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dobryan
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Joined: March 24, 2006
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Location: Brookeville, MD
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T3TRIS
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Joined: October 30, 2017
Posts: 299
Location: Portland, OR
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 Posted: Sun Jan 17, 2021 9:21 pm Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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Agreed, I seem to remember something like that too about tightening and loosening torques, which is why doing 2 clicks on a torque wrench is useless... but I figured the experiment would be fun.
At this point, here’s what we know:
- the wheel hubs heat up quickly and the right side is consistently 20° warmer than the left.
- I unnecessarily overpacked the outer part of the bearings with grease, especially the right side one.
- When the wheels are in the air and spun by hand, the left wheel stops within 2 seconds, the right one within 1 second.
- Taking the brake calipers doesn’t change the wheel spin resistance.
- The axle nuts where theoretically torqued to 246lb/ft or less on the left side and 292lb/ft or less on the right side.
- A loose axle nut, regardless of how loose, doesn’t change the wheel spin resistance.
Other details:
- The outer CV joints are not new but were swapped from side to side.
- The outer CV joints were most likely reassembled with the inner races and outer races clocked differently than when removed.
- The van has a lift and the fender to axle dimension was about 20.5” before a single mile was put on the front end rebuild and 19.75 after 120miles of driving (including lots of off-roading).
At this point, I’m not sure re-torquing the axle nuts and driving it around will create different results, unless it was indeed the brakes dragging. I haven’t decided if I’m going to put it back together to do that test yet or not or just commit to replacing the bearings and not adding grease.
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Guillaume, Jennifer & T3TRIS
87 2-knob Syncro
- 94 Subaru EJ22, 225/70-R16 CLK 16x7 ET37
- Transaxle rebuild, Mexico paint job, Front end rebuild, 320Ah LiFePO4 Battery |
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dobryan
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Joined: March 24, 2006
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Location: Brookeville, MD
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T3TRIS
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Joined: October 30, 2017
Posts: 299
Location: Portland, OR
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| Posted: Sun Jan 17, 2021 9:40 pm Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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| dobryan wrote: |
| I cannot understand how too much grease is really going to cause this system to overheat. |
I’m thinking the excessive grease on the outside of the bearing was getting pushed around when pressing the wheel hub into place. I suspect the grease pushed the outer seal outward ever so slightly as the hub kept moving inward. The wheel hub eventually met the bearing seal, which is pretty stiff and I believe has an internal metal ring. Then it became a fight between the metal wheel hub pushing onto the bearing seal and the plastic protection on the side of the bearing itself resisting. As more pressure was applied with the press, I bet the outer seal and its internal metal ring won the strength fight and was able to keep the grease inside the assembly. Since the grease itself can’t compress and probably wouldn’t seep out of the seal while the hub could still move inward, the outer plastic cage of the bearing itself was the next weak link and got pushed against the bearing balls.
At least that’s what I’ve been thinking since I first remembered I put grease in there, especially when it was pointed out that the grease was unnecessary. Here are drawings I made that might illustrate this:
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Guillaume, Jennifer & T3TRIS
87 2-knob Syncro
- 94 Subaru EJ22, 225/70-R16 CLK 16x7 ET37
- Transaxle rebuild, Mexico paint job, Front end rebuild, 320Ah LiFePO4 Battery
Last edited by T3TRIS on Fri Jan 22, 2021 2:50 pm; edited 1 time in total |
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kaalualu
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Joined: June 09, 2011
Posts: 274
Location: Big Island, Hawaii
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| Posted: Sun Jan 17, 2021 11:03 pm Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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Sounds like brakes are dragging.
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T3TRIS
Samba Member
Joined: October 30, 2017
Posts: 299
Location: Portland, OR
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| Posted: Mon Jan 18, 2021 12:04 am Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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| kaalualu wrote: |
| Sounds like brakes are dragging. |
So, just to be sure, after reading all of these comments and further tests that I did, you still believe that it’s brakes dragging?
