Shimano Dura Ace SL-7402 8-speed shifters with 7-speed cassette
03-12-23, 10:36 AM
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Shimano Dura Ace SL-7402 8-speed shifters with 7-speed cassette
Can Shimano Dura Ace SL-7402 8-speed shifters be used with a 7-speed cassette?
03-12-23, 11:09 AM
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03-12-23, 11:58 AM
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03-12-23, 12:12 PM
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03-12-23, 01:11 PM
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Yes it will. It isn't "ideal", because 8 speed is 4.8mm per cog vs 7 speed at 5mm. But if you center the indexing under the 4th cog, you'll only have .4mm of error on the 6th and 2nd cog. H and L stops will take care of 1st and 7th positions.
I've done the opposite - used a 7 speed Shimano shifter on 8 speed with no issues, tuning it the same way.
I've done the opposite - used a 7 speed Shimano shifter on 8 speed with no issues, tuning it the same way.
03-12-23, 03:54 PM
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Are you perhaps forgetting that the 2-3 spacer on a Shimano 7s cassette isn't 3.1mm like the rest of them?
It's a yet-thicker 3.3mm in that position, and usually a darker color (except when partially built onto the 2nd cog).
The 3.3mm spacer could be swapped out for a 3.1mm spacer in that position (likely without preventing the lockring from compressing the cog stack), if a second "donor" cassette is available(?).
A full turn of the barrel adjuster moves the derailer about 1.3mm (a bit more for 74xx Dura-Ace), putting these very small spacing differences into perspective.
03-12-23, 04:14 PM
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It's raining, so here I go again...
Are you perhaps forgetting that the 2-3 spacer on a Shimano 7s cassette isn't 3.1mm like the rest of them?
It's a yet-thicker 3.3mm in that position, and usually a darker color (except when partially built onto the 2nd cog).
The 3.3mm spacer could be swapped out for a 3.1mm spacer in that position (likely without preventing the lockring from compressing the cog stack), if a second "donor" cassette is available(?).
A full turn of the barrel adjuster moves the derailer about 1.3mm (a bit more for 74xx Dura-Ace), putting these very small spacing differences into perspective.
Are you perhaps forgetting that the 2-3 spacer on a Shimano 7s cassette isn't 3.1mm like the rest of them?
It's a yet-thicker 3.3mm in that position, and usually a darker color (except when partially built onto the 2nd cog).
The 3.3mm spacer could be swapped out for a 3.1mm spacer in that position (likely without preventing the lockring from compressing the cog stack), if a second "donor" cassette is available(?).
A full turn of the barrel adjuster moves the derailer about 1.3mm (a bit more for 74xx Dura-Ace), putting these very small spacing differences into perspective.
And are you talking about Shimano IG cassettes or HG? They're different. Where did the OP say it was a Shimano cassette?
Last edited by Kontact; 03-12-23 at 04:27 PM.
03-12-23, 04:57 PM
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First of all, now you're really digging.
The cog width doesn't change the fact of Shimano 7-speed's asymmetrical cog spacing (as in every one of Shimano's 7s freewheels and cassettes).
All 7s IG, HG and even UG cassettes and freewheels have identical asymmetric cog spacing, despite any cog-thickness differences..
What might have confused you is that the "compact" and other Shimano 7s cassettes having an 11t smallest cog often have a couple of millimeters of spacer attached to the 2nd-position cog, with a ~1mm perforated spacer next to that.
Where the asymmetric spacing of Shimano 7s becomes suddenly glaring is when one uses a low-normal derailer on any 7s cogset, putting the asymmetric spacing feature at the wrong end of the shifter's asymmetric indexing sequence. I once had fun figuring that severe problem out for a local shop's head mechanic, as Shimano never promoted their asymmetric spacing that I can recall (from some dozen years of attending their technical seminars).
Last edited by dddd; 03-12-23 at 05:00 PM.
03-12-23, 05:39 PM
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First of all, now you're really digging.
The cog width doesn't change the fact of Shimano 7-speed's asymmetrical cog spacing (as in every one of Shimano's 7s freewheels and cassettes).
All 7s IG, HG and even UG cassettes and freewheels have identical asymmetric cog spacing, despite any cog-thickness differences..
What might have confused you is that the "compact" and other Shimano 7s cassettes having an 11t smallest cog often have a couple of millimeters of spacer attached to the 2nd-position cog, with a ~1mm perforated spacer next to that.
