Vintage frame + carbon seatpost?
07-22-12 | 07:37 AM
#1
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Cottered Crank
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From: Chicago
Bikes: 1954 Raleigh Sports 1974 Raleigh Competition 1969 Raleigh Twenty 1964 Raleigh LTD-3
Vintage frame + carbon seatpost?
So I had the Raleigh Competition torn apart anyhow after the powder coat for the frame and was building it back up only to find the seatpost I had originally planned to put on it wasn't really a 27.2 
I put it into the frame and it went THWOP as fell all the way down into the seat tube -nothing but net, nuts to butts.
I needed the seatpost that I was using before in the testing R&D mode of this bike for my CX bike and am riding that almost every day now for training so I had to buy another 27.2mm post anyhow for this bike.
Nashbar is selling the Ascent carbon seatpost for $35-ish so I figured if I had to buy a nice seatpost for this bike I might as well give CF a try. It's not a whole ton of money and really nice alloy post is going to cost nearly that much anyhow.
Since I had the frame apart anyhow I decided to clean out the seat tube really well with a hone -careful not to go nuts and remove any metal -just polish it up a little and maybe remove a half a thousandths of an inch at the most. Then I swabbed it out really well using a bit of twine all the way down and out the bottom at the empty BB shell and hitching a rag soaked with alcohol inline so I could pull it up and down repeatedly and really clean out the bore. After a few rag changes I was able to move on to paper towels and watch as they started to come out really clean. Now it looks almost like the bore of a clean gun-barrel when I shine light up it so I am sure there are no burrs, rust, or any residual grease in there. I also bought some carbon paste to use with this post so I can be sure of good grip and not have the post get stuck.
I've been told that the seatpost binder needs to be tightened only as tight as you would screw in a lightbulb with a carbon post. Something between 60-80 inch/lbs or thereabouts. Too tight and it'll crack
The seatpost and lug are in really nice shape -nice and round with no smooshing or anything -I made sure of that before I sent it out for refinishing.
This is my first carbon seat post and I'm all ears about hints/tricks. This frame is already smooth as silk on the road but will I notice any more improvement with the carbon post? I'm only saving about 50g over a comparable alloy post with this particular post as it really isn't super light at 250g but is more of a "comfort" post than a weight-saving carbon item. But every little bit counts as my front rack, decalleur, handlebar bag and associated mounting hardware all weigh in at WELL over a kilo even before I put the first item into it.
What can I expect? Is a carbon post over-kill with a steel bike? Is it all placebo the raving reviews about how great they are?
I put it into the frame and it went THWOP as fell all the way down into the seat tube -nothing but net, nuts to butts. I needed the seatpost that I was using before in the testing R&D mode of this bike for my CX bike and am riding that almost every day now for training so I had to buy another 27.2mm post anyhow for this bike.
Nashbar is selling the Ascent carbon seatpost for $35-ish so I figured if I had to buy a nice seatpost for this bike I might as well give CF a try. It's not a whole ton of money and really nice alloy post is going to cost nearly that much anyhow.
Since I had the frame apart anyhow I decided to clean out the seat tube really well with a hone -careful not to go nuts and remove any metal -just polish it up a little and maybe remove a half a thousandths of an inch at the most. Then I swabbed it out really well using a bit of twine all the way down and out the bottom at the empty BB shell and hitching a rag soaked with alcohol inline so I could pull it up and down repeatedly and really clean out the bore. After a few rag changes I was able to move on to paper towels and watch as they started to come out really clean. Now it looks almost like the bore of a clean gun-barrel when I shine light up it so I am sure there are no burrs, rust, or any residual grease in there. I also bought some carbon paste to use with this post so I can be sure of good grip and not have the post get stuck.
I've been told that the seatpost binder needs to be tightened only as tight as you would screw in a lightbulb with a carbon post. Something between 60-80 inch/lbs or thereabouts. Too tight and it'll crack
The seatpost and lug are in really nice shape -nice and round with no smooshing or anything -I made sure of that before I sent it out for refinishing.This is my first carbon seat post and I'm all ears about hints/tricks. This frame is already smooth as silk on the road but will I notice any more improvement with the carbon post? I'm only saving about 50g over a comparable alloy post with this particular post as it really isn't super light at 250g but is more of a "comfort" post than a weight-saving carbon item. But every little bit counts as my front rack, decalleur, handlebar bag and associated mounting hardware all weigh in at WELL over a kilo even before I put the first item into it.
