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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 |
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Question re chrome steel bearings
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 |
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Question re chrome steel bearings
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 |
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Question re chrome steel bearings
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 |
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Question re chrome steel bearings
"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 |
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Question re chrome steel bearings
"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 |
#7
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Question re chrome steel bearings
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 |
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