Winter Project – Converting Front Axle Drum to Disc

[Indycars]

I'm converting from a 2-bend axle with drum brakes to a 4-bend axle with disc brakes. It makes sense to order everything from one place so if something does not fit, it will be easy to remedy the problem, everything will be coming from Speedway. It presently has 1962 Econoline spindles and brakes that will need a new home in the near future.

The components ordered are .....

Spring Over Front Tube Axle, Chevy Spindle, 4 Inch Drop, Plain

Plain Chevy Wilwood Front Brake & Tradit. Steering Kits, 48 Inch Axle

Wilwood 150-8850K 7112 BP-10 Brake Pad Set, DLIII/BDL/FDL, .49 Inch

Super Glide® T-Bucket Front Spring, Standard Eye, Plain

Speedway Stainless 1-3/4 Inch Leaf Spring Front Suspension Pivot

Transverse Leaf Spring Shackles w/ Nylon Bushings, Stainless





I'm trying to stay with my manual 1" MC, so that's why I went with the 4 piston Wilwood caliper. My thinking was they will have more stopping power over the 2 piston or even the single piston, making up for the required higher pressures of a disc brake. If this doesn’t work like I need, then there is a proportioning valve. Test, make changes, restest.

This Single Piston GM caliper 4.4 SqIn [ I think is also an option ]
1978-88 GM Metric G-Body Brake Calipers, IMCA Approved, 7/16-20
Wilwood Disc Brakes - Caliper Part No: 120-8925

2 – Piston Caliper Piston Area = 2.4 SqIn [ This was an Option ]
Wilwood Disc Brake Kit 1949-54 Chevy Spindles, 2-Piston, Steel Rotor
Wilwood Disc Brakes - Caliper Part No: 120-10188

4 – Piston Caliper Piston Area = 4.8 SqIn [ My Calipers ]
Forged Dynalite-1.75/.380
Wilwood Disc Brakes - Caliper Part No: 120-6818

If you need to take a deep dive into brakes and enjoy numbers then this website is your place. You can download his Excel spreadsheet or I have included it below after I modified it to include an the addition of a 2nd system so you can compare two systems side-by-side.

BillaVista.com-Brake Bible Tech Article by BillaVista

If you want to download the Excel file from his website, this is what you are looking for. It’s a very long web page.

 

[old round fart]

I think the 1” bore master will be fine. Just about all the masters on Speedway and Spirit are 1” bore.

 

[AltBantam]

Wilwoods have a max psi of 1200. With a 1" MC and a 6 to 1 pedal ratio the MC is make 759 psi with 100lbs of foot pressure. At 200lbs foot pressure, it is 942 psi. The formula to calculate this is Pounds applied x pedal ratio x MC bore area. For 1" MC the area is .785". From what I have read before, 900 psi is the min for Wilwood brakes, which is why many people use smaller diameter MC, to increase psi. But since T buckets are lighter than most cars, it probably won't matter as much.

 

[Indycars]

Do you have any links? I didn't see any numbers for min/max pressures on the Wilwood website. I would be interested in reading more!

FYI,

 

[Indycars]

I want to mention that an excellent contact at Speedway is (Of Course) Rick in Tech Support at extension 0063. It’s far faster to go to Sales and then ask for his extension. Don’t go to Tech Support, you will be on hold for quite a while typically. You might have to leave your number and he will call you back.
Rick does not work on commission, he does like to talk and will spend time to research your questions. Tell him Rick from Yukon sent you. It’s an inside joke. LOL!
The image below is my original spring capture plate from 1979 and next to it the new one. It’s twice as thick at a ½”. It’s was tapped for 3/8-16 thread and will be attached with ARP SS 12 pt bolts, nuts and flat washers, the nuts are to lock it and keep it from coming loose. Nickle anti-seize will be used on the threads since it’s stainless.

The original ¼” plate was not strong enough as you can see how it was bending around the spring from being tightened.




I cut a relief for the spring curvature with a file, although once the spring is loaded it will be almost straight for those 3-1/2” above the capture block. I used my digital angle finder to set the block at ~ 7° and then tried to hold the file parallel with the vise jaws for my reference.



I started with some flap wheels 60 grit, then some 120 grit to get the spring surface somewhat smooth and ready for paint.




The flap wheel left some low spots, so I came back and block sanded with some 220/320 grit and WD-40. I only had to block sand the last 4-1/2" on the end of each leaf, it's the only part that will be showing or the Nylon Button will slide on.




I’m going to paint the spring with Cerakote “Black Velvet C-7300” and then “High Gloss Ceramic Clear MC-160”.
To make sure the spring works as freely as possible where the Nylon Button rides on the leaf below it, I will spray “Micro Slick C-110” by Cerakote to reduce the friction even further.




Later, time to let my fingers recuperate !
.

 

[Chief]

I'm impressed

 

[Indycars]

Thanks @Chief!

Where in Oklahoma are you? I'm in Yukon Oklahoma.

 

[Indycars]

Forgot to post the product links for my post #5, so here they are!

https://www.summitracing.com/parts/ARP-615-2500
https://www.summitracing.com/parts/ARP-401-8321
https://www.summitracing.com/parts/ARP-400-8537
Cerakote - MICRO SLICK DRY FILM LUBRICANT COATING (AIR CURE)
Cerakote - BLACK VELVET
Cerakote - HIGH GLOSS CERAMIC CLEAR
.

