Ads |
#22
|
|||
|
|||
On frame stiffness
On Thursday, June 8, 2017 at 6:01:15 PM UTC-7, jbeattie wrote:
On Thursday, June 8, 2017 at 7:38:28 AM UTC-7, Frank Krygowski wrote: On 6/8/2017 9:46 AM, wrote: On Thursday, June 8, 2017 at 5:43:52 AM UTC-7, AMuzi wrote: On 6/7/2017 10:17 PM, John B. wrote: On Wed, 7 Jun 2017 07:20:09 -0700 (PDT), jbeattie wrote: On Wednesday, June 7, 2017 at 5:28:46 AM UTC-7, AMuzi wrote: On 6/7/2017 12:13 AM, John B. wrote: On Wed, 7 Jun 2017 09:34:58 +1000, James wrote: On 07/06/17 08:03, jbeattie wrote: On Tuesday, June 6, 2017 at 7:09:56 AM UTC-7, wrote: On Monday, June 5, 2017 at 7:56:58 PM UTC-7, James wrote: https://cyclingtips.com/2017/06/cycl...ffness-matter/ Interesting that some pros want a less stiff frame early season, and more stiff frame later in the season. Other interesting bits too. Well, if you're flexing a frame and getting power back that's fine. But at the same time there are frictional loses and you're only getting back a portion of it. There was a noticeable difference between riding a Colnago Dream with carbon forks and the Colnago C40. The C40 was stiff and I had to pedal complete circles on a hard climb or the bike would stop at the point of one down stroke to the next. The Dream did it less. A steel bike absolutely does not do this. Now there may be a preference about one way or another but I don't believe so. I think that this really is something that works better and while I haven't said anything to the group I generally ride with most of them are returning to steel. The podcast is all about BB stiffness which is just one aspect of frame stiffness. Of course a soft frame is an energy sponge. Try sprinting on a double-suspended mountain bike. Small difference in BB stiffness between racing bikes, however, probably makes little difference. Dual suspension MTB is a totally different beast. It has built in energy absorbers (shock absorbers). Rigid frames do not. I'm far more sensitive to front-end stiffness than BB stiffness. I had a first-gen Cannondale 2.8 with aluminum forks that was like sprinting on a pogo stick. I wanted to throw it away after my first race on it but instead bought a pair of Kestrel forks which rode a lot like steel (they had a steel steerer). I had a custom steel sport-touring frame that rode the same way -- lots of slop. My last steel racing bike was very stiff, but when I resurrected it last and used it as my winter bike, it was not magical in any way. The top-tube was too short; it was heavy and probably less "planing" than my CAAD 3. What steel has going for it is resistance to mechanical damage. With thin walled tubes (0.4mm & below), not even that. This whole steel-is-magical thing reminds me of going back to vinyl and realizing how many bad recordings there are. It's more about the implementation than the material. I agree. One of the things I've always wondered about when people start talking about BB flex. It would be a relatively simple problem to built a steel frame bike with gussets of bracing for the BB, but no one seems to have. Looking at Eddie Marckx, Sean Kelly or any of the other top riders of the "steel Era" and none of their bikes seemed to have any visible BB bracing. Yoshi Konno of 3Rensho, c.1990: https://www.pedalroom.com/bike/3rensho-njs-chrome-6748 The linking is odd so in that series go to the BB photo. The Serotta Colorado used an ovalized seat tube at the BB to add stiffness. That was '86-87. Earlier steel frames also used chain stay bridges. If you wanted a super-stiff BB after the late '70s early '80s, you bought a Klein or Cannondale, assuming you could handle the aesthetic shock of fat tubes. -- Jay Beattie. But that was one or two bicycles. I'm looking at bikes ridden by top riders, I mentioned Eddie Marckx, Sean Kelly, et al, and I don't see any frame stiffeners or wide tubes on bikes shown in photos of the top rider of that era. In fact, based on memory - always a questionable practice - I don't remember a lot of talk about frame stiffness until about the time that Cannondale started selling aluminum bikes. . Sean Kelly victory photo on a Vitus 979. https://www.flickr.com/photos/chicovelo/2207332160/ (virtually overdone pasta for stiffness, not even al dente) I don't know what you're seeing in that picture Andrew. I do remember seeing wheels distort on a hard sprint but not frames. Though I'm sure that someone like Kelly could. But how do you distort a frame sideways with the tires distort so much in that plane? What Andrew is alluding to isn't visible in that photo. But about the same time, I test-rode my friends Alan frame, which I think was pretty similar to the Vitus. I had absolutely no trouble flexing the frame sideways in a sprint, far enough that the chain scraped on each side of the front derailleur's cage in turn. It was super light but super flexible; but people did win races on it. BTW, the owner of that frame passed away recently, and I miss him. But before he died he sold that bike to another friend of mine. It's still going strong - even though it's not going stiff, so to speak. -- - Frank Krygowski I wonder how the Vitus descended. If you're a nervous descender, being on a spring