Please don’t take this the wrong way as I truly welcome all tips I can get, however I’ve received many tips from people who are only familiar with 2WD vans only for them to realize how different the front components are from a Syncro. The wheel bearings we’re talking about here are quite different in design for instance. As a matter of fact they have to be pressed into the steering knuckle of the Syncro and the wheel hub then gets pressed into the bearing itself. Removing the bearing also destroys it. Here are some photos of ours in that process:
That being said, if you’re insisting on the brakes, I truly didn’t change anything to the brake system since before the front end rebuild. I replaced the calipers and rotors within the last few thousand miles and also bled the brake fluid.
| Abscate wrote: |
| While the calipers are off see if you can move the pistons with finger pressure. |
While we’re on the topic, I couldn’t move the piston any further in with finger pressure. The piston seems to want to stay where it is when I remove it from the caliper bracket.
Unfortunately regarding brake testing, I’ve started taking the front end apart again, so it wouldn’t be too practical to test more braking theories.
Looks like I’m pretty committed to replacing those bearings I guess... By the way, before I took it all apart, I removed the CV axle completely and reinstalled the wheel for a spin test. The right side (the stiff one) now stopped spinning within 2 seconds instead of 1 second. I imagine the internals of the front differential were creating their own resistance, on top of the bearing seals. Loosening the axle nut didn’t seem to change anything as far as making the wheel spin easier.
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Guillaume, Jennifer & T3TRIS
87 2-knob Syncro
- 94 Subaru EJ22, 225/70-R16 CLK 16x7 ET37
- Transaxle rebuild, Mexico paint job, Front end rebuild, 320Ah LiFePO4 Battery |
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Wellington
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Joined: September 21, 2004
Posts: 1884
Location: Montreal
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| Posted: Mon Jan 18, 2021 3:59 am Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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You imply you are going to change the bearings again.
What brand of bearing are you using?
May I suggest you measure the OD and ID before installing, there must be a spec in the Bently.
Did you disassembly your CV joints and repack them? You sure you got the cages correctly orientated?
One you have the hubs pressed back on, try spinning the wheels with no half shaft and no calipers mounted.
I'm thinking to change you flexible brake lines for new, my money is sticking brake pads. |
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djkeev
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Joined: September 30, 2007
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| Posted: Mon Jan 18, 2021 4:51 am Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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I will clearly state that I am NOT a syncro guy.
I've seen them, never worked on one.
And this probably is not your problem but your photos don't show it so
I will ask.
Good shop practice demands that the part of the bearing you are pressing be supported.
When you press the bearing into the knuckle, you are clearly pressing the outside large diameter edge as you do so...... BRAVO! Excellent job!
You then show pressing the hub into the center of the bearing, and here is my question, on the backside, down against the table do you have a pipe, a block, a something that supports the inner race as the hub is pressed down into it?
If yes, I'll shut up, fold my hands and continue to watch this riddle get solved.
If no, then I'll say that this assembly mistake probably is not your friction but I will say you damaged your bearing during assembly.
Look up BRINELLING in bearings, not usually immediate bearing death but......
The possibility also exists something may have chipped or cracked with the extreme unsupported stresses incurred.
Dave
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Steve M.
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Joined: July 30, 2013
Posts: 6829
Location: Fort Lauderdale, Fl.
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| Posted: Mon Jan 18, 2021 6:32 am Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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I gotta tell you...that's a nice paint job on all the bits and pieces!
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T3TRIS
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Joined: October 30, 2017
Posts: 299
Location: Portland, OR
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| Posted: Mon Jan 18, 2021 10:31 am Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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| Wellington wrote: |
You imply you are going to change the bearings again.
What brand of bearing are you using?
May I suggest you measure the OD and ID before installing, there must be a spec in the Bently.
Did you disassembly your CV joints and repack them? You sure you got the cages correctly orientated?
One you have the hubs pressed back on, try spinning the wheels with no half shaft and no calipers mounted.
I'm thinking to change you flexible brake lines for new, my money is sticking brake pads. |
Thanks for the additional inputs on what could be wrong. I did disassemble the CV’s and repacked them but I did not mark the inner and outer races before taking it apart. That means that the inner race and outer races of the front outer CV joints could be clocked differently than when I took them off. The front outer CV’s though don’t seem to care about clocking the inner and outer races for articulation. An inner or rear CV will bind right away if you install them wrong, these seem to move perfectly fine when reassembled (there’s not narrow or wide shoulders on the races). The inner cage was installed with the chamfer facing the axle.