What can I expect? Is a carbon post over-kill with a steel bike? Is it all placebo the raving reviews about how great they are?
07-22-12 | 08:01 AM
#2
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From: PAZ
The main thing to watch out for is the stress riser that is caused by the uppermost portion of the seat lug above the binder bolt ears. A good-sized bump hit while seated is enough to cause a carbon post to crack at this point; I only wish I didn't know this from experience 
I had one of the old Flite carbon seatposts in a Gios Compact frameset a number of years ago in London and this scenario happened to me. Broke the post nearly halfway around the circumference and I ended up riding the last 15 miles standing up.
The shop still happily replaced my post with a new one, which I retired to the display case.
Personally, I wouldn't risk it - although $35 is pretty inexpensive for a carbon post, you would want to avoid the long ride standing up!
Remember, most of the carbon post/frame interfaces utilize a seatpost collar, spreading the clamping force evenly about the circumference of the post. I'd imagine this approach is meant to eliminate the issue I had.
DD
I had one of the old Flite carbon seatposts in a Gios Compact frameset a number of years ago in London and this scenario happened to me. Broke the post nearly halfway around the circumference and I ended up riding the last 15 miles standing up.
The shop still happily replaced my post with a new one, which I retired to the display case.
Personally, I wouldn't risk it - although $35 is pretty inexpensive for a carbon post, you would want to avoid the long ride standing up!
Remember, most of the carbon post/frame interfaces utilize a seatpost collar, spreading the clamping force evenly about the circumference of the post. I'd imagine this approach is meant to eliminate the issue I had.
DD
07-22-12 | 08:29 AM
#3
Decrepit Member
Joined: Aug 2005
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From: Santa Rosa, California
Bikes: Waterford 953 RS-22, several Paramounts
Just my personal opinion, but when I bought the Campy carbon Record group for my Waterford, it came with a carbon seatpost. I used it for nearly a year, but the black carbon contrasting with the polished stainless of the Waterford frame just didn't look right to me. Also, the dire warning in the instructions threatening serious injury or death if I overtightened the binder bolt was a compete turnoff. The 220mm Carbon record post weighs 190g.
Long story short, I replaced it with a 330mm alloy Thomson Elite that weighs 230g, and I love it. My $.02.
Lots of riders are on carbon seatposts without killing or maiming themselves, but I decided to play it safe.
Long story short, I replaced it with a 330mm alloy Thomson Elite that weighs 230g, and I love it. My $.02.
Lots of riders are on carbon seatposts without killing or maiming themselves, but I decided to play it safe.
07-22-12 | 09:21 AM
#4
My bikes became Vintage
Joined: Aug 2005
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From: Ontario, Canada
07-22-12 | 09:37 AM
#6
Thread Starter
Cottered Crank
Joined: Aug 2010
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From: Chicago
Bikes: 1954 Raleigh Sports 1974 Raleigh Competition 1969 Raleigh Twenty 1964 Raleigh LTD-3
The main thing to watch out for is the stress riser that is caused by the uppermost portion of the seat lug above the binder bolt ears. A good-sized bump hit while seated is enough to cause a carbon post to crack at this point; I only wish I didn't know this from experience
I had one of the old Flite carbon seatposts in a Gios Compact frameset a number of years ago in London and this scenario happened to me. Broke the post nearly halfway around the circumference and I ended up riding the last 15 miles standing up.
The shop still happily replaced my post with a new one, which I retired to the display case.
Personally, I wouldn't risk it - although $35 is pretty inexpensive for a carbon post, you would want to avoid the long ride standing up!
Remember, most of the carbon post/frame interfaces utilize a seatpost collar, spreading the clamping force evenly about the circumference of the post. I'd imagine this approach is meant to eliminate the issue I had.
DD
I had one of the old Flite carbon seatposts in a Gios Compact frameset a number of years ago in London and this scenario happened to me. Broke the post nearly halfway around the circumference and I ended up riding the last 15 miles standing up.
The shop still happily replaced my post with a new one, which I retired to the display case.
Personally, I wouldn't risk it - although $35 is pretty inexpensive for a carbon post, you would want to avoid the long ride standing up!
