the Optima OUSCI, Great job Chris, watch for a feature on this truck soon.

[INSIDIOUS '86]

Originally Posted by robnolimit

Oh yes, I was gettin to that. Hydro-boost units use the pressure from the power steering, (hydrolic pump) And have a great amplifier advantage. There are many factors here too, such as p/s pump output, hydroboost bore size, and the pressure loading of the acumulator. As a general rule, I would use a multiple of 3.5 to 1 for most hydro units. The downside is a loss in pedal feel, some of this can be gained back by lowering the pedal ratio.

Next up, the good, the bad, and the ugly of all these items.

So how would one go about lowering the pedal ratio? I gave some stainless braided lines on my truck and fit the first time I can feel the brakes but I'm switching to hydro boost so if feel is affected how do I change this? Mines an 86 Chevy shortie
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[gringoloco]

Any tricks of the trade for stabilizing a solid axle over mid-corner bumps?
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[robnolimit]

http://youtu.be/OWnW2VkgfVY Hellboy in action.

[robnolimit]

Originally Posted by gringoloco

Any tricks of the trade for stabilizing a solid axle over mid-corner bumps?
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Front or rear? what year?

[gringoloco]

Originally Posted by robnolimit

Front or rear? what year?

Rear, in a 67-72. I know this is an inherent issue with a solid axle vs IRS, just wondering if there is anything that can be done to 'tame' the unsettling on less than perfect surfaces mid corner. Seems like the other modifications made to increase handling (poly arm bushings, longer panhard, anti-sway bar) will reduce articulation of the axle and contribute to the 'skipping' feeling.

[robnolimit]

OK, some yes, some no. First off, I'll say that I'm not a big fan of urathane in the trailing arm bushings. It's one of the only spots I'd say no to. If I was going to change the front pivit, I would fab in a uni-ball (steel) or a Monster-ball (delron lined) This would allow full articulation without any axle shift. If you don't want to do that, stay with the rubber here. Second, almost every spring and shock I've seen is too stiff, WAY too stiff for a goood handling vehicle, of any kind. Lets face it, we're not going to the high banks at Daytona. Food for thought, a stock rear spring has appx 600 lb/in, where as my Hellboy truck currently has 150 lb/in springs. I am looking into 'A' body springs to check out compression hieghts vs. spring rates, to see if we can make use of them. The longer panhard rod, especially if it is a low mount unit, will help eliminate the side-skip. And, if the springs and shocks were correct, then the swaybar could do it's job, and you'd never feel the bump. A mercedes 550 can do it, why not us?

[jayman68]

Originally Posted by gringoloco

Any tricks of the trade for stabilizing a solid axle over mid-corner bumps?
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Originally Posted by gringoloco

Rear, in a 67-72. I know this is an inherent issue with a solid axle vs IRS, just wondering if there is anything that can be done to 'tame' the unsettling on less than perfect surfaces mid corner. Seems like the other modifications made to increase handling (poly arm bushings, longer panhard, anti-sway bar) will reduce articulation of the axle and contribute to the 'skipping' feeling.

Good question!

Thanks for the info Rob, let us know about the 'A' body springs.