uniberp Posted July 21, 2009 Share Posted July 21, 2009 I replaced a front axle that was clicking-clunking, did the brakes while I was in there, and reassembled the whole thing. Before I lowered teh car so I could tighten the axle nut, I noticed the whole assembly shook as if a wheel bearing was loose. "AhHa, I said, that's the source of high speed vibration." So I disassembled it and took the hub to shop to have a new bearing pressed. Happily reinstalled the hub, connected tie-rod and balljoint, bolted up strut and brake caliper, and tightend everything but the axle nut. Lo and behold, it still rocked a little the same way as if before the bearing was replaced. "What the heck?" The old bearing felt to the hand quite loose but not grindy. The new bearing was smooth as is should be. Yet the new assembly moved visible, maybe .125" at the tire edge, and I could feel the movement. Oh wait, as I write I realize the preload on the inner race is set by the axle nut. Or that the inner races are tightened against the spacer by the axle nut. My bad. Nevermind. Oh well, it still seems to feel tighter while driving now. I guess it was worth the extra $90. Link to comment Share on other sites More sharing options...
idosubaru Posted July 21, 2009 Share Posted July 21, 2009 So that is normal? I had this happen after a shop did some front bearings for me. One of them had a bit of play like you said and the shop told me it was normal. It was the first time I had ever done bearings so i took their word for it. Those bearings worked and lasted just fine, so I always assumed the guys were right. Link to comment Share on other sites More sharing options...
CNY_Dave Posted July 21, 2009 Share Posted July 21, 2009 The preload confuses me a little bit. I think when properly installed the inner faces of the two inner races are supposed to be in contact with each other, but I can't for the life of me figure out what keeps them in contact other than the inner race friction fit on the hub. When you press the hub into the inner races, you don't drive a wider portion of the hub against the outboard inner bearing, the outboard inner bearing could move further outboard if it was a loose fit on the hub. The inboard inner race rests against the face of the outer CV joint. The only time you set the bearing preload is when you press the hub into the inner races by driving against the hub and supporting the inboard inner race. That is, the friction of the hub to the outboard inner race drives the outboard inner race against the inboard inner race. As long as the 2 inner races are touching, the preload is correct. If the outboard inner race is a loose fit on the hub, it may never be driven against the inboard inner race. Or is there a step in the hub I'm forgetting about that bottoms against the outboard inner race? Dave Link to comment Share on other sites More sharing options...
Fairtax4me Posted July 21, 2009 Share Posted July 21, 2009 Or is there a step in the hub I'm forgetting about that bottoms against the outboard inner race? There should be a step that sits against the outboard inner race. Otherwise it might be pressed on too far and the hub would rub against the outter race. Then with no room to get a tool between the only way to remove the hub form the bearing would be to destroy it because the outboard inner race would be pulled out of the bearing assembly. The axle nut should not affect bearing preload on this type of setup unless the hub was installed incorrectly. Are you sure the movement wasn't because of a worn ball joint or tie rod end? Were the lug nuts tight or just snug enough to hold the wheel on? Link to comment Share on other sites More sharing options...
CNY_Dave Posted July 21, 2009 Share Posted July 21, 2009 There should be a step that sits against the outboard inner race. Otherwise it might be pressed on too far and the hub would rub against the outter race. Then with no room to get a tool between the only way to remove the hub form the bearing would be to destroy it because the outboard inner race would be pulled out of the bearing assembly. That's what I think, but I distinctly remember there not being a step there because there was no hint (on the assembly) on how far to press in the hub. It was easy getting the outboard inner race off the hub because there was a gap between the inner race and the outer edge of the hub. It seemed there was the possibility of pressing the hub in too far and pressing it into the outer oil seal. Well, it's been 10,000 miles or so... The axle nut should not affect bearing preload on this type of setup unless the hub was installed incorrectly. Are you sure the movement wasn't because of a worn ball joint or tie rod end? Were the lug nuts tight or just snug enough to hold the wheel on? Or maybe the axle nut was never fully tightened, but I have to imagine the bearings would not last so long. Dave Link to comment Share on other sites More sharing options...
johnceggleston Posted July 21, 2009 Share Posted July 21, 2009 i'm going to play dummy here, not hard for me. the nut may not do any thing to set the bearing properly, but it certainly does do something to protect the bearing when there is a load on it. what's the difference?? there must be a very fine line between the two. Link to comment Share on other sites More sharing options...
