"R. Ashford Little II" wrote:
>
> How often or at what interval should the wheel bearings be replaced?
> I've got a TR6.
Depends to a considerable extent on degree and type of maintenance,
driving conditions and on the type of lubricants used. Older Triumphs
have particular problems with especially front wheel bearings, because
there's only a felt wiper installed at the inner bearing. If you have to
go through lots of water on the roads where you drive, that felt wiper
allows quite a bit of water to be introduced into the hub.
Many people don't realize that the greases commonly used and specified
for the bearings in older cars are soap-based. Driving through lots of
water then flushes out the water-soluble constituents of the grease,
leaving the fiber fillers, which have very poor lubricating capacity.
This inevitably leads to accelerated bearing wear.
Another consideration is the melting point of the grease used.
Particularly in cars with disc brakes, under hard use, brake
temperatures can go beyond the melting points of older greases, causing
them to run out, which causes eventual bearing failure.
The last consideration in bearing life has a lot to do with the kind of
maintenance they receive. Many cleaning solvents in use today leave a
very fine film of residue, which can prevent grease from contacting the
surfaces to be protected. If a bearing is cleaned with a commercial
solvent, it should always then be washed in gasoline, which will strip
off the solvent film, and allowed to air-dry. It's also very important,
if the bearing is dried with compressed air, to not let the rollers or
races to spin when doing so. Doing such will cause early failure of the
bearing, because, without lubricant, the bearing surfaces are easily
damaged.
Also, one must be careful in how the bearings are packed. There are
pressure packers which work well, but taking the time to properly
hand-pack a bearing works just as well with no additional expense. It's
not enough to smear the bearing with grease. Rather, the grease should
be worked into the bearing by filling the palm of the hand with grease,
then dragging the bearing into palm, effectively wedging grease into all
the small spaces of the bearing.
Today, fortunately, there are many good synthetic greases which are not
completely soap-based, and do not wash out easily, and have high melting
temperatures, and I would recommend any good grade of synthetic bearing
grease suitable for disc brake use.
As for replacement intervals, it depends upon the condition of,
particularly, the races and the rollers during inspection. If the
rollers show signs of scoring around their diameter, they will not last
much longer and should be replaced. Same for scoring of the races, or if
there are signs of any discoloration or bluing on the roller cage. If
one is using a non-waterproof NGLI #2 grease, I would inspect bearings
every 12,000 miles. Using waterproof high-temperature NGLI #1, or a good
waterproof synthetic grease, rated for disc brake use, that interval
could probably be increased to 30-40,000 miles.
If there are none of the above signs of wear, there's no reason the
bearings, for normal street use, can't be cleaned, repacked and re-used
until they do show signs of wear. Racing would be another matter,
particularly because the high braking loads in racing create sustained
high temperatures in the hubs, and inspection and/or replacement should
be on a greatly accelerated schedule.
Hope that helps.
Cheers.
--
Michael D. Porter
Roswell, NM (yes, _that_ Roswell)
[mailto:mporter@zianet.com]
The gulf between content and substance continues to widen....
/// triumphs@autox.team.net mailing list
/// To unsubscribe send a plain text message to majordomo@autox.team.net
/// with nothing in it but
///
/// unsubscribe triumphs
///
/// or try http://www.team.net/cgi-bin/majorcool
|