Remember, most of the carbon post/frame interfaces utilize a seatpost collar, spreading the clamping force evenly about the circumference of the post. I'd imagine this approach is meant to eliminate the issue I had.
DD
I"m not an engineer but I've got a ton of experience fabricating things and it seems to me that the irregular shape of the seat lug (compared to a typical seatpost collar on a modern bike) might be an issue as you said and a tiny little bit of a semi-rounded chamfered opening should help that a ton.
The over-tightening thing shouldn't be an issue as I never allow anyone else to work on my bikes or touch a tool to it if I can help it. That's why I purchased the CF assembly paste to help with seatpost retention with the extremely low specified torque. I work as an electrician and have built high-voltage switchgear so I'm pretty familiar with the importance of torque values around dissimilar metals and some of the composite insulators used in gear. Inch-pounds make a difference between something that works or breaks and then blows up. Once you get up over 15-20kv things start to get really interesting when they blow up.
07-22-12 | 09:40 AM
#7
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Cottered Crank
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From: Chicago
Bikes: 1954 Raleigh Sports 1974 Raleigh Competition 1969 Raleigh Twenty 1964 Raleigh LTD-3
Wait until I get the 1" threadless carbon fork...
07-22-12 | 09:47 AM
#8
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From: PAZ
Would it be worth it to counter-bore/ream just the tiniest bit of the rim at the "pointy bit" of the lug so that it doesn't dig into the carbon and start this stress riser as easily? I'm thinking of just using a bit of 400-grit sandpaper to make sure there isn't a shear knife-blade of a corner at the lip there where the upward-pointing parts of the seat lug might cause an issue. a more rounded lip rather than a sharp 90-degree angle should help a lot and not be at all noticeable with the seatpost (either the carbon or another alloy) in.
When I upgraded the Davidson to 8-speed and all-modern components, I thought about sticking a carbon post on that build. I guess I was trying to convince myself the failure I had was a one-off
So I get where you're coming from as regards the aesthetics; it would really look cool, even if the weight of the bike didn't come down appreciably. I just wouldn't take the chance after my experience.DD
07-22-12 | 09:52 AM
#9
From the first post I assume the planned seat post was smaller than 27.2. I would think giving the seat lug ear slot a bit of a radius would help prevent a big stress riser, but would expose the raw steel. As this is a Raleigh Competition, I would also expect the seat tube to not be perfectly round in its bore. Carbon wants round, no cutting of epoxy during insertion. Think about all the alloy seat post you see with zig-zagging... no go for carbon.
From a safety, lawyer avoidance perspective, I think a carbon wrapped thin alloy tube would be a better design. Way back I think a few makers made those...
I would stick with aluminum. I bought a Campagnolo steel seat post a while back, I was amazed it was so light. I have not seen one on ebay in quite a while unfortunately.
I have two Steel Campagnolo seat posts, the earliest is from the early 1950's. the last form the late 1990's or early 2000's, things cycle.
From a safety, lawyer avoidance perspective, I think a carbon wrapped thin alloy tube would be a better design. Way back I think a few makers made those...
I would stick with aluminum. I bought a Campagnolo steel seat post a while back, I was amazed it was so light. I have not seen one on ebay in quite a while unfortunately.
I have two Steel Campagnolo seat posts, the earliest is from the early 1950's. the last form the late 1990's or early 2000's, things cycle.
07-22-12 | 09:56 AM
#10
My bikes became Vintage
Joined: Aug 2005
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From: Ontario, Canada
I'm not altogether a zealot for period correctness where all dates have to match because that becomes prohibitively expensive. I'll use parts that "look" about right if that's all I can afford. Carry on!
07-22-12 | 03:02 PM
#11
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From: S.F. Bay Area
Bikes: Motobecane Grand Record, Colnago Super, Mondia Super, Mondia Special, Mondia Prestige (for sale 55cm),Titan Star, Titan Exklusiv, Windsor
I put a VeloCarbon SP in a Titan Steel frame when I started building it about 5 years ago. Both measured-out at 27.2 . At the time, I had no idea the implications invovled when mating steel w/ carbon. When I began riding it, I noticed the seatpost slowly slipping down into the tube. No matter how hard I leaned on that binder-bolt, the post would keep on slipping. That's when I asked a question in the Mechanics Forum on how to solve the problem. They recommended a cmpd called Tacx. I ordered some online & the slipping issue was resolved...The tube will last a lifetime , as you only need a little for it to grab.