I spun the wheel without brakes and it resisted the same as with the brakes on. Without the CV axles and no brakes, the wheel stopped spinning in 2 seconds instead of 1 second. I can remove the outer CV, put it back into the hub without the shaft and spin it again. I bet the wheel would stop in 2 seconds same as without the whole axle.
You think the stainless brake hoses can be at fault? I replaced those when I did the pads, rotors and of course, bleeding.
| djkeev wrote: |
You then show pressing the hub into the center of the bearing, and here is my question, on the backside, down against the table do you have a pipe, a block, a something that supports the inner race as the hub is pressed down into it?
If yes, I'll shut up, fold my hands and continue to watch this riddle get solved.
Look up BRINELLING in bearings, not usually immediate bearing death but... |
Thanks Dave! Yes the inner race of the bearing was supported when I pressed the hub back into the steering knuckle. As a matter of fact, it was challenging to find the right combo of tubes and blocks to support it! I’m glad we got all the adapters from harbor freight!
I’ll look into brinelling and see how that could apply here. I think it’s what’s happening to our outer CV joints but not sure about a new bearing.
Enjoy the riddle!
| Steve M. wrote: |
| I gotta tell you...that's a nice paint job on all the bits and pieces! |
Thanks! Believe it or not, even the LCA and radius rods were powder coated but the first off-roading mile took care of making sure you’d never know! I have a whole thread for the front end rebuild story.
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Guillaume, Jennifer & T3TRIS
87 2-knob Syncro
- 94 Subaru EJ22, 225/70-R16 CLK 16x7 ET37
- Transaxle rebuild, Mexico paint job, Front end rebuild, 320Ah LiFePO4 Battery |
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valvecovergasket
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Joined: October 10, 2018
Posts: 1491
Location: pnw
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| Posted: Mon Jan 18, 2021 11:01 am Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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| T3TRIS wrote: |
| While we’re on the topic, I couldn’t move the piston any further in with finger pressure. The piston seems to want to stay where it is when I remove it from the caliper bracket. |
theres a reason most non-schwarzenegger humans need these tools to push pistons back during a brake job
i dont think ive ever moved a brake piston by hand. but im also not a body builder...
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MarkWard
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Location: Retired South Florida
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| Posted: Mon Jan 18, 2021 11:20 am Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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In theory, the grease you added could be creating friction. That's a stretch diagnosis. Unfortunately, the bearings would likely be destroyed removing the hubs.
If it were me, I'd spend some more time driving it. I don't think you are hurting anything at this point.
In Florida nothing evaporates, but we do get a dry day every now and then in the winter. When you were washing your van down, if it was low humidity, the wheel centers drying ahead of everything else might be nomal. If the water was boiling off, then I'd say you have a problem.
As I said, even functioning brakes make heat. I wouldn't be too alarmed yet. As long as the hubs don't seize, and the plan is the tear it apart, you don't have much to loose driving it some more.
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dabaron
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| Posted: Mon Jan 18, 2021 11:24 am Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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| valvecovergasket wrote: |
i dont think ive ever moved a brake piston by hand. but im also not a body builder... |
i push my caliper piston back with a wrench spanning the piston and then use my hands to squeeze the piston in as i apply force to the wrench. i have done it this way for 20 years. i'm not the hulk.
i had no clue there was a tool to do this.
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djkeev
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valvecovergasket
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| Posted: Mon Jan 18, 2021 11:32 am Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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ive used a pry bar between brake pads and a c clamp in a pinch as well, but my point is with my dainty hands anyway ive never moved one inward by hand any appreciable amount.
regardless, nothing hes described here sounds at all like dragging brakes IMO. not to mention theres not accompanying smell of hot/burning brakes.
