Rear brake caliper rubbing on radius arm/forward watts linkage

[KnifeySpoony]

Anyone else dealt with this issue. I think it cropped up after changing from OEM 1.5deg DeDion ears to 2.0deg ears, reducing the clearance. I don't hear or feel anything while driving. Anyone put spacers between the DeDion tube and ear to increase clearance? Can I modify the brake caliper in any way? Or is this the straw that pushes me over the edge to upgrade to the race rear brake setup (which I assume is much less bulky a caliper)?

[MV8]

A 1/4 inch thick shim plate between the steel axle and the aluminum bearing carrier/caliper brkt would help but the inner cv tripod would ride 1/4 inch further out in the inner cv cup  under all conditions (probably ok) and the rear track would increase 1/2 inch.

 

OEM type calipers typically have some material that can be removed safely, observing wall thickness.

[sf4018]

If you go with the race rear brakes, I believe there’s no handbrake, does CA require one for road use? 

[KnifeySpoony]

Yes, but they also "require" a few other things i already don't have. 

[MV8]

If it doesn't rub (i.e. doesn't roll far enough or have enough suspension travel), you don't need to do anything.

[KnifeySpoony]

Oh it's definitely rubbing. The links are all scratched up through the powder coat. (is my picture not showing?)

[MV8]

I didn't assume what the scratches were from. As the outboard pad wears down, the contact will be worse with the floating caliper.

I suggest going back to the old ears, keeping fresh pads on, or fixed calipers.

[KnifeySpoony]

The pads are fresh. There is clearance with the car sitting (maybe 4mm or so); but under lateral load, the rear axle deflects significantly laterally.

 

I had previously considered the fixed calipers but then changed my mind as I've happy with the stock rear calipers with uprated pads. The upgrade isn't cheap and involves replumbing the rear, as well plumbing in a proportioning valve (in the cockpit ideally). But I'm leaning more that way.

[MV8]

I've seen the watts side linkage two different ways. I've not considered which way is correct or better. Does the forward link connect to the top or the bottom of the swivel?

[KnifeySpoony]

The forward (longer) link goes to the top arm of the bellcrank. 

[sf4018]

You know you want to do the brake upgrade 🙂.

[KnifeySpoony]

Ugh, kinda but honestly I don't really need more performance, and also I'm lazy don't really want another car project at this time tbh.

[MV8]

Push-pull the dedion tube from side to side while observing the A frame bushes and joints at the attachments to see if the lateral movement is excessive versus the tube rocking normally on the center joint. An inch longer top arm on the bellcrank of the watts would probably be enough, have no significant effect on the watts system, and could quickly be returned to original if you don't mod your original bellcrank.

Fabbing a new upper link is another alternative but it would need to be heavier. A jig for the existing arm length would be drilled, then an essentially identical arm made but either: A) about six inches of solid rod would be bent to clear the spring and caliper and inserted into the tube ends or B) simply bent to clear (slightly longer tube so slightly heavier).

I wonder if the upper link clears without the watts system. I'm guessing the standard upper link is the same length as the watts kit upper link.  

[KnifeySpoony]

I don't feel any movement in the watts linkage joints. I hadn't thought about modding the bellcrank; I do wonder how that would change the geometry as it moves through it's "arc". I kinda like the new upper link idea but I would need to outsource that as I have no fab equipment nor ability. I assume the standard radius arm is of same/similar length, although I think it attaches directly to the DeDion tube, so lower down.