How to renew Stock Brake Caliper sliding surface?

Mark Olson

Mark Olson

True Classic
I believe the stock brakes would work fine if they were new. When I consider the "sliding" mechanism for the caliper and look at my calipers it does not fill me with confidence these will work like they were new. Here is a closeup of one of the sliding surfaces on one of my rear calipers:
PXL_20201103_022528129.jpg


As you can see it is significantly pitted. The front calipers are a little better but still pitted.

Has anyone tried renewing these sliding surfaces, and if so how did you do it?

I have thought of filing it down, but this would probably reduce the engineered tension. I have thought of using JB Weld for a filler but am not sure how well it would stand up.

Of course the other option is to buy new calipers, and if I do that I will spend a bit more and upgrade the brakes all around. However I believe the stock brakes would work okay for my purpose and would like reuse what I have............if I can find a reasonable way to do it.
 
Are you sure that the pitting is a bad thing? The pits would hold lubricant better than a flat surface, and the contact area (high points) between caliper and the wedge would be reduced, for less friction.
As long as the joint isn't too loose I think the pitted surface might be OK?
 
This is an interesting topic that I don't recall being addressed either here or on MIRA. Almost all discussion has been about corroded wedges. I don't have an answer but am curious to see what others say.
 
I am thinking swiss file dressing on both the calipers and wedges. Assemble with caliper grease.
 
I think you're right - those are aluminum so they shouldn't pit on their own like that. When I disassembled my rear brakes that same area along with the shims were very pitted. The shims look to be treated steel so they could rust in place and that rust could end up pitting the aluminum? But it wouldn't pit along the entire area. So while it seems that a manufacturer of those calipers would run the edge thru a mill to face the surface it doesn't look like it.

I used some mechanical filing on mine to attempt to "clean them up" and it worked ok...
IMG_5179.JPG

IMG_5180.JPG

IMG_5181.JPG


I ended up getting larger 38mm 124 rear calipers from Autoricambi which do indeed have machined surface. Maybe a fellow member here can comment on the remanufactured units MWB offers and if the surface is prepped. Here's what my new rears look like out of the box - note the scoring already from assembly, that aluminum sure is soft!
IMG_5176.JPG

IMG_5177.JPG

IMG_5178.JPG
 
darwoodious said:
note the scoring already from assembly, that aluminum sure is soft!
Click to expand...
Was that from pushing the wedge in from the front (recommended) or sliding in from the side? Hopefully with a good coat of copper grease on all surfaces it'll be minimised next time, but worth checking the wedges for any sharp edges. Pushing the second wedge in from the front doesn't cause the caliper to crab as it pushes back evenly against the carrier springs.
 
darwoodious said:
I think you're right - those are aluminum so they shouldn't pit on their own like that. When I disassembled my rear brakes that same area along with the shims were very pitted. The shims look to be treated steel so they could rust in place and that rust could end up pitting the aluminum? But it wouldn't pit along the entire area. So while it seems that a manufacturer of those calipers would run the edge thru a mill to face the surface it doesn't look like it.

I used some mechanical filing on mine to attempt to "clean them up" and it worked ok...
View attachment 38030
View attachment 38031
View attachment 38032

I ended up getting larger 38mm 124 rear calipers from Autoricambi which do indeed have machined surface. Maybe a fellow member here can comment on the remanufactured units MWB offers and if the surface is prepped. Here's what my new rears look like out of the box - note the scoring already from assembly, that aluminum sure is soft!
View attachment 38033
View attachment 38034
View attachment 38035
Click to expand...
My X1/9 rear calipers that I bought from Autoricambi last year also had milled surfaces.
 
Anyone use Teflon wedges? I believe they were factory spec for what must be the last generation of cars to use this brake caliper design.

For the bid it is worth, whenever I do brakes on a Fiat I polish all of the mating/sliding surfaces &’of course use copper or caliper grease. My first thought is that some pitting may not be problematic, but I have not fully thought the possibilities through.
 
likely so. I don't know. They were part of a casual conversation with some friends a few months ago when someone had come across a small batch of them. Apparently, they aren't incredibly easy to find in any part of the world. Personally, I have found my archaic polishing & lubricating method to be fully adequate for road uses.
 
Fiataccompli said:
Personally, I have found my archaic polishing & lubricating method to be fully adequate for road uses.
Click to expand...
Especially with the better brake greases available today. If they worked decent for several years with the older type of lube, then they should do as least as well today. But I have to say I'm not a fan of the sliding wedge caliper design in general.

I had some front calipers rebuilt by a professional company recently. Normally I do this sort of thing myself, but in this case I was able to get it done at no cost so why not. I'll have to take a look to see how they left those 'sliding' surfaces - machined, polished, or just cleaned.
 
no, it's terrible by today's standards. But, be honest, maybe the whole car is & that has nothing to do with why we love them anyway. So, that's to say, yes, i'm sure you are correct.
 
I have filed mine in the past. I use the newer ceramic grease which so far has done well (the last couple of years). My car sits out in the rain when it rains so it is a good test as the very open OE alloys allow plenty of water to get to the caliper area.
 
We have all bought Xs and spiders with caliper wedges were practically welded in place by corrosion through non-use. Last thing you want to do is leave those calipers static. If you have refurbished your brakes and smoothed and lubed the sliding surfaces then you have done all you can do. But if you then let the car sit for a month you kind of negate all that work, especially if you park the car outside. Usually it's just the wedges that need routine checking.

Too bad there is no way to convert them to sliding pins like modern calipers. And while you can certainly do a caliper conversion to modern calipers, the conversion is expensive.
 
I've learned that racing pads is another solution as they don't last very long. Replace the pads and lube every season and the breaks won't seize. 😁
 
carl said:
We have all bought Xs and spiders with caliper wedges were practically welded in place by corrosion through non-use. Last thing you want to do is leave those calipers static. If you have refurbished your brakes and smoothed and lubed the sliding surfaces then you have done all you can do. But if you then let the car sit for a month you kind of negate all that work, especially if you park the car outside. Usually it's just the wedges that need routine checking.

Too bad there is no way to convert them to sliding pins like modern calipers. And while you can certainly do a caliper conversion to modern calipers, the conversion is expensive.
Click to expand...

I went to Punto Turbo sliding pin calipers in front, with ventilated disks. Yes, it was expensive.
 
Here is the caliper with JB Weld on the sliding surface, filed and sanded. Very smooth now, would probably work well.........at least for a while.

Caliper JBWeld.jpg
 
Mark Olson said:
Paul, where did you get these, and did they fit without modification?
Click to expand...

Excuse me, brain fade. Uno Turbo front brakes. It was a long search, the calipers and vented discs are from England, I can look up my source if need be. The carriers are in high demand in Europe, I had little luck until I found a forum member who had a rusty set tucked away.

They bolt right on, and clear my 13 inch CD30 wheels nicely.

Bernice (Rupunzel) did a description of the installation:

 
You must log in or register to reply here.
Back
Top