Scarebird ECONOMY Disc Brake Conversion

[Sam Buchanan]

1 hour ago, jfish said:

$320 may not be a bad price to pay. I will have to get a quote from my machine shop to compare.

 

I suspect a machine shop would charge far more than that to make a pair of hubs from scratch. Scarebird's vendor no doubt just loads a CAD file into their machine and hits "Start".........

[Sniper]

As best I can figure it, the econo kit requires the original hub to be machined down a bit to allow the rotor to slide one.  Not that your machine shop has to make a new hub. 

 

I would probably convert to studs as well at this point.  Those two options ought to be less than new aluminum hubs.

[Sam Buchanan]

I assumed jfish was talking about having a machine shop build a pair of hubs like Scarebird offers. Maybe he was saying he was going to get a quote for modifying his hubs.........I might have mis-read his post.

 

I do agree that having a machine shop press in new studs while cutting down the old hubs would be the best way to modify them instead of using bolts with unknown yield strength.

Edited July 24, 2022 by Sam Buchanan

[jfish]

On 7/18/2022 at 4:37 PM, grea235 said:

I saw the hubs.   I'm passing on them for now.  I'm going to go with my own hubs and not stud them unless I absolutely have to.  I assumed that they had to get studded for clearance, but apparently not.  I can trim down the hub flange.  I have the economy DGE G30 coming.  I asked for the install guide and they emailed it to me.  Ordered all Raybestos off of Rock auto.  179 for everything including shipping.  Don't need the dust caps.  Calipers are rebuilds and the picture shows pins as well.  We'll see.

 

If it helps anyone, this is what they listed for the DGE G30:

 

Part	Application	NAPA	Wagner	Raybestos
Rotor	1993-96 Ford Probe front	4886318	BD125274	96318(R)
Caliper, LH	1979-85 Cad. Eldo front	SE4680	TQM25048	RC5248
Caliper, RH	1979-85 Cad. Eldo front	SE4679	TQM25049	RC5247
Brake Hose (15”)*	1979 Seville front	36845	F98912	BH36845
Brake Hose (17”)*	1979-82 El Dorado front	36959/36960	F98914/98914	BH36959/3696
Brake pads	1983-92 S10 4WD	TS7070AM	MX154	EHT154
Dust cap	1983-2010 Ranger 2WD	NAPA 735142		Dorman 618-503

Two points here:

 

The old hubs are pretty thin near the edge so I was able to cut down the OD with a grinder in about 20 minutes.

 

I bolted the wheel, probe rotor and old hub together using the lug screws I had. 

The old lug screws were a few threads short of full engagement in the hub.  Newer lug screws I had from Andy Bernbaum fully engaged the hub's threads.

Will attach a picture later.

 

[jfish]

9 minutes ago, jfish said:

Two points here:

 

The old hubs are pretty thin near the edge so I was able to cut down the OD with a grinder in about 20 minutes.

 

I bolted the wheel, probe rotor and old hub together using the lug screws I had. 

The old lug screws were a few threads short of full engagement in the hub.  Newer lug screws I had from Andy Bernbaum fully engaged the hub's threads.

Will attach a picture later.

 

Here is the picture.

The Bernbaum lug screw is on the right. What's left of a rivet is in the middle and an old lug screw is on the left.

[grea235]

Thank you!  I will absolutely check that once I get the hub turned down.  I believe I have all the parts and the correct attitude.  I'm going to check the master cylinder for the residual valve and since I have to drain it anyway, I'm plumbing in the in-line 2/10 valves.   I should be starting on it next weekend.

[Adam H P15 D30]

On 7/31/2022 at 10:38 AM, grea235 said:

Thank you!  I will absolutely check that once I get the hub turned down.  I believe I have all the parts and the correct attitude.  I'm going to check the master cylinder for the residual valve and since I have to drain it anyway, I'm plumbing in the in-line 2/10 valves.   I should be starting on it next weekend.

This is what you're looking for.  I removed the rubber portion and reinstalled the metal part, no other valves added.  Did it in the car..

 

 

[grea235]

Thank you.  It's on the list!

[Sniper]

31 minutes ago, Adam H P15 D30 said:

This is what you're looking for.  I removed the rubber portion and reinstalled the metal part, no other valves added.  Did it in the car..

 

 

  Did that last weekend on my conversion.  That metal cup is two pieces with the rubber RPV inside the two.  They come apart, if you put a small punch inside one of the holes you can see in the picture and tap, then move to the hole directly opposite and tap some more you can separate the two metal pieces and remove the RPV.  Then reassemble the two metal pieces and reinstall.  I think that is also a stop for the piston so I didn't want to leave it out.  If it turns out I need more volume I will pull it.

