Brake pedal pulsation after replacing front suspension

[82DMC12]

Pulsating brakes!

Yesterday I installed my front suspension from the frame up. DPI Spec Suspension, coilovers, powder coated ARB, Superflex ARB bushings, SKF bearings, Amsteer upper and lower ball joints, powder coated wishbones, poly wishbone bushings, powder coated hub, powder coated knuckle, serviced my rack. Every washer and bolt replaced. HOWEVER I did not replace the brakes - that was going to be a separate job later this year. I did get the rotors turned (12.2 mm) at an independent shop so I wouldn't have to remove them from the hub again later and risk ruining my new bearings.

Everything has been torqued once with jacks on the LCA's to simulate vehicle weight. I will be checking torque again tonight on ramps. I have not yet had an alignment but it seems to be pretty close (same threads on tie rods before and after and caster is set "neutral" with the caster arms i.e. not pulling back or forward on the LCA beyond the LCA's natural position). Rotor is torqued to spec to the hub and I made sure to file any imperfections down on the hub before installation (red loctite on the screws). Rotors appear to turn evenly through the calipers. I did notice the passenger side wheel doesn't "free wheel" when you spin it, it turns around two or three times before stopping and you can tell there's something about the bearing that's stiff but I think that is normal for most cars with the wheel off the ground. It's not related to the disc or caliper, it's the bearing 100%.

I took it for a first road test this morning and there's fairly strong brake pedal pulsation. I'm guessing there's something wonky with my calipers or the pads, or maybe one of my SS flex brake lines got bent or something while moving stuff around (didn't disconnect calipers, zip tied them up to the front fender stays). My understanding is brake pulsation is nearly exclusively a brake problem and not a suspension problem. I did bed the brakes a few times but it didn't make a difference. However I noticed that "hot brake smell" immediately after each emergency stop. Maybe it's old brake dust burning off the pads since I really don't drive aggressively.

Thoughts?

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[jangell]

I have no help to offer, but I have the exact same problem and I haven't been able to figure out what it is.

In my case, I replaced all the LCA and UCA bushings and ball joints, the front shocks with stock-like shocks, and the sway bar bushings, and welded a plate under the LCAs. Torqued with the suspension loaded, just like you. I installed the UK Big Brake system about 3 years ago.

Admittedly, I think my pulsing was happening before I did all those replacements, but there was so much vibration from worn-out bushings that it was hard to distinguish them.

I'll be eagerly following this thread.

-- Joe

[82DMC12]

Did you do anything with your brakes when you did all that suspension work?

I was smart enough to know I should do something about the discs because of course you're likely to wreck your bearings when pulling the hub off. I was going to do a full brake rebuild next month.... I had the rotors turned at a good shop but maybe they didn't do a good job. I think I'm going to order pads and rotors and change them so I can eliminate them as a possibility. Maybe I'll get lucky and pull the hub off only a few days after installation and find it comes off without self-destructing. I did grease the spindle well so I might have a chance....

[jangell]

Almost nothing. I had put one of the calipers in the front frame extension while I was working, and forgot to pull it back through before putting the steering knuckle back on. I disconnected the line, ran it behind the knuckle, and reattached it, then bled the brakes all the way around. I doubt that caused the problem. Other than that, I didn't do anything to the brake system.

When I did the brake upgrade, I did have to replace the front wheel bearings. They basically just disassembled themselves as I pulled them off. I have two spare bearings now, which I can press in if it happens again, but since the bearings are now I don't expect it to be an issue. I removed the wheel when I did much of the suspension work anyway, just to make access easier. They're not hard to press in with a basic Harbor Freight press. You can grind down the outside of an old bearing to use as a tool to push the new one in, although you'll have to use a socket or something to get the old bearing out of the hub first.

My rotors are part of the new brake system. I did use a dial indicator on them (as best I could; I haven't done that kind of thing before), and as best I can tell, they're flat -- at least the outsides, which is the only part I tested. I didn't replace my pads, but they should be good.

It really, really seems like this should be a brake issue, but I can't fathom what it is. My car doesn't seem to pull left or right. I even swapped the front wheels and rotors left and right to see if anything changed, but there was no effect.

-- Joe

[82DMC12]

Heh I did the same thing with my calipers. Both were marooned on the wrong side of the knuckle when I was done. Luckily I just disconnected the new ball joint from the wishbone, moved it to the correct side, and reattached the ball joint mount. Much nicer using lock nuts instead of those stupid factory studs you have to grind off.

[jangell]

I hadn't done the uppers yet (they were for another weekend), so the brake line was the simplest choice. When I made the same mistake when I did one of the uppers, I removed the UCA pivot bolt (since I'd just put it in) and pulled the caliper through that. The nylock had been a real pain to get on for that upper (the ball wanted to spin a lot).

And I had to grind off both of the upper ball joint shafts as well. Those nuts just wouldn't turn separately from the balls.


Also, a possible warning about the nylocks: when I did the lower ball joints, I got the ones that use nylocks. Either there was a fault in the nylocks, a fault in the ball joint shaft threads, or a fault in how I installed them, because I lost a nut on a highway-to-highway on ramp (the other nut wasn't very tight for a nylock either, which was odd, but it didn't fall off). Luckily, it was saved by the rim, which made a loud grinding sound and shaved off some aluminum, and I was able to safely pull over. The ball joint shaft completely separated from the steering knuckle and dragged through the gravel the instant the wheel dropped off the pavement. Luckily, there was no real damage (some scrapes on the LCA and I needed a ball joint). I've since put in new ball joints with castle nuts.

