It seems like you can't trust much at all these days
03-01-20, 05:27 PM
#26
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Whenever I buy a vintage racer I disassemble all the components to clean and lube where applicable. The jockey wheels on the RD always gets cleaned and a dab of gear oil(around 90w) . I am typically looking at 40 year old+ bike components. It is prudent when buying a used bike for sure and the age of the bikes I have bought , I think a necessity.
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03-01-20, 05:27 PM
#27
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My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.
My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.
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03-01-20, 08:01 PM
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If a shop manager pays anything out side of the flat rate pay, that is a personal incentive not acknowledged by corporate management.
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03-02-20, 10:24 AM
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Let’s say 50T chainring. 11T shimano pulley. 100 crank rpm = chain speed of 50 * 100 teeth per minute = 5000T/min. Same chain speed for pulleys, so 5000T/min. 5000/11 = 454rpm? Pretty fast. People think the load is low... but those derailleurs put a solid amount of tension on the chain. Maybe my math is wrong. Although bearing or bushing drag doesn’t scale linearly with rpm.
03-02-20, 10:32 AM
#30
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03-02-20, 10:54 AM
#32
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Damn, I just checked and no one has done any pulley lubrication on any of my front derailleurs.
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03-02-20, 09:12 PM
#34
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Let’s say 50T chainring. 11T shimano pulley. 100 crank rpm = chain speed of 50 * 100 teeth per minute = 5000T/min. Same chain speed for pulleys, so 5000T/min. 5000/11 = 454rpm? Pretty fast. People think the load is low... but those derailleurs put a solid amount of tension on the chain. Maybe my math is wrong. Although bearing or bushing drag doesn’t scale linearly with rpm.
Jockey wheels don't work very hard-- as evidenced by the fact that they're plastic, and last thousands upon thousands of miles with little to no maintenance.
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03-03-20, 08:41 AM
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It's really just the chainring to cog ratio-- the pulleys will spin at whatever the ratio of the gear being used. So in 50/11 @ 90rpm, the jockey wheels will be turning ~410rpm, just like the 11T cog. But in say 34/17, the pulleys will be turning ~180rpm, just like the 17T cog.
Jockey wheels don't work very hard-- as evidenced by the fact that they're plastic, and last thousands upon thousands of miles with little to no maintenance.
Jockey wheels don't work very hard-- as evidenced by the fact that they're plastic, and last thousands upon thousands of miles with little to no maintenance.
I don't think that's right--doesn't that imply that the number of teeth on the pulley varies directly with the number on the cog? Obviously that's wrong. If the chain ring size and rate is held constant, the number of teeth the pulley will advance per turn of the crank is the same regardless of which cog is engaged. Thus, the correct answer is the rate of the crank times the ratio of the chain ring teeth to the pulley wheel teeth. Cog size is irrelevant.
03-03-20, 10:26 AM
#36
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Not worried about power loss at all. It is just that those pulleys need to be properly lubed like any other mechanical moving part>
03-03-20, 10:32 AM
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What problem are you trying to “fix” by pulling the derailer off and/or disassembling it? There is no need for that to be done for any general reason. And do you know how much grease is needed in the bearings of a derailer. I’m assuming that the jockey wheels you are talking about are the common sleeve bearing. These are the worst bearings on the bicycle but they somehow work without issue for thousands of miles. I’ve got hundreds of them at my local co-op that are old, crusty, dirty, and mistreated that work just fine without anything being done to them. Seldom do I run across one that has any problem turning freely.
Taking something apart to put more grease in it for no reason other than you think it needs more grease is wrongheaded. It might even be detrimental. We tend to overload bearings on bicycles with grease and all it does is attract dirt to get into the bearings that we think need more grease. The load on bicycles is small and the friction reduction needs are very low. Slathering grease in a thick layer on everything isn’t a general solution to a problem that probably doesn’t exist.
Taking something apart to put more grease in it for no reason other than you think it needs more grease is wrongheaded. It might even be detrimental. We tend to overload bearings on bicycles with grease and all it does is attract dirt to get into the bearings that we think need more grease. The load on bicycles is small and the friction reduction needs are very low. Slathering grease in a thick layer on everything isn’t a general solution to a problem that probably doesn’t exist.
Now as to the rest of what you say, yes, we have all seen the guy riding by with his bike sounding like a rattle trap, and a totally rusty chain. But the question is-------------how far will his bike go before a break down**********????
03-03-20, 10:38 AM
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Not to worry, the RD was bought last summer, and probably sat around months before it was pulled. And I just lubed them, and didnt suck on them, and washed my hands afterward.
