Rear drum to disc brakes on a IRS, CMC.

Please take pictures as you go.  I have EXACT same issue with a '71 IRS chassis and exact same 2L 4 bolt Fuchs.  I keep looking at articles on using shorter axles and reducing size of trailing arms.  That looks like a lot of work and $ though.

I've pretty much decided when I decide to going to disc in rear, I'll sell the 2L Fuchs and go with CIP1 replica 5 bolt Fuchs with 5" offset. Believe 2L Fuchs are ET40 so a 4.32" offset.  I'd therefore pick up over 1/2 of clearance between wheel wheel. (I'd use rotors pre-drilled for the 5x130mm Porsche pattern)

Although I love the strength and lightness of the 2L Fuchs - they have gotten valuable. just the proper lug bolts are worth $10 each. And wheels seem to go for $600-800 for 4 - I've seen them for more too. So pocket book wise it would be a wash.  I prefer the fully polish version from CIP1 as the painted ones are painted wrong and would take refinishing (if you wanted an authentic look).

Please don't let me discourage you.  

I put AC rear disk brakes on my “project” CMC car and it was an easy job. I like the quality of the kit, but that’s from somebody who has never driven his car. I don’t know about the Fuchs and clearance, but I had to swap my 5.5 inch Vintage 190 wheels for the 4.5 inch version (using 175 Yokohama tires) due to clearance issues with my IRS suspension.

 

Yeah, the 2L Fuchs are 5.5x15" with ET40 mm offset.  I really don't want to go to 4.5" rims.  I even have 1/2" spacers on front to fill the front wheel wheel better.  I have 185/65x15 tires.  I suspect 165/80x15 would have been better choice but not great selection there in a sport tire.

Greg;

I must have this tire measurement thing all wrong.  Does not  the 65 tire give you an overall short wheel tire height, possibly placing the widest part of the sidewall below the top of your wheel well?   .65 x 185 = 4.73" x 2 [top and bottom tire]  plus 15" wheel.  vs. .80 x 165 = 5.2" x 2 + 15"

Boy I am glad I have not yet clicked on the buy @ ACN

While I'm waiting to better understand the tire/wheel fitment, is there a source of instructions to take off all the wheel drum pieces and install the rotor, calipers and new dual master?  I now have a single master, can I use the current plumbing?  I am getting older, duh, and move slow. 

Thanks,

 

Art

YES, the 185/65 are wider at tread and shorter at sidewalls.

	185/65	165/80	Difference
Sidewall Height:	4.73''	5.2''	0.47''
Section Width:	7.28''	6.5''	-0.78''
Tire Height:	24.46''	25.4''	0.94''

Thanks.

I guess Greg, we are in such a minority, (CMC and 2.0 Fuchs), not many opinions for us to draw from.  I was hoping to convert for:

Much easier maintenance and adjustment. New shoes or new pads, no brainer !

Better stopping power

I won't give up yet.

Remember this thread?

https://www.speedsterowners.co...ow-my-irs-suspension

 Except now $300 exchange

@Drumagination , it could just be the picture, so sorry for highlighting this.... you may want to consider getting longer studs for your wheels.   Looks like no studs are coming through the lug nuts on your rear tire...  

vey usefulntable @WOLFGANG , many thanx

I also just installed the AC rear disc brakes. I selected AC because of their claim of 0 increase in track. But, when they compared the disc to a drum, they discovered that there was a slight increase and they machined some off the surface of the disc hub. Now my wheels seem to be in the same place as with drums. I had them press in studs too.

Michael,

A question or two:

When you title them AC, do you mean aircooled .net ?

What wheels are mounted on this setup? What is the wheel offset?

Is your CMC, an IRS rear?

Is your CMC standard width or the wide version?

Lastly who did you have shave off the disc hub,  by how much and what did it cost for the machining?

Thanks very much;

Art

AC is AC Industries. They are owned by SoCal Imports: https://socalautoparts.com/ 

I have 5.5" 4 lug wheels with the extra inch on the inside.  I got them from the Beck folks years ago.  They were wheels they used on Spyders at the time.  I don't know if they still sell them. If your current wheels fit now they will fit with the disc brakes if they machine the hubs.

I have a standard width CMC with IRS.

SoCal shaved the hubs.  My receipt doesn't show a charge for shaving the hubs.  Maybe they didn't charge for that.

My order from them included metal brake lines I didn't use.  I used braided stainless lines with banjo fitting from the calipers to the connection at the tunnel.  I got them from Airkewld.com.  They are specifically for the AC calipers.

I also used the master cylinder from SoCal.

If you order, maybe you can tell them you want what they did for Michael McKelvey.

Thanks  Michael  !!