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surlyjoe
08-14-2013, 10:12 AM
Looking for advice on my 71 c10. I have been reading a few of Ron Sutton's posts on brakes and how to build a balanced system and have a few questions. This truck is a budget build for the most part. Forgive me on some of the details as I have just been given the green light on the project.

My truck is 71 long bed, hoping to convert to short bed.
Coils in the rear. 4-6 drop, upgrade sway bar and track bar, good ps box. Basically upgraded stock.
I am not sure on the weight of the truck. It will have an ls of some description. ~3500lbs?
17 or 18 inch wheels. Performance tires but not extreme.
Main use will be as a driver, it might see an autocross once a year.
My goal is to have a nice driving truck that does everything well.

My current plan for brakes is to use stock later year 12" with d52 caliper. Stock caliper or maybe the willwood ones. For the rear I am open to options but considering the willwood floating caliper setup. I can use whatever master cylinder works best for the system and I am leaning toward power brakes to make it user friendly for other drivers.

What is a good front rear bias for a truck?
If using the 12" fronts described above which d154 rear caliper will work best with the system?
What brake number can this system achieve with optimal master cylinder and booster?

Thanks
Joe

GEARBOXGARAGE
08-14-2013, 10:45 AM
There is a good conversation going on in another thread (see link below) Post #22 from bovey gets into exactly what you're looking for. We're currently setting up a '66 C10 with Wilwood D52 front/D154 rear, and a '71 C10 with D52 front/Dynalite rear, but don't have any drive time yet to see just how much of a difference there is between the two. Remember to watch the front rotor thickness, as there are 2 different sizes, 1" and 1-1/4" thick, so make sure you reference the corresponding D52 size.


https://www.pro-touring.com/showthread.php?101080-Soft-Pedal-vs-Axle-Runout-solutions-Willwoods-(fixed-callipers)-on-a-12-bolt-GM/page2

-Mike

Ron Sutton
08-14-2013, 11:36 AM
Hi Joe,


Looking for advice on my 71 c10. I have been reading a few of Ron Sutton's posts on brakes and how to build a balanced system and have a few questions. This truck is a budget build for the most part. Forgive me on some of the details as I have just been given the green light on the project.
So ... your wife said it was ok? :lol:
I know EXACLY what you mean. :)

My truck is 71 long bed, hoping to convert to short bed.
Coils in the rear. 4-6 drop, upgrade sway bar and track bar, good ps box. Basically upgraded stock.
I am not sure on the weight of the truck. It will have an ls of some description. ~3500lbs?
17 or 18 inch wheels. Performance tires but not extreme.
Main use will be as a driver, it might see an autocross once a year.
My goal is to have a nice driving truck that does everything well.

My current plan for brakes is to use stock later year 12" with d52 caliper. Stock caliper or maybe the willwood ones. For the rear I am open to options but considering the willwood floating caliper setup.
The Wilwood D52 & D154 calipers make for great street brakes. They're beefy, billet aluminum, powder coated red or black, have stainless steel pistons, come in big enough piston sizes you can make them work well without going to race pad compounds ... and they're floating, so no pad knock back issues.

I can use whatever master cylinder works best for the system and I am leaning toward power brakes to make it user friendly for other drivers.
I'm going to suggest the 1-1/8" Wilwood dual M/C on a booster.

What is a good front rear bias for a truck?
In the chart below, I am "pretty sure" the stock chart is correct, but I could be off on the amount the rear drums produce. Regardless, I think you'll end up happy somewhere around a 70/30 brake bias split. FYI: Most cars are closer to 65/35.

If using the 12" fronts described above which d154 rear caliper will work best with the system?
What brake number can this system achieve with optimal master cylinder and booster?

Thanks
Joe


I worked out three options in the chart below. All use the 11.88" rotor & dual piston Wilwood D54 caliper in front ... and 12.19" rotor & dual piston Wilwood D152 caliper in rear.

Option #1 is with the D152 calipers in rear with the tiny 1.125" pistons. This combo increases your braking force about 9%. The front brake bias may be too much & I do NOT suggest putting an adjustable proportioning valve on the front.

Option #2 uses the D152 calipers in rear with the larger 1.625" pistons. This would create too much rear braking force, which is easy to balance by placing an adjustable proportioning valve in the rear system. Chart #2 shows the raw brake bias as 60.6/39.4 F/R ... and below it, shows the adjusted numbers to achieve a 70/30 balance. After balancing, this combo will provide a total braking force of 2944#. This increases your braking force by 19% over the stock brakes 7 be a pretty good street brake system.

Option #3 is the same as #2 ... but with 1 step up in brake compound ... from BP-10's to BP-20's. This option would provide a total braking force of 3346#. That is 35% more braking force than stock. I feel this may be on the edge of being too aggressive for a street driven pick up.

My suggestion is Option #2 ... with the BP-10 pads ... and if after you drive it some, if you feel you want or need more aggressive braking, you can always upgrade to the BP-20 pads.

Let me know if you have questions.



