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Author Topic: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?  (Read 10176 times)

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Offline EP73Pinto

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I have a 73 Pinto with 4 x 4 1/4 bolt pattern that is used only for auto-x and hill-climb's. I'm going to convert to a 8" rear end so I can put in a locker. I would also like to convert to rear disc brakes. I'm not really interested in converting to a five lug setup. I have too many sets of 4 lug wheels to consider that. Is there a ford that came with the 4 lug 8" rear end that would be easy to pull parts from. It's important that they will fit inside the 13" wheels as well. I've tried searching and couldn't find anybody who has done this. Thanks.

Offline racer99

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #1 on: March 29, 2012, 09:01:47 AM »
I did a 7.5 with a traclok and discs in my old EP Pinto but we
ran 15x7s with cantilever sidewall slicks.
Worked really well.

To keep your 13s the rotors are going to be
small diameter for sure.
You might use the 7.5 disc components,fab a
caliper bracket to fit the 8 in. and turn down the rotors.

Or junkyard scrounge on some import stuff.

Offline D.R.Ball

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #2 on: March 29, 2012, 07:38:01 PM »
Use the parts off of a 1987-88 Thunderbird Turbocoupe and see if Carrie's still makes the bracket for the 8" rear end. Or try Speedway for one of theirs, also try Racer Walsh...See if you can find a copy of Car Craft with Turbo Joe's Poisonous Pinto they had a good write up of his Pinto with a parts list and sources.You still should be able to find a copy.

Offline EP73Pinto

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #3 on: March 29, 2012, 08:54:30 PM »
Thank you D.R.Ball. That's exactly the info I was looking for. :-)

Offline bbobcat75

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #4 on: March 29, 2012, 10:10:32 PM »
if you are able to do and do so, post some pics!! thanks
 
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1978 mercury bobcat wagon 2.3l - soon to have a 88 tc drive line
1975 ford pinto - drag car - 2.3l w/t5 trans - project car

Offline racer99

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #5 on: March 30, 2012, 08:49:15 AM »
I have the Poisionous Pinto article saved
on my laptop if you cant find it.

Here,use this.

http://pintopage.fordpinto.com/Poisonous%20Pinto.htm

Offline Bigtimmay

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #6 on: March 30, 2012, 12:04:55 PM »
Use the parts off of a 1987-88 Thunderbird Turbocoupe and see if Carrie's still makes the bracket for the 8" rear end. Or try Speedway for one of theirs, also try Racer Walsh...See if you can find a copy of Car Craft with Turbo Joe's Poisonous Pinto they had a good write up of his Pinto with a parts list and sources.You still should be able to find a copy.

Good luck with this option and trying to use a 13 cause a 14 inch wheel wont even clear smallest you can fit is a 15
1978 Mercury Bobcat 2.3t swapped.Always needs more parts!

Mike Modified

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #7 on: March 30, 2012, 02:09:09 PM »

Offline dick1172762

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #8 on: March 30, 2012, 03:02:34 PM »
Problem with a 71/73 Pinto is not the lack of brakes at the rear, but the lack of brakes at the front. Spend your money/time on a better set up front as they do 90% of your stoping on a race car when you've got both feet on the pedal. If you really must, look at a 85 (13B) RX7 rear brakes. I've raced RX7's with rear drums and rear disk, and it made little or no differance in the way it stopped.
Its better to be a has-been, than a never was.

Offline cossiepinto

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #9 on: March 31, 2012, 09:11:11 AM »
Try Speedway Engineering (different from Speedway Motors) at www.1speedway. com .  They sell a mini-stock full floater rear end for 8-inch components.  They also sell the same thing for 8 3/4 Mopar and Ford 9-inch.


I considered this rear end for my car, but decided instead on the mini quick-change with floating axles. 


They also sell rotor adapters for just about any configuration, will weld on your caliper brackets for you, etc. etc.


Lots of mini-stockers still use 13-inch wheels, per rule book, so they might just have the solution for you, so you can keep using your wheels.


They also sell hubs and rotor adapters for the Pinto spindle that match up to the floater.  I bought these for my car, too.  I'm attaching a pic of the wheel on my car, so you can see the hub's grease seal.


Good luck with your project!

Offline cossiepinto

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #10 on: March 31, 2012, 04:36:23 PM »
I found a pic of the front hub with the rotor adapter, rotor, and caliper in place.  Mine are for fitting 15" wheels.  You can call them to see if they can make adapters for 13" wheels.

Offline EP73Pinto

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #11 on: April 02, 2012, 04:13:52 PM »
The only reason I would like to convert to rear disc is to eliminate the difference in response time between disc and drum brakes. Drum brakes naturally respond quicker than disc brakes and are prone to lockup. The factory master cylinder is designed to counter this by sending brake fluid to the front brakes before the rear. I am changing to a reverse master cylinder pedal assembly. This assembly uses separate master cylinders for front and rear and doesn't account for the different response times. I'll look into the RX7 brakes. Thanks for all of your input.