Log1call Posted July 21, 2009 Share Posted July 21, 2009 The axle pulls up against the inner bearings inner race and the disk/hub pulls up against the outer bearings inner race. The nut holds the two inner bearing races tightly together which applies the correct amount of preload to the bearings. It is important to tighten the axle nut while the wheel is still up in the air though, otherwise there is a possibility that the bearing inner races may not align correctly. I always rotate the wheel as I tighten the nut and then loosen, rotate and tighten again to ensure everything is aligned and square, then I tighten the nut fully once the car is on the ground. With new bearings in good housings there should be no play at the wheel from the bearings. Link to comment Share on other sites More sharing options...
CNY_Dave Posted July 22, 2009 Share Posted July 22, 2009 The axle pulls up against the inner bearings inner race and the disk/hub pulls up against the outer bearings inner race. The nut holds the two inner bearing races tightly together which applies the correct amount of preload to the bearings. It is important to tighten the axle nut while the wheel is still up in the air though, otherwise there is a possibility that the bearing inner races may not align correctly. I always rotate the wheel as I tighten the nut and then loosen, rotate and tighten again to ensure everything is aligned and square, then I tighten the nut fully once the car is on the ground. With new bearings in good housings there should be no play at the wheel from the bearings. I still say I didn't see a shoulder for the outboard inner race to rest against, even though I know there should be. The inner race was easy to get a hold of to pull from the hub, unlike a toyo I just helped out on where the race was up against a shoulder. This'll teach me not to take pics... Dave Link to comment Share on other sites More sharing options...
hohieu Posted July 22, 2009 Share Posted July 22, 2009 Log1call is absolutely correct. It's the outer race the holds everything stationary inside the housing (knuckle). There's a step on inboard side of the housing for the rear and the outboard side for the front as well as a retaining clip on the opposing side. Preload is set when tightening the axle nut, which presses the inner races against one another and the rollers against the tapered rolling surfaces of the outer race. Now if you have play in the entire knuckle assembly, then there's a problem with either the lateral or trailing link bushings. Link to comment Share on other sites More sharing options...
CNY_Dave Posted July 22, 2009 Share Posted July 22, 2009 What I would clarify is that no matter how much you torque the nut, you will not increase the force/pressure on the rollers (or balls) (which is what I would call preload). The preload is set by the dimensions of the inner races, and axle nut torque (axle stub stretching) need only be sufficient to keep road forces from separating the two inner races where they meet. Dave Link to comment Share on other sites More sharing options...
uniberp Posted July 23, 2009 Author Share Posted July 23, 2009 Thanks all. Yes, there is NOT an adjustable preload on the bearing. When the axle nut is pulled tight, it is set to a specific tolerance and load. NO amount of excess torque (unless destructive) will change the preload. What was interesting was the difference between a worn-but-still-good bearing and a new bearing. Quieter and handling feels tighter. The ball joint and TRE were still quite stiff as they should be. I'd now recommend (front) wheel bearing replacement at 150k. That and the new GR2's make it feel as nice as my 08, albeit slower. What I would clarify is that no matter how much you torque the nut, you will not increase the force/pressure on the rollers (or balls) (which is what I would call preload). The preload is set by the dimensions of the inner races, and axle nut torque (axle stub stretching) need only be sufficient to keep road forces from separating the two inner races where they meet. Dave Link to comment Share on other sites More sharing options...
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