Rear derailuer position
- Thread starter Biker2772
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Specialeyes
Guru
- Location
- Essex
I would say that's fine provided that when you're in big-big (i.e. the rear derailleur is at 1 and the front derailleur is on the largest chainring) that the derailleur pulley cage isn't stretched out past about the 4 o'clock position.
It's hard to tell, as you don't say whether you have a double- or triple-chainring up front, but as a rule, when you're in small-small you want the rear mech to be swung backwards but still with some spring 'bounce' applying tension to the chain - usually just shy of horizontal.
There will be folks along in a moment to correctly point out that both of these extreme gear combinations are to be avoided, as they're inefficient, cause additional drivetrain wear and are overlapped by more drivetrain-friendly combinations
It's hard to tell, as you don't say whether you have a double- or triple-chainring up front, but as a rule, when you're in small-small you want the rear mech to be swung backwards but still with some spring 'bounce' applying tension to the chain - usually just shy of horizontal.
There will be folks along in a moment to correctly point out that both of these extreme gear combinations are to be avoided, as they're inefficient, cause additional drivetrain wear and are overlapped by more drivetrain-friendly combinations
Hi, thanks for the reply.
I forgot to mention that I have 3 chainrings at the front. Based on the information I provided, is the rear derailuer position still fine?
Ajax Bay
Guru
- Location
- East Devon
OP - another picture with the chain on large/large please and bonus one on small/small for a decent answer.
For the avoidance of doubt, I nevertheless attempt not to cross chain, despite the possible efficiency gain.
Well actually (and just talking efficiency here), the losses with the worst chain-line offset (a 'diagonal' chain) are really quite small (<0.5%). You will gain more (chain still within spec + 0.5%) by staying large/large (eg 50/25) rather than sensible Jim's 34/17, because the losses over the smaller chain ring and smaller sprocket is 2+% (cf large/large). On large/large each link of the chain has to straighten through a smaller angle, particularly exiting the rear sprocket under tension.
For the avoidance of doubt, I nevertheless attempt not to cross chain, despite the possible efficiency gain.
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Smokin Joe
Squire
- Location
- Bare headed cyclist, Smoker
If that is on the middle ring the chain is too short.
Ajax Bay
Guru
- Location
- East Devon
I have found the reference for my 'efficiency' stuff above, in case anyone's interested.
"Human Power" Number 50 Spring 2000
TECHNICAL JOURNAL OF THE IHPVA
On the efficiency of bicycle chain drives - James B. Spicer et al (John Hopkins Uni)
"The efficiencies of bicycle drive trains have been studied to understand energy-loss mechanisms in these systems. The results of this study indicate that chain tension and sprocket [= chain ring and rear sprocket] size primarily determine chain-drive efficiency."
"Typically, a 2–5% loss difference was measured between the 52–11 and the 52–21 sprocket combinations."
"It was found that chain-line offset and chain lubrication have a negligible effect on efficiency under laboratory
conditions. "
"Human Power" Number 50 Spring 2000
TECHNICAL JOURNAL OF THE IHPVA
On the efficiency of bicycle chain drives - James B. Spicer et al (John Hopkins Uni)
"The efficiencies of bicycle drive trains have been studied to understand energy-loss mechanisms in these systems. The results of this study indicate that chain tension and sprocket [= chain ring and rear sprocket] size primarily determine chain-drive efficiency."
"Typically, a 2–5% loss difference was measured between the 52–11 and the 52–21 sprocket combinations."
"It was found that chain-line offset and chain lubrication have a negligible effect on efficiency under laboratory
conditions. "
Ajax Bay
Guru
- Location
- East Devon
Chian is on middle ring and '6' so (guessing) next to smallest sprocket.
I think the chances of achieving large/large are nil, so as Joe says: the chain's too short. But a simple image will confirm that or otherwise.
Dale 1956
Well-Known Member
- Location
- Caribou, Maine
I always set my chain with it on the big chain ring up front and the small cassette on the rear just a little shy from 6 O clock I have done this from 2009 till now never had any trouble with this setup.
cyberknight
As long as I breathe, I attack.
- Location
- Land of confusion