80840

Ron Sutton
08-14-2013, 11:38 AM
There is a good conversation going on in another thread (see link below) Post #22 from bovey gets into exactly what you're looking for. We're currently setting up a '66 C10 with Wilwood D52 front/D154 rear, and a '71 C10 with D52 front/Dynalite rear, but don't have any drive time yet to see just how much of a difference there is between the two. Remember to watch the front rotor thickness, as there are 2 different sizes, 1" and 1-1/4" thick, so make sure you reference the corresponding D52 size.


https://www.pro-touring.com/showthread.php?101080-Soft-Pedal-vs-Axle-Runout-solutions-Willwoods-(fixed-callipers)-on-a-12-bolt-GM/page2

-Mike

Hi Mike,

I asked Joe to start another thread, so we didn't hi-jack Bovey's thread.

I'm glad you're enjoying it. Chime in if you have comments or questions. :twothumbs

bovey
08-14-2013, 07:52 PM
Okay, so I'm going to ask a similar question. Instead of giving you what I want to use or am using - let's blank slate it.

Rob from No Limit just made some interesting comments in my soft petal vs. axle end play and got me thinking.

Many of us run 67-72 GM trucks. Mine weights 3950 (no options) as it's a long box - short boxes are a bit lighter. Keeping the 5x5 stock bolt pattern to keep it simple - would you be able to give an ideal brake set-up to start? I think it's safe to assume 18" wheels as any smaller and the tire selection is limited (IMHO) and feel free to spec the rear-end, FF, etc. Most of us are street machines that will autocross a few times a year - just like Joe, just like me, etc.

Would you spec different parts for manual vs. assisted?

If this is an unfair question or does not have enough detail - feel free to ask for specifics or decide on them. I'm more than happy to do some homework if needed.

Cheers,
Bovey

Ron Sutton
08-14-2013, 08:26 PM
Okay, so I'm going to ask a similar question. Instead of giving you what I want to use or am using - let's blank slate it.

Rob from No Limit just made some interesting comments in my soft petal vs. axle end play and got me thinking.

Many of us run 67-72 GM trucks. Mine weights 3950 (no options) as it's a long box - short boxes are a bit lighter. Keeping the 5x5 stock bolt pattern to keep it simple - would you be able to give an ideal brake set-up to start? I think it's safe to assume 18" wheels as any smaller and the tire selection is limited (IMHO) and feel free to spec the rear-end, FF, etc. Most of us are street machines that will autocross a few times a year - just like Joe, just like me, etc.

Would you spec different parts for manual vs. assisted?

If this is an unfair question or does not have enough detail - feel free to ask for specifics or decide on them. I'm more than happy to do some homework if needed.

Cheers,
Bovey

Hi Bovey,

No worries. Answer these questions & I'll be back on here tomorrow.

I have a few questions. They might sound odd, but humor me please.

What will be the primary use of the truck?
Will you run AutoX or track days ?
What are your primary braking objectives?
What size & kind of tires will you run?
Do you have an overall braking goals?
Do you prefer to go manual or boosted?
Are you planning to run stock or aftermarket pedals?

.

bovey
08-14-2013, 08:34 PM
Nope. None seem odd. But it's really late here and I need to be up in, ugh. 5 hours. I'm going to think about these and reply tomorrow. Most are easy and I do have one question back at you. You ask about tires and not wheels/weight. Is there a reason? I'll be back asap.

GEARBOXGARAGE
08-15-2013, 03:38 AM
Hi Mike,

I asked Joe to start another thread, so we didn't hi-jack Bovey's thread.

I'm glad you're enjoying it. Chime in if you have comments or questions. :twothumbs




Ron,

No hi-jacking intended, so I apologize if it came across that way. Joe's questions seemed to fall inline with bovey's conversation so I though it would be helpful to point him in that direction.

Thanks,
-Mike

bovey
08-15-2013, 05:02 AM
Mike. Your question is great. It is highly related, and having it as it's own post will be better for other board members. And yeah - it has got me thinking. Sadly, this trucks section was not alive until after I had pulled the trigger on my upgrades... it's just money (lol... sigh)

Ron Sutton
08-15-2013, 06:39 AM
Ron,

No hi-jacking intended, so I apologize if it came across that way. Joe's questions seemed to fall inline with bovey's conversation so I though it would be helpful to point him in that direction.

Thanks,
-Mike

Hi Mike,

It did not come across that way. I just didn't want you to think we were ignoring you. :)

surlyjoe
08-15-2013, 07:05 AM
Thanks for the replies everyone. I am interested to see the blank slate answer. But for my needs I think option two that you outlined Ron will be on the money. Ron, thanks very much for your time spent on the calculations. A learning experience for sure. It appears as though you can have a pretty good brake system for not too much money which is cool.

Ron Sutton
08-15-2013, 07:53 AM
Nope. None seem odd. But it's really late here and I need to be up in, ugh. 5 hours. I'm going to think about these and reply tomorrow. Most are easy and I do have one question back at you. You ask about tires and not wheels/weight. Is there a reason? I'll be back asap.

