I just completed a 7 speed freewheel to 8 speed cassette conversion. I was able to keep the vintage Shimano SIS rear derailer, as many on the net had said.
When I first tried it out, the derailer was preventing extreme gear combos. It couldn't do the left most chainring and rightmost cassette cog, and vice versa. The middle chainring could use all cassette cogs. I had since adjusted the rear derailer to allow all combos.
It made me wonder... Should extreme combos be allowed? It seems to put side bending forces on the chain, as it is straight when on the ring/cogs but then has to bend diagonally. How do 9 cog cassette users deal with this?
I just completed a 7 speed freewheel to 8 speed cassette conversion. I was able to keep the vintage Shimano SIS rear derailer, as many on the net had said.
When I first tried it out, the derailer was preventing extreme gear combos. It couldn't do the left most chainring and rightmost cassette cog, and vice versa. The middle chainring could use all cassette cogs. I had since adjusted the rear derailer to allow all combos.
It made me wonder... Should extreme combos be allowed? It seems to put side bending forces on the chain, as it is straight when on the ring/cogs but then has to bend diagonally. How do 9 cog cassette users deal with this?
The conventional wisdom is that severe cross-chaining (small/small and big/big sprocket combinations) should be avoided since they place excessive single-side strain on the chain and will increase the rate of chain wear. It has been observed that some der setups have problems shifting into those combinations reliably; in my experience, this is most often observed with low-end ders.
The same would hold true for 9-speed and 10-speed cassettes, but most such setups employ better grades of der and shifter; these tend to be able to handle the cross-chaining more predictably in most cases, but that still doesn't make it a good idea to use those gear pairs.
-- Typoes are a feature, not a bug. Some gardening required to reply via email. Words processed in a facility that contains nuts.
I just completed a 7 speed freewheel to 8 speed cassette conversion. I was able to keep the vintage Shimano SIS rear derailer, as many on the net had said.
Quoted message said:
Quoted message said:
When I first tried it out, the derailer was preventing extreme gear combos. It couldn't do the left most chainring and rightmost cassette cog, and vice versa. The middle chainring could use all cassette cogs. I had since adjusted the rear derailer to allow all combos.
Quoted message said:
Quoted message said:
It made me wonder... Should extreme combos be allowed? It seems to put side bending forces on the chain, as it is straight when on the ring/cogs but then has to bend diagonally. How do 9 cog cassette users deal with this?
Quoted message said:
The conventional wisdom is that severe cross-chaining (small/small and big/big sprocket combinations) should be avoided since they place excessive single-side strain on the chain and will increase the rate of chain wear. It has been observed that some der setups have problems shifting into those combinations reliably; in my experience, this is most often observed with low-end ders.
I wouldn't worry about that as much as the gouging it does on the aluminum chainwheel, and these cost more than chains, or at least they did. Chains need replacement anyway, but chainwheels should last many chain lives.
Quoted message said:
The same would hold true for 9-speed and 10-speed cassettes, but most such setups employ better grades of der and shifter; these tend to be able to handle the cross-chaining more predictably in most cases, but that still doesn't make it a good idea to use those gear pairs.
Chains at a steep angle to the derailleur eat up idler wheels fast. Focus on the parts you don't want to replace often.
I just completed a 7 speed freewheel to 8 speed cassette conversion. I was able to keep the vintage Shimano SIS rear derailer, as many on the net had said.
When I first tried it out, the derailer was preventing extreme gear combos. It couldn't do the left most chainring and rightmost cassette cog, and vice versa. The middle chainring could use all cassette cogs. I had since adjusted the rear derailer to allow all combos.
It made me wonder... Should extreme combos be allowed? It seems to put side bending forces on the chain, as it is straight when on the ring/cogs but then has to bend diagonally. How do 9 cog cassette users deal with this?
More recent bike designs are less tolerant of bad combos for a couple of reasons: thinner sprockets and shorter chainstays (not to mention much more expensive cassettes).
