Drilling Drop-Spindles for the Stock Backing Plate (have you?)

[Busstom]

I noticed that my stock backing plates will fit on my AC Industries (SoCal Imports) drop spindles. 

I'm drilling a bit smaller than stock (10-32), so I'm assuming I'm in the margin of safety (afterall, their "aftermarket" OE style for Ghias is drilled for the plate already).

Anyone else ever done this?  How many miles have you put on them, if so?

(nothin' like a little potential destructive testing to "shake em out!)

Thanks!

[Ohio Tom (DdK)]

Sorry dude, I'm not quite following what you are doing or asking.
Can you please clarify a little more?
Thanks.

[Busstom]

Hey Tom, thanks for asking...now I'm wondering how many people are just confused by my post.  

So, with drum brakes, a backing plate mounts to the spindle, then the wheel cylinder and shoes mount on that backing plate.  On disc brakes, the caliper mounts directly to the spindle, but there is still a backing plate, however it's only there to shield the rotor from debris and excess water from the roadway.

As I'm sure you're aware, most aftermarket spindles (such as my drop spindles) make no provision to mount those protective plates.  Most guys just leave the rotors hangin' out in the wind.  I'm guessing some spindle designs won't even accept them.  But my AC Industries spindles from SoCal Imports will accept them, so I drilled and tapped three 10-32 holes in each one to screw the plates down.

Here's the weird (sketchy) part...I've never drilled ductile iron, but it's rather soft, and much of the chips coming up is literally a graphite-like powder.  I know iron has a tiny percentage of graphite, but man, this is like black powder.  I'm gonna run 'em!  I doubt I weakened them much, they're pretty beefy castings.  I'm more concerned about the quality of the Chinese manufacture  

Anyway, sorry for the windy response.  I'll post some pics and update as the miles pile up.

Steve

[Mike Lawless]

That's pretty much just the way cast iron cuts. There are different grades of cast iron, and some machine more like "cast dirt" than iron. (Take a shovel full of dirt, melt it down, pour it into a mold). Cheap grey iron is most likely what you have there. It's merely a carrier for the steel spindle that is pressed in. It does have a pressed in steel spindle, does it not?

That said, I did drill and tap a set of spindles for 3/8" bolts to hold on a caliper bracket for a wilwood caliper with no problems (CB Spindles), so I doubt a couple of 10/32 holes are gonna cause any grief

[Busstom]

It does have a pressed in steel spindle, does it not?

Sure, it has a pressed in spindle.  For certain, there has to be some ductility so that it flexes under stress without cracking.  I guess I shouldn't be too concerned. 

[Bruce Tweddle]

I'm drilling a bit smaller than stock (10-32),

Rather than asking this question, why wouldn't you just drill and tap them the stock VW size? 
M7.

[jgerock]

I have the CB dropped disc brake spindles (no backing plates installed) and haven't had any issues so far.  I did notice the speedo cable is very close to the upper trailing arm (potential wear issues?).



I'm also running the CB rear kit (914 rotors with Golf/Jetta calipers)

[rossi46]

Drilled my drop spindels the other day, used the back plate as a template and drilled and tapped the spindles to M6x1.0mm no problems, back plates fit fine with no catching  

[Busstom]

Thanks for your follow-ups guys.  I don't have any problems thus far either (except for the Meyle German ballljoints which are waayyyyyy too tight in the torsion arms - those are gonna have to come back out).

I too noticed that the speedo cable has to bend fairly sharpyly around the BJ boot.

[jgerock]

Keeping sort-of on track - what front shocks are you folks using?  I have KYB GR2 all-around and the front end seems too stiff.

My car has a CB narrowed axle beam with Avis-style adjusters, Berg caster shims, new torsion leaves, CB dropped spindles, 145-15 XZX tires at no more than 26psi pressure.  Right now, the adjusters are all the way up for ground clearance.

I've read where stock shocks work much better (or ones that are worn out) on a lowered VW.