[Adam H P15 D30]

Exactly ^^^^^^^  Easy to disassemble / reassemble so no need to leave the metal part out.

[jfish]

Good news.

My wheels clear the disk brakes!

The 15" long Cadillac Seville hose fits OK and you can get it on Amazon if you search BH36845 for $12.

Sorry the pictures are sideways but there does not seem to be any way to fix it.

[grea235]

This is on the agenda for me this weekend.  I appreciate the insights and options you've all presented.  The clarification on the residual valve dissassembly was really helpful.

 

In addition, I'm replacing the rear brake hose and lines.

[jfish]

Getting closer to the end.

Made the mounting plate for the Wilwood MC.

Will do the spacer tomorrow.

[jfish]

A sketch to show how I am mounting the Wilwood MC behind the original MC.

[Sniper]

Someone took drafting in HS, good work

[jfish]

Wilwood master cylinder is mounted and centered.

Should be ready for a test run soon.

[Sam Buchanan]

I'll be interested in hearing how you dial in the proportioning valve.

[jfish]

On 8/25/2022 at 4:47 PM, Sam Buchanan said:

I'll be interested in hearing how you dial in the proportioning valve.

Me too.

Just trial and error I guess. Never done it.

[jfish]

I am using 2 pistons from the Mopar MC and the Mopar connecting rod along with the Wilwood connecting rod to actuate the new Wilwood MC.

I tapped the end (5/16-24) of one of the pistons to take the Wilwood connecting rod.

 

Not related to this but so far I can only get about 0.9" of travel at the Wilwwod cylinder.

Wilwood says you should be able to totally bottom out their cylinder for safety and that requires about 1.1"

 

[Sniper]

The push rod is going to have some vertical travel as you use it, remember it is moving in an arc.

 

I wonder if the double piston idea is causing it to bind?

[Sam Buchanan]

3 hours ago, jfish said:

 

Not related to this but so far I can only get about 0.9" of travel at the Wilwwod cylinder.

Wilwood says you should be able to totally bottom out their cylinder for safety and that requires about 1.1"

 

 

I couldn't get the full 1.1" travel, either, the geometry of the brake pedal/linkage won't provide it. I'm pleased with how the cylinder works on the road but I wonder if one circuit failed the lack of full travel might reduce the amount of pressure available for the remaining circuit.

[jfish]

19 hours ago, Sniper said:

The push rod is going to have some vertical travel as you use it, remember it is moving in an arc.

 

I wonder if the double piston idea is causing it to bind?

No, it's not binding.

If I remove the brake pedal pad, I can pull on the brake pedal arm from under the car until it passes thru the floor of the car and the arm is horizontal.

At that point the new MC has bottomed out.

[jfish]

17 hours ago, Sam Buchanan said:

 

I couldn't get the full 1.1" travel, either, the geometry of the brake pedal/linkage won't provide it. I'm pleased with how the cylinder works on the road but I wonder if one circuit failed the lack of full travel might reduce the amount of pressure available for the remaining circuit.

The existing brake pedal arm is 10.5" long and the short arm that pushes on the MC is 1.5" for a 7:1 ratio.

I think to get up to 1.1" travel the shorter arm needs to be longer (not easy to do) to about 1.8".  Would also make the pedal harder to push by about 20%.

Yes I think this could be a problem if one brake circuit failed.

[Sam Buchanan]

56 minutes ago, jfish said:

The existing brake pedal arm is 10.5" long and the short arm that pushes on the MC is 1.5" for a 7:1 ratio.

I think to get up to 1.1" travel the shorter arm needs to be longer (not easy to do) to about 1.8".  Would also make the pedal harder to push by about 20%.

Yes I think this could be a problem if one brake circuit failed.

 

I couldn't see a way to make the short arm longer without taking the assembly apart, welding some extra length and redrilling. Certainly doable, but hoping this will never be an issue. The lack of full travel is there, I just don't know the real-world implications.....hopefully not any for our low-performance/speed cars.

 

Thinking through this....if a rear wheel cylinder let go and loss of pressure in the rear brakes occurred, the master cylinder chamber for the front brakes would still have the same volume of fluid as before. So while total vehicle braking efficiency would be reduced, the front brakes should still function. Reduced braking is better than no braking as would be the case if something pops in a single-chamber master cylinder system. 

Edited August 29, 2022 by Sam Buchanan

[pflaming]

Scarebird duplicated Rusty Hopes” disc brake mounts. I asked Rusty about that, he concurred and said there was nothing he could do about that. I have two Rusty Hope kits and will get one more for my sportster. I have fabricated a very nice floor shipfter fo my ‘50 truck but wont put it on the market for that reason.  I don’t support duplicators.