Unequal spacing of cogs in 7-speed Dura Ace cassette
07-11-18, 05:31 AM
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Unequal spacing of cogs in 7-speed Dura Ace cassette
On my Dura Ace 7-speed cassette, I noticed that the width of the (1st position) threaded cog with spacer is slightly less than the width of the (2nd position) cog with spacer which is equal to the width of a spacer plus a regular cog. So the spacing between the first and second cogs is slightly less than the spacing between each of the other adjacent pairs of cogs. Why might that be so?
07-11-18, 07:48 AM
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'Need to know which Dura Ace free hub are you working with.
Dean
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07-11-18, 07:50 AM
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Are you perhaps missing a thin spacer from behind the threaded cog? A slight difference is not too relevant, since the first cog's position is set by the low limit and you set the indexing (if used) to make the shifting line up anyway.
07-11-18, 10:40 AM
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Is it causing you problems shifting? If not, don't worry. I think that on some they do space them slightly different to optimize shifting.
07-11-18, 12:19 PM
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On my Dura Ace 7-speed cassette, I noticed that the width of the (1st position) threaded cog with spacer is slightly less than the width of the (2nd position) cog with spacer which is equal to the width of a spacer plus a regular cog. So the spacing between the first and second cogs is slightly less than the spacing between each of the other adjacent pairs of cogs. Why might that be so?
07-11-18, 03:36 PM
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I'll be ordering a digital calipers and will post precise measurements regarding the spacing once it arrives.
07-11-18, 03:38 PM
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07-11-18, 03:41 PM
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There's no thin spacer between the threaded cog and the second cog.
07-11-18, 05:11 PM
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I just measured a 7-speed cassette for a 7400 Dura Ace freehub.....that was conveniently removed from the hub for another issue. I have good quality digital calipers and here is what I found:
1st position cog with integral spacer (threads on to the 32 mm portion of the hub body) is 4.98 mm.
2nd position cog with integral spacer (splined on inside diameter) is 5.16 mm.
The cog plus separate spacer combination for the 3rd through 7th positions varied from 4.95 to 4.99 mm.
I run this cassette in friction mode, since my index shifter for the rear derailleur is a 6-speed model.
'Hope this is helpful.
Dean
1st position cog with integral spacer (threads on to the 32 mm portion of the hub body) is 4.98 mm.
2nd position cog with integral spacer (splined on inside diameter) is 5.16 mm.
The cog plus separate spacer combination for the 3rd through 7th positions varied from 4.95 to 4.99 mm.
I run this cassette in friction mode, since my index shifter for the rear derailleur is a 6-speed model.
'Hope this is helpful.
Dean
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07-12-18, 05:12 AM
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I have the 1989 8speed DA-7400. Be aware that dura-ace from that period is different cable pull ratio, different thread on the last cog (is smaller than standard uniglide. so they could fit 11T .. while normal non-duraace uniglide had 13T or 12T)
RD and shifter must be both dura-ace or both non-duraace to work on 8speed indexing (or a weird combo of standard 9speed shifter with dura-ace RD will work ok for 8speed but using only 8 out of the 9clicks the shifter has). Might be true for 7speed as well.
https://www.sheldonbrown.com/dura-ace.html
RD and shifter must be both dura-ace or both non-duraace to work on 8speed indexing (or a weird combo of standard 9speed shifter with dura-ace RD will work ok for 8speed but using only 8 out of the 9clicks the shifter has). Might be true for 7speed as well.
https://www.sheldonbrown.com/dura-ace.html
07-12-18, 02:06 PM
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I have the 1989 8speed DA-7400. Be aware that dura-ace from that period is different cable pull ratio, different thread on the last cog (is smaller than standard uniglide. so they could fit 11T .. while normal non-duraace uniglide had 13T or 12T)
RD and shifter must be both dura-ace or both non-duraace to work on 8speed indexing (or a weird combo of standard 9speed shifter with dura-ace RD will work ok for 8speed but using only 8 out of the 9clicks the shifter has). Might be true for 7speed as well.
https://www.sheldonbrown.com/dura-ace.html
RD and shifter must be both dura-ace or both non-duraace to work on 8speed indexing (or a weird combo of standard 9speed shifter with dura-ace RD will work ok for 8speed but using only 8 out of the 9clicks the shifter has). Might be true for 7speed as well.
https://www.sheldonbrown.com/dura-ace.html
The reduced size locking cog is only partially true. Later DA hubs had the larger threading for standard threaded sprockets:
https://www.velobase.com/CompImages/H...65FF7FC9C.jpeg
vs the earlier:
https://www.velobase.com/CompImages/H...4A67CD046.jpeg
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