Soft Pedal While Turning

[Alex01]

So that’s damage from the brief time you had it on to replace your old one?

That was the condition it was in after pulling it off Tom's jeep with about 35k miles or so on them. I installed that one to confirm it was the problem. I will likely order a new knuckle to have on the shelf. Or just wait until bonus time and splurge on a BBK.

 

[DrDmoney]

Yes, the pedal is firm and it brakes straight. I did not swap over the lines at this point since I didn't want to add another variable. My thought was they worked previously so I wanted to at least get back to where I was a week ago before I started messing with the brakes. I could have saved lots of time/money/frustration if I just replaced the knuckle and added washers to start with.

Agreed never make more than one change at a time to find the cause. Since that’s where the pad rests when it’s neutral, why is it moving around so much that it’s wearing into the guides on the knuckle? It should be clipped tight into the piston, and barely riding on the guides. Is the clip bent causing it to push into the caliper guides

 

[mrblaine]

Glad you figured it out, I think you would have to stick weld it with a high nickel rod to fix it. Thanks for the offer though.

Nope, just wire brush it clean to get it rust free and hit it with a Mig. The weld pulls carbon out of the iron and turns it nearly carbide hard. Takes a hard disc on a grinder to make it flat again.

 

[DrDmoney]

I’m still having a hard time conceptualizing why that would cause a soft pedal. It would seem that if that was causing the pads to bind up you would get a hard pedal early with no braking on that side then it would pull the other way

 

[Alex01]

I’m still having a hard time conceptualizing why that would cause a soft pedal. It would seem that if that was causing the pads to bind up you would get a hard pedal early with no braking on that side then it would pull the other way

I'm sure Blaine knows the exact reason but I would guess since the piston wasn't able to fully cycle a bit of air was trapped in the system. I likely introduced it when I elected to swap the calipers but ignored the knuckle. When I went to bleed the system the pad likely fell into that groove and couldn't push the last bit of air out. The affected side was still braking but likely more on the front side of the rotor since the rear was locked in place. Instead of clamping both pads together it was, in essence, pulling the front side pad against the rotor. (Blaine did I get remotely close )

Like I said previously I think my initial issue was caused by piston knockback as Blaine told me within moments of me asking him. Which was caused by the caliper contacting the shock mount on a full turn. (fixed with spacers)

It was one of those fun issues that could have been avoided if I paid more attention to the parts (knuckle). The part I'm kicking myself about is I noticed the damaged area when I re-assembled everything the first time but blew it off since it looked like it was purposely put there.

 

[DrDmoney]

I'm sure Blaine knows the exact reason but I would guess since the piston wasn't able to fully cycle a bit of air was trapped in the system. I likely introduced it when I elected to swap the calipers but ignored the knuckle. When I went to bleed the system the pad likely fell into that groove and couldn't push the last bit of air out. The affected side was still braking but likely more on the front side of the rotor since the rear was locked in place. Instead of clamping both pads together it was, in essence, pulling the front side pad against the rotor. (Blaine did I get remotely close )

Like I said previously I think my initial issue was caused by piston knockback as Blaine told me within moments of me asking him. Which was caused by the caliper contacting the shock mount on a full turn. (fixed with spacers)

It was one of those fun issues that could have been avoided if I paid more attention to the parts (knuckle). The part I'm kicking myself about is I noticed the damaged area when I re-assembled everything the first time but blew it off since it looked like it was purposely put there.

Works for me.

 

[Gollywomper]

Nope, just wire brush it clean to get it rust free and hit it with a Mig. The weld pulls carbon out of the iron and turns it nearly carbide hard. Takes a hard disc on a grinder to make it flat again.

That’s great to know. Both my knuckles have some groves. Any preheat before welding needed?

 

[Alex01]

That’s great to know. Both my knuckles have grooves similar.

I wonder if that's what is causing your pull left/right issues??

 

[Gollywomper]

I wonder if that's what is causing your pull left/right issues??

Maybe? The constant slight left pull is still there. The right pull on let off is gone after squaring axles. My grooves are only on the inner pad area they are about the same depth as those but about 3-4 times longer. I guess with new pads it might be hanging up a bit and nut fully releasing. I have been keeping an eye out for another pair of used knuckles. I have only found them with grooves. Now that I know they can be repaired I will pick up a set a fix them if the price is right. It very well could be causing a pad to drag just enough. Hmmm
I will take my temp gun with me tomorrow and check some temps after a no brake stop and see.

Great. Another project. ......A very timely post. Lol

 

[tomtaylz]

Maybe? The constant slight left pull is still there. The right pull on let off is gone after squaring axles. My grooves are only on the inner pad area they are about the same depth as those but about 3-4 times longer. I guess with new pads it might be hanging up a bit and nut fully releasing. I have been keeping an eye out for another pair of used knuckles. I have only found them with grooves. Now that I know they can be repaired I will pick up a set a fix them if the price is right. It very well could be causing a pad to drag just enough. Hmmm
I will take my temp gun with me tomorrow and check some temps after a no brake stop and see.

