I use thick washer to pre-load the front wheel bearings in the hub...then remove and insert tapered split washer and re-torque to 150 ft/lb...stopping short of over torqueing as Alex has noted, if using a single hole CV.

No failures.   Even our +200lb man bouncing on 12" wrench set the proper torque for the new CV & bearings in Queensland!

Incidentally, Ken N. in Ipswich, Qld. said setting pre-load with tapered roller bearings was easier/more accurate than with ball bearings.

I do not have machine shop, just a drill, a jig saw, and a shade tree.  Made a proper size flat washer.
This is not a joke, I am not robster.

While you didn't use a thick, flat washer to seat the bearing, I heartily recommend investing in one.

Our host doesn't have them, but they're easily sourced for purchase or borrowed.

For example:

TOOL21 

TLS3011 

Also, don't over-grease the tapered roller bearings - it's another cause for failure.

Page 62 of the Timken Tapered Roller Bearing Catalogue has some guidance on proper lubrication.

Timken-Tapered-Roller-Bearing-Catalog.pdf

Front wheel bearing failure on the Gore Hwy. in Queensland gave no warning and simply 'blew up'.  Was travelling at about 60 mph so rolled to a stop then drove slowly a few yards up the highway to a flat spot off the road (no paved or level shoulder).  Bearing failure was instant & total.

Inner race was stuck to the CV and we did not have a brass drift to dislodge it.  Installed new CV & bearings.  Hub and original CV were inspected afterwards and found to be fit for service!

Understood. Then i think you have some wear going on inside the hub/bearings and am surprised you are not getting any nasty noises. 
Big Al had the same problem with a Mini pick up i was driving for him at MMN in Canada. I ended up using a washer to move the castle nut closer to the hole so it could be driven around for the weekend but this was not a long term solution. You can try this and run it around the block a few times and re check it but it seems like you need to pull it apart and see where the wear is.

Sorry, Malsal. I did NOT tighten everything down with a flat washer first. The problem isn't with getting the teeth to line up with the hole, the issue is that if it were packed in further, allowing the castle to thread on further, it would be behind the hole and the cotter would be in front of the teeth of the cotter. Does that make sense?

Maybe I should stop and take a picture.

I have to ask again. Have you pulled it all down tight with a flat washer first before installing the tapered one ? As the recommended torque is 180lbs plus and you seem to be comfortable with torquing it to 150lbs just put a little more torque on it to line up the nut with the hole.
Take no notice of the "specialist" there are no shims, the only "adjustment" you can make is to shorten the spacer between the bearings if you need to.

Last question (lie): 

With the castle installed to 150lb the hole is a little too "in front of" the castle for the cotter to be "in the teeth" of the cotter. Does that make sense?

Washer needed? Shim? Where does the shim sit? Between the castle and the taper?

there is time.

when I bought my mini 13 yrs ago, one front wheel was wobbly. Local shop had no clue about its mini bearings and neither did I. They tightened it a little, (sort of 40 -50 lbs, not 150+ lbs) and I drove it for a few months. No rumbling as in impending bearing failure. Wheel did not fall off. After getting a Haynes manual,  my sons and I replaced both inner and outer tapered rollers 9 on both fronts),  tightened it properly, and no issue since then. 

if the bearings are well lubricated, why will it burn up? A blown front bearing is more likely to happen in loose castle nut, than in tight one. Use Ultra high temp axle grease and you have no issues. Someone said to be easy on putting grease in the inner space(the space in between two bearings), im like really? i put grease in every spaces i see inside the assembly, i have no worries because there are two oil seals that prevents grease from spewing out, at least i know that my bearings are very well protected.

When you torque it to spec are you doing this with the tapered washer or a flat washer first then installing the tapered washer ? If you are re tightening it then something is wearing or not snugged up correctly. You will hear the bearings well before they burn up.

As I see it, there are two things that can happen (worst case) with the castle nut backing off.

