Rear Hub Bearings I am no expert on bearings (although I know a man who is, and he has about 10 million or more in stock...)
but in every case the first number in the reference tells you what the construction type is. Thus:
1 = double row ball, self aligning
2 = double row ball, extra wide, self aligning
3 = double row ball ball, double thrust (used as a poor replacement for the original MDJT pinion bearing)
4 = double row ball, rigid
5 = thrust, various types
6 = single row ball, rigid
7 = single row ball, angular contact, i.e. single direction of thrust
M = single row ball with filling-slots - MAX capacity
N = single row roller, rigid
Of course, this is a gross simplification, and is only the system used by RHP and SKF among others.
R. & M. tended to letters, thus LJ 40 for the 6208 (80 x 40 x 18) and other makers confused the issue. I buy max-load brgs marked 1208 (made in U.S.A. by "New departure" - anybody ever heard of them?) which are not the self-aligning type.
The ones bought by Joe Potter which started off this thread are probably 7208 BGC3, not 72088, and from the pics definitely look to be thrust types.
Various bearings have been tried in our rear hubs, some very expensive and not much better. The most promising improvement would seem to be a double row 4208 type with a dynamic load rating of 8,400 lbs. (against 5,650 for the 6208 and 6,440 for the M2080). However, it is 23mm wide instead of 18mm, so mods have to be made, but that's another story...
Happy MotoringG !!
Roger
Re: Rear hub bearings
-
Joe Gates
- Posts: 52
- Joined: Tue Oct 23, 2001 12:52 pm
REAR HUB BEARINGS
A while back I replaced rear bearings a-la Sherrell with shims to pinch up the gap between the hub extention and the bearing itself to eliminate wheel play. However, after a trip of some 1000 kilometers, it appears that this has not satisfactorily prevented a recurrence of play in the near-side rear wheel/hub. It has been suggested I consider replacing the standard bearings with those used (I believe) in the MGA or B which has a double row of ball bearings (SKF #4208ATN9).
The axle housing from the shoulder on which the bearing rests to the end of the thread measures 30mm. The said bearing measures 23mm and the MGA/B octagonal nut measures 7mm, so is there any reason why I should not pursue this route and simply use Locktite in lieu of a locking washer? Not only will this offer two rather than one row of ball bearings which should reduce opportunity for play, but the latter has eleven in circumference per row as opposed to nine in total for a standard bearing which also seems to suggest a better load-bearing capacity.
Comments will be appreciated.
Joe Gates
TC8675
Johannesburg, S. Africa
[Non-text portions of this message have been removed]
The axle housing from the shoulder on which the bearing rests to the end of the thread measures 30mm. The said bearing measures 23mm and the MGA/B octagonal nut measures 7mm, so is there any reason why I should not pursue this route and simply use Locktite in lieu of a locking washer? Not only will this offer two rather than one row of ball bearings which should reduce opportunity for play, but the latter has eleven in circumference per row as opposed to nine in total for a standard bearing which also seems to suggest a better load-bearing capacity.
Comments will be appreciated.
Joe Gates
TC8675
Johannesburg, S. Africa
[Non-text portions of this message have been removed]
-
ROSS TAYLOR
- Posts: 46
- Joined: Thu Nov 28, 2002 3:15 am
Re: REAR HUB BEARINGS
To use a 4208 bearing you would have to machine 5mm off the spiggot on the inside of the hub to allow the hub to bed onto the face of the rear bearing carrier,if you fit a 7208 angular contact bearing and lock it up as it should be you will increase the dynamic load capacity by 500 lbs and the static load capacity by 1000 lbs
regards Rossco P Coaltrain
regards Rossco P Coaltrain
----- Original Message -----
From: Joe Gates
Sent: Saturday, 21 December 2002 10:22 PM
To: MG-TABC Group
Subject: [mg-tabc] REAR HUB BEARINGS
A while back I replaced rear bearings a-la Sherrell with shims to pinch up the gap between the hub extention and the bearing itself to eliminate wheel play. However, after a trip of some 1000 kilometers, it appears that this has not satisfactorily prevented a recurrence of play in the near-side rear wheel/hub. It has been suggested I consider replacing the standard bearings with those used (I believe) in the MGA or B which has a double row of ball bearings (SKF #4208ATN9).
The axle housing from the shoulder on which the bearing rests to the end of the thread measures 30mm. The said bearing measures 23mm and the MGA/B octagonal nut measures 7mm, so is there any reason why I should not pursue this route and simply use Locktite in lieu of a locking washer? Not only will this offer two rather than one row of ball bearings which should reduce opportunity for play, but the latter has eleven in circumference per row as opposed to nine in total for a standard bearing which also seems to suggest a better load-bearing capacity.
