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6/7 speed Freewheel dimensions

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6/7 speed Freewheel dimensions

Old 10-09-21, 10:59 AM
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Aardwolf
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6/7 speed Freewheel dimensions

Hiya folks,
I'm an old git with dodgy knees so I was looking at fitting a lower gear on my 1982 Holdsworth Avanti.

Dropout spacing is 126mm
It's currently got the original Regina Corsa freewheel (14-15-16-17-18-19).
So I was looking at fitting the Shimano Hyperglide 7 speed freewheel (14-16-18-20-22-24-28) MF-TZ500-7

I've got it to fit in with an OLD of 127mm, but the (8 speed) chain is too close to the chain stay with no spacers on NDS.
I've ordered a thinner cone to try in the NDS, but it occured to me that the 6 speed version might be thinner or give more chain clearance:
Shimano Hyperglide 6 speed freewheel (14-16-18-21-24-28) MF-TZ500-6

From the photos on Amazon it looks like it does have more clearance:



Does anybody have the measurements that would confirm this ?
eg. freewheel width from shoulder to face of 14T cog.
Any other useful ideas considered

Cheers.
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Old 10-09-21, 12:02 PM
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If a thin washer added to the DS gives you room, go with that.
https://www.sheldonbrown.com/cribsheet-spacing.html

Last edited by Bill Kapaun; 10-09-21 at 12:13 PM.
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Old 10-09-21, 12:12 PM
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Yep, I'm going to try that.

I've got several axle spacers of 0.5mm and 1.0mm.
I'm trying to keep the OLD down though and 127.5 or 128mm is getting a bit too large.
But it would probably fit and the frame is steel so the dropouts should cope.

I'm using a new (Weldtite) axle which has cones 1mm wider than the original axle (which has 1 pitted cone and a different thread).
So I should get another 1mm of adjustment when the new cone arrives.

Last edited by Aardwolf; 10-09-21 at 12:27 PM. Reason: spelling
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Old 10-10-21, 10:43 AM
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Running a 9 speed chain will help you a very slight amount. I’m running one bike with a .5mm spacer on DS and a 9 speed chain with a 7 speed freewheel.

I’ve adopted a 2mm rule on spreading, not cold setting, the dropouts, although others will go beyond that.

John
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Old 10-10-21, 11:14 AM
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I've padded it out to 128mm and I can still hear the 8 speed chain rubbing slightly.
I'll try 128.5 and hope the thinner cone will fit (Wheel Manufacturing CN-R098) which gives me back 4.4mm

On the upside my Suntour VX RD is handling 28T just fine - it's rated at 26T max.
Then I'll measure the dishing and see how terrible it is.
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Old 10-10-21, 12:00 PM
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7-speed freewheels are usually a tiny bit wider than 6-speed. I'd try the Shimano 6-speed freewheel rather than add spacers to the axle.

(The extra cog on this particular 7-speed freewheel doesn't add any value, IMO.)
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Old 10-10-21, 12:05 PM
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This is a common problem in going from 6 to 7. A 1 mm spacer should take care of the problem.
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Old 10-10-21, 12:13 PM
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You're probably right about the width, it looks that way in the pictures anyway.
Amazon is just too easy, 6 speed turning up tomorrow for £20.

So I'll be able to give the width measurements anyway
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Old 10-10-21, 12:51 PM
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Here's one of Sheldon Brown's cribsheets about it: https://www.sheldonbrown.com/cribsheet-spacing.html

While 6- and 7-speed do technically fit in the same nominal OLD, you do have to sacrifice a little clearance with the latter, and not all bikes have that clearance to spare.
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Old 10-10-21, 01:20 PM
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Yep I saw the cribsheet, that and https://www.sheldonbrown.com/harris/freewheels.html is why I tried the 7 speed.

Regina Corsa measures 30.15 mm
Shimano MF-TZ500-7 measures 33mm, but Sheldon Brown says 31.9mm
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Old 10-11-21, 12:17 PM
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And the results are in.

Measurement from hub side of inside sprocket to dropout side of smallest sprocket:
30.15 mm Regina Corsa
33mm Shimano MF-TZ500-7
29.5mm Shimano MF-TZ500-6

So 6 speed Shimano has 3.5mm more leeway than the 7 speed version

Took 3mm off DS and added 1mm to NDS to give OLD 126.29mm.
Can't hear chain rubbing and dishing should be about right.
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