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UPDATED QUESTION - Front tapered bearing upgrade

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tosoutherncars

tosoutherncars

Jedi Knight
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Hi all,

I'm installing new tapered bearings (30205 and 30303) during reassembly of Milo's front suspension.

QUESTION - when I attempt to reassemble, the disc isn't perfectly centered between the two pads. It's flush against the outboard pad, and with maybe a 2mm gap on the inside. (Picture to follow shortly.) Pads are brand new and very meaty.

Has anyone experienced this before? Do I just run it like this, until the outside pad wears slightly? It's pretty tightly bound up! I could grind a mm off the caliper housing, which would just about center things... but should I have to? The axle retaining nut is on, and torqued until some resistance is felt when turning the wheel.

TIA,
Duncan
 
Updated question: see above.

Here's a picture that illustrates the problem... with the caliper bolted up to the kingpin assy, the disc is seized onto the inner pad.

padgap.jpg
 
Did you retain the inner sleeve that keeps the correct spacing on the bearings. I have read that this is fairly important and should be shimmed to keep everything correct..
 
Hi Scott,

No, I didn't... There's some debate, but the Timken rep suggested *not* using it (see my next post for details.)

I'll have to go out and stare at it, but I get the feeling that, even if I were to use the spacer, and/or shim it, it would move the disc in the wrong direction! :p Must check though.
 
Found Where I read Such.. "Quote" Also, the tapered bearing is often installed without the spacer which may lead to premature wheel stub failure. (In order to install a spacer w/ the tapered bearing it may be necessary to either shorten or shim the spacer.) .....If you use tapered bearings it is strongly advised that a spacer is used.

-Daniel Stapelton "How to power tune ytour midget / Sprite." I dont however know if this would relate to your disc alignment...
 
Timken rep's discussion & install instructions follow (edited for length)

"In theory the spacer is clamped between two bearing inner races and
effectively creates a shaft of a larger diameter. The ability for
this theory to work you need a high clamp load. In the Spridget
design the ability to have a high clamp is limited by the small
thread size. Basically the threads start to deform before you have a
high enough clamp load applied. This theory is used on some Heavy
Duty truck axles.

As an ex MG Midget owner I know what you are going through and
hopefully can help you.

As you say trimming or shimming can be done on the spacer to achieve
the required setting. However the benefits you would gain would be
outweighed by the problems of achieving the correct width.

We would suggest that you rebuild the hub with the Timken bearings
you have and not use the spacer. The bearing inner races should be
greased before they are fitted on the shaft. The hub should be
rotated as the axle nut is tightened. This is to ensure that the
rollers are correctly seated. You should tighten the nut until you
can no longer rotate the hub by hand. The nut should then be backed
of until you can feel a slight axial movement of the hub. The cotter
pin should then be fitted. You should be looking to have an axial
endfloat in the bearings of between 0.001" and 0.003"."

I might think that competition Midgets might benefit from measuring, trimming or shimming a spacer. But I really question whether it's necessary for a road car, and Jeff's advice (above) makes a lot of sense to me.

That aside, though, it doesn't address the issue of centering the caliper ass'y on the disc. Thoughts on that issue, anyone?
 
My guess is that the inner bearing does not have the correct radius on the inner race to fully seat against the shoulder of the stub axle, moving the hub outboard.
The correct part number for the bearing should be 30205<span style="color: #FF0000"><u>X</u></span>.
Just working from memory here, so you may want to double check me.
Jeff
 
Hi Jeff,

The inner and outer radii of the Timken bearings are exactly the same as those of the spherical ball bearings. The only dimensional difference is in their width (hence the question of whether to reuse the stock spacer that fits between the inner & outer bearings.

I think you're 90% right... I'm guessing that the inner roller bearing is slightly *wider* than the original, axially. It seats beautifully in the hub, and the hub mounts nicely onto the axle, but the whole thing sits about 1mm too far out. (Maybe not even that much; just enough for it to bind when a caliper with brand new pads is torqued down.)

I can't find a 30205S listed in the Timken catalogue, but I'll do some calling around!
 
you might need to machine a couple 'thou off the flenge on the caliper or the bracket
 
Apologies if this is an annoying suggestion... but is it possible that the problem is with the caliper? A stuck piston perhaps? You probably already checked this, but I just wanted to throw it out there just in case.
 
You MUST have the correct rear radius on the inside bearing.

Push the rear bearing only on the spindle and tap the inner race GENTLY with a drift to seat it against the shoulder of the upright. Take a .001" feler gage and if you can get it between the shoulder and the back of the bearing you dont have the right bearing as Jeff says above. The Timken number for the right bearing has an X suffix.