is the kiss of death. I've been content on lots of different materials, but I have to say that my CF SuperSix is the best descending bike I've ever owned. It's hard to explain without sounding like a dopey bike review, so I won't. I had an original 1984 Cannondale that I really liked. Super-stiff, but the biggest advancement in stiffness was years earlier when I switched from my Detto cycling/bowling shoes with nail on cleats to Duegi with birch soles and plastic bolt-on cleats. Super fast! Stiff bikes are the kiss of death in a descent. Predictable handling is necessary and that means softer reactions to bumps. My Time VXR was so stiff that if you hit a bump on a descent it could literally throw your hands off of the bars. Even minor bumps that can hardly be felt on a steel bike could throw you off course in a turn. Until you've ridden a really stiff frame you have no idea of just how awful they are. |
#23
|
|||
|
|||
On frame stiffness
On Thursday, June 8, 2017 at 4:23:40 PM UTC-7, Doug Landau wrote:
It was worse than that. I bought one just for the comparison point. It would shift when sprinting. Well there are extremes of everything. But what I've found is that you can have a LOT of soft handling and be able to ride well. But the NORMAL stiffness of a hard titanium frame like my Colnago BiTitan was just too much. And it was softer than most CF frames. Not to say there aren't some soft CF frames. My Dream HP actually rides well. |
#24
|
|||
|
|||
On frame stiffness
On Friday, June 9, 2017 at 11:40:04 AM UTC-4, wrote:
On Thursday, June 8, 2017 at 4:23:40 PM UTC-7, Doug Landau wrote: It was worse than that. I bought one just for the comparison point. It would shift when sprinting. Well there are extremes of everything. But what I've found is that you can have a LOT of soft handling and be able to ride well. But the NORMAL stiffness of a hard titanium frame like my Colnago BiTitan was just too much. And it was softer than most CF frames. Not to say there aren't some soft CF frames. My Dream HP actually rides well. A guy that I worked with at a bike shop in the 1980s had an Alan or Vitus (pretty sure it was a Vitus) that had the aluminium frmae with standard size tubes. He put clip-on aero bars on it and when he tried to ride it at any speed it squirmed all over the place. he said he thought he'd crash any second until he got his hands back on the drop bar. Needless to say he immediately took those aero bars off again. Cheers |
#25
|
|||
|
|||
On frame stiffness
On Friday, June 9, 2017 at 8:36:30 AM UTC-7, wrote:
On Thursday, June 8, 2017 at 6:01:15 PM UTC-7, jbeattie wrote: On Thursday, June 8, 2017 at 7:38:28 AM UTC-7, Frank Krygowski wrote: On 6/8/2017 9:46 AM, wrote: On Thursday, June 8, 2017 at 5:43:52 AM UTC-7, AMuzi wrote: On 6/7/2017 10:17 PM, John B. wrote: On Wed, 7 Jun 2017 07:20:09 -0700 (PDT), jbeattie wrote: On Wednesday, June 7, 2017 at 5:28:46 AM UTC-7, AMuzi wrote: On 6/7/2017 12:13 AM, John B. wrote: On Wed, 7 Jun 2017 09:34:58 +1000, James wrote: On 07/06/17 08:03, jbeattie wrote: On Tuesday, June 6, 2017 at 7:09:56 AM UTC-7, wrote: On Monday, June 5, 2017 at 7:56:58 PM UTC-7, James wrote: https://cyclingtips.com/2017/06/cycl...ffness-matter/ Interesting that some pros want a less stiff frame early season, and more stiff frame later in the season. Other interesting bits too. Well, if you're flexing a frame and getting power back that's fine. But at the same time there are frictional loses and you're only getting back a portion of it. There was a noticeable difference between riding a Colnago Dream with carbon forks and the Colnago C40. The C40 was stiff and I had to pedal complete circles on a hard climb or the bike would stop at the point of one down stroke to the next. The Dream did it less. A steel bike absolutely does not do this. Now there may be a preference about one way or another but I don't believe so. I think that this really is something that works better and while I haven't said anything to the group I generally ride with most of them are returning to steel. The podcast is all about BB stiffness which is just one aspect of frame stiffness. Of course a soft frame is an energy sponge. Try sprinting on a double-suspended mountain bike. Small difference in BB stiffness between racing bikes, however, probably makes little difference. Dual suspension MTB is a totally different beast. It has built in energy absorbers (shock absorbers). Rigid frames do not. I'm far more sensitive to front-end stiffness than BB stiffness. I had a first-gen Cannondale 2.8 with aluminum forks that was like sprinting on a pogo stick. I wanted to throw it away after my first race on it but instead bought a pair of Kestrel forks which rode a lot like steel (they had a steel steerer). I had a custom steel sport-touring frame that rode the same way -- lots of slop. My last steel racing bike was very stiff, but when I resurrected it last and used it as my winter bike, it was not magical in any way. The top-tube was too short; it was heavy and probably less "planing" than my CAAD 3. What steel has going for it is resistance to mechanical damage. With thin walled tubes (0.4mm & below), not even that. This whole