Why does the Left-rear caliper fail rather than the Right?

[DPDISXR4Ti]

I have three data-points that support the theory that the left-rear caliper is more prone to seizure/failure than the right, as follows...

1) Left calipers - new or rebuilt - are pretty much not available for purchase.
2) I've had a left caliper fail
3) I've had a left caliper seize (sort of, but not really) after converting to a VW caliper/ Ford Focus rotor setup

#3 above is what got me thinking. In fact, the caliper wasn't really seized - I "fixed" it by putting a little more length/slack into the e-brake cable. In doing so I found that the e-brake seems to clamp down more on the left side than the right. Has anyone else noticed this? I suspect many left calipers have been replaced needlessly, which is why there's an imbalance in availability.

Discuss....

[john keefe]

I like your analysis. I'd also say that the stock rear calipers are nothing to brag about, and being the "shorter distance" from the ABS system head, probably get overworked in time vs. the right rear. Having had one apart a while ago, it seemed to me that the piston cylinder wall gets worn more at an off-center axis, leading to piston snag and poor return. Doesn't take very much deviation to cause problems. Eventually, that results in seizing, or at least minimized travel of the piston under braking, thus reduced performance which appears as seizing.

Not all that unusual for pre-ABS systems. I noticed similar with the two sets of TBird rear calipers I've had, where the stock TBird brake-line was a shorter route from the line-Tee to the left rear. I've sometimes wondered if the staggered rear brake-line lengths might be some design aspect to compensate for the "normal" driving conditions of driver-only (no passengers).

We used to have neighbors when we lived more towards the coast. They were both very nice; he was average build, and she was extremely large (north of 375, to be polite). If you had to get out of town, there was basically one, winding two-lane up a steep coast hill. She commuted "over the hill" daily. Her husband saw me working on the SHO's brakes one day, and complained that he was constantly replacing front and rear left brake pads and rotors at the dealers, and they couldn't figure it out... Did I know what might could cause it, or was there some design issue in the car that I knew of... Pretty obvious what the cause was, but all you could do was politely say you had no idea, though design flaws do happen.

[Ed Lijewski]

I call Baloney.

On my '88 the right rear caliper stuck in applied position. On my '89 on getting it I found the left rear caliper arm frozen in a half braking position (no amount leverage would move it). So each caliper appeared to have the lever arm shaft (or something internal) not moving and/or not retracting fully.

I agree re current/recent non-availability of left calipers. I tarried on ordering a replacement left for my '89; there was a rebuilt one with no core on Ebay for $65. But I dallied and delayed and a few weeks later it was gone. So then getting one from MPM was my only choice (at double the cost plus core).

I picked up two installed but hardly used rebuilt (L/R) rear calipers from a Scorpio parts listing here to have in reserve.

I think the disparity in caliper availability on Ebay or elsewhere just reflects the scarcity of cores for rebuilding.

YMMV

[andyofcolumbusmerkur]

A lot of cars live in Urban areas and stay parked out in the street. You will see some of these cars with totally rusted out drivers side doors with decent passenger side doors. Even if the car isn't driven in bad weather other cars are splashing salt water onto them. At least in Ohio. So I can imagine all kinds of things on the drivers side failing more often. Bikers often wonder why their tires seem to wear uneven. This you can blame on the mild arch of the road, which is made that way so rain water will run off. I always seem to wear out the right tires faster from making more sharp right turns with too much throttle. Weird highway off ramps that turn while going downhill could really make a side to side difference if it were a daily commute type of thing.

[john keefe]

I call Baloney.

I think the disparity in caliper availability on Ebay or elsewhere just reflects the scarcity of cores for rebuilding.

YMMV

Which begs the question... if Ford produced the same number of L&R calipers for installation and spares (why wouldn't they?), then why would LR NOS/rebuild-cores be far more scarce that RR's? Supply & demand; the demand for NOS/rebuilt-core LR calipers (evidently) far exceeds that for the RR, indicating the LR's are in some way much more prone to failure. And IMHO and observation the cause is as I wrote previously. Let's agree to call it quasi-educated Baloney.

[Ed Lijewski]

But Ford's calculations for LR caliper availability certainly didn't extend for 33 years.

And rebuilders likely rely on data such as below to determine whether to continue to acquire cores and rebuild LR calipers, wouldn't you agree?

Screenshot_20211229-145510_Lite.jpg (637.26 KiB) Viewed 12461 times

YMMV

[john keefe]

Sorry, I'm evidently a little slow today after a week's worth of Christmas excitement and grog... Not quite grasping how the data translates into the much smaller volume (in U.S.) production numbers for Merkurs.

I guess it depends how you look want to look at it. I can see your point that a rebuilder could look at availability of cores as evidence of popularity. IOW, "If there are so many RR cores being rebuilt, then those must be the ones in higher demand, and the LR's must be doing OK."