You can bet I made damn sure the new upper ball joint nylocks were tight and properly torqued and that the ball wasn't simply spinning when I later swapped those. I"m guessing that they're much less likely to have a problem than the lowers, or else they'd sell them with a castle nut option as well.


Anyway, back to the pulsing, I notice that it is definitely correlated with speed. The slower I go, the slower the pulsing. That makes it seem very likely that it's something in the rotors, except I can't find anything wrong with the rotors. If it was the calipers I'd expect it to be at a constant rate, since they wouldn't know anything about the wheel rotation.

-- Joe

[David T]

There are 2 possible sources. One is something loose in the suspension allowing it to move creating the pulsation. The other source is a problem with the rotors. Maybe the surfaces are not parallel or the rotor is not mounted correctly to the hub. You check the rotors with a dial indicator and you should be within 2-3 thousands of an inch. You mount the dial indicator on the frame touching the rotor surface and slowly rotate the rotor watching the dial indicator. You check both sides of each wheel. As for the pulsation, recheck the sway bar attachment points. Any looseness will allow the wheel to move fore-and-aft. Some pulsation would be expected till the rotor surfaces get "bedded" in again after being resurfaced.

[82DMC12]

Thanks guys. I was having second thoughts about the ball joint nylocks last night as well. I am going to go pick up some new castle nuts and then drive the car up on ramps and check everything again, also re-torque everything for the suspension. If it all looks good I guess I'll try to remove the hubs and pray the bearings don't separate after only 12 hours being installed.

[Bitsyncmaster]

Thanks guys. I was having second thoughts about the ball joint nylocks last night as well. I am going to go pick up some new castle nuts and then drive the car up on ramps and check everything again, also re-torque everything for the suspension. If it all looks good I guess I'll try to remove the hubs and pray the bearings don't separate after only 12 hours being installed.

The bearings pull apart because the inner race gets stuck on the hub. I bet yours just pulls off easy.

[82DMC12]

Yep. Got the driver side off no problem so far. Haven't found any smoking guns yet.

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[82DMC12]

I also bought some Castle nuts and tried to put them on the lower ball joints. These are DPI LCA's with UK Amsteer ball joints pre-installed and they came with nylock nuts. There is absolutely no way I can tighten the castle nut down far enough to fully expose the cotter pin hole. I would need probably two more revolutions past where the nut literally stops. I don't think you would want to drill two holes in the same ball joint stud. I'm considering putting blue loctite on a new nylock nut, and then tightening a second nut on top of the nylock.

I bought the castle nuts at Napa Auto this morning and they are identical in every dimension to the original Castle nuts.

Terrible idea, or better than a nylock alone?

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[jangell]

I have the same (I think) UK lower ball joints, and I was able to get the castle nuts to work. For the I uppers I had to tap the UCA down with a hammer to get the shaft down far enough, or is just spin the ball.

So maybe the shaft just isn’t far enough up?

For my lowers, they seemed to just work. That said, one of the castle nuts wouldn’t quite line up with the hole while tight, and I couldn’t tighten it more, so I had to leave it slightly looser than I’d like, but the exceedingly strong pins that I used make me confident that it’s not going anywhere.

— Joe

[82DMC12]

I was talking to someone else who has the same ball joints. He also said he was able to get the cotter pin in. I guess it's possible that it's not all the way inside the taper, I did have these knuckles powder coated but the powder coating was very thin inside the taper. The only way I could prove it is if I separated the ball joint from the knuckle again and sand it out the taper and then sanded the powder coat off of where the nut goes. That doesn't sound very appealing right now considering I've never been able to separate a ball joint without totally destroying it.

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[82DMC12]

One other thought. I found some other castle nuts at a hardware store that are a bit shallower and would almost certainly work. However I'm not sure about the quality of them - I don't think they are intended for automotive use... Maybe it's worse to put junky Castle nuts on with a cotter pin rather than a good hardened nylock nut with loctite on it.

I'm trying to put these on with a jack under the LCA and pushing up so high that it's slightly lifting off of my jack stands. I've definitely got the pressure!

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[jangell]

A hammer might work too. Tap the bottom of the LCA to push it up towards the knuckle. The impact might work better than an even pressure from a jack.

Or you could brace knuckle from above (assuming there’s somewhere to brace against, although I don’t think there’s anything above that except fiberglass?), then jack up against the LCA like a press. Just make sure it doesn’t push too hard and damage something else, that is.

If you have two UK ball joints, it be worth measuring the distance from the hole to the top of the shaft on both to see if they match. Maybe one was just drilled wrong?

— Joe

[82DMC12]

It's literally impossible to make the hole line up with the castle nuts. The New Castle nuts are within 0.2 mm equal measurement to original Castle nuts. I'd have to thread a castle nut at least two more threads down the ball joint shaft to have any hope of getting all the way into the hole.

At this point, if I want to use Castle nuts, it appears my options are to find a different castle nut that is shallower, file the grooves down on my new Castle nuts so that they will match the hole, but risking the integrity of the nut, or possibly grind the powder coat off of the knuckle but I don't think it's thick enough to make a difference. https://uploads.tapatalk-cdn.com/20210927/fe247102c7b19b3644194257b93be81e.jpghttps://uploads.tapatalk-cdn.com/20210927/ff368834e7ce6e54dc75b36035c54d04.jpghttps://uploads.tapatalk-cdn.com/20210927/f2f6c3f3fbdcc7e3980dc5e8b2b6d35d.jpghttps://uploads.tapatalk-cdn.com/20210927/ee5a475008f95db0cdf016e5c12a94db.jpg

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