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I am running a 1x8 speed drivetrain. Currently using a narrow/wide chainring which seems to be doing a good job of keeping the chain on thus far but I'd like the added security of a clutched mech.
Shimano changed the actuation ratio with dynasys so I can't use an indexed 8-speed shifter. If I switched over to friction would my bar-end shifter (mounted to a Thumbie) have enough travel to use all of the cassette?
Shimano 8 speed pulls 2.8mm per shift, Dynasys pulls 3.4mm per shift,
For 8 speed That 2.8 translates to 4.8mm of mech movement ("2:1" actuation was actually always 1.7:1)
Dynasys rear mechs shift 3.95mm for that 3.4mm of cable pull so it's about 1.16:1.
7 x 2.8 = 19.6mm of total cable pull for an 8 speed shifter.
9 x 3.4 = 30.6mm of cable pull Which is how much cable a dynasys mech will require to traverse its full range....
But wait... there's more; SRAM's "1:1" - 8 speed shifters pulled 4.3mm per shift 7 x 4.3 = 30.1mm, pretty close to the required overall cable pull range a dynasys mech needs...
8 speed cassette pitch is 4.8mm,
4.3 x 1.16 = 4.988mm that's tantalizingly close to getting a Shimano Dynasys mech to speak 8 speed indexyness... Hmmm, couple of washers under the bolt head to tweak the leverage ratio as some have done with 9 speed SRAM shifters and Dynasys mechs... could work?.
cookeaa - Member
Shimano 8 speed pulls 2.8mm per shift
I presume that's an average? The pull depends on where the shift is in the arc.
I think it does come down to whether the bar end shifter travels beyond it's 8th click in friction mode.
normal shimano thumbies would come to a stop way past the 12 o clock position so no problems there. I'm running one without problems on a 9 speed cassette.
It would be worth measuring the total amount of cable your thumbies pull, I can't imagine it would be much more than ~20mm, to traverse a Dynasys mech through its full range you need to pull ~30mm.
It does occur to me that a simple intermediate lever or pulley of some sort could be employed to simply change cable pull betwixt lever and mech, surely someone has made such a thing... Right?
like them rollermajigs? designed for using non v brake levers with v brakes?
Thanks for all the maths. [i]Looks[/i] like my suspicisions are correct and it won't work, but I'll attempt to measure the cable pull of the bar end shifters tonight.
Whole idea behind this bike is simplificity, hence the 1x8 drivetrain, so perhaps I should just put up with a bit of chain slap and get a short cage road derailleur.
OP - I swore by my Suntour XC Pro 8 speed thumb shifters and M900 XTR cassettes user till the end of 2012. You know, "9 speed just a fad" and all of that 🙄 I still have a stockpile of spare NOS cassettes, and at least one spare set of shifters.
Then I got a bike that was 10 speed. Believe it or not, they have made a lot of progress in the last 20 years. 10 speed is fantastic! The clutch derailleur is a huge improvement; the drivetrain is so quiet. I won't go back, that's for sure. My full suspension bike got a 10 speed upgrade within a few months as well...