Comments will be appreciated.
Joe Gates
TC8675
Johannesburg, S. Africa
[Non-text portions of this message have been removed]
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-
Clifford Lockrow
- Posts: 16
- Joined: Tue Jul 02, 2002 1:49 pm
Re: REAR HUB BEARINGS
I had this problem with my TC. After many attempts of "pinching up" the bearings, new gaskets, shims etc I finally discovered that the bearing carriers were so worn that the bearings were slopping around in the carrier. I repalaced the carriers and since then no problems with leakage, wobble etc. You could do the same with boring out the old bearing carrier and inserting a sleeve and boring back to original size. You might check this out.
Joe Gates wrote:
Joe Gates wrote:
> A while back I replaced rear bearings a-la Sherrell with shims to pinch up the gap between the hub extention and the bearing itself to eliminate wheel play. However, after a trip of some 1000 kilometers, it appears that this has not satisfactorily prevented a recurrence of play in the near-side rear wheel/hub. It has been suggested I consider replacing the standard bearings with those used (I believe) in the MGA or B which has a double row of ball bearings (SKF #4208ATN9).
>
> The axle housing from the shoulder on which the bearing rests to the end of the thread measures 30mm. The said bearing measures 23mm and the MGA/B octagonal nut measures 7mm, so is there any reason why I should not pursue this route and simply use Locktite in lieu of a locking washer? Not only will this offer two rather than one row of ball bearings which should reduce opportunity for play, but the latter has eleven in circumference per row as opposed to nine in total for a standard bearing which also seems to suggest a better load-bearing capacity.
>
> Comments will be appreciated.
>
> Joe Gates
> TC8675
> Johannesburg, S. Africa
>
> [Non-text portions of this message have been removed]
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
-
Joe Gates
- Posts: 52
- Joined: Tue Oct 23, 2001 12:52 pm
Re: REAR HUB BEARINGS
Cl;ifford Lockrow wrote
"...the bearing carriers were so worn that the bearings were slopping around
in the carrier. I repalaced the carriers and since then no problems with
leakage, wobble etc. You could do the same with boring out the old bearing
carrier and inserting a sleeve and boring back to original size. You might
check this out."
Well said, as the bearing carrier is a bit worn, so I am also contemplating
"hard chroming" the interior of the carrier in lieu of sleeving. But I
still ponder the merits of a double row of ball bearings.
Joe
"...the bearing carriers were so worn that the bearings were slopping around
in the carrier. I repalaced the carriers and since then no problems with
leakage, wobble etc. You could do the same with boring out the old bearing
carrier and inserting a sleeve and boring back to original size. You might
check this out."
Well said, as the bearing carrier is a bit worn, so I am also contemplating
"hard chroming" the interior of the carrier in lieu of sleeving. But I
still ponder the merits of a double row of ball bearings.
Joe
-
Roger Furneaux
- Posts: 292
- Joined: Mon Dec 13, 1999 4:38 pm
Re: REAR HUB BEARINGS
hi Joe - it is quite probable that the bearing is rocking on the axle
casing, which will be the case if it slid on easily. It should be an
interference fit, i.e. you need to encourage it with a hammer! Having
hexagonal nuts tightened up with a torque wrench to 140 lbsf. ft. also
helps! If the bearing is loose in the carrier, you could try hard-chroming
and grinding back to spec. (79.93mm +0.05mm - 0.00mm) or buy a new one from
me (CNC machined from solid)
You certainly can use the double row 4208 type brgs, without the tab
washers, but I would recommend a locking grub screw. You have to have hex
nuts: torque up as usual, and if a flat is not uppermost, remove and grind
some off the back. Drill and tap for a grubscrew which will locate in the
tab washer slot. I have this arrangement on the off-side of TC0978, and a
heavy duty M208 brg. on the other. No play in over 8000 miles.
Seasons Greetings!
TCRoger
Joe Gates wrote:
casing, which will be the case if it slid on easily. It should be an
interference fit, i.e. you need to encourage it with a hammer! Having
hexagonal nuts tightened up with a torque wrench to 140 lbsf. ft. also
helps! If the bearing is loose in the carrier, you could try hard-chroming
and grinding back to spec. (79.93mm +0.05mm - 0.00mm) or buy a new one from
me (CNC machined from solid)
You certainly can use the double row 4208 type brgs, without the tab
washers, but I would recommend a locking grub screw. You have to have hex
nuts: torque up as usual, and if a flat is not uppermost, remove and grind
some off the back. Drill and tap for a grubscrew which will locate in the
tab washer slot. I have this arrangement on the off-side of TC0978, and a
heavy duty M208 brg. on the other. No play in over 8000 miles.
