Question re chrome steel bearings

Some bearings in two of my shock pivots are shot, one almost frozen solid,
so I located their replacements:

http://cgi.ebay.com/10-6900-RS-Seale...QQcmdZViewItem

I asked the vendor if the races are made of stainless steel and the balls
themselves are made of chrome steel, because I don't want the exterior of
the races rusting. The vendor said no, all the metal in the bearing is
chrome steel. But Wikipedia says chrome steel is just another term for
stainless steel:

http://en.wikipedia.org/wiki/Chrome_steel

Can anybody with some metallurgical expertise clue me in here? Is Wikipedia
correct? If it's incorrect, does this chrome steel have similar corrosion
resistance to stainless steel?

My original bearings did not rust at all. But they are located near the rear
dropouts. They don't rotate much at this location and take the brunt of
impact; other Ventana owners report these wear out two to three times as
quickly as the other pivot bearings.

Thanks,

Brian

---------------------------------
www.radioparadise.com
DJ-mixed modern & classic rock, world music, electronica, & more.
100% commercial-free

On Tue, 27 Mar 2007 16:23:21 GMT, "Brian Ray"
wrote:

Some bearings in two of my shock pivots are shot, one almost frozen solid,
so I located their replacements:

http://cgi.ebay.com/10-6900-RS-Seale...QQcmdZViewItem

I asked the vendor if the races are made of stainless steel and the balls
themselves are made of chrome steel, because I don't want the exterior of
the races rusting. The vendor said no, all the metal in the bearing is
chrome steel. But Wikipedia says chrome steel is just another term for
stainless steel:

http://en.wikipedia.org/wiki/Chrome_steel

Can anybody with some metallurgical expertise clue me in here? Is Wikipedia
correct? If it's incorrect, does this chrome steel have similar corrosion
resistance to stainless steel?


Alloy Steels have a tremendous variation in constituents and
characteristics. You can call any steel that has as its main alloying
element Chromium a "chrome steel", but not all such are what are
commonly termed "stainless".

In small percentages, Chromium tends to increase the hardness and/or
hardenability, and increase the toughness and wear resistance of
steels. Typical values for Cr in these steels are about 1.5%

In high percentages it also greatly increases corrosion resistance;
depending on who you are reading, this must be somewhere above at
least 10% Cr. Frequently there are significant amounts of other
metals, such as nickel, molybdenum, titanium, copper, etctera, some of
which also contribute to corrosion resistance.

The lower CR steels will have less corrosion resistance than stainless
steels, but are probably better for the bearings - you could cover
them with a thin layer of thick grease if you are worried about their
look.


My original bearings did not rust at all. But they are located near the rear
dropouts. They don't rotate much at this location and take the brunt of
impact; other Ventana owners report these wear out two to three times as
quickly as the other pivot bearings.

Thanks,

Brian

---------------------------------
www.radioparadise.com
DJ-mixed modern & classic rock, world music, electronica, & more.
100% commercial-free

Even stainless steels will rust, and there are several types of
stainless (like grade-8 and grade-10, i believe), and there are even
grades tuned for 'marine' usage, which have the highest corrosion
resistance but perhaps other properties such as hardness are not as
good.

Another option if you really want durability is to get cermanic
bearings, they typically have 2x the lifetime and they also wear much
more slowly when the reserve of grease is completely gone, although
they cost about 4x as much as regular press-fit bearings. Don't buy
them for reduced rolling resistance as loose balls have much lower
resistance. If you're looking at higher durability, however, they
might make some economic sense ...

Once you've pressed in 5 or 10 sets of bearings there is imho a good
chance that the press-fit will fail (e.g. become loose), so you might
want to consider premium bearings in this location. I have a MAVIC
551 rear hub and the 6001 bearing cartridges were slipping under load
and so the mechanic at my LBS super-glued them in, which fixed the
problem - at least for now.