1) the wheel falls off.
2) the bearings burn up. 

Question: what would the symptom be if the bearings were burning up?

I used impact wrench to shoot the clotter pin into the next hole. so it's tight, and as i drive ,the bearing will sit in. then after one week i will retighten the nut as needed. i'd rather tighten it the first time than drive with a slightly loose castle nut, the bearing gets misaligned and will eat the side of the bearing assembly and even if you tighten it, it's no use, because it's already damaged.

Lost front hub torque returning from MME 2006 and retorqued to 150 ft/lbs ...at home 500 miles later had 75 ft/lbs remaining...worn face on the S drive flange.

When in outback Australia without a torque wrench & blown wheel bearings up front.  Got my +200 pond travel mate to bounce on the end of a 12" long wrench to snug up the Metro drive flange.

PHOTO: we are undoing the castle nut...looked the same snugging it up after new CV & bearings

I have a length of 1/2 inch thick steel bar 3 inches wide and a foot long. I machined a radius and two bolt holes so I can bolt a hub to it by the caliper ears. Chuck it in a really big vise to build ball joints and set up bearing pre load. I use a impact to snug the castellated nut. It does not hurt using the the big flat washer to pull it up before adding the taper washer. On drive flanges I take a bucket full to a local machine shop and have them indexed and faced lightly. If there is any indication of the bearing races spinning in the hub I pitch it. They are not that expensive. 

I have been building hubs for awhile and I save every spacer that come out of old sets. I have a length of tube that can be parted at different lengths if required. I also keep shims I use for testing, When to tight add shims till I have measurable end float using dial indicator, do the math and find or machine a spacer. I understand a better life though chemicals but I can't except glue as a replacement for a proper press fit. 

I know the 7 inch disc use a replaceable spacer but have never seen one on a Cooper S 7.5 set up. Clearly I have not seen everything. As for how tight I like 150 and on to the next slot that lines up. Steve (CTR)

You're probably  right Alex.  Although, it worked for me.  When I looked at a drawing of an s hub it seemed obvious.  However, now I'm wondering it it would be possible for the drive flange to be so worn that it would hang up before being fully seated on the inner bearing race.

I wasn't suggesting that this would be a solution for an oversized spacer..rather it would be the consequence of using a properly sized spacer with a worn flange.

More careful examination of the drawing suggests that the width of the ridge where the outer bearing races sit against the hub is the real controlling factor. 

Cheers, Ian

Not being daft Ian, but how does the condition of the drive flange seating face affect the spacer in between the bearing races ?

If the spacer in the middle is too thick (quite common) no amount of monkeying about with the flanges or CV face will alter it or pull it up tighter...

After 50 years or so you'll notice a bit of slop   I'll let you know how things progress....

While the hub will wear if the outer bearing shell spins, the wear that can be resolved by machining the spacer is actually on the inner face of the drive flange.  (Very?) Early Ss had a tapered spacer just like the one on the outside on the inner face as well.  If there was wear, these could be easily replaced rather than having to change the whole drive flange....  

Mind you, its easier to  find a whole new flange these days (don't ask me how I know.....)

Cheers, Ian 

A similar conversation to this with long time OMO member Richard Smith had to do with bearing play after new races, bearings and bearing preload spacer.

Even after new bearings were install there was still too much play in the hub. It was believed to be worn hub surface or face where the race is seated.

I've never given much thought to the load on the surface where the race is seated against the hub.

A digital micrometer was used to measure the distance between the races and then the spacer was measured, true to form the spacer was too wide not allowing a proper bearing seating. After the spacer was machined (several times) there was a perfect fit.

Wondering how many miles you can drive before the hub wears to the point of needing replacement. 

Me, machining the spacer down (FREE) is cheaper than a new hub.

Edit, doesn't like the shortened name for Richard. Although Mr. Smith doesn't go by Richard, I'm not able or allowed to post his shortened name here. Funny 

Yes just get the alignment done asap and check the torque settings.