Seasons Greetings!
TCRoger
Joe Gates wrote:
>A while back I replaced rear bearings a-la Sherrell with shims to pinch up
>the gap between the hub extention and the bearing itself to eliminate wheel
>play. However, after a trip of some 1000 kilometers, it appears that this
>has not satisfactorily prevented a recurrence of play in the near-side rear
>wheel/hub. It has been suggested I consider replacing the standard
>bearings with those used (I believe) in the MGA or B which has a double row
>of ball bearings (SKF #4208ATN9).
>
>The axle housing from the shoulder on which the bearing rests to the end of
>the thread measures 30mm. The said bearing measures 23mm and the MGA/B
>octagonal nut measures 7mm, so is there any reason why I should not pursue
>this route and simply use Locktite in lieu of a locking washer? Not only
>will this offer two rather than one row of ball bearings which should
>reduce opportunity for play, but the latter has eleven in circumference per
>row as opposed to nine in total for a standard bearing which also seems to
>suggest a better load-bearing capacity.
-
Roger Furneaux
- Posts: 292
- Joined: Mon Dec 13, 1999 4:38 pm
Re: REAR HUB BEARINGS
Ross - please note that the 7208 is a thrust bearing and should not be used
in wheel hubs! The races are asymmetric and can only take axial load in one
direction (the 7207 is used either side of the crownwheel). In any case, the
load capacity of the 7208 is only marginally better than the 6208, whereas
the brg. originally specified was the LJBL 40, which is now the M208.
ocTagonally
TCRoger
Ross Taylor wrote:
in wheel hubs! The races are asymmetric and can only take axial load in one
direction (the 7207 is used either side of the crownwheel). In any case, the
load capacity of the 7208 is only marginally better than the 6208, whereas
the brg. originally specified was the LJBL 40, which is now the M208.
ocTagonally
TCRoger
Ross Taylor wrote:
>To use a 4208 bearing you would have to machine 5mm off the spiggot on the
>inside of the hub to allow the hub to bed onto the face of the rear bearing
>carrier,if you fit a 7208 angular contact bearing and lock it up as it
>should be you will increase the dynamic load capacity by 500 lbs and the
>static load capacity by 1000 lbs
-
Dave & Diana Dwyer
- Posts: 50
- Joined: Fri Jun 08, 2001 1:31 am
Re: REAR HUB BEARINGS
Joe
When you say "play" in the hub, do you mean in-and-out, or do you mean that
the wheel wobbles?
The rear wheel bearing comes in two versions: 6208 (standard) and 208 (heavy
duty). Vertical load ratings are 6208= 2900Kg, 208= 3800Kg.
A TC weighs approx 800Kg, so each rear wheel bears about 200Kg of vertical
load. This means the 6208 has a safety factor of about 14 in the vertical
plane.
The axial load rating of the 6208 is 1800Kg. At the point of sliding you
should be able to exert a max side load of 200Kg to each wheel (OK, weight
transfer might mean 300 on the outer wheel). In this case the safety factor
in the sideways plane is about 6.
The TC axle construction is described as "semi-floating" and in this setup
the halfshaft takes the 'wobble' load. The bearing has no leverage to
withstand that kind of load: if that load were intended, there would be
#two# bearings spaced about 6" apart as in the Lotus and other IRS cars.
If the halfshaft is loose in the splined hub your wheel will wobble,
regardless of the bearing. Shimming the fit of bearing/bearing
carrier/splined hub will reduce the possibility of the bearing carrier
sliding in/out on the bearing outer shell, but it won't stop any wheel
wobble.
All of which is a long way of saying that I don't see any point in using
double row bearings.
Regards
Dave Dwyer
J2, TA, TC
When you say "play" in the hub, do you mean in-and-out, or do you mean that
the wheel wobbles?
The rear wheel bearing comes in two versions: 6208 (standard) and 208 (heavy
duty). Vertical load ratings are 6208= 2900Kg, 208= 3800Kg.
A TC weighs approx 800Kg, so each rear wheel bears about 200Kg of vertical
load. This means the 6208 has a safety factor of about 14 in the vertical
plane.
The axial load rating of the 6208 is 1800Kg. At the point of sliding you
should be able to exert a max side load of 200Kg to each wheel (OK, weight
transfer might mean 300 on the outer wheel). In this case the safety factor
in the sideways plane is about 6.
