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Hub overhaul

Old 08-27-06, 11:04 PM
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Hub overhaul

Relatively new to bicycle mechanics, but I've been having fun disassembling/breaking/attempting to reassemble some old bikes.

Now to the point. I have two questions:

First, I decided to overhaul the hubs on a 1993 Cannondale road bike with RX-100 hubs. For all I know, this is the first time they've been serviced. Did some research, found that the most common bearing ball size for front hubs is 3/16. Stopped by a shop before opening hub, asked for 3/16 ball bearings, mechanic said he only had 5/32, but that they use them all the time without problem as a replacement in hubs using 3/16. Disassembled hub - existing balls definitely appear to be at least 3/16 (unscientifically measured against a tape), but to the eye appear much larger than the 5/32s. The shop owner has apparently been in business for many years, and was highly recommended by a friend who has had years of good service there. Thoughts and opinions? Is it advisable to use the smaller size?

Second question. Both cones on the front have almost identical gouges, no bigger than 0.5mm, at one point of the ball bearing pathway (see photo). From what I've read, I should trash them in favor of new cones. Opinions? Also, what could have caused this? The axle appears straight. There was no play in the hub when it was mounted on the fork. Any thoughts, opinions, advice, or flames?

Oh, one more thing. Anyone have a spare set of cones for RX-100 hubs? Top dollar/euro/sterling paid, as long as it's under five of them.

Patrick
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Old 08-27-06, 11:37 PM
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I personally would not use a different ball size for rebuilding that hub. Bearings are cheap enough, and you should be able to find them at another shop, or even online for just a couple dollars. Heck, go all out and buy expensive "premium" bearings for a smoother hub...the difference is negligable at best, the bearing race having as much to do with quality as the bearing. The RX100 was a cheap hub and you should only expect the according quality.

As for the cones, it looks like a manufacturing defect to me. There are several compatible cones available to fit the RX100 hub. Nice compatability chart here.
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Old 08-28-06, 05:47 PM
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I know RX-100 is low end, and that's part of the reason I asked the question. Will these gouges have a detrimental or catastrophic effect on the bearings, or might it work okay? I've ridden the bike occassionally (no more than 20 miles/week) with no serious problems, but I don't know when the cones were damaged (if not a manufacturing defect). I was noticing a slight vibration coming from the front, which is why I opened the hub up.

Edit: The old bearings do not show any signs of serious wear, so I question the severity of the defect in the cones.

Thanks to the info you provided, I did find a shop online with the appropriate cones. But with $8 shipping, I can't justify buying only the cones and some bearings. Looks like I might end up with some new tools and maybe a smaller inner chainring.

But the point was to save money! I'll end up spending more than a new hub would cost...I need some fiscal discipline.

Patrick

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Old 08-28-06, 07:18 PM
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Originally Posted by JunkYardBike
I know RX-100 is low end, and that's part of the reason I asked the question. Will these gouges have a detrimental or catastrophic effect on the bearings, or might it work okay? I've ridden the bike occassionally (no more than 20 miles/week) with no serious problems, but I don't know when the cones were damaged (if not a manufacturing defect). I was noticing a slight vibration coming from the front, which is why I opened the hub up.

Edit: The old bearings do not show any signs of serious wear, so I question the severity of the defect in the cones.

Thanks to the info you provided, I did find a shop online with the appropriate cones. But with $8 shipping, I can't justify buying only the cones and some bearings. Looks like I might end up with some new tools and maybe a smaller inner chainring.

But the point was to save money! I'll end up spending more than a new hub would cost...I need some fiscal discipline.

Patrick
This is the issue isn't it, you know you have a relatively low end hub, any idea how good, bad or ugly the cups are? Typically low end hubs are mated to low end rims, and use low end spokes. You might be best off to use the existing wheel to true up your wheel truing skills, and then buy a new a new machine built wheel, and properly tension and true the new wheel. It may still be low end, but new low end beats mostly worn out low end any day.
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Old 08-28-06, 07:27 PM
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The cups seem to be in great condition - very, very minor scratches. The wheels are quite true as well. I've only had to make minor adjustments. But I suppose I'll see what happens as I put more miles on them.
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Old 08-28-06, 08:18 PM
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JunkYardBike,

The cones are definitely damaged, as you've seen. They may be interchangeable with cones from similar Shimano models: take 'em into a shop, ask to rummage through their parts box, and squint at whatever you find.

The ball bearings may *appear* fine to the naked eye, but believe me, if the cone looks like that they are NOT. Just yesterday I overhauled an old headset and was ready to replace it because it felt so rough. The ball bearings looked perfectly shiny and new, but I tried replacing them anyway. $1 worth of bearings later, the headset was running flawlessly smooth. The moral of the story is: bearing damage can be invisible to the naked eye. Do yourself a favor and get new Grade 25 bearings in the right size. Absolutely *the best* $1-5 maintenance you could ever do on your bike!
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Old 08-29-06, 05:33 AM
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DO NOT use the wrong size bearings! I can't believe your LBS recommended 5/32" bearings when ALL Shimano hubs I've ever seen use 3/16" balls. You definitely need a new mechanic. You may be able to get the proper size balls at an auto parts shop and certainly at an industrial supply house (Granger, McMaster-Carr, etc.). Get Grade 25 balls, not Grade 200 or 300 (lower numbers are better).