You said you're going to run 18" wheels. If I know the width, I'll have a pretty good idea of weight. 5# one way or another is not the key, because we're already going to increase braking force significantly ... more than enough to account for these heavier wheel & tire combos. Vehicle weight is more important. And how much grip you have ... with tire width & type ... affects how greedy we can get on braking force.

tazzz25906112
08-15-2013, 09:22 AM
Ron is right on the money with some of his questions/points and you may also want to consider the type of pad compound you'll be running and the trade offs that some of them create as well.... Some of the brake companies will provide info if you call their tech/order lines,, but you'll have to know to ask the right questions in may cases... Follow Ron's advice as it'll most likely be very good.

Also with respect intended to Ron, double check with the brake manufacture that you chose that Ron's impute is constant with their systems and how they gauge usage... I know my driving style upon being seen/reviewed with one of my TA's resulted in the manufacture advising I change out a package altogether and after doing so,,, the brakes were exactly what I was after...

The point of all that is the impute of the intended use and being realistic about the braking systems capabilities over a group of intended use/s are as everything in life,,, trade offs.... Braking systems characteristics (strengths and shortfalls) are no exception...

Ron Sutton
08-15-2013, 09:30 AM
Thanks for the replies everyone. I am interested to see the blank slate answer. But for my needs I think option two that you outlined Ron will be on the money. Ron, thanks very much for your time spent on the calculations. A learning experience for sure. It appears as though you can have a pretty good brake system for not too much money which is cool.

Joe, your system was easy to figure out, because you already had a desired path with Wilwood's floating GM replacement calipers.

Bovey's request to build a blank slate brake system will be MUCH more involved, as there are a lot of good brake companies out there. I don't want to trivialize the work & technology all the smart brake guys utilized to build good parts & systems ... but when you're comparing the 6-10 top brake brands against each other ... and they'll all really good in the key areas of brake performance ... then personal preferences come into play.

It reminds me of spark plugs, oil & beer. There are a lot of good brands. Every guy has his own preference & he'll spend hours telling you why his oil, beer or spark plug is "the best". We have dyno tested and/or raced dang near every kind of oil & spark plug you can imagine ... and in the end, there are often a few inferior products with more hype than performance ... but usually a lot of top brands that all work great.

As far as beer goes, I am doing my best to try them all too. :lol:

For street brakes, I think a person needs to consider Baer, PBR/Kore 3, Wilwood, SSBC & possibly other big & small brands I'm didn't mention. AFCO is coming out with newly designed stuff soon. Several companies make direct replacement GM calipers but with different piston sizes, including AFCO, Wilwood, Howe, etc. For racing brakes, a person may want to consider Wilwood, AP, Brembo, PFC, Alcon & many smaller brands.

So if several companies all make systems that will achieve the braking goals you have ... at some point, style, brand name, personalities, allegiances, etc ... come into play. Price obviously comes into play. But people pay more for what they want every day. If price was the only thing that mattered, we'll all own & drive Yugos. For some people, if 3-4 systems all look to perform the same, they will then buy the one costing less. Others will spend more money to get a brand they like, or a style that looks cool, or deal with a person they bonded with, etc, etc.

There is no formula or calculation for these personal preference things. :)

Some factors often overlooked at the time of purchase ... but that I think are important in a Pro Touring brake system ... in my opinion ... are:
Variety of pad compounds available & their characteristics
Brake pad wear & cost
Rotor wear & cost

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I have a story for you ...

Decades ago, I bought an Epson laser printer for $600. It was mid-priced in the market then. Cartridges were $99. Then cartridges went up to $129 ... then $149 ... then $199. Epson had their printer buyers "captured" ... and in my opinion ... were taking advantage of their customers. The next time we went to buy a cartridge for it ... three years later, they were $249 ... which I could not bring myself to pay. I was pissed. By that time, equal quality laser printers were on the market for $300 .... with a cartridge.

But I learned my lesson ... and researched how cartridges were priced by different companies ... for their older models. HP didn't raise the prices of their cartridges for their older models. I bought a HP printer ... have been happy with the cost of operation ... and bought many more HPs over the years.

---------------------------------------------------------------------------------------------------------

The moral of this story is ... if money matters to you ... to pay attention to TCO ... Total Cost of Operation ... and not just the initial cost of purchase. Buying brakes is not like buying a set of cylinder heads. You may have those cylinder heads on your engine for years & require no service. But brakes wear ... requiring routine pad & rotor replacement. Initial cost is important, but my advice is to look at the bigger picture. Brake pads & rotors are wear items. What are those going to cost you year after year?

I see brake pads with premium prices ... because of the model of car or caliper they're for ... and the same compound pad is substantially less for a different car or caliper. The reasons can be based on lower production volumes ... or because the car is high end ... or the caliper uses a unique Epson cartridge ... I mean brake pad shape ... and they have you "captured". In the end ... you don't care "why" they're charging you more ... just that they are.

