Rear Disc Brake + Narrowed IRS Arm - Anyone solve it?

[mkhanshaw]

I created a problem for myself:

I needed 1" narrowed IRS arms for my custom Beetle project. Its a 1954 Pan converted to IRS. I am going to run a Wilwood Rear Disc Brake kit I purchased from Russell @ Oldspeed.

Problem is, the caliper bracket he puts in the kit (EMPI 22-2863) will not clear/sit flat to the mating surface due to how the arms were narrowed. I never told the guy narrowing the arms that I was going to run discs, so in hindsight I know its on me..

Has anyone ran into this issue? I either need two caliper brackets that work with this set up or get one fabbed somehow.

Just wonder if anyone has gone through this and what you did about it. Here are some pictures:

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54 Oval

[RLFD213]

You’re probably gonna have to clearance those brackets and find a way to reenforce them since you’re taking material off.

[slayer61]

I have grown to despise empi parts. My empi brakes are being replaced by Strange brakes from Ron Lummus. He is also a provider of narrowed trailing arms.... just sayin
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[NJ John]

Clearance the backside of the brackets on a milling machine. Grind that arms. Hopefully everything with stay structurally sound.
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[mkhanshaw]

Thanks guys.

The Empi bracket I wouldn’t trust to do any clearancing on but I think I am going to have to grind and re weld the arms. Thankfully if my geometry skills are still working, I feel like I won’t need much. I’ll need to seam weld the arm after.

Yes Lummus makes narrowed arms but there is no way I could have foreseen all this. I bought my dual Wilwood master cylinder from Ron.i also bought from reputable people for everything else I went to Russell first at OldSpeed to make the arms too and do it all in one place but he was too busy and recommended someone else for me.
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54 Oval

[Bruce]

After you finish grinding on the TAs to clear the bracket, I think the next part that won't fit is the rotor.
Can you post a pic from the same angle of your second pic above, but from further away?
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[raygreenwood]

Not everything EMPI makes is crap. Most everything yes.....but those brackets are actually very well made and have pretty damn consistent machine work.

I have a set of those very brackets along with a set of the other more compact type 1 EMPI cast brackets. I am putting together a rear dosc set up for my 412....whose rear brakes are 100% all type 3 parts ....except type 4 uses a trailing wishbone and a totally different stubborn axle along with twin roller bearings.

In order to properly use those brackets with type 1 or 3 STOCK drum replacement, the machine work to the flat area where the bearing cover seats ....must be within 0.001" to about 0.002" max of the combined thickness of the STOCK backing plate and bearing cover....or it allows the bearing inside to spin over time which will destroy the machined surface in your trailing arm.

It's even more critical on type 4 because with twin roller bearings, it must be accurate enough to maintain proper preload/clamping on the roller bearing outer race...or no Bueno.

And, my point is.....that the machine work both sets of brackets that I have is flat, planar to both sides, accurate for the inner bore size and bolt hole centerline and is within 0.001. To the factory stack up (oversized which means I can lap it if I need to).

No.....those brackets are actually excellent and are not the problem you have. The problem you are having is with the welding and parts size of your aftermarket trailing arm.

Ray

[Clatter]

Sounds like you have the right idea.

wouldn’t be scared to do surgery on those arms.
They’re pretty tough/thick.

Looks like they just need clearanced a little.
Reinforce with some weld as needed.

Long and you go slow and don’t get too much heat in them so theu move around,
I’m sure you’ll be fine.


And like Bruce says, be sure and mock up everything as you go..


Sucks that they’re coated already.
Such is life!
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Bus Motor Build

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There is no such thing as patina.
It does not exist!

[raygreenwood]

Wait....wait....before you go tearing up anything or grinding on it......put your rotor on the stub axle without any caliper brackets installed. You will need a couple of washers for spacers between the flange on the trailing arm and the outer bearing cover while you do this.

Without using the bracket yet....Take a caliper with pads, pins and springs installed and using a few feeler gauges as wedges and spacers....clamp the calipers with pads to the rotor like it would kind of be installed. Now, measure the lateral distance that the bolt mating surface of the caliper is to the face area under the outer bearing cover on the trailing arm. You are looking to find the offset.

In other words.....as mentioned....mock this up.

It's very possible depending on the caliper configuration....that you have those PARTICULAR caliper brackets installed..... backwards. Yet....looking at it I do not think you do.....but you need to mock this up anyway to find out what your rotors and calipers actually require for the bracket. From my experience....betting that no matter how the kit was set up you will need some shims.

Also I found this out. Effectively you generally have 3 different angles or quadrant you could install those brackets.
In the ideal factory world, rear calipers would be installed on the forward side of the rotor to get the weight/mass closer to the pivot point and farther away from the centerline of the wheel to limit the sprung weight effect.

I found on mine, that the only locations these brackets would allow caliper installation is on top at 12 o'clock, on bottom at 6 o'clock or at rear at 9 or 3 o'clock.

6 o'clock is undesirable because your calipers are down way closer to mud, mush and water and usually the bleeder valve is in poor position. Rearward at 3 or 9 (depending on which side you are viewing from) is usually the easiest with the least interference but has longer and harder to solve e-brake cable issues. I found on mine that 12 o'clock is the best mix.

Also, check this out. The empi 22-2857-0 is actually a more compact, lower offset part that has all of the same bolt spacing and machine work as the ones you have. Because I am dealing with a totally different caliper than you are in my set up....this is the bracket that works better for me....and....it fits backward from what you have those installed and likely has no interference issues with the welds.

https://mooreparts.com/products/empi-22-2857-rear-...right-each

Ray