Where the asymmetric spacing of Shimano 7s becomes suddenly glaring is when one uses a low-normal derailer on any 7s cogset, putting the asymmetric spacing feature at the wrong end of the shifter's asymmetric indexing sequence. I once had fun figuring that severe problem out for a local shop's head mechanic, as Shimano never promoted their asymmetric spacing that I can recall (from some dozen years of attending their technical seminars).
The cog width doesn't change the fact of Shimano 7-speed's asymmetrical cog spacing (as in every one of Shimano's 7s freewheels and cassettes).
All 7s IG, HG and even UG cassettes and freewheels have identical asymmetric cog spacing, despite any cog-thickness differences..
What might have confused you is that the "compact" and other Shimano 7s cassettes having an 11t smallest cog often have a couple of millimeters of spacer attached to the 2nd-position cog, with a ~1mm perforated spacer next to that.
Where the asymmetric spacing of Shimano 7s becomes suddenly glaring is when one uses a low-normal derailer on any 7s cogset, putting the asymmetric spacing feature at the wrong end of the shifter's asymmetric indexing sequence. I once had fun figuring that severe problem out for a local shop's head mechanic, as Shimano never promoted their asymmetric spacing that I can recall (from some dozen years of attending their technical seminars).
Low normal derailleurs are going to screw with the indexing if you're using a top normal shifter because the shifters are built for the non-linear swing arm motion of the parallelogram. So while we talk about the fixed amount of cable pull per click, the shifters actually have variable click spacing to reflect the non-linear arc that the derailleur moves through. If you use a hanger saver that pushes a Shimano derailleur another cm outboard, you'll find the indexing doesn't work right because the derailleur is working in the wrong part of its arc. Switch to alternate B cable routing and suddenly it works right.
Sram Exact Actuation refers to the cam on the bottom of the RD that forces the cable to have a linear affect on the swing arc. So they have actual fixed pull ratios.
03-13-23, 05:29 PM
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Thinking more about this, it seems likely that you saw the spacer thickness, presumed that the cogs were all identical thickness, then misunderstood how derailleurs have variable actuation ratios, then tried to fix a top/low normal mismatch and concluded without evidence and against all documentation that 7 speed Shimano is asymmetric.
And then you insult me because of your reasoning errors.
Here's a chart that shows the actual cable pull of early six and seven speed shifters. You'll note that they appear to need pull more cable as the derailleur moves toward the lower gears and the parallelogram becomes parallel to the chainline.
You're welcome.
And then you insult me because of your reasoning errors.
Here's a chart that shows the actual cable pull of early six and seven speed shifters. You'll note that they appear to need pull more cable as the derailleur moves toward the lower gears and the parallelogram becomes parallel to the chainline.
You're welcome.
03-13-23, 05:54 PM
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Of course any derailer goes too far out of linearity to index with when you start adding 1cm spacers under the mounting bolt.
But I don't think it's going to prove much.
I have noticed that many 6s and 7s SIS rear derailers seem to lose linearity when used across 8-or-more-cog cassettes, struggling to index the largest cog. But I never recommended using an older SIS rear derailer with the wider cassettes, and Shimano perhaps began stamping the "integrated-8 SIS" lettering into those derailer's cage because of this. What was happening in that case was that the wider cassette would sit asymmetrically under the 6 - or 7-speed derailer's more-limited range of usefully-indexed cage travel.
I've learned that lesson the hard way more than once, and have also seen others bring their newly-built vintage bikes by with the same sort of subtle indexing issue.
Lots of low-normal derailers got used (with normal 9-speed SIS shifters) and somehow had no problem indexing 8 or 9-speed systems, so what happened to the "asymmetric non-linearity" of which you speak? Was that perhaps only a 7s derailer thing?
Repeating myself here, easily verified, ALL Shimano 7s cassettes and freewheels ever sold by Shimano have had the same, asymmetrical cog spacing.
From your un-sourced chart, which I can find no fault with, what one actually notices is that the end-cog spacing appears greater on both ends of the cassette, simply because of what you pointed out in another post (having to do with the limit screws controlling the outside positions).
And also, that the 74XX Dura-Ace indexing, from the very beginning, had a higher actuation ratio built into the rear derailer.
But I don't think it's going to prove much.