Great. Another project. ......A very timely post. Lol

I had a set for sale but it sounds like Alex might have stole them and they might have a small notch

 

[Alex01]

I had a set for sale but it sounds like Alex might have stole them and they might have a small notch

I may be temporary borrowing the drivers side until I get a replacement lol.

If you have access to a welder you could likely fix the ones you got. If you don't your local exhaust shop probably has the ability to put a weld in the groove. Google "knuckle has groove tj" it's the first result on wrangler forum.

 

[Gollywomper]

I may be temporary borrowing the drivers side until I get a replacement lol.

If you have access to a welder you could likely fix the ones you got. If you don't your local exhaust shop probably has the ability to put a weld in the groove. Google "knuckle has groove tj" it's the first result on wrangler forum.

Yes I can weld them. Just thought have a set done would make for an easier swap. I just looked at my driver side. It isn’t very bad at all, doesn’t seem to be catching the pad. At least the pad moves freely in and out with Jeep not moving. There may be some unseen forces with the rotor spinning.

 

[Gollywomper]

Was a bit bummed about taking the knuckles off, since I just put I all together. Lol
Guess there is no reason I can’t take caliper off and weld the knuckle while in place?

 

[DrDmoney]

Was a bit bummed about taking the knuckles off, since I just put I all together. Lol
Guess there is no reason I can’t take caliper off and weld the knuckle while in place?

It might be harder to grind/file

 

[Gollywomper]

It might be harder to grind/file

Mine are only scared on the outer area. Will have to see I guess. If mine is dragging it should show with a temp gun tomorrow. Will come up with a plan then.

 

[mrblaine]

It might be harder to grind/file

The weld is about the same hardness as a file. It would take someone a very long time to file it. A new flat hard disc is the easiest way to do it and watch the cut as you go to get it flat. I use a known good pad to check the fit and slide it back and forth at the correct angle to make sure I have the size correct.

 

[mrblaine]

I may be temporary borrowing the drivers side until I get a replacement lol.

If you have access to a welder you could likely fix the ones you got. If you don't your local exhaust shop probably has the ability to put a weld in the groove. Google "knuckle has groove tj" it's the first result on wrangler forum.

Most exhaust shops weld with small wire at low voltage. Ask them to turn the heat up if you have them do it.

 

[mrblaine]

I think those marks where the cause to the problem of why I couldn't get the pedal to firm up. I believe I has having the lose of power issue because the caliper was contacting the new shock mount at full bump. I added a few washers to the stops to prevent that issue.

That is an important tidbit. That was causing the piston knockback and the initial problem you described which was soft or loss of pedal after a turn in a particular direction.

The spongy pedal was due to the ends of that pad never letting the piston extend or move out to compensate for pad wear. With the ends locked into those notches, it was moving the caliper over each time you used the brakes instead of moving the pads evenly.

Under normal use, the piston extends and then the caliper splits the movement evenly by the caliper body moving inboard pulling the outer pad inward and the piston moving the inner pad outward which creates a self centering clamp if you will.

When the pedal is released, the caliper seal retracts slightly which pulls the piston back in so the brakes don't drag and cause excessive wear and or overheat. All of these movements are very tiny measured by a few thousandths of barely perceptible motion. And, a good idea for anyone working on their brakes. Have someone hop in and push the pedal hard and release it while you watch each corner. You should get the "sense" of some movement, but not really see much in the way of actual movement. If you see movement like the caliper squaring up to the rotor as the pressure builds, find out why, that is not normal.

This one though, was doing all the movement in the caliper body against the stationary pad. I suspect that if you compare the pads, you may find that the outer is a lot more worn than the inner. Likely the caliper had to bow open a bit with a lot of extra movement to pull the outer inward to clamp the rotor and upon release, the rotor would move the caliper back.

Check the inner pad for cracks at where the friction layer meets the backing plate. If the pad was bowed very much, it will crack the friction layer loose from the backer.

 

[mrblaine]

Agreed never make more than one change at a time to find the cause. Since that’s where the pad rests when it’s neutral, why is it moving around so much that it’s wearing into the guides on the knuckle? It should be clipped tight into the piston, and barely riding on the guides. Is the clip bent causing it to push into the caliper guides

The only things holding the caliper in place to keep the pads where they go relative to the rotor are two guide sleeves that bolt to the knuckle. They have rubber dust boots that goes through holes in the caliper and then fit over the guide sleeves. They have grease in them. If the dust boots get worn and allow the relatively high weight of the caliper to bounce the pad against the softer iron in the knuckle reaction bars (sliders) it will wear those slots.

 

[mrblaine]

That’s great to know. Both my knuckles have some groves. Any preheat before welding needed?

Nope, just turn the heat up slightly and go for it after you wire brush them to shiny.