Front Hubs

[Cottontop]

Background - Several years ago after several miles of "spirited" Interstate driving (at speeds higher than I want to admit to) I pulled of the I'state and as I stopped at the stop sign at the end of the ramp, I heard an ominus, brassy, "ker-lunk!"

I knew immediately what it was. When I went to look, sure enough, my right front knock-off was lying on the pavement next to the tire. The fine brass threads had been pulled out by the spinning of the wheel on the braked steel splined hub.

I called home and my wife brought me a new knock-off. I have driven "gingerly" since then.

Logic tells me that the newer style course threads should be stronger than my fine threads. Logic also tells me that if I installed brand new front splined hubs along with my new chrome wire wheels that the wheel should NOT spin on the hub and I should not be relying on the knock-off to keep the wheel from spinning on the hub.

Question A - Will new fine thread front hubs with new wheels prevent a recurrence of what happened AND/OR as long as I am buying new hubs, should I go ahead and buy the course thread hubs ?

Question B - IF the answer is to go ahead and buy new course threads, Will the course thread hubs FIT on my fine thread hub axles or do I need to (try to) buy new axles to accomodate the course thread hubs ? I know that the bearings are different.

I have a V8-Automatic car and used to frequently spin the wheels on the rear splined hubs (it would just unscrew the knock-offs). When I re-did the car 10 years ago, I installed new splined hubs and haven't loosened one since. Inspection shows that the rear splines are in VERY good shape with no perceptible damage.

What are your recommendations ?

Thanks,

Tim

 

[Dave Russell]

Background - Several years ago after several miles of "spirited" Interstate driving (at speeds higher than I want to admit to) I pulled of the I'state and as I stopped at the stop sign at the end of the ramp, I heard an ominus, brassy, "ker-lunk!"

Logic also tells me that if I installed brand new front splined hubs along with my new chrome wire wheels that the wheel should NOT spin on the hub and I should not be relying on the knock-off to keep the wheel from spinning on the hub.

I have a V8-Automatic car and used to frequently spin the wheels on the rear splined hubs (it would just unscrew the knock-offs). When I re-did the car 10 years ago, I installed new splined hubs and haven't loosened one since. Inspection shows that the rear splines are in VERY good shape with no perceptible damage.

What are your recommendations ?

Thanks,

Tim

Hi Tim,
I think you have the answer already. The knockoff is NEVER intended to prevent rotation.

On a well fitting hub & wheel, there is no particular strain on the knockoffs. By design, there is a small relative rotation movement between the wheel splines & hub splines. See below. This rotation tends to tighten the knockoffs when there is forward rotation of the wheel.

Braking or acceleration of the hubs in relation to the wheels would have no great affect on whether the caps unscrewed or not unless the splines slipped, which they won't do unless things are worn or you apply enough power to strip the splines. The only other time that a cap might actually unscrew without stripped splines, is if the car is towed backward.

Some pretty high powered cars used to work ok without stripping the splines, provided both the wheel splines & the hub splines are in very good condition.

The coarse hub threads would be stronger as far as supporting greater cornering loads, I don't know how hard you push the corners.

Just for fun, a description of the Rudge-Whitworth self tightening hub feature is quoted:
--- "One of the endearing mysteries of the wire wheel is that the spokes are not ... indeed, can never be ... in compression, the weight of the stationary car is suspended from those spokes which are uppermost in the wheel. when the wheel and locking cap are loosely fitted, therefore the upper portion of the outer taper is pulled firmly into contact with that of the locking cap taper, and the lower portion of the locking cap thread is in contact with that of the hub. A slight clearance then exists between the tapers at the bottom, and also between the threads at the top. As the car moves forward, a different portion of the wheel rim takes the weight, and relative movement occurs between wheel centre, locking cap and hub. The effect of this is to tighten the locking cap, and the locking action continues until there is firm contact between the tapers all round, when it ceases. The clearances involved are, of course, minute, but the locking action is nevertheless, completely positive and entirely automatic." ----

A new spline, hub or wheel, will have a flat portion on the top of the spline. If the spline is worn to the point that the spline is triangular, no flat on top, It is nearing the point of stripping.
D

 

[glemon]

I am confused by your description of what happened. Did the spinner simply come off (unscrew) strip the threads, or did the wheel strip the splines.

The first situation could come from a variety of things, but may indicate worn splines, if the threads stripped (never heard of that, but can't tell by the description) you probably need new hub and spinner or knock off.

If the wheel spun on the hub you need a new hub and wheel, spinner may be OK.

Issue is not fine or course threads.

I agree with Dave to a point, the spinner is not designed to keep the wheel from turning, however, I have always wacked my spinners on very tight, both as insurance from accidental coming off and to keep the wheel on tight and prolong the life of the splines.

In theory the knock-offs self tighten, but I trust the old 2 lb lead hammer more than theory. I think the self tightening thing is somewhat dependent on the condition of the hubs and splines, if they are worn (probably worn to the point you should replace them) then in my experience sometimes it doesn't work.

I tighten them on until it stops moving easily with the hammer (very slight movementeach hit) then give it 10-15 more medium whacks, not light taps, never monster hits, just nice medium good control hits.

 

[Randy_Gay]

Tim,
The axle shafts have different diameters. I'm not gonna say it can't be done, but it's not a simple switch to go from fine to coarse.

 

[Randy Forbes]

Tim,
The axle shafts have different diameters. I'm not gonna say it can't be done, but it's not a simple switch to go from fine to coarse.

I suppose it could be done, if you were to source an outer wheel bearing that matched the i.d. of the new hub (smaller) and the o.d. of the spindle/stub axle. It would be easier going the other way...

If you had access to a BJ8 parts car, you could get the spindles & brake calipers and make it all work (using new hubs & rotors, along with rebuilt calipers).

 

[Cottontop]

Issue is not fine or course threads.

It is worn splines on my existing hubs.

I'd like to thank you four for your inputs and opinions.

You have confirmed what I was thinking. "Buy new fine-thread front hubs, put the knock-offs on tight, and go have some fun".

Maybe "Santa" will bring them /bcforum/images/%%GRAEMLIN_URL%%/angel.gif

Thanks again

Tim

 

[nevets]

Dave - interesting description of how wire wheel spokes are only in tension. I wonder what happens when the wheel encounters a defect in the road surface, wouldn't that create a momentary upward shock to the wheel, putting the spokes closest to the road in compression?

 

[Dave Russell]

If you "ping" the spokes with the weight of the car sitting on the wheel, there doesn't seem to be much difference in tension between upper & lower spokes. This would indicate that the normal tension is much greater than that needed to support the car's weight.

I don't really know if it would put compression on the lower spokes. Since all of the spokes are under quite a bit of tension normally, the bump might just increase tension on the upper spokes while reducing tension on the lower spokes, but not completely removing tension on the lower spokes.

In any event, the situation would be very short term.
D

 

[GregW]

I’ve never laced a wheel before, but don’t the spokes just slip through the hub? So in theory, any bump in the road would just push the spoke further into the hub center?

 

[Randy Forbes]

I’ve never laced a wheel before, but don’t the spokes just slip through the hub? So in theory, any bump in the road would just push the spoke further into the hub center?

The rim would have to deform in order to do that (even if just momentarily).

I've never laced a wheel either, so I don't know how much preload is applied to the nipples before the actual trueing process takes place.

I once had a roommate with a TR4A that relaced a set of chrome rims/hubs with black painted spokes (looked great) but he sent them out to be trued.