- Don Gillies
San Diego, CA

Brian Ray wrote:
Some bearings in two of my shock pivots are shot, one almost frozen solid,
so I located their replacements:

http://cgi.ebay.com/10-6900-RS-Seale...QQcmdZViewItem

I asked the vendor if the races are made of stainless steel and the balls
themselves are made of chrome steel, because I don't want the exterior of
the races rusting. The vendor said no, all the metal in the bearing is
chrome steel. But Wikipedia says chrome steel is just another term for
stainless steel:

http://en.wikipedia.org/wiki/Chrome_steel

Can anybody with some metallurgical expertise clue me in here? Is Wikipedia
correct? If it's incorrect, does this chrome steel have similar corrosion
resistance to stainless steel?

read it again. two things are relevant:

"Chrome Steel is a rarely used historical or alternative name for
Stainless Steel"

the pertinent term there is "rarely used historical".

then we have: "The chromium component of chrome steel would only provide
/some/ corrosion resistance."

my emphasis.

however, the article is not as clear as it could be. in modern usage,
stainless steel is high chromium content for oxidation resistance.
chrome steel is lower alloy steel where the chromium is used for better
hardenability/strength control, usually in conjunction with carbon and
other ingredients like manganese, vanadium, molybdenum, etc. steel
bearing balls are usually one of three types:

1. simple case hardened carbon steel.
2. /modern/ "chrome steel".
3. stainless steel.


My original bearings did not rust at all. But they are located near the rear
dropouts. They don't rotate much at this location and take the brunt of
impact; other Ventana owners report these wear out two to three times as
quickly as the other pivot bearings.

that's a brinelling thing.


Thanks,

Brian

---------------------------------
www.radioparadise.com
DJ-mixed modern & classic rock, world music, electronica, & more.
100% commercial-free

"Donald Gillies" wrote in message
...
[...]
Another option if you really want durability is to get cermanic
bearings, they typically have 2x the lifetime and they also wear much
more slowly when the reserve of grease is completely gone, although
they cost about 4x as much as regular press-fit bearings.

This time around I'm just going to replace like with like and see how things
go. This pivot barely pivots much as it's sitting out at the arc of the
suspension's path. I'm concerned that ceramic balls will just beat the snot
out of the races even more than steel balls in this location.

Once you've pressed in 5 or 10 sets of bearings there is imho a good
chance that the press-fit will fail (e.g. become loose), so you might
want to consider premium bearings in this location. I have a MAVIC
551 rear hub and the 6001 bearing cartridges were slipping under load
and so the mechanic at my LBS super-glued them in, which fixed the
problem - at least for now.

As I was wrestling these little demons in and out of their press fittings
using every dang thing I had on hand--bearing drivers, bench vise, and an
impromptu bearing press of bolt, nut, and washers--this struck me as a risk.
The bearings at all other pivots went in and out much more easily. They
weren't just sliding in and out by any means, but the lesser-worn bearing
spun more smoothly once outside the fitting (though one could still feel it
was shot). I went at the inside of the these fittings with a Dremel, soft
attachment, and some polishing compound then experimentally tapped the
original bearings back in with an effort on par with the other pivots.

No doubt I'll be supergluing or Loctiting their replacement's replacements
in there at some point, if they do not first fly out of the fittings as I'm
plumetting down some hill. My reach may extend my grasp in this little
amateur mechanic adventure.

Thanks for the info,

Brian Ray

"jim beam" wrote in message
news
Brian Ray wrote:
[...]
however, the article is not as clear as it could be. in modern usage,
stainless steel is high chromium content for oxidation resistance.
[...]
My original bearings did not rust at all. But they are located near the
rear dropouts. They don't rotate much at this location and take the brunt
of impact; other Ventana owners report these wear out two to three times
as quickly as the other pivot bearings.

that's a brinelling thing.

Yeah, makes me wonder if a ball bearing is the best thing to put at this
pivot. The other end of the subframe is of course the shock, and it pivots
in a like small arc on bushings. But now I'm playing amateur mechanical
engineer on top of playing amateur bike mechanic.

Thanks for the info,

Brian Ray

Brian Ray wrote:
"jim beam" wrote in message
news
Brian Ray wrote:
[...]
however, the article is not as clear as it could be. in modern usage,
stainless steel is high chromium content for oxidation resistance.
[...]
My original bearings did not rust at all. But they are located near the
rear dropouts. They don't rotate much at this location and take the brunt
of impact; other Ventana owners report these wear out two to three times
as quickly as the other pivot bearings.
that's a brinelling thing.

Yeah, makes me wonder if a ball bearing is the best thing to put at this
pivot.

maybe, maybe not. maybe a journal bearing would be much more robust.
but, they're subject to much more stiction. bottom line, ball bearings
give a better ride. they get brinelled out, but hey, just replace them.
repack with marine grease as a science experiment - the calcium
sulfonate is supposed to help mitigate some of the brinelling.

The other end of the subframe is of course the shock, and it pivots
in a like small arc on bushings. But now I'm playing amateur mechanical
engineer on top of playing amateur bike mechanic.

Thanks for the info,

Brian Ray