I have noticed that many 6s and 7s SIS rear derailers seem to lose linearity when used across 8-or-more-cog cassettes, struggling to index the largest cog. But I never recommended using an older SIS rear derailer with the wider cassettes, and Shimano perhaps began stamping the "integrated-8 SIS" lettering into those derailer's cage because of this. What was happening in that case was that the wider cassette would sit asymmetrically under the 6 - or 7-speed derailer's more-limited range of usefully-indexed cage travel.
I've learned that lesson the hard way more than once, and have also seen others bring their newly-built vintage bikes by with the same sort of subtle indexing issue.
Lots of low-normal derailers got used (with normal 9-speed SIS shifters) and somehow had no problem indexing 8 or 9-speed systems, so what happened to the "asymmetric non-linearity" of which you speak? Was that perhaps only a 7s derailer thing?
Repeating myself here, easily verified, ALL Shimano 7s cassettes and freewheels ever sold by Shimano have had the same, asymmetrical cog spacing.
From your un-sourced chart, which I can find no fault with, what one actually notices is that the end-cog spacing appears greater on both ends of the cassette, simply because of what you pointed out in another post (having to do with the limit screws controlling the outside positions).
And also, that the 74XX Dura-Ace indexing, from the very beginning, had a higher actuation ratio built into the rear derailer.
Last edited by dddd; 03-13-23 at 06:54 PM.
03-13-23, 06:38 PM
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Following up on my own post here, just measured the cog thicknesses on the older 7s cassette I pictured.
What I found argues for the asymmetry of Shimano 7s cog spacing being even greater than would be indicated by the thicker (3.3mm vs. 3.1mm) plastic 2-3 cog spacer alone.
That 2nd-position (2nd smallest) cog is fully three tenths of a millimeter (2.06mm vs. 1.76mm) thicker than the rest of the larger five cogs!
Makes sense from a durability standpoint, and also kicks out the 2-3 cog-center spacing an extra .15mm on top of the .2mm added spacer thickness.
This helps me better understand why this can be so noticeable at times, in cases where perhaps an 8s shifter or low-normal derailer is used with a 7s Shimano freewheel or cassette.
One can usually sand down a plastic or alloy cassette spacer with sufficient accuracy (using a digital caliper to guide such modifications), that's what I used to do in order to make Shimano 7s cassettes index with Suntour Accu-7 drivetrains. It's even simpler to harvest needed alternative spacers from discarded 7s and 8s cassettes (at least if the needed thickness can be found for whatever Franken-drivetrain is being put together).
Of course then all of SRAM's and Sunrace's 7s cassettes or freewheels use the same asymmetric spacing as Shimano's.
What I found argues for the asymmetry of Shimano 7s cog spacing being even greater than would be indicated by the thicker (3.3mm vs. 3.1mm) plastic 2-3 cog spacer alone.
That 2nd-position (2nd smallest) cog is fully three tenths of a millimeter (2.06mm vs. 1.76mm) thicker than the rest of the larger five cogs!
Makes sense from a durability standpoint, and also kicks out the 2-3 cog-center spacing an extra .15mm on top of the .2mm added spacer thickness.
This helps me better understand why this can be so noticeable at times, in cases where perhaps an 8s shifter or low-normal derailer is used with a 7s Shimano freewheel or cassette.
One can usually sand down a plastic or alloy cassette spacer with sufficient accuracy (using a digital caliper to guide such modifications), that's what I used to do in order to make Shimano 7s cassettes index with Suntour Accu-7 drivetrains. It's even simpler to harvest needed alternative spacers from discarded 7s and 8s cassettes (at least if the needed thickness can be found for whatever Franken-drivetrain is being put together).
Of course then all of SRAM's and Sunrace's 7s cassettes or freewheels use the same asymmetric spacing as Shimano's.
03-13-23, 06:46 PM
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Man, love how well that you dig!
Of course any derailer goes too far out of linearity to index with when you start adding 1cm spacers under the mounting bolt.
That's the funniest come-back to date. At least I don't think it's going to prove much.
I have noticed that many 6 and 7s SIS rear derailers seem to lose linearity when used across 8 or more cog cassettes, struggling to index the largest cog. But I never recommended using an older SIS rear derailer with the wider cassettes, and Shimano perhaps began stamping the "integrated-8 SIS" lettering into those derailer's cage because of this. What was happening in that case was that the wider cassette would sit asymmetrically under the 6 - or 7-speed derailer's more-limited range of cage travel.