You need new cones too.

Good quality bearing balls and cones can be obtained mailorder from Bike Tools Etc.
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Old 08-29-06, 07:18 AM
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Originally Posted by JunkYardBike
Relatively new to bicycle mechanics, but I've been having fun disassembling/breaking/attempting to reassemble some old bikes.

Now to the point. I have two questions:

First, I decided to overhaul the hubs on a 1993 Cannondale road bike with RX-100 hubs. For all I know, this is the first time they've been serviced. Did some research, found that the most common bearing ball size for front hubs is 3/16. Stopped by a shop before opening hub, asked for 3/16 ball bearings, mechanic said he only had 5/32, but that they use them all the time without problem as a replacement in hubs using 3/16. Disassembled hub - existing balls definitely appear to be at least 3/16 (unscientifically measured against a tape), but to the eye appear much larger than the 5/32s. The shop owner has apparently been in business for many years, and was highly recommended by a friend who has had years of good service there. Thoughts and opinions? Is it advisable to use the smaller size?

Second question. Both cones on the front have almost identical gouges, no bigger than 0.5mm, at one point of the ball bearing pathway (see photo). From what I've read, I should trash them in favor of new cones. Opinions? Also, what could have caused this? The axle appears straight. There was no play in the hub when it was mounted on the fork. Any thoughts, opinions, advice, or flames?

Oh, one more thing. Anyone have a spare set of cones for RX-100 hubs? Top dollar/euro/sterling paid, as long as it's under five of them.

Patrick

Why guess at the proper size of the bearings. Get your self a 1" micrometer and learn how to use it. This is invaluable for all kinds of mechanic work. You'll be able to I.D. the diameter down to thousandths of an inch (or even 10 thousandths if you have the right model of mikes). If you don't feel comfortable with converting thousandths to fractional measurements, the machinist market is flooded with good quality dial calipers, some that are marked on the dial in fractional measurements to simplify things. Its odd that to work on bikes you need BOTH a fractional and metric dial caliper or micrometer. Once you verify the correct size ball bearings then you can deal with the BOZO mechanic who recommended the wrong size and confront him with his bad advice directly because you will no what you need with no uncertainty at all.
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Old 08-29-06, 07:30 AM
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Originally Posted by masi61
Why guess at the proper size of the bearings. Get your self a 1" micrometer and learn how to use it. This is invaluable for all kinds of mechanic work. You'll be able to I.D. the diameter down to thousandths of an inch (or even 10 thousandths if you have the right model of mikes). If you don't feel comfortable with converting thousandths to fractional measurements, the machinist market is flooded with good quality dial calipers, some that are marked on the dial in fractional measurements to simplify things. Its odd that to work on bikes you need BOTH a fractional and metric dial caliper or micrometer. Once you verify the correct size ball bearings then you can deal with the BOZO mechanic who recommended the wrong size and confront him with his bad advice directly because you will no what you need with no uncertainty at all.
Good advice, I would recommend a cheap metal vernier caliper, with metric and inch increments. Reads to 1/128 inches, .1 mm, more than enough for bicycling applications. And, probably most important, it can be used for a very accurate measurement of chain stretch/wear. Less than $10 at home stores, discount auto parts.
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Old 08-29-06, 07:41 AM
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Originally Posted by masi61
Why guess at the proper size of the bearings. Get your self a 1" micrometer and learn how to use it. This is invaluable for all kinds of mechanic work. You'll be able to I.D. the diameter down to thousandths of an inch (or even 10 thousandths if you have the right model of mikes). If you don't feel comfortable with converting thousandths to fractional measurements, the machinist market is flooded with good quality dial calipers, some that are marked on the dial in fractional measurements to simplify things. Its odd that to work on bikes you need BOTH a fractional and metric dial caliper or micrometer. Once you verify the correct size ball bearings then you can deal with the BOZO mechanic who recommended the wrong size and confront him with his bad advice directly because you will no what you need with no uncertainty at all.
Of course you're right...I've been meaning to get a caliper ruler. But I was relatively certain the bearings needed were 3/16, and both I and the mechanic knew that 5/32 was the incorrect size. It was his opinion/experience that 5/32s work in place of 3/16s...and he didn't have any 3/16 in the shop. He claimed to have used them before with no problems. Was he so desperate for a $1 sale? Maybe. I wanted to say no, but I have confrontation issues. Besides, a friend has used this mechanic for years and raves about him.

Not that I'll ever go back there again.

Thanks for all the help!
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