Is this a reasonable angle for a rear derailleur ? Just considering a purchase and unsure.thanks

mrandmrspoves

Middle aged bald git.
Location
Narfuk
Hard to tell just from a photograph but it looks overstretched and not quite on your lowest gear. A few extra links in the chain would sort it.
 

ColinJ

Puzzle game developer
It looks normal to me - that's what happens if you put it on the big chainring and one of the bigger sprockets.

Normally, you would try to avoid the biggest couple of sprockets when on the big ring and the smallest couple of sprockets when on the small ring because the chain has to bend a bit far sideways which makes it noisier and wear more quickly.

The length of the chain should be such that nothing breaks if you use the big ring and the biggest sprocket at the same time. As I mentioned above, you normally wouldn't do that but sometimes you will forget and do it without thinking. If the chain is way too short then you could have problems. Check by standing next to the bike and lifting the back wheel off the ground while you test it. It should be obvious if the bike is struggling in that combination. If so, then do as @mrandmrspoves suggests and use a longer chain.
 
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Lzzao

New Member
It looks normal to me - that's what happens if you put it on the big chainring and one of the bigger sprockets.

Normally, you would try to avoid the biggest couple of sprockets when on the big ring and the smallest couple of sprockets when on the small ring because the chain has to bend a bit far sideways which makes it noisier and wear more quickly.

The length of the chain should be such that nothing breaks if you use the big ring and the biggest sprocket at the same time. As I mentioned above, you normally wouldn't do that but sometimes you will forget and do it without thinking. If the chain is way too short then you could have problems. Check by standing next to the bike and lifting the back wheel off the ground while you test it. It should be obvious if the bike is struggling in that combination. If so, then do as @mrandmrspoves suggests and use a longer chain.[/QUOTE
Thanks, really helpful
 
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Lzzao

New Member
Thanks - very helpful.
 

Ajax Bay

Veteran
Location
East Devon
it looks overstretched and not quite on your lowest gear. A few extra links in the chain would sort it.
This.
I have to say to all those who have commented that this RD/chain set up is 'fine' or 'normal' or that 'there's nothing wrong' that the RD cage is already struggling (at 4 o'clock ish) at an unreasonable angle to cope and the chain is not yet on the largest sprocket (and I suspect might not go there). The chain is too short: at least one, possibly two one inch links.
But this would not affect a decision to purchase or otherwise, just need to factor in the immediate requirement for a new chain (and a cassette if it then slips when power applied).
 
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ColinJ

Puzzle game developer
I stick by my original statement!

I just put my bike in big-big to see what it looked like, and as expected the derailleur is significantly more stretched out than that shown in the original picture.

Big to big.jpg


It isn't a gear selection that one should ever use, but I have done by accident a few times when tired. I had already checked that it worked when choosing my chain length and no harm is done when I do select it. (When I hear extra noise from the transmission, I realise my mistake and change to a more sensible combination.)
 

Ajax Bay

Veteran
Location
East Devon
Good picture, Colin.
Of course one tries to avoid going large-large but as you say, sometimes it happens (increased risk in the (rural) dark ime). The reason for the "extra noise from the transmission" is the system complaining it's stressed. The tension in the return section of the chain will be higher than by design (tension governed and kept broadly constant by the cage return spring).
A rule of thumb I'd support is that, with the chain in large-large the cage should not be closer to the horizontal than 45 degrees. The method of chain length determination which wraps the chain round large-large, not through the RD, and adds one one inch link to the result (adjusting up to the nearest integral number of one inch links) will achieve this.
Whatever, a short chain on a bike I might buy would not be a factor in my decision to purchase, or not.
 
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