ever loosening wheel bearings....

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08 Apr 2012 15:48 #8831 by srshaw3
So, I installed my new wheel bearings a couple of weeks ago, and I noticed a vibration the other day. I found they were loose, but the collars were not (meaning they had not backed off).

So, I adjusted them again, using the process to tighten the collar mechanically while turning the rotor, back it off, and then finger tighten it. They seemed fine.

A few days later, and they were loose again..... Both sides....

What am I missing here?

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08 Apr 2012 17:13 #8832 by 928mac
Stan I have never been in there. Are they the tapered bearings with two cones.

If so, sometimes the cone/rases do not seat all the way and you really have to crank them tight to seat everything before you loosen them off and set to the correct preload. If they are new bearings they can be set tighter as they will ware.

Brad

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08 Apr 2012 17:36 #8833 by the flying scotsman
Need more info Stan........which bearings? which 928?

Brad theres 2 sets of brgs per hub.

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08 Apr 2012 18:09 #8834 by srshaw3

Stan I have never been in there. Are they the tapered bearings with two cones.

If so, sometimes the cone/rases do not seat all the way and you really have to crank them tight to seat everything before you loosen them off and set to the correct preload. If they are new bearings they can be set tighter as they will ware.

Brad

Need more info Stan........which bearings? which 928?

Brad theres 2 sets of brgs per hub.


Front bearings, '90 GT.

If worst case scenario is that I need to keep adjusting them until I have them properly seated, I can live with that. It is a quick process to do, once it has been done a few times :)

I am always hesitant to over tighten things, I did it too often when I was a teenager and didn't yet have a torque wrench. In this case a torque wrench can not be used.

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08 Apr 2012 20:58 #8840 by srshaw3

ok........did you take the hub off?

If not they might not be centered in the races.

BTW.......the vibration will wreck the bearings.....they should be set correctly before driving.


I took the hub off to replace the bearings of course. I also woosed out on punching the races out myself, and had a local shop do it, as they do such work all the time.

The rotors seem to spin just fine, making me think they are set right.

This problem is not much different than where I started, as the bearings needed adjustment, so I figured why not change them since the car has 165k on it. I was getting the vibration before changing them, and am now adjusting them as the vibration shows up.

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08 Apr 2012 22:10 #8847 by srshaw3

Stan....I meant did you take the hub off and do both sets per side? Just wanted to be clear of course.

the proceedue per the WSM is very specific:


Yes, those are the directions I followed, the level of torque to be applied is subjective and I am probably more inclined to not torque too much.

Inner and outer wheel bearings and races were replaced on both sides of the front of my '90 GT. The actual bearing and race install, in the hub, was performed by a local service shop.

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08 Apr 2012 23:08 #8851 by 928mac

In my personal experience when first installing the hub after new brgs I tightend the nut very hard to fully seat everything then backed it off then reset the nut per the WSM.

Recall your seating 4 cones and 2 races per side.


isn't that just 2 tapered bearings and 2 inner races? per wheel

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15 Apr 2012 20:31 #8929 by curtisr
Stan,

Same thing happened to me. I replaced the bearing races, pressed in new cups and, of course, updated the seals as well. After that I turned the clamping nut as directed by various posters (elsewhere) and what I found in this excellent youtube video:
(demonstration on a 944).



Thought I: 'Hey, this is just like my old bicycle wrenching days!!! A repack...what could be easier?!' Famous last words, right? :D Sure enough, I could feel a vibration during my test drive. What's this?! Well, what I didn't do was follow the adjusting of the clamp by putting the wheel back on to see what the additional leverage one gets had to say about my handiwork. Two adjusting sessions and test drives later, I thought the problem must be about getting the grease worked in (or is that worked out?) Anyways, afterwards I spoke to a local expert who suggested that leaving a little play was a good idea thanks to the magic of thermal expansion. Certainly, a little play seems to disappear after a 15-20 minute drive...

When I used to set up the old style cup-and-cone, loose-bearing bicylce wheels for track racing it was fine machine oil and some play to be sure. Not that there was much expansion--to my knowledge anyways but, one just felt better for this type of set-up.

Roger C.

Attached files [img]media/attachments/9122=1031-P2200002 resized.jpg[/img]

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15 Apr 2012 20:53 #8932 by srshaw3
Video looks great, thanks. Definitely not how I was using the screwdriver....

I did drive @400 miles this weekend, and while there is still something going on in the front end, it may not be the bearing any more. I will check it again, just to be sure.

At one point I was told I had a bent wheel, but I have received so much incorrect information from mechanics, I am hesitant to act on it.

I did have loose bearings before all this started, and thought refreshing them on a 165k mile 928 with unknown service was a modest investiment :)

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18 Apr 2012 09:14 #8950 by SeanR
Stan, I've had this happen on my car a couple of times when I installed new bearings. Have not had it happen on a customers car though, makes no sense to me but it happened. Just test it with the wheel on and if it's loose, go in and re-tighten it, unless it was really, really loose, there won't be any damage.

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23 May 2012 09:25 #9286 by srshaw3
I felt the vibration returning, so I checked it again today, and it was loose again.....

I am wondering at some point how does one determine if the spindle has been worn down, or is that possible?

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23 May 2012 12:52 #9289 by srshaw3

.....or the new bearings are no good?!


Well, I changed the bearings because the right side was loose, and I had adjusted it once already, so since the car has 165k+ miles and I had no idea how old the bearings were, or when they had been repacked, I chose to change them. There isn't an issue on the left side, just the right side, same as before....

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23 May 2012 14:30 #9290 by srshaw3

process of ellimination would determine that the bearing rides on 2 components so either one or all are worn.

Then whatever is determined to be the root cause is replaced with a new bearing.


I agree Malcolm, that is why I asked how to determine if the spindle is worn.

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30 May 2012 16:45 #9366 by 928mac
Hello Stan,
did you replace the bearing cup in the hub for each bearing assemble.
IMO that is where it is getting loose. If the hard cup was not perfectly clean and did not seat in the hub correctly, then as you tighten it or drive it the bearing cup will walk into the hub more causing the bearing to be loose. IMHO
this is why I said that when you tighten it really really crank it tight while turning the wheel against the rotation of the nut until you can not tighten it any more.
Then back it off and set the preload
This is the only thing I can think of that is wrong.

I hope it helps Stan, give it a try or take it all apart, wash the hub clean and see if you can see any space behind the bearing cup where it is not seated against the hub

www.google.com/url?sa=t&rct=j&q=bearing%...Y_HH24B_oXUloaLri_fQ

www.google.com/url?sa=t&rct=j&q=bearing%...x8eBzdzkb3PXuQONKtqA

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30 May 2012 21:02 #9367 by srshaw3
Hi Brad,

I think the cup you are referring to is what I call a "race". Yes, they were replaced. I suspect the spindle or hub is worn, as there was a "loose" issue before I swapped them out.

I checked the right side again last week, and it took another 1/2 turn of adjustment, and my suspicion is that it is now at the bottom of the threads, as I really could not turn it any farther with a reasonable amount of force.

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30 May 2012 22:10 #9368 by srshaw3

Stan,

if your convinced you have one side good one side bad then measure both and see if theres significant diff. then take steps.

Brad does have a valid point but given the amount of time its perhaps too late to get them correct.


well, not necessarily convinced, but it is the direction I lean in, and it is what I plan to do next, I just haven't gotten to it yet :)

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