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6s shifters on a 7s cassette

Old 03-29-13, 12:15 PM
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anonymouse_
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6s shifters on a 7s cassette

I'm currently overhauling a pug Europa (https://velospace.org/node/18221) which has a 7 speed cassette on the back. The shifters I have are 6-speed downtube indexed Shimanos (SL-S434 https://velobase.com/ViewComponent.as...e1260&Enum=104). Will using these shifters mean I'm only able to access gears 1-6, or will the indexing be wrong i.e. I'll be missing gears?

If finding 7-speed shifters is the only option, does anyone have any suggestions?

Thanks!
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Old 03-29-13, 01:02 PM
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The chain will rattle on some gears and probably not shift right in SIS mode. They'll work fine if you rotate the little thing to put them in Friction mode -- I'm using "6-speed" shifters on my new 7-speed bike this way. Otherwise, 7-speed downtube shifters pop up quite often in the C&V For Sale section.
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Old 03-29-13, 02:42 PM
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I have see where some 6 speed indexed Shimano downtube shifters actually will shift into the 7th position however if you hit a hard bump, it could drop back to the 6th position since its not a 100 percent solid selection but it normally works just fine. The 6 speed and 7 speed cogs should be the same spacing if not extremely close.
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Old 03-29-13, 02:57 PM
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Thanks for the replies... looking at a set of 105 7 speed shifters on ebay right now.

https://www.ebay.co.uk/itm/SHIMANO-10...item20d0e85950

not really sure what sort of price these things should go for...worth it? Also just to mention I'm running an Exage 500EX derailleur on the back, I'm assuming no compatibility issues using the 105 shifters?
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Old 03-29-13, 03:18 PM
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Hmm.... that might be an okay price for brand-new. Used would be cheaper, and DT shifters last a long time. Cable pull should be compatible.
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Old 03-29-13, 05:08 PM
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Originally Posted by anonymouse_ View Post
Thanks for the replies... looking at a set of 105 7 speed shifters on ebay right now.

https://www.ebay.co.uk/itm/SHIMANO-10...item20d0e85950

not really sure what sort of price these things should go for...worth it? Also just to mention I'm running an Exage 500EX derailleur on the back, I'm assuming no compatibility issues using the 105 shifters?
The price is about right for Nos 105 but you really don't need to spend this much on a basic Pug build. You should be able to find a set of good used SIS compatiable 7 speeds for around $15. Or you can get a new set of basic 7speed DT shifters with cables and shipping for around $20.
https://www.amazon.com/SunRace-7-Spee...speed+shifters
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Old 03-29-13, 05:56 PM
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The indexing will be wrong, so you'll need to switch them to friction mode.

useful spacing cribsheet here:
https://sheldonbrown.com/cribsheet-spacing.html

On second thought; there is some indication that you may be able to make them index if you use the alternate cable routing. see here:
https://www.ctc.org.uk/cyclists-libra...gears/shimergo
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Old 03-29-13, 06:29 PM
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Originally Posted by xenologer View Post
The indexing will be wrong, so you'll need to switch them to friction mode.

useful spacing cribsheet here:
https://sheldonbrown.com/cribsheet-spacing.html

On second thought; there is some indication that you may be able to make them index if you use the alternate cable routing. see here:
https://www.ctc.org.uk/cyclists-libra...gears/shimergo
Why is that? The super common ultra six spacing is identical to the 7 speed shimano spacing. 5mm. The 6 speed Shimano shifters are 5mm like the 7 speeds.
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Old 03-29-13, 06:37 PM
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I'm pretty sure it is because the RD ends up being adjusted 5-6mm wider which is right at the ends for one that was originally intended for 6peed which gives a lower tolerance for cable erer or slop. New cables and compresionless lined shift cables can help a lot when trying to get a touchy none standard setup to work.
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Old 03-30-13, 02:59 AM
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Originally Posted by bobotech View Post
Why is that? The super common ultra six spacing is identical to the 7 speed shimano spacing. 5mm. The 6 speed Shimano shifters are 5mm like the 7 speeds.
My assumption, was that he has a 'regular' 5.5mm 6spd shifter, not an ultra6 shifter. Don' have specs for his parts, might want to verify which it is.
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Old 03-30-13, 03:26 AM
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Have found that 6 speed indexed shifters work rather well with 7 speed cassettes / freewheels because of the nearly identical steps... it will index over 6 and then the extra travel in most dt shifters will take you that extra step.

With 7 speed shifters and 6 speed blocks you end up with a dead position that does nothing.
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Old 03-30-13, 01:35 PM
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I'm not sure whether these are 6 or ultra6, but the model number is SL-S434. Can't find anything convincing online about them. I'm going to put them on the bike tomorrow and see how they shift before venturing for the pricey 105s on ebay.

I'll let you know how I get on.
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Old 03-30-13, 01:40 PM
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The sideways motion of the top pulley 'centron', may make up for slight errors..
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Old 03-30-13, 02:45 PM
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To the best of my knowledge, Shimano ever made any ultra-6 parts. Just for kicks, I tried setting my six-speed 105 shifters for SIS mode -- while the smallest 4 sprockets of my 7-speed cassette shifted reliably, the shifts got noisier and less predictable toward the big end. So don't get your hopes up about this pairing.
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