80 replies to this topic

[Bench Racer]

Johnny, to answer your question.

There has been a gap forever on front axle bearing assembles with rear wheel drive. Granted there are some older British cars that have spacers between the inner races. 

Not smart enough to post other complete assemblys with stub axle.

With this assembly the stub axle would be on the right side of these parts

Please note there is no spacer between the cones (inner races), there is a end gap between the cones (inner races). 

My best words to answer your question is, no the cones (inner races) will not spin/rotate because the axial load/force applied by the the nut through all the bearing parts into the stub axle is greater that the radial load/force applied by the tire/wheel/hub/outer race rotating. 

IMHK, there should be clearance between the ends of the Miata inner races.

This assembly has what I call real outer races/cups which is more costly to manfacture and assemble than the outer races machined into the hubs as the Miata outer races are.

[Johnny D]

Yes, I'm in the not smart enough either camp.

 

The gap that "forever" has been there, is not just there because it's not tq'd when you look at it?

 

I saw the midget sketch online with fixed spacer, seemed to be important distance with the bearing load angle.

The Miata hub has a fixed distance, seems that a fixed distance for the inner races would be needed as well.

It still has the spacer, just split in half for assembly purposes.

IDK

J~

[Bench Racer]

 

 

Yes, I'm in the not smart enough either camp.

 

J~

 

For those in Johnny's camp, within the picture in post #41 there is no cone (inner race) shown inside the caged bearings fo rthe inner bearing like there is a cone shown within the bearings for the outer bearing. Let's use the 1990 Miata FSM torque numbers of 123/159 foot pounds of torque. Have you noticed as you incrementaly torque the nut from 123 ft lb to 159 ft lb the wheel assembly does not rotate with the same freedom? You could torque the nut all the way to whatever ft lb value greater than 159 ft lb provided the inner races didn't touch and the wheel assembly would have less freedom to rotate. If Miata or the bearing manufacture intended for there to be no inner race end gap they could give a torque value of 300 ft lb and and the wheel assembly would have the same freedon to rotate as if it were torqued to the 159 ft lb value. Johnny, becasue you state your in the "not smart enough camp", you obiviously have in your life time taken apart minimal different rear wheel drive front wheel bearing hubs. Lastly please scroll to page 8 of this address http://www.sanjuan.e...il Seals TB.pdf  , the inner race inside edges do not touch. There are many different bearing assemblys for many different functions.

[ChrisA]

^  Bench, the SKF reference of 216 is Nm not ft-lbs. SKF just provided the maximum value in both measurement units.

[Bench Racer]

Chris, thanks.

[davew]

You guys are trying to turn apples and bannanas into oranges. never going to happen. A gt3 car vs an old GM diagram vs a Miata with a lot of mis information.

 

To start, lets settle on some terminology.

The spindle is the metal spike that sticks out from the upright

There are 2 inner races, one inboard and one outboard. These are the silver metal parts you remove to gain access to the ball bearings

There are 2 sets of ball bearings that ride in a plastic retainer to keep them evenly spaced

The outer races for the ball bearings are machined into the hub, which also has the lug studs installed and spins with the wheel.

When assembled I will call it a front bearing assembly.

 

The inner races fit tight on the spindle and do NOT spin. Although not a precision fit, there is virtually no gap between the spindle and inner race inner diameter. The inboard inner race, when installed, bottoms out on the flange at the base of the spindle. When you tighten the nut, the outboard inner race must contact the inboard inner race. If it did not contact, the tension on the ball bearings would cause binding. Picture the 2 inner races installed with no hub or bearings. If the inner races had a gap between them, tightening the nut would decrease the gap in the "U" the ball bearings ride in. The positioning of the inner races has to be very precise. Just a couple thousands of an inch would cause bind or looseness. Any grease stuck between the inner races will change the relative positioning of the races. I feel this is why retorqueing the nut sometimes helps. This machine tolerance seems to be one of the differences between cheap and expensive bearings.

 

I do not feel the torque on the nut is going to squeeze the inner races enough to change their relative position. There is very little, if any preload on these bearings. Any endplay is what we are discussing here.

 

The diagram above from Dewy, shows a system as used by virtually all rear drive manufacturers for 50+ years. The key factor being the cotter pin to lock the nut in place. Neither the inner race (often referred to as a cup) nor the outer race (part of the bearing "cone") touch. End play/preload is adjusted by tightening the nut and then locking it in place with the cotter pin. There have been multiple versions of this system over the years, some use a castle nut, some a castled lock ring, some a bend over tab, some double nut, some have locking screws. But in all cases they use 2 sets of tapered bearings rather than our roller bearings.

 

I have seen both inner races and the outer bearing surface of the hub fail. I assume it is either of the races that fail first and not the bearings. Even poor quality ball bearings are pretty darn good.

