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Cross shiftting
"Cross shifting", i.e., Large chain Ring/large cassette cog or small chain ring/small cog is generally taken as a mortal sin. But with a triple chain ring what limits are made to the shift pattern when on the center ring? Assuming that the chain line through the center line of the 5th cog, on a 9 speed cassette, and the center line of the center chain ring? It appears to me that considering the actual distance between the three chain rings versus the actual distances on the cassette that the center chain ring should be able to shift to any cog without problems. John B. Slocomb (johnbslocombatgmaildotcom) |
Cross shiftting
On Jul 16, 5:30 am, John B. Slocomb wrote:
"Cross shifting", i.e., Large chain Ring/large cassette cog or small chain ring/small cog is generally taken as a mortal sin. But with a triple chain ring what limits are made to the shift pattern when on the center ring? Assuming that the chain line through the center line of the 5th cog, on a 9 speed cassette, and the center line of the center chain ring? It appears to me that considering the actual distance between the three chain rings versus the actual distances on the cassette that the center chain ring should be able to shift to any cog without problems. A good setup should allow shifting to any combination without problems, but for riding along you ideally want a straight chain line, so as you shift more toward one end or the other of the cassette for more than some brief circumstances, consider finding a combination that moves the chain laterally at the front and rear together, rather than shifting way back and forth at one end. (too long sentence) |
Cross shiftting
On Jul 16, 8:38 am, Dan O wrote:
On Jul 16, 5:30 am, John B. Slocomb wrote: "Cross shifting", i.e., Large chain Ring/large cassette cog or small chain ring/small cog is generally taken as a mortal sin. But with a triple chain ring what limits are made to the shift pattern when on the center ring? Assuming that the chain line through the center line of the 5th cog, on a 9 speed cassette, and the center line of the center chain ring? It appears to me that considering the actual distance between the three chain rings versus the actual distances on the cassette that the center chain ring should be able to shift to any cog without problems. A good setup should allow shifting to any combination without problems, but for riding along you ideally want a straight chain line, so as you shift more toward one end or the other of the cassette for more than some brief circumstances, consider finding a combination that moves the chain laterally at the front and rear together, rather than shifting way back and forth at one end. (too long sentence) For me this amounts to two modes of operation: Outer chainring with a few, closely spaced outer cogs for most riding, and middle chainring with a few middle-to-inner cogs for gnarly steep climbing. (The inner ring is for some as yet unimagined scenario, like hauling heavy loads out from the bottom of the Grand Canyon. The inner cog is reserved as bail-out gear and pie-plate.) On my liesure (whjeelie) bike, the two modes are middle ring with a couple of middle-ish cogs for riding around town, and outer ring with a couple of outer cogs for top speed to the fire station. |
Cross shiftting
On 16 jul, 14:30, John B. Slocomb wrote:
"Cross shifting", i.e., Large chain Ring/large cassette cog or small chain ring/small cog is generally taken as a mortal sin. But with a triple chain ring what limits are made to the shift pattern when on the center ring? Assuming that the chain line through the center line of the 5th cog, on a 9 speed cassette, and the center line of the center chain ring? It appears to me that considering the actual distance between the three chain rings versus the actual distances on the cassette that the center chain ring should be able to shift to any cog without problems. John B. Slocomb (johnbslocombatgmaildotcom) Middle ring should shift any cogs. Large chainring avoid two largest cogs; small chainring avoid two smallest cogs. It is that simple. Lou |
Cross shiftting
On Jul 16, 1:30*pm, John B. Slocomb wrote:
"Cross shifting", i.e., Large chain Ring/large cassette cog or small chain ring/small cog is generally taken as a mortal sin. But with a triple chain ring what limits are made to the shift pattern when on the center ring? Assuming that the chain line through the center line of the 5th cog, on a 9 speed cassette, and the center line of the center chain ring? It appears to me that considering the actual distance between the three chain rings versus the actual distances on the cassette that the center chain ring should be able to shift to any cog without problems. John B. Slocomb (johnbslocombatgmaildotcom) I always like to think that the smallest sprocket must only be used with the outer ring and the biggest sprocket must only be used with the smallest ring. This help reduce the strains imposed on the derailleur pulley spring(s) and sometimes is the only way to shift cleanly over the entire range without having a drooping chain. Depending upon your derailleur it might be as well to limit the mid ring off the bottom two sprockets (if its a racing type der). |