The TC axle construction is described as "semi-floating" and in this setup
the halfshaft takes the 'wobble' load. The bearing has no leverage to
withstand that kind of load: if that load were intended, there would be
#two# bearings spaced about 6" apart as in the Lotus and other IRS cars.
If the halfshaft is loose in the splined hub your wheel will wobble,
regardless of the bearing. Shimming the fit of bearing/bearing
carrier/splined hub will reduce the possibility of the bearing carrier
sliding in/out on the bearing outer shell, but it won't stop any wheel
wobble.
All of which is a long way of saying that I don't see any point in using
double row bearings.
Regards
Dave Dwyer
J2, TA, TC
-
Joe Gates
- Posts: 52
- Joined: Tue Oct 23, 2001 12:52 pm
Re: REAR HUB BEARINGS
Roger, Dave, et al
The fit to axle casing is definitely interference fit, as is the fit in the
carrier - until the bearing gets to the carrier shoulder where it slides a
millimeter or so on the horizontal. I expect that hard chroming the carrier
is the way to go to repair the consequence of wear and tear. That said, I
suspect that the half-shaft/splined hub fit is also suspect as there is some
evidence of oil leakage. Will have this attended to when I fit new half
shafts.
Joe
The fit to axle casing is definitely interference fit, as is the fit in the
carrier - until the bearing gets to the carrier shoulder where it slides a
millimeter or so on the horizontal. I expect that hard chroming the carrier
is the way to go to repair the consequence of wear and tear. That said, I
suspect that the half-shaft/splined hub fit is also suspect as there is some
evidence of oil leakage. Will have this attended to when I fit new half
shafts.
Joe
-
Victoria
- Posts: 8
- Joined: Mon Jan 31, 2000 12:16 pm
Re: REAR HUB BEARINGS
Hi Joe and Ross,
an interesting thread (pardon the pun) and one I hope is followed up as i
would be interested in the outcome. Will this lessen the oil ingress or do
we need to go the Roger seal route?
Clem TC 7218
-----Original Message-----
From: ROSS TAYLOR [mailto:rossmvt@msn.com]
Sent: 21 December 2002 01:52
To: Joe Gates; MG-TABC Group
Subject: Re: [mg-tabc] REAR HUB BEARINGS
To use a 4208 bearing you would have to machine 5mm off the spiggot on the
inside of the hub to allow the hub to bed onto the face of the rear bearing
carrier,if you fit a 7208 angular contact bearing and lock it up as it
should be you will increase the dynamic load capacity by 500 lbs and the
static load capacity by 1000 lbs
regards Rossco P Coaltrain
an interesting thread (pardon the pun) and one I hope is followed up as i
would be interested in the outcome. Will this lessen the oil ingress or do
we need to go the Roger seal route?
Clem TC 7218
-----Original Message-----
From: ROSS TAYLOR [mailto:rossmvt@msn.com]
Sent: 21 December 2002 01:52
To: Joe Gates; MG-TABC Group
Subject: Re: [mg-tabc] REAR HUB BEARINGS
To use a 4208 bearing you would have to machine 5mm off the spiggot on the
inside of the hub to allow the hub to bed onto the face of the rear bearing
carrier,if you fit a 7208 angular contact bearing and lock it up as it
should be you will increase the dynamic load capacity by 500 lbs and the
static load capacity by 1000 lbs
regards Rossco P Coaltrain
----- Original Message -----
From: Joe Gates
Sent: Saturday, 21 December 2002 10:22 PM
To: MG-TABC Group
Subject: [mg-tabc] REAR HUB BEARINGS
A while back I replaced rear bearings a-la Sherrell with shims to pinch up
the gap between the hub extention and the bearing itself to eliminate wheel
play. However, after a trip of some 1000 kilometers, it appears that this
has not satisfactorily prevented a recurrence of play in the near-side rear
wheel/hub. It has been suggested I consider replacing the standard bearings
with those used (I believe) in the MGA or B which has a double row of ball
bearings (SKF #4208ATN9).
The axle housing from the shoulder on which the bearing rests to the end of
the thread measures 30mm. The said bearing measures 23mm and the MGA/B
octagonal nut measures 7mm, so is there any reason why I should not pursue
this route and simply use Locktite in lieu of a locking washer? Not only
will this offer two rather than one row of ball bearings which should reduce
opportunity for play, but the latter has eleven in circumference per row as
opposed to nine in total for a standard bearing which also seems to suggest
a better load-bearing capacity.
Comments will be appreciated.
Joe Gates
TC8675
Johannesburg, S. Africa
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