They also tried to disuede me from using a Carbon post in a steel frame. Needless to say, I didn't listen. But so far, it's still in one piece...glup!
They also tried to disuede me from using a Carbon post in a steel frame. Needless to say, I didn't listen. But so far, it's still in one piece...glup!
Last edited by 1 Lugnut; 07-22-12 at 03:18 PM.
07-22-12 | 04:20 PM
#12
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I've put plenty of CF seatposts into C&V steel frames, mostly Ironman models, and I've used the exact Ascent seatpost to which you refer.
Not knowing anything about torque or tolerances, I simply tightened up the binder bolt to what I thought was right, and rode the bike.
No problems whatsoever. They actually look pretty good in some frames. I remove the lettering, however, can't abide that, given a choice.
I've also used CF Satori and CF Bontrager posts in steel frames, no problems whatsoever.
Not knowing anything about torque or tolerances, I simply tightened up the binder bolt to what I thought was right, and rode the bike.
No problems whatsoever. They actually look pretty good in some frames. I remove the lettering, however, can't abide that, given a choice.
I've also used CF Satori and CF Bontrager posts in steel frames, no problems whatsoever.
Last edited by RobbieTunes; 09-24-20 at 10:24 AM.
07-24-12 | 05:04 AM
#13
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Cottered Crank
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From: Chicago
Bikes: 1954 Raleigh Sports 1974 Raleigh Competition 1969 Raleigh Twenty 1964 Raleigh LTD-3
When I began riding it, I noticed the seatpost slowly slipping down into the tube. No matter how hard I leaned on that binder-bolt, the post would keep on slipping. That's when I asked a question in the Mechanics Forum on how to solve the problem. They recommended a cmpd called Tacx. I ordered some online & the slipping issue was resolved...The tube will last a lifetime , as you only need a little for it to grab.
07-24-12 | 07:37 AM
#14
self propelled lifer
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From: Manitoba
Bikes: 1962 Dawes Galaxy; 72 Gitane Interclub;73 Peugeot PR10;78 Torpado Luxe;73 Grandis; 81 Raleigh/Carlton Comp; 85 Bianchi Stelvio; 87 Bianchi Brava; 73 Bottechia Special; 1969 or70 Bob Jackson
Not sure why you'd bother, the weight you save will be insignificant on a steel frame. The main attraction of carbon seatposts on non carbon frames, was similar to that of carbon forks, they helped smooth out the harshness associated with aluminum frames when they were all the rage.
If you do use it it should be torqued to correct values, believe me the last thing you want is a broken carbon fiber seatpost, talk about Vlad the Impaler....
If you do use it it should be torqued to correct values, believe me the last thing you want is a broken carbon fiber seatpost, talk about Vlad the Impaler....
07-24-12 | 08:55 AM
#15
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From: Canada's Capital
Bikes: Sekine RM40 1980, Miyata 1000LT 1990, Raleigh Mixte Sprite 1980, Raleigh Grand Prix 1979
Some are saying this is OK to put a carbon seat post into a steel frame, and I suppose if you're really careful/brave, and as recently mentioned - use a torque tool to make sure you're tightening the clamp to the correct amount. Over tightening the clamp will cause a stress fracture within the carbon that you might not see right away, but will ultimately cause the seat post to fail.
However, I'm not convinced that torquing it to only the max recommended value is even a safe idea.
It's generally NOT recommended to put a carbon seat post into a steel frame at all due to the differences in the clamp style of steel frames tending to 'bite-in' to the post at the top and back of the clamp, unlike modern aluminium and CF bikes which use a separate clamp piece that applies more even pressure around the seat tube and more predictable torquing.
There's really no advantage to using carbon fiber parts on a steel bike, if you want a light-weight post with a dark look, buy a colored aluminium seat post.
However, I'm not convinced that torquing it to only the max recommended value is even a safe idea.
It's generally NOT recommended to put a carbon seat post into a steel frame at all due to the differences in the clamp style of steel frames tending to 'bite-in' to the post at the top and back of the clamp, unlike modern aluminium and CF bikes which use a separate clamp piece that applies more even pressure around the seat tube and more predictable torquing.