My suggestion for guys on limited to modest car budgets is ... before committing to a brake system ... research how many pad compounds are available for this caliper. Is there adequate range for what you're doing ... and how much $ are they? Compare costs of the same pad across several different calipers. That will be enlightening. (Yes, pad volume matters, and this will be enlightening for you also.)

Same with rotors. Rotor options really range in features. More so than most guys know. Material plays a big role in the cost. Better material costs more money. Sizes, slotting, drilled holes, type of vanes, processes, etc ... all play a role in price. If you can afford it ... I think you should spend the money to get the quality of rotor that will serve you best & last longer. When you figure out your needs ... and understand what you're looking for in rotors (just like pads) ... do some comparison shopping.

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In my experience & just my opinion ... I think the factors that should guide our buying decisions are ... in order of priority:
1. Performance
2. Initial cost
3. TCO
4. Personal preferences

Think of it this way ... If the brake system won't meet you performance needs .... none of the other stuff matters. For the systems that do meet your needs ... what systems can you afford to buy within your budget? Of those ... which ones will cost you more & which ones less ... over the years (TCO). And when you have it narrowed down to more than one system ... that meets your performance needs & budget ... then personal preferences should simply be the final deciding factors.

Again, just my opinion. I'd be interested to hear other opinions & ideas ... as long as this doesn't devolve into negativity.

Ron Sutton
08-15-2013, 09:31 AM
Ron is right on the money with some of his questions/points and you may also want to consider the type of pad compound you'll be running and the trade offs that some of them create as well.... Some of the brake companies will provide info if you call their tech/order lines,, but you'll have to know to ask the right questions in may cases... Follow Ron's advice as it'll most likely be very good.

Also with respect intended to Ron, double check with the brake manufacture that you chose that Ron's impute is constant with their systems and how they gauge usage... I know my driving style upon being seen/reviewed with one of my TA's resulted in the manufacture advising I change out a package altogether and after doing so,,, the brakes were exactly what I was after...

The point of all that is the impute of the intended use and being realistic about the braking systems capabilities over a group of intended use/s are as everything in life,,, trade offs.... Braking systems characteristics (strengths and shortfalls) are no exception...


Thanks for the input Albert !

.

Wes.Drelleshak
08-15-2013, 11:55 AM
Ron,
What about the difference between caliper bore size, master bore size and brake line size? Can you give us your thoughts on how all three inter mix?
How about brake fluids? min boiling point, DOT 3 and 4. type? etc...... I would be highly interested to here your opinions on the subject.

GEARBOXGARAGE
08-15-2013, 05:25 PM
Ron,
What about the difference between caliper bore size, master bore size and brake line size? Can you give us your thoughts on how all three inter mix?
How about brake fluids? min boiling point, DOT 3 and 4. type? etc...... I would be highly interested to here your opinions on the subject.

X2 on Wes' questions, plus adding in with pedal ratios and how they can affect system efficiency.

-Mike

andrewb70
08-15-2013, 05:39 PM
Ron,
What about the difference between caliper bore size, master bore size and brake line size? Can you give us your thoughts on how all three inter mix?
How about brake fluids? min boiling point, DOT 3 and 4. type? etc...... I would be highly interested to here your opinions on the subject.

I can hopefully chime in with a little bit of tech. The bigger the total caliper piston area, the greater the braking force that will be applied to the pad, and hence the rotor.

The MC size determines the pressure that the caliper will see, given a certain force that is applied to it via the pedal. The smaller the bore, the greater the pressure. However, there are trade offs. The smaller the bore MC, the more pedal travel is required to pump the same volume of fluid, and vice versa.

That's it for my tech...LOL...I am sure that Ron will chime in later.

Andrew

andrewb70
08-15-2013, 05:44 PM
X2 on Wes' questions, plus adding in with pedal ratios and how they can affect system efficiency.

-Mike

Pedal ratio plays a role in the amount of force that is transmitted to the MC. If you had an arrangement where you were pushing directly at the MC, the MC would see the same force that your foot is able to generate. I saw in Ron's charts that he uses 150lb of force, which seems totally appropriate for a healthy male. However, applying 150lbs of force to the MC is not enough to generate the kind of pressure that a caliper is required to function properly. This is where the pedal ratio comes in. On my 1970 GTO, the pedal ratio is roughly 6:1. Essentially what we are doing is using a lever to increase force to the MC. So when I apply 150lbs to the pedal, given a 6:1 pedal ratio, the MC will see 900lbs of force. The pedal ratio is also a compromise between pedal travel and ratio. Increasing the pedal ratio will increase the pedal travel, and vise versa.

Andrew

Ron Sutton
08-15-2013, 06:13 PM
Ron,
What about the difference between caliper bore size, master bore size and brake line size? Can you give us your thoughts on how all three inter mix?
How about brake fluids? min boiling point, DOT 3 and 4. type? etc...... I would be highly interested to here your opinions on the subject.

Hi Wes,
Great questions in short post. The answers may get a lot longer. :)

Let’s take them one at a time, not necessarily in order.