On the other hand, as an engineer, contractor, etc., when something essential like specific wood product, material, hardware, or even trades becomes unavailable (as especially evident during COVID), then the conclusion is that demand has outstripped supply. E.g., Who cares if there's plenty of 3/8" OSB when the demand (and structural requirements) calls for 3/4" 5-layer ply.

I'm no economist, and admit I don't remember a lot from the one business course I took, but this argument is essentially the crux of all the S/D theories. At what point does optimistic (BS?) marketing opinion/forecasting about demand lead to a glut of unwanted product (can you say, Chevy SSR pickup/car), vs. the pragmatic "in-the-moment" view that if a supply is short, and cost is rising for that particular product, then that is the demand, not the glut product. IOW projecting what might happen and dealing with over-projection down the road, VS. keeping your tabs on demand and responding accordingly, at the risk of being so late to respond that a competitor reaps the profits from having a ready-supply to sell.

Limited supply will temporarily drive up cost until overproduction results in excess supply, driving prices back down. EXCEPT if that lack of supply can not be refilled, but demand remains high. Or in this case, if previous demand for LR calipers and rebuilds have exhausted the supply, leaving a glut of RR calipers, and rare, pricey LR's. Which is what I believe we're seeing, and my rationale as below. Again, to me it's OSB vs. 3/4 ply, but I don't know if that makes me "glass half full" kinda' guy.

[john keefe]

That was kinda' a long-winded way of making a "Which comes first, chicken or egg" argument.

Also, I realize that all else being equal, the principle of equal force distribution everywhere in a non-compressible hydraulic system should be the same, regardless of length of the fluid line length. But, you also have the factor of contamination, air-bubbles, old-fluid, etc., and that as braking occurs, the rears experience reduced weight due to forward momentum transfer, with the drivers' side remaining more "loaded" than the passenger side when only the driver is occupying the vehicle. Again, that contributes to overworking of the LR.

[Ed Lijewski]

All of that, and the original question, presumes that there is available a (ample) supply of RR calipers. That hasn't been established. For all we know rebuilt RR calipers may soon be equally unavailable, just as rebuilt master cylinders for late model XRs are unavailable. Serving the need for those has been left to MPM whose rebuilds are very nice an DC not overly pricey. So we pay more, for a nice product, while helping the smaller business stay in business.

I'd say there isn't a scarcity crisis of LR calipers, only loss of or current absence of traditional alternate remanufacturers.

Let's hope MPM doesn't stop offering caliper (and XR MC) rebuilding with core required.

YMMV

[DPDISXR4Ti]

All of that, and the original question, presumes that there is available a (ample) supply of RR calipers. That hasn't been established.

It sure looks to me like it is well established that RR calipers are readily available and LR calipers are not. Thank God for Jeff Herson that we have some L calipers, but I imagine his supply is very limited.

Regardless, the bigger topic here is why does the left side grab first when using the e-brake. Or is that not the case universally? I found it to be true using stock and VW calipers, so it's not a caliper issue per se. Could it be a one-off issue I'm experiencing with an old cable? Sure. I'm trying to figure that part out.

[Ed Lijewski]

All of that, and the original question, presumes that there is available a (ample) supply of RR calipers. That hasn't been established.

It sure looks to me like it is well established that RR calipers are readily available and LR calipers are not. Thank God for Jeff Herson that we have some L calipers, but I imagine his supply is very limited.

Regardless, the bigger topic here is why does the left side grab first when using the e-brake. Or is that not the case universally? I found it to be true using stock and VW calipers, so it's not a caliper issue per se. Could it be a one-off issue I'm experiencing with an old cable? Sure. I'm trying to figure that part out.

Jeff had only one used LR core when I needed one earlier this year, which he then rebuilt and I sent him my stuck caliper arm LR core .

Maybe the issue relates in some way to the side of the cable where the adjuster is; that is, a manual adjustment doesn't completely equalize on the RR side? I've suspected that on both XR and Scorpio but had no fix for it.

YMMV

[john keefe]

I'm wondering what Jeff thinks is the cause. If anyone has seen/worked with a significant number of rear calipers to venture an opinion, probably would be him. We don't have salt on the roads out West here, but I can see some connection from Andy's observation of driver's side salt washing from passing cars.

[Ed Lijewski]

If this is a real road use/service life discrepancy it should have affected Granadas, and Sierras, too. He/they who believe it is should research that.

YMMV

[andyofcolumbusmerkur]

Another thought regarding the crown of the road would be the lateral weight distribution. Just like if you were mowing a slope side to side with a tractor or zero turn. The downhill tire(s) compress a little more and that leaves a stepped look in the lawn. Especially when the tires are aired down to the absolute minimum during those soggy weeks in the early spring. So I could imagine the left wheels breaking loose more often under acceleration and also locking up under hard breaking. This wouldn't effect calipers on the XR but it would on something with ABS, especially in the rear.

[andyofcolumbusmerkur]

Discuss....

Hey you asked for it