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T3TRIS
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Joined: October 30, 2017
Posts: 299
Location: Portland, OR
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| Posted: Mon Jan 18, 2021 11:52 am Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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| valvecovergasket wrote: |
| regardless, nothing hes described here sounds at all like dragging brakes IMO. not to mention theres not accompanying smell of hot/burning brakes. |
Correct. No brake smell...
New data point. I removed the outer CV from the axle and put it back in the hub with the wheel back on (exactly what I wanted to spend MLK day doing...).
When the axle nut was completely loose, the wheel stopped spinning in 2 seconds, as expected (remember it used to be 1 second). I torqued the nut down with my high tech weight method (I still don’t have that torque wrench) and the wheel had more resistance. It was back to 1 second to stop spinning. I backed the nut off a little and still 1 second.
I backed up the nut even more and used a mallet to pound the CV joint back out a little. Still stopped in about a second. I then retightened using less torque, same result. I backed the CV joint the whole way out (when you can slide it out by hand), back to about 2 seconds. I retightened the axle nut and stopped well before it was even tightening, 2 seconds. I tightened more until the nut was finally started resisting, the resistance started growing. Hand tightened some more using a breaker bar, but not tighter than lug nuts (I’d guess well under 90lb/ft), back to 1 second.
Not sure what this adds to the riddle except that maybe the seal on the CV joint itself creates resistance.
The humidity by the way, when I noticed the wheels drying from the center out (only the front ones) was typical for a Portland, OR winter day after the rain. Things were damp out there, it didn’t rain all day but it certainly wasn’t a dry day.
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Guillaume, Jennifer & T3TRIS
87 2-knob Syncro
- 94 Subaru EJ22, 225/70-R16 CLK 16x7 ET37
- Transaxle rebuild, Mexico paint job, Front end rebuild, 320Ah LiFePO4 Battery
Last edited by T3TRIS on Mon Jan 18, 2021 12:22 pm; edited 1 time in total |
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MarkWard
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| Posted: Mon Jan 18, 2021 12:01 pm Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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I will drive my syncro in to work tomorrow and shoot the CV shaft nut with my temp gun when I get there. If your wheel bearing theory is correct, the heat should radiate out from the center. If its brake heat, it should be cooler as you get closer to center.
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T3TRIS
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Joined: October 30, 2017
Posts: 299
Location: Portland, OR
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| Posted: Mon Jan 18, 2021 12:23 pm Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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| MarkWard wrote: |
| I will drive my syncro in to work tomorrow and shoot the CV shaft nut with my temp gun when I get there. If your wheel bearing theory is correct, the heat should radiate out from the center. If its brake heat, it should be cooler as you get closer to center. |
Thanks!! That should be very useful.
Maybe you can even hold your foot on the brake pedal on the way back to create a tiny brake drag and see if your wheel hub and studs get that hot 
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Guillaume, Jennifer & T3TRIS
87 2-knob Syncro
- 94 Subaru EJ22, 225/70-R16 CLK 16x7 ET37
- Transaxle rebuild, Mexico paint job, Front end rebuild, 320Ah LiFePO4 Battery |
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MarkWard
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Joined: February 09, 2005
Posts: 17122
Location: Retired South Florida
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| Posted: Mon Jan 18, 2021 12:32 pm Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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Don't try this at home. The idiots were actually walking in front of the car. You get an idea how quickly you can get crazy heat into disk brakes though.
Link
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mitch5
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| Posted: Tue Jan 19, 2021 12:04 am Post subject: Re: Hot lug nuts and hub after Syncro front end rebuild |
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In that photo before you press the hub into the bearing, the entire outer bore seems to be filled with grease. Seeing a part pressed into a fixed volume with all that grease makes me wonder if its possible that when you pressed the hub in all the extra grease had no where to go and took out the bearing seals. I know that ball bearings are sensitive to lubrication and its possible that with a damaged seal the bearing could overheat.
Disclaimer: I havent gotten around to reassembling my bearings yet so i am not sure how much room there is in there for that grease.
I am impressed with how deep you have dug into this issue, Personally i would dissemble and put new bearings in without all that grease. Syncro hubs are exponentially more expensive than the bearings and if a shop did this work you would probably expect them to replace. Hopefully disassembly will reveal the "smoking gun" |
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