--------------------------------------------------------------------

Brake line size has no effect on brake line pressure or braking force. So brake line size is a moot point in calculating brake systems. Drum brakes require more fluid to operate. More fluid volume through a smaller line increases the frictional losses, so some auto manufacturers used 1/4" brake line for reduced frictional losses with the higher volume of fluid needed. Some manufacturers did not & stuck with 3/16”. Just differences in engineering viewpoints.

A bad side effect of larger diameter brake lines is increased expansion, especially in the flex hoses. This creates a “spongy” feeling in the brakes, reducing brake responsiveness & overall braking to a degree. Since all the race & performance cars I work with have discs on all four corners, I’ve never ran or recommended anything other than 3/16” brake lines. Even the brake fluid recirculators run 3/16” lines.

While we’re on brake lines …
You want to run as much of your brake lines as possible in “hard line” … and the shortest flex lines possible … to reduce “spongy pedal”. In my race cars inches matter. For Pete’s sake … don’t run rubber hose for brake flex lines on performance & race cars. Always run quality, Teflon lined, aircraft style flex hoses to the calipers. Make them as long as they need to be … but no longer. Also, don’t use flex hoses … event the good stuff … in other places “just because it’s convenient.” The less flex hose, the better the pedal pressure & brake responsiveness will be.

I occasionally hear PT guys discussing soft pedals, weak braking and/or long pedal travels. The discussions cover a lot of good things, but often don’t get into flex lines, because many aren’t away they play a role in all of this issues.

--------------------------------------------------------------------

I reworded your question to: “What about the difference between caliper bore size & master bore size?”

Obviously master cylinder piston size & caliper piston sizes play a huge role in determining the overall braking force in a brake system. Simply put smaller master cylinders and calipers with bigger pistons create more braking force. Problems can occur when who ever is making the brake component decisions goes too small on the M/C side for the large-ish caliper piston area being used. Or, said another way, problems can occur if they go too big on the caliper piston area for the small-ish M/C being used.

This is somewhat self policing for knowledgeable brake designers, because working up a brake system with a big pedal ratio … small master cylinders … and big piston area calipers … will usually create too much braking force. You know the old saying, “a little bit of information can be dangerous.” I think they wrote that about brake systems. Which is why I think brake companies don’t post brake formulas on their websites or in their tech books.

Brake rookies can get themselves in trouble trying to get a “meaner” brake system if they combine a big pedal ratio & a M/C of too small volume for the volume of the pistons in the brake calipers.

I think of it like this: The fluid volume in the lines is going to stay a constant. It’s moving back & forth in the lines with the pedal … but the volume in the lines is the same. The single master cylinder (front or rear) … or the half being used in a dual unit … has to have enough piston volume to travel ALL of the caliper pistons on that end of the car … far enough to firmly compress the pads to the rotors.

The bore & stroke of the master cylinder piston determines its volume capacity. (Don’t confuse this with reservoir capacity) If you go to small on the piston size, you run out of travel before you build optimum pressure. The brakes still work. They just can’t travel far enough to build optimum pressure. I’ve heard, but not experienced, that some M/C’s have air issues if they travel too far. They offer some master cylinders with longer strokes, but that is a band aid in my opinion, as that just makes the pedal travel longer.

I suspect everyone picked up on the fact that bigger pedal ratios, smaller master cylinders & big piston area calipers all increase pedal travel with the increased braking force. Long pedal travel is not a bad thing … in moderation. And you don’t want your pedal travel so short the brakes act like an “on/off” switch. You want to be able to modulate the brakes, and that requires feel & moderate pedal travel.

Two common brake system mistakes:
1. Building a system utilizing brake calipers with small piston area & large master cylinders … and having to use big rotors & aggressive race brake pad compounds to achieve the desired braking force. The pedal travel is too short, brakes are too touchy, the aggressive race pads wear out quicker & they wear the rotors out quicker … adding unneeded costs for frankly just moderate stopping power.

2. Building a system trying to get good braking force … utilizing brake calipers with too big of piston area and/or too small master cylinders … because they weren’t clear on how important brake pad compound & rotor size are to the total package … and end up with master cylinder & brake line pressure issues.

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Brake fluid. Oh boy. Brake fluid is like beer, spark plugs & oil. Ask 10 guys & you’ll get 13.5 opinions. :)
I have my own philosophy about brake fluid, based on all my racing experience.

My brake fluid strategy is this:
a. Run a brake fluid with a slightly higher boiling temp than you need.
b. Flush the brake fluid regularly for optimum performance and less problems.
c. Spend as much as you need to achieve “a” … so you don’t have problems.
d. Don’t spend more money than you need, so doing “b” doesn’t feel wasteful.

I share some real world examples. Some may surprise you.

In our 1100# USAC Midgets, they corner so well, with such corner speeds, the amount of braking is very low. After a 40 lap main event, our crew pyro’s the rotors immediately & the hottest brake rotors are around 300°-350° on our fastest cars. If the rotor temps were hotter than that … we had driver or handling issues … and the car’s performance was off.

