tell me about thumbies please

LittleSkink

Retro Guru
On another thread I have been bemoaning transmission issues with a tandem running 8speed Shimano Revoshift

One suggestion was to go to thumbies rather than STI - but I have never used them, dont know how they work - or even which ones would be worth getting s/h

My early road bikes were all friction change down tube shifter style so I am used to how that works (assuming it might be relevant)
 
Very easy to use, normally right hand for rear mech, push towards the front wheel to move up the cassette, 7 speed index, with hidden 8 th click, 6 with hidden 7th

IMO Deore mountings better than Xt in Shimano, not as pretty but more reliable

Suntour probably better than S

Both can run index or friction. In friction can be any speed

Campag, some are 8 speed index only, some only mount to brake levers, so a bit more specific
 
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You can run 7 speed XT thumbies with an 8 speed cassette, and they're as good as you'll get for shifting
 
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makster":171ezm3t said:
, and they're as good as you'll get for shifting

Agree. Love thumbies. Good positive shifts. BITD I ran Suntour with Shimano with no problems.
 
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They're just simple shifter like you friction shift but with little balls that drop in holes to roughly tell you where the index is.
Basically it rough indexing and you tweak the shift to make it better (or the floating holy does it for you).

Gripshift/STI are a more a more precision shift, but you don't get as much 'bodge' as you do a traditional thumshifter.
STI (rapidfire) are thumbies but with ratchets to give the index position and pop the thumb shifter back to it, gripshift you big spring indents to give the index point.
They are all wrapping cable around a cylinder.

If you need to move to thumbies to fix shifting, then something is wrong in you setup.
It could be an old warn sticky revoshift. Clean it up and check it out.
Check cables.
Check mech, chain, cassette.
Check mech hanger.

All these will still cause problems with thumbies, just it easier to bodge around the poor shifting.
 
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FluffyChicken":2knqwvwr said:
If you need to move to thumbies to fix shifting, then something is wrong in you setup.
It could be an old warn sticky revoshift. Clean it up and check it out.
Check cables.
Check mech, chain, cassette.
Check mech hanger.

All these will still cause problems with thumbies, just it easier to bodge around the poor shifting.

Fair point, but groupsets are not designed with tandems in mind where you have a cable run of 2.5m or so. It's further compounded by the pilot being unable to see the rear wheel and cassette in the case of problems.
Shimano's low cable pull per click means that any stickiness in the system can cause indexing issues. These problems are far more likely on a tandem and the possibility of a small fudge on each shift is a big advantage.
 
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E-shifting ;-)
Shimano did/do Tandem 'groupsets', sure I've seen tandem chainset from them.

Bah, just get decent cables or don't run full outers (or do?)

I don't look at my cassette while riding, i tend to look at the trees.
 
The only difference on the tandem groupset was the cranks. There was nothing to address the tetchiness of Shimano's short cable pull per click - which they rectified for 10 speed on MTB and 11 on road.

SRAM's 1:1 is definitely far more tolerant.

The point of being able to see the cassette is to diagnose which way to nudge it if running rattly - something that happens way more often on a tandem. Similarly my stoker knows when to call 'trim up' or 'trim down' for the front mech.
 
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Bah, just so the fettle by feel, and a short push/twist to see if it solves it. The a quick barrel adjust, easy.

;-)
 
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