steel-is-magical thing reminds me of going back to vinyl and realizing how many bad recordings there are. It's more about the implementation than the material. I agree. One of the things I've always wondered about when people start talking about BB flex. It would be a relatively simple problem to built a steel frame bike with gussets of bracing for the BB, but no one seems to have. Looking at Eddie Marckx, Sean Kelly or any of the other top riders of the "steel Era" and none of their bikes seemed to have any visible BB bracing. Yoshi Konno of 3Rensho, c.1990: https://www.pedalroom.com/bike/3rensho-njs-chrome-6748 The linking is odd so in that series go to the BB photo. The Serotta Colorado used an ovalized seat tube at the BB to add stiffness. That was '86-87. Earlier steel frames also used chain stay bridges. If you wanted a super-stiff BB after the late '70s early '80s, you bought a Klein or Cannondale, assuming you could handle the aesthetic shock of fat tubes. -- Jay Beattie. But that was one or two bicycles. I'm looking at bikes ridden by top riders, I mentioned Eddie Marckx, Sean Kelly, et al, and I don't see any frame stiffeners or wide tubes on bikes shown in photos of the top rider of that era. In fact, based on memory - always a questionable practice - I don't remember a lot of talk about frame stiffness until about the time that Cannondale started selling aluminum bikes. . Sean Kelly victory photo on a Vitus 979. https://www.flickr.com/photos/chicovelo/2207332160/ (virtually overdone pasta for stiffness, not even al dente) I don't know what you're seeing in that picture Andrew. I do remember seeing wheels distort on a hard sprint but not frames. Though I'm sure that someone like Kelly could. But how do you distort a frame sideways with the tires distort so much in that plane? What Andrew is alluding to isn't visible in that photo. But about the same time, I test-rode my friends Alan frame, which I think was pretty similar to the Vitus. I had absolutely no trouble flexing the frame sideways in a sprint, far enough that the chain scraped on each side of the front derailleur's cage in turn. It was super light but super flexible; but people did win races on it. BTW, the owner of that frame passed away recently, and I miss him. But before he died he sold that bike to another friend of mine. It's still going strong - even though it's not going stiff, so to speak. -- - Frank Krygowski I wonder how the Vitus descended. If you're a nervous descender, being on a spring is the kiss of death. I've been content on lots of different materials, but I have to say that my CF SuperSix is the best descending bike I've ever owned. It's hard to explain without sounding like a dopey bike review, so I won't. I had an original 1984 Cannondale that I really liked. Super-stiff, but the biggest advancement in stiffness was years earlier when I switched from my Detto cycling/bowling shoes with nail on cleats to Duegi with birch soles and plastic bolt-on cleats. Super fast! Stiff bikes are the kiss of death in a descent. Predictable handling is necessary and that means softer reactions to bumps. My Time VXR was so stiff that if you hit a bump on a descent it could literally throw your hands off of the bars. Even minor bumps that can hardly be felt on a steel bike could throw you off course in a turn. Until you've ridden a really stiff frame you have no idea of just how awful they are. IMO, rider input can cause terrible shimmy which is amplified by a limber front-end. I agree, though, that a steep, super stiff front end can be bad too. If you're getting thrown all over the place, it's hard to steer. I rode a first generation Cannondale with OS straight gauge aluminum tubes for 20 years. No idea how it compared to a CF Time, but I can tell you it was stiff. It had very conventional geometry and was good at descending -- or good enough. I don't remember it being much different than my steel racing bike that had similar geometry. I don't know what they did to that Time to make it so stiff, but I know that it had a reputation for being a bone-shaker. It probably had a steep front end that made it stiff and twitchy. -- Jay Beattie. |
#26
|
|||
|
|||
On frame stiffness
On Fri, 09 Jun 2017 13:30:02 +0700, John B.
wrote: Better then Carbon Fiber :-? Birch *is* a carbon-fiber composite. -- Joy Beeson joy beeson at comcast dot net http://wlweather.net/PAGEJOY/ |
#27
|
|||
|
|||
On frame stiffness
On Sat, 10 Jun 2017 21:20:42 -0300, Joy Beeson
wrote: On Fri, 09 Jun 2017 13:30:02 +0700, John B. wrote: Better then Carbon Fiber :-? Birch *is* a carbon-fiber composite. and it grows on sunny hillsides :-) -- Cheers, John B. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Bicycle Frame Stiffness | bicycle_disciple | Techniques | 9 | January 9th 10 05:40 PM |
Frame Stiffness - What Does It Affect | Phil Holman | Techniques | 14 | January 21st 08 04:06 AM |
Question about frame/fork stiffness | holdmybeerandwatchthis | Techniques | 11 | April 30th 07 09:01 PM |
Seat post stiffness: Compact frame geometry | SteveT | Techniques | 5 | December 29th 06 02:28 PM |
VeloNews on Frame Stiffness | 41 | Techniques | 28 | August 11th 06 02:56 PM |