For these cars we used Castrol GT LMA brake fluid with a dry boiling point of 446°. We changed it during service before every race weekend & never had a problem. It cost about $10 a quart. Not $10 a pint … a quart.

In our 2550# NASCAR Modifieds we ran modern high travel/low roll suspension set-ups that required softer braking for optimum corner speeds. After a 40 lap race, the front brakes would read 450°-500° and the rear brakes 300°-350° … again on our fastest cars. Higher brake temps meant problems. For the Mods, we ran Wilwood 570° brake fluid, costing about $10 for 12oz, replacing it during service for every race weekend. Never a problem.

For the 2900# NASCR Late Models, optimum brake temps were 600° front & 400°-475° rear. We typically ran Motul 600 here … about $18 a pint … & changed it in between every race weekend.

In the GT1 & Trans Am cars, the braking is intense & you can’t mess around. You’re braking hard, often & for a lot of laps. Brembo LCF 600+, AP 660, Motul 660, Wilwood EXP 600 & Endless RF-650 are the brake fluids that work here. Way more money. Still changing it every race.

Why change the brake fluid so often?
a. Heat affects it, braking it down.
b. Moisture kills the boiling point.

Yes moisture gets into “sealed” brake systems. Condensation forms inside the brake lines. Add heat to that & you get steam. Just 3% moisture content drops most brake fluids boiling point in half. Racers & teams that don’t change the brake fluid often enough have braking problems. Fresh brake fluid performs closer to the dry boiling temp. Older brake fluid performs closer to the wet boiling point.

I am not suggesting you change your street car brake fluid this often. Unless you run hard at the track. If you take your “street car” and drive it hard at a road course race track … it is now a race car. For sake of safety & track performance, you’ll want good brakes with no fade.

Castrol SRF is crazy expensive, but is the best at resisting moisture saturation. This is the best brake fluid for guys that don’t want to change it as often & can justify the price. You can see this in the chart below … Castrol SRF has the highest rated wet boiling point.

The “wet boiling point” is a test where the fluid is left exposed for a set time & then tested. The “dry boiling point” is when the brake fluid is new & fresh out of the container.

--------------------------------------------------------------------

Here is my most recent brake fluid chart I use. I update it yearly if new product comes out.

80894

Ron Sutton
08-15-2013, 06:20 PM
Pedal ratio plays a role in the amount of force that is transmitted to the MC. If you had an arrangement where you were pushing directly at the MC, the MC would see the same force that your foot is able to generate. I saw in Ron's charts that he uses 150lb of force, which seems totally appropriate for a healthy male. However, applying 150lbs of force to the MC is not enough to generate the kind of pressure that a caliper is required to function properly. This is where the pedal ratio comes in. On my 1970 GTO, the pedal ratio is roughly 6:1. Essentially what we are doing is using a lever to increase force to the MC. So when I apply 150lbs to the pedal, given a 6:1 pedal ratio, the MC will see 900lbs of force. The pedal ratio is also a compromise between pedal travel and ratio. Increasing the pedal ratio will increase the pedal travel, and vise versa.

Andrew

You're on this like white on rice. :)

Just an FYI ... I normally use 100# of foot braking force as a "baseline" for calculating manual brake systems ... unless I know the driver is small, young, etc.

In these charts for his truck ... I used 150# to simulate boost from the vacuum booster, because I don't have a place in my spread sheet for booster input. I don't assume 150# is spot on accurate ... but as long as I keep it constant through all the comparisons for a specific vehicle ... we still see accurate comparisons from option to option.

andrewb70
08-16-2013, 05:21 AM
You're on this like white on rice. :)

Just an FYI ... I normally use 100# of foot braking force as a "baseline" for calculating manual brake systems ... unless I know the driver is small, young, etc.

In these charts for his truck ... I used 150# to simulate boost from the vacuum booster, because I don't have a place in my spread sheet for booster input. I don't assume 150# is spot on accurate ... but as long as I keep it constant through all the comparisons for a specific vehicle ... we still see accurate comparisons from option to option.




Ron,

I seem to recall that I used 100lb as well, when I was doing the calculations for my system, which is manual. I don't really want to get into a debate between manual and power brakes, but I would just like to say that I love my manual brakes. Everyone has a preference, but there is just something magical about manual brakes. The feel is so linear and the feedback is so precise that it really makes a car easier to drive and more enjoyable. With a manual brake system, the harder you press on the brake pedal, the harder the car will stop. There just isn't any other way to describe it.

Ron, I know that my next question is not exactly precise, and maybe I won't even ask it directly, however, can you please discuss pressure at the caliper? In other words, is there a desired pressure level that the caliper should see given say 100lb of foot pressure? Is there a maximum? I know this is all terribly vague, so this is why I am hoping that you will just discuss it.

Thanks,
Andrew

surlyjoe
08-16-2013, 07:16 AM
My preference would be manual brakes. But I think having power assist will make it easier for the odd time someone else drives the truck. As I typed that I was thinking why am I making it easier for someone else to drive?