There's really no advantage to using carbon fiber parts on a steel bike, if you want a light-weight post with a dark look, buy a colored aluminium seat post.
07-24-12 | 09:32 AM
#16
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From: Hervey Bay, Qld, Australia.
Bikes: Colnago (82, 85, 89, 90, 91, 96, 03), 85 Cinelli, 90 Rossin, 83 Alan, 82 Bianchi, 78 Fountain, 2 x Pinarello, Malvern Star (37), Hillman (70's), 80's Beretto Lo-Pro Track, 80's Kenevans Lo-Pro, Columbus Max (95), DeGrandi (80's) Track.
You could shim the undersized post with brass shim. I have used this method occasionally to fit a desirable post to a frame. I have never had a post slip down the seat tube using this method.
A 27mm Campy super record, 2 bolt, seatpost into a 27.2mm seat tube:
A 27mm Campy super record, 2 bolt, seatpost into a 27.2mm seat tube:
07-24-12 | 09:49 AM
#17
Curmudgeon in Training
Joined: May 2009
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From: Rural Retreat, VA
Bikes: 1974 Gazelle Champion Mondial, 2010 Cannondale Trail SL, 1988 Peugeot Nice, 1992ish Stumpjumper Comp,1990's Schwinn Moab
I am more than willing to put carbon components on my bikes. The seatpost isn't one of the places I'll allow it. When I can get a Ritchey WCS alloy, 1 bolt post at 195 grams (advertised), I see no real point in going with anything carbon. My older WCS seatpost comes in around 240 grams I think, and that's the 2 bolt version.
I watched some poor guy in a road race last year have to ride a long portion of the race with a broken carbon post.
I watched some poor guy in a road race last year have to ride a long portion of the race with a broken carbon post.
07-24-12 | 10:11 AM
#18
Would it be worth it to counter-bore/ream just the tiniest bit of the rim at the "pointy bit" of the lug so that it doesn't dig into the carbon and start this stress riser as easily? I'm thinking of just using a bit of 400-grit sandpaper to make sure there isn't a shear knife-blade of a corner at the lip there where the upward-pointing parts of the seat lug might cause an issue. a more rounded lip rather than a sharp 90-degree angle should help a lot and not be at all noticeable with the seatpost (either the carbon or another alloy) in.
I"m not an engineer but I've got a ton of experience fabricating things and it seems to me that the irregular shape of the seat lug (compared to a typical seatpost collar on a modern bike) might be an issue as you said and a tiny little bit of a semi-rounded chamfered opening should help that a ton.
The over-tightening thing shouldn't be an issue as I never allow anyone else to work on my bikes or touch a tool to it if I can help it. That's why I purchased the CF assembly paste to help with seatpost retention with the extremely low specified torque. I work as an electrician and have built high-voltage switchgear so I'm pretty familiar with the importance of torque values around dissimilar metals and some of the composite insulators used in gear. Inch-pounds make a difference between something that works or breaks and then blows up. Once you get up over 15-20kv things start to get really interesting when they blow up.
I"m not an engineer but I've got a ton of experience fabricating things and it seems to me that the irregular shape of the seat lug (compared to a typical seatpost collar on a modern bike) might be an issue as you said and a tiny little bit of a semi-rounded chamfered opening should help that a ton.
The over-tightening thing shouldn't be an issue as I never allow anyone else to work on my bikes or touch a tool to it if I can help it. That's why I purchased the CF assembly paste to help with seatpost retention with the extremely low specified torque. I work as an electrician and have built high-voltage switchgear so I'm pretty familiar with the importance of torque values around dissimilar metals and some of the composite insulators used in gear. Inch-pounds make a difference between something that works or breaks and then blows up. Once you get up over 15-20kv things start to get really interesting when they blow up.
). It just had two brazed on ears and they were very VERY VERY VERY poorly done. I finally took a dremel to them and threw on a proper collar. I am not suggesting anyone do that to a vintage frame, but yeah the old method is not so good at evenly distributing clamping forces.