 

My opinion; The original bearings with many thousands of miles are the best. The surfaces have work hardened them selves before we start abusing them. Even the super cheap ebay bearings would be fine for a daily driver. Driving style does seem contribute to bearing life. The more abusive to the front tires seem to be more abusive to the bearings also. repack any bearing with a high quality synthetic grease. I like Schaeffer grease, but CV2, Mobil etc all seem to be just as good.

 

For a perminant fix, someone smarter than me would need to design a hub similar to the one in Dewys diagram. It would utilize tapered roller bearings that could be replaced cheaply and still use the stock brake disc. I can visualize it in my head, but I am not a machinist. this would require a cotter pin hole to be drilled into the spindle. I would guess a rice of $300-$600 per pair.

 

That's what I think

Dave

[Bench Racer]

Dave, no disagreement on the physical description of the parts within the front hub. If as you say, a design parameter at the get-go is for the inner race indside ends to touch, zero inner race end gap, HOW COME the inner races of the my spare set of hubs when torqued o 150 ft lb have a .005/.006 inch inner race end gap between the indside ends with no inner race inside end spalling? Another HOW COME would be, why does the failed hub I collected from Jared Gerber #9 at the Farm Major race have spalling on the inner race inside ends? The Jared outer races, the inner races, the ball cage and the balls look visually good. Only queer visual item is the spalling of the enner ends of the inner races. If I were to put the Jared hub together and on a spindle on my car, there is zero dought that at 150 ft lb of torque the 12 and 6 o-clock grip position would produce a woobly hub. That would be the reason Jared changed hubs. I will also suggest if I were to take apart one of the good hubs on my car and do the same measurements I did with my spare hub, I would find inner race inside end gap clearance and no spalling, because there is inner race indside end gap clearance. Did you look at some failed hubs and did the failed hubs have spalling on the inside ends of the inner races. No one wants to answer that question. What created the spalling on the Jared inner races?

 

As a side I have found tapered roller bearings with different outside diameters and 28 mm inside diameters, back load both bearings into a billit machined hub/flange and install screw in studs rather than knurled bolts.

[38bfast]

I agree with you Dave. We would be better off using roller bearings vs balls. I have somewhat started investigating tooling up a part that i want to test.

[Bench Racer]

I agree with you Dave. We would be better off using roller bearings vs balls. I have somewhat started investigating tooling up a part that i want to test.

Both of us.

Dave Dewhurst

 

Ralph, whats your take on the inner ends of the inner races, gap or indside ends touching?

[Keith Novak]

Installation note:

 

they say that you should NOT grease the spindle when installing. some times the hub does not like to slide home. does anyone lubricate the spindle before you install the hub? 

I lightly grease.  It says so in my factory manual.  I've had to look several times to find the torque and it has that little oil can symbol.  BTW the 167-215 Nm should not be confused with 123-159 ft.lb  Whole different set of units.

 

I don't think the inner races should contact.  If so, as Frank said, it would be a critical dimension.  I'm not a machining expert, but I've looked at a few different hubs and races I have sitting around and I don't think any of them are machined to the tolerance I would expect if that dimension was to limit the preload on the bearing.  That would require very high tolerances, particularly considering the heat build up in the hub and the components subject to thermal expansion.

[SaulSpeedwell]

Dave, no disagreement on the physical description of the parts within the front hub. If as you say, a design parameter at the get-go is for the inner race indside ends to touch, zero inner race end gap, HOW COME the inner races of the my spare set of hubs when torqued o 150 ft lb have a .005/.006 inch inner race end gap between the indside ends with no inner race inside end spalling? Another HOW COME would be, why does the failed hub I collected from Jared Gerber #9 at the Farm Major race have spalling on the inner race inside ends? What created the spalling on the Jared inner races?

 

Bench, are you saying the races are spalled somewhere other then where the balls run?  Are you saying it is spalled where the inboard inner and outboard inner races are touching? 

[Bench Racer]

Point A. Bench, are you saying the races are spalled somewhere other then where the balls run? 

Point  B. Are you saying it is spalled where the inboard inner and outboard inner races are touching? 

I have not interfaced with nearly as many hubs/bearings as you. The few good I have had apart never had spalling on the inner ends of the inner races other than the one failed hub from Jared #9. Previous to viewing the failed hub I would have thunk the inner ends of the inner races should not have been touching. My thought would be to costly to control tolerance to acheive torque and inner ends touching. 

 

With the failed hub/bearings, the outer races ball surfaces, inner races ball surfacse, balls, cages, OEM grease all look good/normal.

 

Point A. yes.

Point B. Yes.

 

My pc is at the Geek Squad, untill maybe Tue.