At the end of all this to center eggzacly the rotor in the caliper you must trim the caliper attaching area about .040"....if you dont tho, everything will work fine.
 
That's excellent Jeff & Jerry, I'll go out and to just that. Your test is probably best done with the whole bearing, rather than just the inner? I ask because I think I have already pressed the outer shell into the hub. Ah well, not the end of the world if I have to carefully drift it out again...

Morris, no suggestion is too silly when it comes to me! /bcforum/images/%%GRAEMLIN_URL%%/wink.gif But no, the piston is fully back in its bore.

YES, just checked and I do have the bearing with the S prefix (as is noted on other threads; maybe they've changed their nomenclature). S-30205.

To review, just in case I'm doing something completely back assward... this is what I've done.

- remove ball bearings, drive out bearing outer races
- press in taper bearing races flush with inner step
- grease and install inner bearing, oscillate and push to seat, then cover with rubber seal
*note - rubber seal sits slightly proud of hub rear flange
- mount ass'y on stub axle
- grease and install outer bearing, tab washer
- rotate hub while tightening hub retaining nut until bearings preloaded
- back off until neutral / v. slight endfloat (.001-.003)
 
When I put in the tapered bearings I had to space the calipers by .070" (just had a machinist friend make up two .070" thick washers for each side) and have had no problem since.
Bill
 
Wow, you had to shim it, Bill? I've got to go the other way, and remove some caliper material... must have been different thickness bearings! Do you know what PNs you used, by any chance?

Anyone else done this recently?
 
I will have to look up some info and review what I did- it was about 2 years ago and I don't remember too well.
I'll get the info tomorrow.
Bill
 
OK, here we go. After a day of research, shopping, and websites, I think I have it figured out. There are two issues.

1) When I went to my local parts place, their computer actually listed the tapered bearing conversion for the Midget (!!) and showed the inner bearing as part number... 30205. Shock me. *BUT*... the notes said: "Machine down 1/8". Replace 1/8" washer with 1/16" washer."
So, after some head-scratching, this is how I figure it. The roller bearing is, as suspected, thicker side-to-side than the BB. ID and OD are the same. As far as I can tell, ALL 30205 bearings have the same dimensions, as far as all the manufacturers' websites are concerned. See for example the SKF site - the second-last entry is 30205. There's only one, it's the same ID and OD as all the other 30205s I've found.

My educated guess would be that the X is a special order designation and that Moss, for example, would order a large batch of 30205 bearings with a pre-machined outer race, that might then be labeled 30205X.

So yes, as far as I can see, the OUTER race of the inner bearing needs 1/8" machined off its outboard (flat) surface before it is pressed into the hub, which will move the disk 1/8" inboard. (Obviously, the 1/8 would have to come off the outboard side of the race, since taking it off the inboard side would simply reduce the bearing seating area, without moving anything one way or the other.)

As to the washer, I'll assume that they're talking about the outer retaining tab washer? Or did earlier assemblies have an inner washer of some sort?

2) As to whether the bearing, when pushed on, is flush with the back surface of the hub. This has nothing to do with the I.D. of the bearing - ALL 30205 bearings have the same ID, as far as all the manufacturers' websites are concerned. The last inch of the hub itself is not tapered, so if it fits, it fits (so to speak). BUT, the point at which the axle meets the hub is radiused. And the three 30205 bearings I've seen today all have slightly different radii on their inner bearing corners. All have been almost square, which means that rather than seating all the way back with their rear face against the flat surface of the hub, they hang up just shy of it. I don't want to grind down the radius on the hub, since it's structural. So I may try clearancing the corner of the inner bearing race, to confirm my theory.

So that's it. I don't have a lathe, I'm considering trying to machine down a race in my drill press... what the heck, it's $20 if I have to get a new one.

That said, if someone can find me a link to a stock narrow 30205 bearing, I'll be thrilled. But I've tried Timkin, NTN, SKF, TRW, FAG, Federal Mogul... Yes, they all use prefixes or suffixes to show the manufacturer, but all the ones I've found so far are dimensionally identical. As I say, X must be special-order, for quantity orders of pre-milled outer races.
 
Here's my next zany thought of the night. My original ball bearings are fine...

inner = BB,
outer = tapered bearing

That would allow me to use the stock part on the inside, not having to worry about finding / making a narrowed 30205, etc. And the outer tapered bearing would reduce the slop normally evident in the stock setup.

Crazy?
 
It was too wet today to take the car out of the garage much less open it up to see what I did to it. I didn't have to do any machining except for the spacers and remember that bearings will be pretty hard steel and difficult to work on a lathe of drill press (unless you have a grinder attachment).
Bill
 
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