03-03-20, 11:16 AM
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If you indeed spent all that time in industry you'd know that the one remaining unicorn dairy farm in Japan has had to streamline its operation and no longer offers ear wax, but the stuff from Indonesia can't be used because the breed they raise has different ear hair diameter and it gums up the bearings. And we have a committee about it.
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03-03-20, 11:50 AM
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If you indeed spent all that time in industry you'd know that the one remaining unicorn dairy farm in Japan has had to streamline its operation and no longer offers ear wax, but the stuff from Indonesia can't be used because the breed they raise has different ear hair diameter and it gums up the bearings. And we have a committee about it.
Both the Japanese and the Indonesian wax attract garden gnomes and wombats. I've been using an oil distilled from wooly mammoth dander.
03-03-20, 01:18 PM
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My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.
My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.
03-03-20, 05:42 PM
#44
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I've seen many thousands...somewhere north of 13,000 by now... of rear derailers and very few of them have seized jockey wheels. Some are on nice bikes and some are on bikes that have been mistreated beyond what most people would consider "mistreatment". Only on rare occasions do the jockey wheels not turn freely. Most all of the jockey wheels I see have never had anything done to them since they were installed at the factory. It's just not a wear item when it comes to the bearing.
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03-07-20, 06:40 AM
#45
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What is "properly lubed"? There's no much load on a derailer jockey wheel and there's not much friction developed. The small amount of lube on a jockey wheel is all that is needed. If it weren't we'd see worn out jockey wheels everywhere. I've seen broken ones and even ones that have had all the teeth worn down. But I've not seen any that are rounded out due to wear.
I've seen many thousands...somewhere north of 13,000 by now... of rear derailers and very few of them have seized jockey wheels. Some are on nice bikes and some are on bikes that have been mistreated beyond what most people would consider "mistreatment". Only on rare occasions do the jockey wheels not turn freely. Most all of the jockey wheels I see have never had anything done to them since they were installed at the factory. It's just not a wear item when it comes to the bearing.
I've seen many thousands...somewhere north of 13,000 by now... of rear derailers and very few of them have seized jockey wheels. Some are on nice bikes and some are on bikes that have been mistreated beyond what most people would consider "mistreatment". Only on rare occasions do the jockey wheels not turn freely. Most all of the jockey wheels I see have never had anything done to them since they were installed at the factory. It's just not a wear item when it comes to the bearing.
03-07-20, 08:24 AM
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Late last summer I bought a new RD for my trike. It seemed to work fine. But then yesterday I was doing my pre-season checks, cleaning, and repair on the trike. Among other things, I pull off the RD, pull the sprockets out, and clean and lube them. When I pulled both of them out, there was almost no grease or oil in either one!!! The bearings were glazed over with pretty much dry grease. I guess those of us that do almost all of our service work need to pull apart RDs and other assemblies to make sure they are lubed right before we use them. But why is this**********
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03-07-20, 09:47 AM
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I don't think that's right--doesn't that imply that the number of teeth on the pulley varies directly with the number on the cog? Obviously that's wrong. If the chain ring size and rate is held constant, the number of teeth the pulley will advance per turn of the crank is the same regardless of which cog is engaged. Thus, the correct answer is the rate of the crank times the ratio of the chain ring teeth to the pulley wheel teeth. Cog size is irrelevant.
I think that the first half of the statement was right, because the RD pulley is also 11t,
but in 34/17 the pulley would be spinning 278 rpm, as you suggest.
03-07-20, 10:09 AM
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LDL is right - it's how fast the chain is pulled (links per second) and how many teeth on the pulley gear. You only need to know one other gear and its rotation speed for that. Just ignore the rear cogs and you'll have it right.
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03-07-20, 10:21 AM
#49
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As much as my brain doesn't like it, the pulley speed is just the ratio of it's teeth to the chainring, multiplied by the cadence-- I'm used to having to compute gear speed for gearboxes, I guess. So with a 50T ring and a 90rpm cadence, that little guy is doing about 400rpm.
Which in the terms of a cartridge bearing, is... nothing. In the R/C world we buy bearings by the 10 or 25 pack, because it's not unusual to grenade a bearing every couple of days-- the downside to axle bearings doing 9,000rpm and motor bearings approaching 100,000rpm.
Which in the terms of a cartridge bearing, is... nothing. In the R/C world we buy bearings by the 10 or 25 pack, because it's not unusual to grenade a bearing every couple of days-- the downside to axle bearings doing 9,000rpm and motor bearings approaching 100,000rpm.
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