Ron, for my setup if I went manual would a smaller master cylinder then be required?

Ron Sutton
08-16-2013, 07:46 AM
Hey Andrew,


Ron,

I seem to recall that I used 100lb as well, when I was doing the calculations for my system, which is manual.
I find 100# is a good number for most adult males. That is a moderate amount of leg force. Of course in race teams, we tweak & adjust the system to fit the driver's preference, but 100# is a good starting point. It's not "touchy" ... nor do they have to over exert themselves. I don't want the brake system tiring a driver over the course of 30-60 minute road race.

I don't really want to get into a debate between manual and power brakes, but I would just like to say that I love my manual brakes. Everyone has a preference, but there is just something magical about manual brakes. The feel is so linear and the feedback is so precise that it really makes a car easier to drive and more enjoyable. With a manual brake system, the harder you press on the brake pedal, the harder the car will stop. There just isn't any other way to describe it.
If there was a debate ... you & I would be on the same side of it. In my mind power brakes are for cruisers & hot rods, not track cars. The feel on manual brakes is the key. You have way better modulation control.

Ron, I know that my next question is not exactly precise, and maybe I won't even ask it directly, however, can you please discuss pressure at the caliper? In other words, is there a desired pressure level that the caliper should see given say 100lb of foot pressure?
I know this may sound a bit odd, but I don't "focus" on pressure at the caliper. Of course, it matters ... and I check it ... but it's not my guiding light. My focus is on achieving the net targeted braking force on each end of the car. And I just check to make sure we're not in a danger area.


Is there a maximum? I know this is all terribly vague, so this is why I am hoping that you will just discuss it.

Thanks,
Andrew

You have to get pretty small with the M/C (5/8") to see 1000# with 100# foot pressure. But in a panic stop with 200-250# of foot force turns into 2000-2500# of hydraulic pressure in the lines. That's a lot & into a danger zone.

I am used to working with high quality race calipers ... and as long as I am ... I don't worry about anything 2000# & below for panic stops ... but the normal operating pressure is half that. Frankly, at those high pressures I am more concerned about the hoses & fittings. Sometimes a racer or team will run some aircraft aluminum swivel fitting in the brake system. That's a crash waiting to happen. But when I am working with an OEM caliper or "less than race quality" caliper ... and we're working with 700#+ of line pressure with 100# foot pressure ... then in a panic stop it could be 1500#+. Anything over 1600# & I'm talking to the caliper manufacturer and/or making changes.

As I covered in the conversation about brake lines ... I do care about loss or pressure through flex line expansion. So always buy quality teflon lined aircraft quality lines & keep them as short as you can. 3/16" hardline for everything else.

Lastly, for PT street & track car brake systems, I believe trying to achieve optimum braking with calipers of small piston area is not the best route. If the piston area is small ... you have to achieve braking force through higher line pressures & aggressive race compound pads. For PT street & track car brake systems, most of us need 3000# to 4000# of braking force. I can build a system with over 5000# using stock GM calipers. I think we're over complicating this sometimes.

I prefer systems with larger piston area calipers ... where you can run moderate brake line pressure & "street" compound pads. This is safer, stops the same & costs less to maintain. Just my 2˘

Ron Sutton
08-16-2013, 07:51 AM
My preference would be manual brakes. But I think having power assist will make it easier for the odd time someone else drives the truck. As I typed that I was thinking why am I making it easier for someone else to drive?

Ron, for my setup if I went manual would a smaller master cylinder then be required?

Joe,

Do us a favor. Go measure your current brake pedal.

I need the dimensions from ...
a. Center of pivot to center of foot pedal
b. Center of pivot to center of M/C pushrod mount hole
If there is a second "non-used" M/C pushrod mount hole ... I want that # too.

.

surlyjoe
08-19-2013, 05:58 AM
I finally got a chance to take some measurements.

Pivot to center of pedal was 11.5". Pivot to mc hole was 8.75". There is only one mc hole that I can see.

Ron Sutton
08-19-2013, 07:45 AM
Hmmmm. That doesn't compute.

Can you stick your phone in there & take a side view shot & post it?

surlyjoe
08-19-2013, 08:09 AM
I can, not till later though. I just reread the measurements you wanted and I did them wrong. Sorry two kids that won't sleep has me feeling like a zombie lately. I will get correct measurements tonight.

RobNoLimit
08-19-2013, 03:33 PM
Here's some info to help out. For a '67-'72 C10 (or bigger) the OEM ratio is 6.33-1. Pedal pivit to the center of the pedal head is 14.25". Pedal pivit to the brake input rod hole is 2.25". On most aftermarket power brake kits it is recomended to drill a new hole 1" down on the pedal arm, at 3.25" from the pivit. This nets a 4.38-1 ratio. Also, a lot of aftermarket kits will have a bind if simply bolted into the stock hole, and eventually it will crack the plastic input shield.

surlyjoe
08-20-2013, 06:19 AM
Thanks Rob. I came up with 14" and 2.5", but that is trying to measure the pedal in the truck. My pedal has one hole only, not sure if any came with two.

bovey
08-20-2013, 08:11 PM
Blank Slate - I warn you, this is long. I wanted to answer your questions clearly and give you a good idea of how I build and drive. Thank you in advance for your knowledge - I like many other am grateful for your wisdom and help... wish we had this chat 5 months ago.

