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Seat post collar for carbon seat post
Hello,
I am installing a Cannondale brand carbon seat post on a Cannondale Optimo frame. The instructions state to mount the collar with the bolt facing towards the front on the bike. I see many other bikes (including the pro's) with the collar facing the rear normal position. Will it make a safety issue to install it the "normal" way or should I do like Cannondale recommends? Cheers, Rick in Tennessee |
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Seat post collar for carbon seat post
cycledogg wrote:
Hello, I am installing a Cannondale brand carbon seat post on a Cannondale Optimo frame. The instructions state to mount the collar with the bolt facing towards the front on the bike. I see many other bikes (including the pro's) with the collar facing the rear normal position. Will it make a safety issue to install it the "normal" way or should I do like Cannondale recommends? Cheers, Rick in Tennessee unless both the head and the shaft of the collar bolt are mounted inside pivots, then the clamp, when tightened, goes out of round, and thus can raise the clamping force at certain points on its circumference. with a carbon post, this can cause cracking, and thus, loss of strength. the way to minimize this effect is to mount the collar to the front - the out of round for the collar is kinda-sorta offset by a similar effect from the slot in the seat tube. to summarize: do what the manufacturer says. |
#3
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Seat post collar for carbon seat post
In article
, cycledogg wrote: Hello, I am installing a Cannondale brand carbon seat post on a Cannondale Optimo frame. The instructions state to mount the collar with the bolt facing towards the front on the bike. I see many other bikes (including the pro's) with the collar facing the rear normal position. Will it make a safety issue to install it the "normal" way or should I do like Cannondale recommends? Seat post clamps and seat tube split tops are not round. That is to say they are not round at the bolt and at the seat tube split respectively. When the clamp is tightened, it forms a flat spot where the broken ring is drawn together. Hence, if the bolt and the seat tube split are matched up, they form a flat spot, and the overall clamping action is not round. The edges of the seat tube split are forced directly inward where they chafe on the seat post, gouging the delicate carbon fibre. When you spin the seat post clamp around half a revolution the seat tube split is under the round portion of the seat post clamp. This portion of the seat post clamp does not flatten, so the edges of the seat tube split remain round. The round part of the seat tube is under the potential flat spot of the seat post clamp. The overall effect is to make the entire assembly as round as possible. -- Michael Press |
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Seat post collar for carbon seat post
On Mar 4, 4:26 am, jim beam wrote:
to summarize: do what the manufacturer says. Wouldn't it be wiser to do otherwise and to entirely spare oneself such delicate solutions? Sergio Pisa |
#5
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Seat post collar for carbon seat post
In article ,
"Bill" wrote: "Michael Press" wrote in message ... In article , cycledogg wrote: Hello, I am installing a Cannondale brand carbon seat post on a Cannondale Optimo frame. The instructions state to mount the collar with the bolt facing towards the front on the bike. I see many other bikes (including the pro's) with the collar facing the rear normal position. Will it make a safety issue to install it the "normal" way or should I do like Cannondale recommends? Seat post clamps and seat tube split tops are not round. That is to say they are not round at the bolt and at the seat tube split respectively. When the clamp is tightened, it forms a flat spot where the broken ring is drawn together. Hence, if the bolt and the seat tube split are matched up, they form a flat spot, and the overall clamping action is not round. The edges of the seat tube split are forced directly inward where they chafe on the seat post, gouging the delicate carbon fibre. When you spin the seat post clamp around half a revolution the seat tube split is under the round portion of the seat post clamp. This portion of the seat post clamp does not flatten, so the edges of the seat tube split remain round. The round part of the seat tube is under the potential flat spot of the seat post clamp. The overall effect is to make the entire assembly as round as possible. Does the same reasoning apply to split inserts for adapting 1 1/8 to 1" stems for use with 1" carbon steerer tubes? Sorry, I am not familiar with that assembly. If there is a clamp similar to the seat post clamp, a split tube to be drawn inward, and no other competing considerations, then yes. :^} An everyday assembly that benefits from this consideration is the twist tie used to close a bag. Rather than put it on and twist the ends together as usual; take an extra turn around the bag, then twist the ends together. It is called a round turn. The round turn is more secure. While twisting, there is more mechanical advantage drawing the ligature tight. The round turn eliminates the cusp at the twist of the usual method that can foul the bag. -- Michael Press |
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