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Old 02-02-2015, 08:28 AM   #1
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A question for the bicycle gearheads...

Not a Porsche question, but it is technical, and I know there's a lot of bike people on here.

Dura-Ace MF-7400 6 speed freewheel, likely 80's vintage. Can anyone tell me how many balls are supposed to be in the inner and outer races? I have just taken one apart that I pickeded up used with a pair of wheels and it looks to me like there is room for another 4 or 5 balls in the outer raceway. I'm wondering if someone took this apart before, lost a few balls, and put it back together anyway.

(I did a search and I'm pretty sure no-one has ever asked this question before on this forum! )

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Old 02-02-2015, 08:53 AM   #2
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Old 02-02-2015, 01:58 PM   #3
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I have doe'n my share of working on these things over the years and normally there are balls going all the way "round" but for a small gap, of ether a little less than one ball or almost no gap. I don't know the exact number of balls but you should definitely not have a gap of 4 or 5 balls.
To put it in another way, you should have the whole "ring" filled with balls, but you should not have to press or squeeze the last ball in. Using grease to hold the balls in place is a good idea.
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Old 02-02-2015, 03:32 PM   #4
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Agree with Bfan, the races should be filled until the last ball won't fit without force. I used to run a 7400 Groupo on my Cannondale Crit frame I raced in the 80's and 90's, changed to Campy and high flange wheels later. I think I still have the old parts around somewhere (I never throw bicycle parts away!), just have to find the cassette and cluster to count. Best answer is to measure the bearing diameter and hit a quality bike shop for a bag O' bearings. I always just stock bags of all sizes and go from there. By the way, I still have and ride that Criterium frame! Hard to choose between that one and the 'ancient' Raleigh steel though. Depends whether I want fast or comfortable!
As for post two: Haters gonna be haters. Get a life dudes and dudettes!
Oh, and if they 'roll eyes' enough, they may spot a brain back there. Doubt it.

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Old 02-02-2015, 05:46 PM   #5
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Quote:
Originally Posted by Mark_T View Post
... someone took this apart before, lost a few balls, and put it back together anyway.
^^ Yes. ^^

Old mechanics either fill the race with balls or use a full race minus one ball (if they believed the old wives' tale about clearance).

Be sure to get the preload correct when you put it all back together.

(I still ride my late-90's Kestral 200 SCi carbon with 7-spd Campy Chorus).
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Old 02-02-2015, 06:34 PM   #6
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I worked at a bicycle shop while in college and do my own work when needed and I agree with call comments. Leave enough space for the ball bearing to be able to move around. If it's minus 1 then so be it. Use good grease and check for pitting on the race on the hub and the cone fitting that holds the ball bearings in place. I too have bicycles from the 80's/90's still in great shape. Good luck.
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Old 02-02-2015, 08:04 PM   #7
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Thanks for all the replies. I'll get a few 1/8" balls and fill in the gap.

I'm just getting back into cycling after a break of some 30+ years. I do most of my riding on the trails with a hybrid type bike in the summer and I just picked up a '88 Trek 560 for riding on the rollers over the winter (love the rollers!) and for longer rides next summer.
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Old 02-02-2015, 08:24 PM   #8
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... getting back into cycling after a break of some 30+ years.
... with 6 speed freewheel you will pick up right where you left off.
jk mate. I like the vintage stuff too. You just have turn-off the part of your mind used to a 11sp cassette.
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Old 02-03-2015, 03:12 PM   #9
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Actually, I left off on a 5-speed freewheel in '76, so I guess it was more like 40 years ago. This '88 Trek is way advanced compared to what I used to have. It will do just fine.

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