Lots of low-normal derailers got used (with normal 9-speed SIS shifters) and somehow had no problem indexing 8 or 9-speed systems, so what happened to the "asymmetric non-linearity" of which you speak? Was that perhaps only a 7s derailer thing?
Repeating myself here, easily verified, ALL Shimano 7s cassettes and freewheels ever sold by Shimano have had identical, asymmetrical cog spacing.
From your un-sourced chart, which I can find no fault with, what one actually notices is that the end-cog spacing appears greater on both ends of the cassette, simply because of what you pointed out in another post (having to do with the limit screws controlling the outside positions).
And also, that the 74XX Dura-Ace indexing, from the very beginning, had a higher actuation ratio built into the rear derailer.
I'm getting the popcorn ready...
Of course any derailer goes too far out of linearity to index with when you start adding 1cm spacers under the mounting bolt.
That's the funniest come-back to date. At least I don't think it's going to prove much.
I have noticed that many 6 and 7s SIS rear derailers seem to lose linearity when used across 8 or more cog cassettes, struggling to index the largest cog. But I never recommended using an older SIS rear derailer with the wider cassettes, and Shimano perhaps began stamping the "integrated-8 SIS" lettering into those derailer's cage because of this. What was happening in that case was that the wider cassette would sit asymmetrically under the 6 - or 7-speed derailer's more-limited range of cage travel.
Lots of low-normal derailers got used (with normal 9-speed SIS shifters) and somehow had no problem indexing 8 or 9-speed systems, so what happened to the "asymmetric non-linearity" of which you speak? Was that perhaps only a 7s derailer thing?
Repeating myself here, easily verified, ALL Shimano 7s cassettes and freewheels ever sold by Shimano have had identical, asymmetrical cog spacing.
From your un-sourced chart, which I can find no fault with, what one actually notices is that the end-cog spacing appears greater on both ends of the cassette, simply because of what you pointed out in another post (having to do with the limit screws controlling the outside positions).
And also, that the 74XX Dura-Ace indexing, from the very beginning, had a higher actuation ratio built into the rear derailer.
I'm getting the popcorn ready...
03-13-23, 06:54 PM
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Following up on my own post here, just measured the cog thicknesses on the older 7s cassette I pictured.
What I found argues for the asymmetry of Shimano 7s cog spacing being even greater than would be indicated by the thicker (3.3mm vs. 3.1mm) plastic 2-3 cog spacer alone.
That 2nd-position (2nd smallest) cog is fully three tenths of a millimeter (2.06mm vs. 1.76mm) thicker than the rest of the larger five cogs!
Makes sense from a durability standpoint, and also kicks out the 2-3 cog-center spacing an extra .15mm on top of the .2mm added spacer thickness.
This helps me better understand why this can be so noticeable at times, in cases where perhaps an 8s shifter or low-normal derailer is used with a 7s Shimano freewheel or cassette.
One can usually sand down a plastic or alloy cassette spacer with sufficient accuracy (using a digital caliper to guide such modifications), that's what I used to do in order to make Shimano 7s cassettes index with Suntour Accu-7 drivetrains. It's even simpler to harvest needed alternative spacers from discarded 7s and 8s cassettes (at least if the needed thickness can be found for whatever Franken-drivetrain is being put together).
Of course then all of SRAM's and Sunrace's 7s cassettes or freewheels use the same asymmetric spacing as Shimano's.
What I found argues for the asymmetry of Shimano 7s cog spacing being even greater than would be indicated by the thicker (3.3mm vs. 3.1mm) plastic 2-3 cog spacer alone.
That 2nd-position (2nd smallest) cog is fully three tenths of a millimeter (2.06mm vs. 1.76mm) thicker than the rest of the larger five cogs!
Makes sense from a durability standpoint, and also kicks out the 2-3 cog-center spacing an extra .15mm on top of the .2mm added spacer thickness.
This helps me better understand why this can be so noticeable at times, in cases where perhaps an 8s shifter or low-normal derailer is used with a 7s Shimano freewheel or cassette.
One can usually sand down a plastic or alloy cassette spacer with sufficient accuracy (using a digital caliper to guide such modifications), that's what I used to do in order to make Shimano 7s cassettes index with Suntour Accu-7 drivetrains. It's even simpler to harvest needed alternative spacers from discarded 7s and 8s cassettes (at least if the needed thickness can be found for whatever Franken-drivetrain is being put together).
Of course then all of SRAM's and Sunrace's 7s cassettes or freewheels use the same asymmetric spacing as Shimano's.