__________________
1 Super Record bike, 1 Nuovo Record bike, 1 Pista, 1 Road, 1 Cyclocross/Allrounder, 1 MTB, 1 Touring, 1 Fixed gear
1 Super Record bike, 1 Nuovo Record bike, 1 Pista, 1 Road, 1 Cyclocross/Allrounder, 1 MTB, 1 Touring, 1 Fixed gear
07-24-12 | 10:15 AM
#19
Steel80's
Joined: Feb 2007
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From: NJ
Bikes: Breezer Venturi, Schwinn Peloton, Marin Lucas Valley
I have put carbon seatposts on 3 different steel bikes and put hundreds of miles on each. Yes, they are lighter, and road vibration is dampened. I've gotten conflicting advise from mechanics about seatpost shape, bolts, torque, and paste, so I won't repeat any of it. But it can be done, and for 35 bucks it's certainly worth it. I paid more for a Nashbar house brand post.
07-24-12 | 10:25 AM
#20
Wookie Jesus inspires me.
Joined: Mar 2011
Posts: 2,215
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From: Seattle, WA
I've ran a CF seatpost in a steel bike plenty of times. Use a torque wrench.
I don't notice any difference in dampening between a good alu one and a CF one. Thomsons are the absolute best. Tried and true and tough as nails.
I don't notice any difference in dampening between a good alu one and a CF one. Thomsons are the absolute best. Tried and true and tough as nails.
07-24-12 | 10:36 AM
#21
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From: Ohio
Bikes: 1973 Mercian Pro, 1972-73 Peugeot Track, 1983 Lotus Competition, Early 1970s Bottecchia Pro/Giro, 2000 Bob Jackson Special Tourist, 2011 Rivendell A. Homer Hilsen; 1996 Franklin custom
A better upgrade that will actually make you go faster would be better tires followed by more aerodynamic (lower) position and aerodynamic clothing (meaning lycra that fits).
More importantly for your purpose, the idea carbon dampens vibration is another industry/Bicycling magazine-inspired myth. Classic emperor's new clothes. And yes, I've owned and ridden full carbon for 1000s of miles. If you want vibration dampening switch from 700 x 23 to 700 x 25, or simply the and your speed will actually increase at the same time.
Last edited by Mercian Rider; 07-24-12 at 10:48 AM.
07-24-12 | 10:41 AM
#22
Decrepit Member
Joined: Aug 2005
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From: Santa Rosa, California
Bikes: Waterford 953 RS-22, several Paramounts
For the same diameter and length seatpost, you don't give up anything - including weight - by using a Thomson Elite or Masterpiece instead of a CF post.
07-24-12 | 10:42 AM
#23
Wookie Jesus inspires me.
Joined: Mar 2011
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From: Seattle, WA
I agree. Failure mode of carbon for a component that bears most of your weight is unacceptable. Unless you actually race in mountains a few grams doesn't matter. I assume you will not be riding CAT 1 or 2 on your Competition.
A better upgrade that will actually make you go faster would be better tires followed by more aerodynamic (lower) position and aerodynamic clothing (meaning lycra that fits).
And the idea carbon dampens vibration is another industry/Bicycling magazine-inspired myth. Yes, I've owned and ridden carbon. If you want vibration dampening switch from 700 x 23 to 700 x 25, and your speed will actually increase at the same time.
A better upgrade that will actually make you go faster would be better tires followed by more aerodynamic (lower) position and aerodynamic clothing (meaning lycra that fits).
And the idea carbon dampens vibration is another industry/Bicycling magazine-inspired myth. Yes, I've owned and ridden carbon. If you want vibration dampening switch from 700 x 23 to 700 x 25, and your speed will actually increase at the same time.
The seatpost, however, doesn't do jack.
07-24-12 | 10:50 AM
#24
Senior Member
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From: Ohio
Bikes: 1973 Mercian Pro, 1972-73 Peugeot Track, 1983 Lotus Competition, Early 1970s Bottecchia Pro/Giro, 2000 Bob Jackson Special Tourist, 2011 Rivendell A. Homer Hilsen; 1996 Franklin custom
Is there science for that? I assume you're not referring to the red herring "test" Bicycling and others used--comparing a steel spoon and a plastic spoon tapped on a table. That "test" has no applicability to bicycle frames or components going over the road.
How a rider feels road vibration has much more to do with tires selection and pressure, followed by things like geometry and type of saddle.
How a rider feels road vibration has much more to do with tires selection and pressure, followed by things like geometry and type of saddle.