 

[409T]

Thanks for posting the links @Indycars. Too many people simply mention this or that and leave the reader struggling on the internet trying to find sources for the items used.

 

[Indycars]

It's easy enough to do, so why not !

 

[AltBantam]

Indycar, sorry for the late response. Below is the location of the article where I got the 900 psi from. I have seen different articles from different locations, etc. with minimums for Wilwood discs from 900 to 1000 psi. The article explains better than I could so....

Avoiding Common Mistakes: How To Make Your Street Rod Stop

 

[Indycars]

Wilwoods have a max psi of 1200.

The article stated:
To be effective, disc brakes require approximately 900-1,200 psi at the caliper.

Thanks for providing the link, it's appreciated !

The 900-1200 psi is only a recommendation not a maximum of 1200 psi. I think these numbers are
pretty much true for ALL disc brakes. They just take higher pressures than drum brakes.

 

[AusBucket]

The brake place I dealt with when I was building cars stated that pretty well all older cars with unboosted brake systems had a 7-1 ratio on the pedal.

 

[Indycars]

I just measured my pedal at 7.5/1.5=5. This is the reason why I went with the 4 piston calipers with 4.8 in² of
area over the other two possibilities of 2.4 in² and 4.4 in² of area. Time will tell whether this is enough to make
up for the pedal ratio of 5:1.

 

[AusBucket]

It will certainly help. A lot of people make a big deal over the amount of pedal travel when the ratios are approaching 7-1 etc. In reality the pedal actually moves a surprisingly small distance. By contrast the pedal on boosted systems in our every day drivers move quite a fair distance that goes unnoticed. If you need lots of pressure to apply the brakes, then you finish up with a very wooden (hard) pedal. The 6-1 (or better) ratio gives a feel that allows you to modulate the pressure, and is much nicer to use.

 

[AltBantam]

First, on my earlier post I stated brake pressure was calculated by multiplying Foot Pressure x Pedal Ratio x MC Bore area. Sorry, that's wrong, it is Foot Pressure x Pedal Ratio divided by MC bore area. Sorry, brain fart. 100lbs foot pressure on a brake pedal at 5 to 1 produces 500lbs of total force. Divide that by .785, if a Corvette 1" bore MC is used and the applied force to the brake pads is 637psi. The chart Indycars posted shows 633psi, so we know we are in the ballpark. The small the diameter MC you use, the higher force is generated. According to the chart above, a 7/8" MC will produce 833psi. So 200psi more with the same force. What does all this mean? A quick look on Google and the 'average' man can lift 220lbs on a vertical leg press (No age was given). That's approximately 110lbs per leg. If you are fit, that number should higher. Someone who works out could lift twice that. If you are like me, over 55, years of injuries so the legs are no longer as strong as they were 20 years ago... In a panic stop, I am sure I generate 150+ pounds of forces with my right leg. But I would not want to rely on that every time I took the car for a drive. And while I am sure others drive their t buckets with less than ideal brake pressure, I prefer caution when it coms to stopping. So at 60 MPH, do you want to stop within 120ft or 160ft?

 

[AltBantam]

AusBucket is right about pedal travel. Pedal travel is also determined by MC bore length. A shorter bore will change the pedal travel, as will proper bleeding of the system. The Wilwood MC that I have looked at have a 1.1" bore length. I have looked at OEM MC's which are less than an inch.

 

[Indycars]

Time will tell whether this is enough to make
up for the pedal ratio of 5:1.

I should have said ..... "Time will tell whether this is enough to make up for the pedal ratio of 5:1 and the reduced pressure to the front calipers.

 

[AltBantam]

You'll know pretty fast when you go to bed the pads on the Wilwood disc.

 

[Indycars]

I ran into some luck last week. I'm looking to make my 4 radius rods out of SS, but MG the cost is out of this world!!! So this is what I found for 7/8" OD x .083" Wall and .095" Wall.

You probably have one near you that sells cut to order pieces from a full stick (20 ft)

Oklahoma City | Metal Supermarkets
.083 Wall - $375 ..... .095 ($400 for 4 - 32" sticks) This is 8 inches over ½ a stick.

Continental Steel & Tube Co.
.095 Wall - $460 ......(Cut into 4 - 5 ft lengths)
Shipping is $100 and is included in the $460.

I called around locally and found Devin at Piping Alloys but he said they didn’t carry the size I needed. Couple days later I give up and call back to see if they had plain steel. No, they only carry SS. Their prices are essentially the same as Continental Steel for SS and there would still be shipping even thou they are local.

Devin calls me back about an hour later and says he found some that was not in the computer, AND HE WILL CUT IT TO ANY LENGTH I WANT. I bought 10 feet for $192 for 7/8” OD x .095 wall !!!!!!

I took him some Starbucks coffee to say thanks when I went to pickup the tubing.



I bought some threaded tube ends from S&W Performance Group. Yes, they are for .083 wall, but I will turn down the end that goes inside the tube by taking off about .012”. Or I can buy a 18mm drill and drill the tubing to fit the tube ends.

1/2” LH Threaded Tube End for 7/8" X .083 Wall Tubing ⋆ S&W Race Cars
1/2” RH Threaded Tube End for 7/8" X .083 Wall Tubing ⋆ S&W Race Cars
Threaded Tube Ends ⋆ S&W Race Cars