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1/4" balls not right for Shiman FH-RM65 rear hub bearing???

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1/4" balls not right for Shiman FH-RM65 rear hub bearing???

Old 06-24-15, 06:35 AM
  #1  
krfarstad
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1/4" balls not right for Shiman FH-RM65 rear hub bearing???

Hello

I'm having some difficulty with my Shimano FH-RM65 rear hub. I wanted to service the hub and replace the old ball bearings with new ones, after 7 years and thousands of miles with zero servicing so far. As I dismantled the hub, half of the ball bearings immediately vaporized, so I only have about 8 or 9 left. I was going to replace them anyway, so I didn't bother.

I read about the hub on the internet, and it says that there shall be 9 pieces of 1/4" ball bearings on each side of the hub, so I went on ebay and bought 25 of those. To my surprise though, as I had assembled the hub again and applied plenty of grease, the wheel was completely misaligned as I put it back on the bike. Turns out the axle has a lot of play within the ball bearing, because the balls are too small! Frowning, I reinserted the old ball bearings that had not yet taken off. There is only room for 8 of the old ball bearings, and the axle fits snugly in the middle, with no play. WTF?!

As I mentioned earlier, the bike is about 7 years old. Is it possible that the hub design has changed since then? I can only tell the old balls from the new 1/4" ones by the worn surface of the old ones, not by weight or size. It was a very tight fit with 9 1/4" balls, so it's just about possible to squeeze in the ninth ball without any of the other ones popping out.

I ordered a batch of 6.5 mm balls as well (1/4" balls are 6.35 mm) hoping that they are the right size, but I'm worried that it might even be 7 mm balls. What do you guys think? Replies are highly appreciated.
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Old 06-24-15, 07:01 AM
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Measure the old bearing diameter.
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Old 06-24-15, 07:09 AM
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https://www.paul-lange.de/support/sh...RM65-12535.PDF
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Old 06-24-15, 07:31 AM
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You must have done something wrong as I've never seen a Shimano rear hub that didn't take 1/4" bearing balls and 9 per side. The .pdf drawing Bill linked to also confirms that size and number.
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Old 06-24-15, 07:51 AM
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Did you inspect the bearing races?
IF the balls came out in pieces, you may be looking for a new hub.
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Old 06-24-15, 07:57 AM
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Is there a ball that was left behind the race in the hub?

Happened to me once when I replaced the bearings. The axle would not center correctly.

John
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Old 06-24-15, 07:57 AM
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I know it says everywhere that the ball size is 1/4", but to me that is obviously not true since I could fit only 8 of the old balls, and the axle was snug, while I could barely fit 9 1/4" balls, but with a lot of play in the axle. I don't possess tools that allow me to measure the sizes with sufficient accuracy to be able to tell them apart.

I can almost guarantee that I'm not doing it wrong. I did try with the new 1/4" balls and then with the old balls, and the difference was very clear. The balls are not the same size, although the size difference is small.
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Old 06-24-15, 08:49 AM
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AGAIN!
What condition are the races (and cones)
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Old 06-24-15, 11:05 AM
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Originally Posted by Bill Kapaun View Post
AGAIN!
What condition are the races (and cones)
The parts are all OK, nothing broken. When I said that half of the balls vaporized, I mean I lost them once they were out of the hub. I checked inside the hub if some balls are trapped inside, but no. There is still a lot of play in the axle with 1/4" balls. Can you explain which part is the "races"? I'm not all into English bike anatomy jargon (English is not my mother tongue).

To be clear: By play in the axle, I don't mean play in the axle lengthwise direction. The cones are locked adequately such that there is no play in the axle lengthwise direction. The play is so that I can bob the axle around inside the bearing, because the balls are too small, apparently.

Last edited by krfarstad; 06-24-15 at 11:09 AM.
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Old 06-24-15, 12:58 PM
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There are two things working here. How far the cones turn in get the proper cone-ball-race adjustment (very slight radial movement of the axle) and what is the correct overall dimension from locknut to locknut (a result of how far the cones are adjusted).

I guess I have to ask... what happens if you only use 8 new balls? Does everything work okay? There is an aspect that if it works it works and as long as there is not excessive radial or axial play and you can't use 9 new balls. I believe, and someone can correct me, that it is possible to use 1 less ball because the balls will just spread out a little more.

If you can't use 8 or 9 new 1/4" balls, I'm not sure what you can do. But if it were me I'd pick up some Campy 7/32" balls and see how 9 of those would work.

John
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Old 06-24-15, 01:21 PM
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The ball bears against the cone and the race.
Race is part of the hub that the bearing ball rides on. It should be nice and shiny, with no scratches, gouges etc.
Cone is the tapered part that screws on the axle, where the bearing ball rides on. It should be nice and shiny, with no scratches, gouges etc.
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Old 06-24-15, 01:43 PM
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Originally Posted by krfarstad View Post
......I don't possess tools that allow me to measure the sizes with sufficient accuracy to be able to tell them apart.....
Purchase a caliper



In the USA, this one is often on sale at Harbor Frieght for $10- (with coupon). You have far more investment to loose in the hub.
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Old 06-24-15, 02:00 PM
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Originally Posted by nfmisso View Post
Purchase a caliper