Last edited by Mercian Rider; 07-24-12 at 10:54 AM.
07-24-12 | 12:06 PM
#25
Decrepit Member
Joined: Aug 2005
Posts: 10,488
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From: Santa Rosa, California
Bikes: Waterford 953 RS-22, several Paramounts
Is there science for that? I assume you're not referring to the red herring "test" Bicycling and others used--comparing a steel spoon and a plastic spoon tapped on a table. That "test" has no applicability to bicycle frames or components going over the road.
How a rider feels road vibration has much more to do with tires selection and pressure, followed by things like geometry and type of saddle.
How a rider feels road vibration has much more to do with tires selection and pressure, followed by things like geometry and type of saddle.
Originally Posted by Calfee Design
Composites can be molded into structural members with complex cross sections with relative ease. They also have some very impressive mechanical properties. The 6061 and 7000 series aluminum used in bike frames is roughly one-third as heavy as steel, one-third as stiff, and, at best, is about 80 percent as strong as the 4130 cro-moly steel used in most bike frames. Titanium is roughly two-thirds the weight of steel, one-half as stiff, and about 60 percent as strong as steel. The carbon fiber composite most used by bicycle manufacturers is less than one-quarter the weight of steel, but it is about as stiff (which makes it almost four times as stiff on a weight-to-weight basis), and it is roughly four times as strong in tension. Carbon fiber also has a better fatigue life than steel, titanium, or aluminum, and the resins typically used to bond the fibers offer extremely good vibration damping.
Vibration and shock damping are two important factors that affect the cyclist. However, they are two of the least understood subjects in materials science. There are so many variables involved – including how atoms in a material absorb and dissipate vibrational energy, how the structure is built, what type of paint and plating are applied – that it is hard to predict how a structure will react to vibrational input. Composite’s vibration damping is far superior to any metal, which is why it is the preferred material for race car springs and high performance airplanes. The smooth ride quality is one of the first things people notice about carbon fiber bicycle frames.
Sophisticated finite element analysis programs and laminated-plate theory help define the properties of a composite structure. An inherent difference between composites and metals is that composite products are constructed in layers, or plies, of directional material. Interfacial adhesion and the potential for delamination (separation) under shear or compressive loads must be considered when analyzing an advanced composite design. This information is essential when addressing the variable requirements of a bicycle.
Composites differ from metals in that they don’t carry loads equally in all directions, but bear loads best in tension. A composite is similar to a bundle of strings soaked in a layer of glue or resin. The bundle can bear more weight, and flex less, if pulled from end to end or flexed like a diving board than if compressed or loaded transversely. The changing face of the bundle’s performance occurs because the real strength of the bundle comes from the string, not from the resin. The primary function of the resin is to lock the fibers in place, transfer loads among fibers, protect the fibers from environmental forces, and give the structure impact strength. The directional nature of the fibers’ load-bearing abilities changes the rules of structural design.
Vibration and shock damping are two important factors that affect the cyclist. However, they are two of the least understood subjects in materials science. There are so many variables involved – including how atoms in a material absorb and dissipate vibrational energy, how the structure is built, what type of paint and plating are applied – that it is hard to predict how a structure will react to vibrational input. Composite’s vibration damping is far superior to any metal, which is why it is the preferred material for race car springs and high performance airplanes. The smooth ride quality is one of the first things people notice about carbon fiber bicycle frames.
Sophisticated finite element analysis programs and laminated-plate theory help define the properties of a composite structure. An inherent difference between composites and metals is that composite products are constructed in layers, or plies, of directional material. Interfacial adhesion and the potential for delamination (separation) under shear or compressive loads must be considered when analyzing an advanced composite design. This information is essential when addressing the variable requirements of a bicycle.
Composites differ from metals in that they don’t carry loads equally in all directions, but bear loads best in tension. A composite is similar to a bundle of strings soaked in a layer of glue or resin. The bundle can bear more weight, and flex less, if pulled from end to end or flexed like a diving board than if compressed or loaded transversely. The changing face of the bundle’s performance occurs because the real strength of the bundle comes from the string, not from the resin. The primary function of the resin is to lock the fibers in place, transfer loads among fibers, protect the fibers from environmental forces, and give the structure impact strength. The directional nature of the fibers’ load-bearing abilities changes the rules of structural design.