Quick truck review:
1971 GMC 1500 - long box. It will always be a long box - it will never, ever be a shortie.
Last weight in - 3950 lbs - 4110ish lbs with driver.
427 LSX/AFR225s/BS3/t56 Magnum/Spec3+
3:73 Auburn limited slip
Stock rear-end, but looking into a full floater OR your reco.
I do plan on keeping the suspension simple. I plan on doing a chassis for the truck and am trying to avoid dumping a lot of cash into my current set-up.


1) Primary Use
Primary use of the truck is street duty - it needs to be at home in rush hour traffic as it is on a track, or best it can be. I put up with a lot, manual everything, no A/C in a black on black truck living downtown in a city that has worse traffic than LA. It does have power steering now that I'm autoX it.

I built this truck to drive - no trailers. Parts and combinations are selected on toughness to get me to the track - race - an get home.Sometimes the drive to the track can be days. I've only ended up on a flatbed once - after driving 2600 miles to run the Maxton Mile and blew a pulley tensioner 15 miles from home. I'd like to add it was not the tensioners fault...

Out of interest. As of this week-end, I've owned this truck for 25 years (first 8 building it). 95% of the time I'm on major highways. I've personally put 145 000 miles on the truck - only changed the brake shoes once - the rear drums look like they have never been used, and the stock front rotors are still on the truck which has 200 000 miles on it. Even the rubber brake pedal looks like new. On serious road trips it sees 1000 miles a day, but those days are done with a 1 year old, so let's race it. It's either open road at high speed, serious traffic or a race track situation - just trying to give you an idea of my driving characteristics.

2 and 3) Primary Braking Objectives/ autoX vs. Track Days

I'm not 100% sure how to answer this. But here goes. It's a street machine - the truck will see both autocross and track time - run times can vary between 50/60 seconds and 15 minutes - based on experience so far and the race events that happen in my area. Track size varies between 1.5 and 2.5 miles in length.

Here is a link to two tracks I run - make sure you use satellite mode.
https://maps.google.ca/maps?ie=UTF-8&q=canadian+tire+motorsport+park&fb=1&gl=ca&hq=canadian+tire+motorsport+park&hnear=0x89d4cb90d7c63ba5:0x323555502ab4c477,Toront o,+ON&cid=0,0,6723439528136509502&ei=ITYUUtXIL8fd2QWxuYCoAg&ved=0CJMBEPwS

I think I'm up for changing pads at the track (needs to by quick/easy), as I'm changed the tires anyway - BUT if there is a pad for both street and track that would be ideal. But the noise of even Hawk HP+ pads does annoy me - but I'm trying to get over it.


3) Tires
Street - 18 or 19s - wheels and tires will be as wide as I can go with a stock chassis. Rear will receive a small tub. OPEN TO TIRE RECOS.

Front
9.5" or 10" wide wheel
275/285/295 - depends on manufacturer

Rear
11" - 12" wheel
335-ish - more concerned with height - aiming for 27/28" tall


Race - 18" - Toyo 888s - maybe Hoosier A6 or R6 or G-Force Rival (Rivalsizes not great for my application).

Front - Toyo R888
9.5" or 10" wide wheel
285/30/18 - 24.8" D - 11.3" Overall width - stiff wall
295/30/18 - 25.1" D - 11.8" Overall width - stiff wall

Rear Toyo R888
11" or 12" wheel
335/30/18 - 26" D - 13.3" Overall width


4) Over all braking goals. I may have answered this in 3. But I want to maximize the braking potential, but this vehicle is dual purpose - yes, I know, a compromise. I want to make it as track ready as I can, BUT it must remain drivable and safe on the street. I bolt my 1 year old son into
it. It's my only vehicle.

5) Manual - I like the feel of it. Unless you object.
Besides if I wanted it to drive like a new car, I'd buy a new car.

6) Stock brake pedals. But can modify. However, I plan on changing to after market pedals when I chassis it - If it's a came changer for you - I'd consider doing it now. HOWEVER, I do think for a majority of the board members, stock pedals would make this combo most useful. I'm very willing to be a tester.

7) Your follow-up question --- On the brake pedal, what is the distance from the center of the upper pivot to:

a. The closest master cylinder push rod connection hole
--- 2.5"

b. The second master cylinder push rod connection hole.
--- Nope - only 1 hole - but I own a drill press

c. The center of the foot pedal
--- 14"


NOTE: I have the ability, space and interest to build cooling ducts.

Cheers
Bovey (and Trucky)
Yes, Trucky, my girlfriend, now wife named "him" years ago. And. It. Stuck.