In the USA, this one is often on sale at Harbor Frieght for $10- (with coupon). You have far more investment to loose in the hub.
Or line up 9 balls against a straight edge and see if they measure 2-1/4".
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Old 06-24-15, 02:18 PM
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Originally Posted by krfarstad View Post
To be clear: By play in the axle, I don't mean play in the axle lengthwise direction. The cones are locked adequately such that there is no play in the axle lengthwise direction. The play is so that I can bob the axle around inside the bearing, because the balls are too small, apparently.
Don't understand. IME, using smaller balls will only make the cone sit further in. Unless the dust shield interferes, usually not a problem as such. Likewise, using bigger balls will leave the cone further out. But no play in either case.
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Old 06-24-15, 02:59 PM
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Originally Posted by Slash5 View Post
Measure the old bearing diameter.
Originally Posted by nfmisso View Post
Purchase a caliper



In the USA, this one is often on sale at Harbor Frieght for $10- (with coupon). You have far more investment to loose in the hub.
Exactly! (Although I prefer a dial caliper; no batteries to fail at the wrong time!)

Why ask on the Forum when you can become the answer man yourself..?
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Old 06-24-15, 03:05 PM
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Originally Posted by HillRider View Post
You must have done something wrong as I've never seen a Shimano rear hub that didn't take 1/4" bearing balls and 9 per side. The .pdf drawing Bill linked to also confirms that size and number.
The new shimano xt rear hubs take 3/16 ball bearings,

https://cycle.shimano-eu.com/media/te...9830758219.pdf

But yes this is an older hub and so should be 1/4. Not so sure that will remain the standard; we'll see what Shimano does.
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Old 06-24-15, 04:59 PM
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Originally Posted by krfarstad View Post
I know it says everywhere that the ball size is 1/4", but to me that is obviously not true since I could fit only 8 of the old balls, and the axle was snug, while I could barely fit 9 1/4" balls, but with a lot of play in the axle. I don't possess tools that allow me to measure the sizes with sufficient accuracy to be able to tell them apart.

I can almost guarantee that I'm not doing it wrong. I did try with the new 1/4" balls and then with the old balls, and the difference was very clear. The balls are not the same size, although the size difference is small.
How did you test-fit the balls in the hub? I would recommend putting in a bead of grease in the race, placing the balls in the hub, then place the cone on top to push the balls into the correct position with regard to the cone and race. You should see where they sit, and you should be able to nudge them around to fit 9 balls on each side.

I've rebuilt Shimano hubs this way for 30+ years. The rear hubs have always had 9 1/4" balls.
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Old 06-24-15, 05:40 PM
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Originally Posted by bikemig View Post
The new shimano xt rear hubs take 3/16 ball bearings,

https://cycle.shimano-eu.com/media/te...9830758219.pdf

But yes this is an older hub and so should be 1/4. Not so sure that will remain the standard; we'll see what Shimano does.
The .pdf you link to is interesting in its own right. The drawing shows part No. 4 as "13 pieces" while the parts list No. 4 says "Steel Ball (3/16") 20 pieces" I wonder which is correct.

Anyway, the OP's hub is specifies by Shimano as requiring 1/4" balls, 18 pieces (9 per side).
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Old 06-25-15, 10:06 AM
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Originally Posted by rmfnla View Post
Exactly! (Although I prefer a dial caliper; no batteries to fail at the wrong time!)

Why ask on the Forum when you can become the answer man yourself..?
It all comes down to: if you are not willing to invest in the tools required to do the job properly - including measurement tools - you will save a LOT of money by paying a professional to do the job. The pro will have to fix whatever you mess up in addition to the initial problem - if there was even an initial problem.
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Old 06-25-15, 10:28 AM
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Originally Posted by HillRider View Post
The .pdf you link to is interesting in its own right. The drawing shows part No. 4 as "13 pieces" while the parts list No. 4 says "Steel Ball (3/16") 20 pieces" I wonder which is correct.
Looks like 13 loose on the drive side and 7 in a retainer on the non-drive side.
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Old 06-25-15, 10:49 AM
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Originally Posted by HillRider View Post
The .pdf you link to is interesting in its own right. The drawing shows part No. 4 as "13 pieces" while the parts list No. 4 says "Steel Ball (3/16") 20 pieces" I wonder which is correct.

Anyway, the OP's hub is specifies by Shimano as requiring 1/4" balls, 18 pieces (9 per side).
13 seems 'about right".
13*3/16=2-7/16. (although twelve 3/16" would be the same as nine 1/4")
9*1/4=2-1/4"
CTC measurements.

I've noticed most of the new front road hubs use 11 balls instead of 10.
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Old 06-25-15, 11:20 AM
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Originally Posted by nfmisso View Post
It all comes down to: if you are not willing to invest in the tools required to do the job properly - including measurement tools - you will save a LOT of money by paying a professional to do the job. The pro will have to fix whatever you mess up in addition to the initial problem - if there was even an initial problem.
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Old 06-25-15, 01:26 PM
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Originally Posted by HillRider View Post
The .pdf you link to is interesting in its own right. The drawing shows part No. 4 as "13 pieces" while the parts list No. 4 says "Steel Ball (3/16") 20 pieces" I wonder which is correct.
Part number Y00091210 on that tech doc is a bag of 20 bearings, the number of bearings in a bag doesn't always match the required amount shown on the tech docs.

Example: https://www.paul-lange.de/support/sh...-MX80-3390.pdf

If the hub drawing is correct it would need 24 bearings.
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