So, now with the trailing arm off & old bearing out & new timken in freezer I started to measure with my digital calipers & get:
Trailing Arm recess=2.950" room temp (95F today)
Bearing O.D. =2.9525" cold (maybe 20F)
Interference = .0025"

Is 2 1/2 thousandths OK? I'll heat the trailing arm recess prior to installing, but bet I'll only gain maybe a thousandth, leaving 1 1/2 thou interference for the press to overcome....

But, the next question is more disturbing...the hub to ID of the bearing is:
Hub O.D. = 1.6520" warm
Bearing I.D. = 1.6475" cold
Interference = .0045"

Of course I've put the hub into the freezer and will wait for the bearing to come to room temp prior to assembly, but I'm guessing I'll still be dealing with .003" interference there and that seems like a lot....need someone with bearing fit tolerances to chime in here.....anyone?

When is the last time your calipers were calibrated ?

No matter what calipers you get, they are only good for +/- .001. Since you are using the jaws on the Id of one, and the od on the other, I wouldn't trust your measurements. If you have standards to check your calipers, might want to do it. See if one of your local guys has a mic set and good starett telescoping gauges.

I never heated the trailing arm installing bearing. I froze the bearing, applied a coat of lithium grease, pushed it into the housing while still cold. Used a 1/4" flat plate to drive it in and seat the bearing flush.

Pulling the hub through the bearing, I used a homemade tool from all thread, spacers that supported the back side of the bearing and pulled it in.

Never worried about interference fit. This is automotive stuff, not aerospace and the tolerances allowed are like shooting the side of a barn with a blunderbuss.

thats funny...but true.
fat peice of steel and a dead blow (shot filled, plastic outer) hammer.
I heat the arm and drive it in liike Ron described above. its not that hard. just keep it going in STRAIGHT.

The "proper way" would be to use a hydraulic press and only press on the outer race. Beating them in may get you there but it's a hack job. The difference between the height of the inner race and outer race is minimal and a 1/4" plate would most like flex enough with a firm blow to contact the inner race and to the balls. Given a choice, I would heat the arm before I would beat on the bearing. However, I would be lying if I said I never beat in a bearing

The proper way......
Click to view attachment

i had my bearings in the freezer for about 2 weeks. cleaned the inside of the trailing arm with scotch brite and applied a thin coat of grease. it took only some light tapping with the rubber mallet.

I have done many of these. it only takes some tapping. its not a hammer-fest. they go in easy.
removing the trailing arm is a waste of time. there are many times when using a hammer is OK if one is not beligerent about it. using a press does allow you to stick out your pinky while doing it :"the proper way"

Yep, you're right about the positioning of the jaws....lots of error available there, which is why I use the technique of multiple, multiple measures with constant light pressure on the thumbwheel and only recording the highest on ID or lowest OD reading. Also, the absolute measurement isn't the point or to be trusted, it's the relative measurement that's useful as I took these readings back to back with the pieces right next to each other. Even though it's a cheapo digital, I'd stack up the relative measurements against any other instruments within the tolerances we're looking at....
That said, taking your advice about error in the positioning, with both pieces cold this morning I got .0015" intereference on the bearing ID to the hub OD...looks OK to me.....on to the assembly!

He said the trailing arm was already off.....

I don't see the logic in suggesting to the man to beat on a bearing with a hammer which is the method most likely to damage a bearing when he has the arm in his hands...... A threaded rod is another alternative if on the car. If beating on a bearing works for you that's great, I guarantee you will never find that method in a repair manual. However, when people come here asking for help I think it's important to at least provide them with methods best suited for success as well as the lesser desirable methods if you don't have the proper tools.... Take a look on the Bird Board and you will find thread after thread of people having issues after beating bearings in and out.

My worries are this.....People in the future do a search and find a thread like this and all they see is the hammer method. Haven't we done them an injustice? Yeah, my pinky is out but I'm not ashamed....I'm just trying to help people that are asking for help...

The all thread method is way better than a hammer!

I have bearing press plates that come in 6 different sizes and I took a large washer that I ground to fill in the final edge of the bearing! By using the press plates and the washer it eliminated any flex that may have pushed on the inner race.

Once you have the all thread in and the edges of the bearing started you can switch to air tools to finish pulling the bearing in!

I have done this 6 or 7 times with no problems!

Bearings and a hammer .....if you force it in the balls will not have room to rotate .... ....Arbor press is the best ...you can feel things moving ,,unlike a hydrolic press....JMO..I have replaced thousands of bearings in my 23 years here at the B*$#@g company and have not one failer .....dont get in a hurry use the proper tools and for god sakes put the hammer down...even the slightest damage to a bearing or race will reduce its life by half if not more ...good luck with the project ....again JMO

NSK has some good info on there web site with pixs

http://www.nskamericas.com/cps/rde/xchg/na...ml.........look up fractures ...thats what you will be doing to the bearing when you strike it with a hammer

Proper way is to press the arm down onto the bearing...

http://www.youtube.com/watch?v=T6CxhlpOvng


https://www.youtube.com/watch?v=T6CxhlpOvng

Another proper way, freeze bearing, put grease outside edge and place a 2x4 on it and beat it in. Done.
as stated before - keep straight.

Picked up this kit last year, works with the hubs on the car, using only wrench effort, removing and installing.

Click to view attachment

http://www.sirtools.com/hub_kit.htm

looks like a nice set ....wish i had one like that ...I just to set the record strait i destroid a bearing in my 914 I purchase from PMB by not using the proper tools ...it cost me time and a new bearing ...again take your time and good luck

Using a hammer is asking for trouble ...

okay new bearing is pressed in new hub pulled in all installed nut tightened all to hell and everythings real good no play at all. Play time!!!

Nice if you have $400 to blow the last time I looked for doing bearings about once every two years.

No beating/tapping required. if you freeze the bearing and apply a thin coat of grease into the arm the bearing will just slide right in all the way.

2 times outta 10. Very rare.

Maybe I should buy a lottery ticket. I installed two new bearings a couple of days ago, and after having the bearings in the freezer overnight, both rears slid right in by hand with zero effort.
Once in, they quickly expanded and stuck right where they should be.