Offline 71hotrodpinto

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #12 on: April 02, 2012, 04:19:41 PM »
I found a pic of the front hub with the rotor adapter, rotor, and caliper in place.  Mine are for fitting 15" wheels.  You can call them to see if they can make adapters for 13" wheels.

Slick setup. So was this custom or did you buy part numbers off the shelf to make this happen?
 I also have wheels that i dont want to have to change, yet to go to a standard wilwood setup i would have to get 5 lug wheels. Alot of extra effort and money that i dont need to deal with.
 Thanks for any help on this.
Robert


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Offline cossiepinto

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #13 on: April 03, 2012, 07:15:11 AM »
71 Pinto,
 
On one of my other posts you'll find the triple master cylinder set up I used (Tilton).  The pedals are overhung, with the master cylinders inside the car.  I used Wilwood Dynalite II calipers and the largest rotors I could fit inside 15" wheels.
 
The hubs are from Speedway Engineering ( www.1speedway.com ), and are 4.25 on 4 lug pattern (standard Pinto).  They fit Pinto spindles using standard Pinto bearings and races.  If you use GM calipers (common for the roundy-round racers), you can find caliper brackets that will bolt onto the Pinto spindles.  I tried several times to fabricate brackets for the Dynalites that were satisfactory, but was never happy with them.  Then Wilwood same out with a 2" dropped Pinto spindle that mate up GM-style caliper brackets (they use a 4-bolt bracket), and I adapted the Dynalites to those brackets.  This solved the problem I was having with trying to bolt up calipers that were parallel to the rotors.
 
As far as the original question on this string is concerned, the only unknown is whether Speedway Engineering has adapters for the hub-to-rotor for 13" wheels.  I've not tried to source rotors smaller than 10.75 inches.

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #14 on: April 03, 2012, 07:35:58 AM »
73Pinto,
 
One of the reasons drum brakes are popular on live axle rear ends (like the 8 and 9 inch Fords) is that drums aren't susceptible to axle end play like disc brakes are.  The axle end play knocks the disc brake pads back, so when you first apply the brakes, the brake pistons have to take up the extra slack before they start rubbing on the rotors.
 
The way to fix the problem is to use a different style axle-retention rear end (like the later Lincoln/T-bird) or to use a floating axle rear end like the racers use.  That's the rear end the Speedway Engineering sells. 
 
I did a lot of shopping around and finally decided on the Speedway Engineering rear for a number of reasons, not the least of which was the added benefit of the matching mini-stock front hubs.
 
Then I made a boo-boo.  In a fit on craziness, I went ahead and bought the quick-change rear end!  That required me to change the location/size (now smaller) of the fuel tank. 

Offline Bobcat Racer

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #15 on: April 03, 2012, 09:45:28 AM »
For our road race Bobcat we turned the axle flanges down on a lathe to fit inside of a Ford Fiesta front disc brake rotor and fabricated up a bracket to attach the caliper.  Since the Fiesta ran 12" wheels, the setup fits with no problem inside of a 13" wheel.
The good:
Parts are dirt cheap- Rock Auto has calipers and rotors on closeout last time I checked
The bad:
The caliper bracket we made doesn't have the bleed screw at the highest point so bleeding the brakes has to be done with the caliper removed from the rotor.  It's a three man job.  One to pump the brakes, one to hold the caliper, and one to turn the bleed screw.
 
All in all, the new setup works perfectly with the stock master cylinder.

Offline D.R.Ball

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #16 on: April 07, 2012, 01:16:22 AM »
Here is the part number for the Currie brake adapter, check to ensure the rear end is a big or small bearing housing.  Part number is CE-6011BCM cost is about 149.00 the good news is that the Cobra Disc Brake Calipers should be the same as the 1988 T-bird Turbocoupe.... Double check with Rockauto.com to check part number for the calipers.

Offline wingman72

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #17 on: June 05, 2012, 02:52:17 PM »
you can find an 8" rearend in some  V6 Pinto and Bobcat wagons, or V6 Mustang II's
Kyle
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Offline Stevonator

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #18 on: June 07, 2012, 11:29:40 PM »
I have 2 Speedway Engineering Mini Stock Quick change rears that I am retiring. My circletrack race truck is making to much power for them and blowing the ring and pinions out of them. Right now they are literally disassembled and waiting to go for scrap. I can build these to suit with brand new everything (R&P, bearings, seals) in them if there is interest. Otherwise they have a date with a furnace. Right now they are set up with aluminum spools and 55 1/2" from hub flange to hub flange. I'd rather see them do something than melt...but talk to me soon.....other wise they melt.

Offline Stevonator

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #19 on: June 07, 2012, 11:39:03 PM »
I also happen to have a surplus of the Wilwood calipers you see above....and yes we use 4 bolt pattern and inside of a 13" wheel.

Offline EP73Pinto

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Re: Is there a way to convert a 4 Lug 8 inch axle to disc brakes?
« Reply #20 on: June 09, 2012, 01:39:57 PM »
I would be interested in one of your rear ends. The only thing is I live in oregon and Shipping would be killer. How much would you want for one. Is it already equipped with the discs?