Wheel Bearings - Preload Question

[Menaces Nemesis]

I'm genuinely curious about this, not trying to instigate, or downplay anyone's commonly accepted procedure, just trying to glean some understanding for myself and others who may be curious too, so please bear with me...

I can understand if we've just pressed in new bearing cups (mated with new cones of course) that we'd want to be certain that the new components are fully seated in the drums and spinning true, so torquing to hundreds of pounds would make sense (which seems like would translate to literally tens of thousands of pounds of linear force applied to the components). I also understand that we need to get the new, excess grease pushed out from between the components so we can get an accurate feel of how much play we have, but the bearing cages are open and unsealed inside and out, so I can't imagine there we be any hydraulic pockets to overcome. So, what exactly is it that requires so much force to be used to seat rigid, seemingly uncompressable, previously used and seated components? Please be descriptive in your responses, and please don't reply by saying something like "just because thats the way it's always been done". Instead, please state exactly what shifts within an assembly of used, previously seated bearing components, or is so resistant to finding it's way "home" that requires so much force (especilly if there's no wheel(s) attached to the drum). Thanks in advance for your replies. - MN.

 

[Floridianson]

No it is a good question. They don't say percisely why but something about RP618 which must be an industry standard. It was not said before in this thread but in other threads the dial indicator was talked about. So if we want to do it right then the high preload then preload then dial indicator would be the correct way. One would think our shade tree way would be good for our military stuff that does not run heavy loads at high speeds but correct is correct. Guess if I was running a shop I would insist on the dial indicator.https://www.truckinginfo.com/151567/are-your-wheel-bearings-adjusted-properly

 

[Menaces Nemesis]

No it is a good question. They don't say percisely why but something about RP618 which must be an industry standard. It was not said before in this thread but in other threads the dial indicator was talked about. So if we want to do it right then the high preload then preload then dial indicator would be the correct way. One would think our shade tree way would be good for our military stuff that does not run heavy loads at high speeds but correct is correct. Guess if I was running a shop I would insist on the dial indicator.https://www.truckinginfo.com/151567/are-your-wheel-bearings-adjusted-properly

Thanks Floridianson. Very informative read. A search for RP 618 led me to the 8 steps on Timken's site here;https://www.timken.com/pdf/10420_Wheel Bearing Adjustment_Poster.pdf Sub-step "D" of step 8 is kinda what I do when I grab 2 opposing lugnuts and shove the drum in and out... just gotta figure out how to get my "tiny thunk" calibrated to .001"-.005"

 

[silverstate55]

My guess would be due to wear, however little or excessive...not to mention temperature variations that expand/contract metals, possibly causing minute movements & changes in the bearing races and seating of components over time. A good bit of pressure to re-seat everything together should put it all back in order.

But then again I’ve been known to not know what in the heck I’m talking about.....

 

[Floridianson]

OP talks about walking the rollers up race to there correct place in another thread. So sounds good to me and I don't believe you could ever correctly feel the lash without a dial indicator. So guess we barn yard them or buy a dial indicator. I barn yard.

 

[rustystud]

OP talks about walking the rollers up race to there correct place in another thread. So sounds good to me and I don't believe you could ever correctly feel the lash without a dial indicator. So guess we barn yard them or buy a dial indicator. I barn yard.

That is why I always bring the torque to over 200 ft Ibs. then back off until jam nut is free again and then slightly tighten again. No need for the dial indicator. Every mechanic I have ever known does it this way.

 

[Floridianson]

I don't know Timken says use a dial indicator so we take the time to do it right these days. Thought you even said it awhile back dial indicator was the only correct way. What if it is a customer then he has to pay the price. I will do my own old military stuff as said the TM's way but as I said if I ran a shop today working on new trucks then we would use the dial indicator as called for. Mechanics make mistakes too so this would just insure they were awake when they did the work. Todays trucks run big weights and long miles compared to our old stuff that most likely sits in the driveway or just for fun use. Close enough for government work is the old joke and I believe we should hold to higher standers in everything we do in life and or teach. https://www.timken.com/pdf/10410_Manual Wheel Bearing Adj Procedures Sell Sheet.pdf

 

[Floridianson]

Found this. How would we teach a person that has limited experience with what the lash should feel like. No we would use a dial indicator to double check what we have done. We seem to think the old TM's are the bible and just because I did it that way does not make it correct. In one of your post you did say measure so what is the correct way to measure without a dial indicator. We guess or we know, old school or new school of thought. https://www.anythingtruck.com/commercial/740-wheel_bearing_adjustment.pdf

 

[rustystud]

Found this. How would we teach a person that has limited experience with what the lash should feel like. No we would use a dial indicator to double check what we have done. We seem to think the old TM's are the bible and just because I did it that way does not make it correct. In one of your post you did say measure so what is the correct way to measure without a dial indicator. We guess or we know, old school or new school of thought. https://www.anythingtruck.com/commercial/740-wheel_bearing_adjustment.pdf

Yes I believe in one of my earlier posts I did say to use the dial indicator. That is the "correct" way. I guess I should have explained the correct way to do it since trying to "tell" someone how it should feel instead of actually "showing" someone is a big difference. What is tight to someone is loose to someone else. But after decades of experience and knowing how a properly mounted hub feels like I can get by without the dial indicator.

 

[DavidWymore]

When doing the hubs on my '62, I found the tricky part was that the second nut would push the first nut in on the slop in the threads and tighten the bearings tighter than my initial adjustment, so some fiddly trial and error was necessary.

Indicator is definitely the way to go for schooling over the internets.