Cross shiftting
"John B. Slocomb" wrote in message ... "Cross shifting", i.e., Large chain Ring/large cassette cog or small chain ring/small cog is generally taken as a mortal sin. But with a triple chain ring what limits are made to the shift pattern when on the center ring? Assuming that the chain line through the center line of the 5th cog, on a 9 speed cassette, and the center line of the center chain ring? It appears to me that considering the actual distance between the three chain rings versus the actual distances on the cassette that the center chain ring should be able to shift to any cog without problems. As far as the chain and rear der are concerned all the cogs are in play from the middle ring. Not all setups will run without the chain rubbing the front der cage or big chainwheel. If you can trim the front der all's good. |
Cross-Chaining
On 7/16/2011 7:30 AM, John B. Slocomb wrote:
"Cross shifting", i.e., Large chain Ring/large cassette cog or small chain ring/small cog is generally taken as a mortal sin. But with a triple chain ring what limits are made to the shift pattern when on the center ring? Assuming that the chain line through the center line of the 5th cog, on a 9 speed cassette, and the center line of the center chain ring? FYI - This is normally referred to as "cross-chaining". It appears to me that considering the actual distance between the three chain rings versus the actual distances on the cassette that the center chain ring should be able to shift to any cog without problems. Say screw it and get a Schlumpf bottom bracket and Rohloff hub. watching for the delivery truck :) -- Tºm Shermªn - 42.435731°N, 83.985007°W I am a vehicular cyclist. |
Cross-Chaining
On Jul 16, 7:43*pm, "T°m Sherm@n" ""twshermanREMOVE\"@THI
$southslope.net" wrote: On 7/16/2011 7:30 AM, John B. Slocomb wrote: "Cross shifting", i.e., Large chain Ring/large cassette cog or small chain ring/small cog is generally taken as a mortal sin. But with a triple chain ring what limits are made to the shift pattern when on the center ring? Assuming that the chain line through the center line of the 5th cog, on a 9 speed cassette, and the center line of the center chain ring? FYI - This is normally referred to as "cross-chaining". It appears to me that considering the actual distance between the three chain rings versus the actual distances on the cassette that the center chain ring should be able to shift to any cog without problems. Say screw it and get a Schlumpf bottom bracket and Rohloff hub. Or a bent with very, very long chains g. --D-y |
Cross-Chaining
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Cross shiftting
On Jul 16, 7:30*am, John B. Slocomb wrote:
"Cross shifting", i.e., Large chain Ring/large cassette cog or small chain ring/small cog is generally taken as a mortal sin. But with a triple chain ring what limits are made to the shift pattern when on the center ring? Assuming that the chain line through the center line of the 5th cog, on a 9 speed cassette, and the center line of the center chain ring? It appears to me that considering the actual distance between the three chain rings versus the actual distances on the cassette that the center chain ring should be able to shift to any cog without problems. Sheldon Brown has a gear "visualizer", and there's another one called "Gerz" that makes charting pretty easy. It seems to me that with the 30/42/52 triple I have, run against 8sp and 9sp cassettes with 13-23 or 14-26t cog spreads, you wind up with gear ratios that favor running the two or three cogs most in line with both the inner and outer rings, while the middle ring works over four or five cogs, overlapping so to speak with the inner and outer rings on one cog. It's been a few years, maybe I'm misremembering but I think this "question" pretty much takes care of itself in practice if you will. Meaning, you're keeping the chain fairly straight while you use "same ratios" (or close duplicates) of gears you might find by "crossing" farther on any of the ring/cog combinations. Not to say you shouldn't "be able" to use any cog/chainring combination without either drooping the chain (which invites unshipping and/or dragging in the dirt) or binding/breaking the rear derailleur due to too short a chain, but why not use the chain in happier combinations? --D-y |
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