[SaulSpeedwell]

That doesn't really make sense to me, Bench - unless the inner races "spun", which they certainly should not.  This could be a fluke data point that isn't related to the general theme of failures.

 

I have "spun" rear hubs inside the inner races (failure of the press fit due to bearing starting to "seize").  It leaves an odd witness mark behind, like that of thinly spread frosting - but I wouldn't describe it as "spalling", which is has a very specific appearance when talking about the bearing races and balls/rollers.
 

[Bench Racer]

That doesn't really make sense to me, Bench - unless the inner races "spun", which they certainly should not.  This could be a fluke data point that isn't related to the general theme of failures.

 

Maybe spalling is a poor choice of words to describe the different marks I view. The normal view is the ends of both inner races being ground with no other interfearance marks. Maybe a better description would be to say what I view are craters from the end surfaces axially banging back and forth against each other. They don't look like rotational craters. Maybe I need to view these ends under a scope rather than an eye piece. Maybe I need to find some time and put this hub/bearings back together, on a sindle and at 12 and 6 and wobble the sucker. I see nothing of the bearing balls, inner or outher races visually damaged.

 

Other than this one pair of inner races, my thoughts would be that the ends of the inner races never touch even when torqued to specification because I've never viewed the ends being anything other than a ground surface. Limited parts viewed.

 

Have you ever viewed the inside ends of the inner races being anything other than a ground surface? Have you measured the end gap when torqued to specification. I've measured two different hubs and both measured a .005/.006 inside end gap/clearance. Keith measured an end gap to be the thickness of a sun flower plastic bag, no touch for his inner race ends.

 

I've asked others to view their failed hubs, inner race inside ends as to what they view, no responses to date.

 

Brandon's parts guys increased the torque from 140 lb ft to 160 lb ft and the wobble went away. Is that saying the inner races have a clearance gap and the ball bearing functions the same as a tapered roller bearing?

 

Untill a hub/bearing manufacture provides the information, there is some unknown relative to inner race inside end gap clearance or no clearance. Because of the tolerance manufacturing costs and the couple measurements I've completed which show a gap, I'm thinking clearance gap. 

[Pat Ross]

Bench,

 

When either the inner race, outer race, or balls lose material the ends of the two inner races will move toward each other.  When they do they can rub against each other.  Has the "spalling" been noticed in bearings that are still in good shape, or only in those that have failed?

 

Pat

[Bench Racer]

Pat, I understanad as wear takes place the indside ends of the inner races will will move closer together.  I have four good hubs/bearings and they all have a gap between the inner ends of the inner races.
I have one failed hub From Jared Gerber #9 at the Major race at Blackhawk Farm. This is the hub with the inside ends of the inner races that have spalling/craters/doesn't look like rotational (not perfect ground surfaces as my other 4 hubs, guess, ends have not touched) which I presume is because the ends axially touched. Everything else visually looks good. Again, my number of hubs/bearings/races viewed is minimal. I'm looking for others to add their info. I did send an e-mail to NTN bearing asking the question, are inner ends of inner races per design to touch or should there be inner race inside end clearance. My computer has been at the Geek Squad since the 23rd, it took a large $hit and they have not been able to find/bring back my e-mail stuff (lost e-mail to NTN), just got it back. The only reason for my posting is I would like to know, inner race inside end touch or inside end clearance. Other than Saul, where O where are the folks who sell blueprinted front hubs????
Hey, maybe I'm the only one that don't know $hit. 

[Keith Novak]

I'll pull my hub this weekend and see if the ends of the races touch.  The one I "measured" and found a gap was off the car and not a failed hub.  The one on my car was one I bought in a pinch from CarQuest (their premium bearing).  It definitely had different races than the NTN because I tried to interchange them and they didn't fit.  These had play after one long weekend, uniformly whether you checked at 12 and 6, 9 and 3, etc.  This may not tell much about the Mazda comp hubs, but it may be an indicator that dimensional differences on white box brands may lead to very early failure.

[davew]

I must have missed something.

 

How are you measuring the gap between the inner races with the hub mounted and torqued to ??? foot pounds.

 

Dave

[Johnny D]

I must have missed something.

 

How are you measuring the gap between the inner races with the hub mounted and torqued to ??? foot pounds.

 

Dave

 

X-ray vision

J~

[Ron Alan]

I must have missed something.

 

How are you measuring the gap between the inner races with the hub mounted and torqued to ??? foot pounds.

 

Dave

I'm staying out of this discussion but super glad you posted what you did Dave(races touch)...I thought i was a lone loon bird!

For what its worth...have had the same front bearings for 3 years(may or may not have been the oem but I repacked them twice)and they are still good. And other than me in HPDE no slouches have driven my car!