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Carbon seat stays: Function or fiction?(25 posts)

Carbon seat stays: Function or fiction?flyswatt
Jan 30, 2002 7:26 AM
Do carbon seat stays really work in dampening vibrations etc? I have heard several manufactors that do not produce Carbon stayed bikes say that there is no benifit just a 50g wieght increase over a standard Alu bike and an increase in the chance of a frame break at that point. Of course those who do produce them wax on about the benifits in comfort and weight.
Mike Burrows of Lutus super bike and Gaint TCR fame says that only frame design and not material will effect the comfort level. I understand that diffences in materials fatigue levels might lead to Ti and Carbon bikes being built with more flex in the design than Alu but is this true for those with just carbon stays?
I have heard some people say that diffence in frame comfort levels from different materials are so small (unless some from of suspenions is used)that it is imposible to tell and that any differences felt are in the riders head i.e. test show that the Cannondales Cad 6 frame has less flex than many Alu bikes but because the Stays look curvy and thin people believe they are more forgiving.
I can't prove it either way...TJeanloz
Jan 30, 2002 8:34 AM
But in 2000, the Bianchi Giro was an all 7000 series Kinesis aluminum (easton tubing) bike. In 2001, they thinned out the seatstays, and then wrapped them with CF- so it wasn't a true carbon stay, but it was different. There were no other changes to the bike, in terms of spec. I was convinced that it was purely cosmetic. We had two 57's, one a 2000, and one a 2001 that we set up identically (same tire psi etc.). And there was a discernable difference. Not huge, but clear. A lot of the low end vibrations of the road (or our parking lot as the case was) that were apparent with the 2000 model, were smoothed by the 2001. I was surprised, but I could only attribute it to the stays.
By way of analogy...PdxMark
Jan 30, 2002 8:40 AM
Al bikes with Al forks were reputed to be very harsh (I never rode one). The common wisdom seems to be that carbon forks provided sufficient "dampening" that Al bikes can now be reasonably comfortable. So, if it was true for carbon forks, it seems plausible that carbon seat stays an Al bikes could dial-in their ride just a bit more.
Analogy continued...PdxMark
Jan 30, 2002 8:45 AM
So if the thinking about Al frames is correct, it really makes you wonder why one would put carbon stays on steel or Ti bikes...
Analogy continued...Troyboy
Jan 30, 2002 8:48 AM
With all due respect, you are perpetuating myth. This is heresay from people who have never ridden certain types of bikes talking about their characteristics.
I like myth busting... so Al bikes with Al forks were comfy? nmPdxMark
Jan 30, 2002 8:57 AM
I rode one for many centuries without discomfort.Troyboy
Jan 30, 2002 9:03 AM
Matter of fact, when I bought my first alu bike with an alu fork, that bike changed my opinion and the world of cycling, in my opinion. After the steel rigs I'd owned, I jumped on one and WOW. A whole new world of stiffness, responsiveness, etc.

It just doesn't work when people relay heresay about something they know nothing about.
Well, you were being helpful until the last snotty dig...PdxMark
Jan 30, 2002 9:29 AM
We can help each other learn things and figure them out, sharing experience and information, without having to attack each other.

You'll be interested to know that your experience on ONE bike, while very helpful and relevant to sorting out the question at hand (do carbon stays matter), does not create a universal truth that entitles you to act as global truth cop. It's your OPINION. You should learn its limits.

For the thread at hand, your experience helpfully tells us that maybe the whole carbon stay fashion is for naught. That's helpful... Defending the honor of your first Al bike by attacking me does not.
I've had many more than one. No snotty dig.Troyboy
Jan 30, 2002 9:39 AM
I just restated what I mentioned before. It just doesn't work when people relay heresay about something they know nothing about.

I still ride and race the stiffest, most responsive rigs I can find. They are all aluminum. Got three right now, though one is being sold.

I prefer straight blade forks, but have curved as well.
So you're saying carbon forks are the same as Al forks? nmPdxMark
Jan 30, 2002 10:46 AM
I had a Vitus AL fork on an old C-dale criteriumTig
Jan 30, 2002 9:49 AM
Back when the heavy C-Dale steel forks were the only option, I had a noodle-like Vitus fork on it. There were very few choices of fork in those day. For my weight it rode nicer than the steel one. The only problem was the flex I got with deep breaking.

Until more people have ridden CF stays, the jury is still out. Besides, not all CF stays are built the same, nor are the frames that they are on. The differences will be quite varied, as will the resulting ride characteristics.
I like myth busting... so Al bikes with Al forks were comfy? nmFlyswat
Jan 30, 2002 11:34 AM
As far as I can understand Alu bikes have to built to accomadate the fatigue resistance of the Alloy used. So Alu bikes of the past were probably made to be very stiff to avoid flex and therefore the chance of breaking. As tubing and Alloys used have improved and knowledge of the fatigue restistance has grown bikes have been built closer to the limit with more flex. Some manufacturers preffer to build stiff frames as they believe that flex = loss of power. I think what Mike Burrows means is Frame design is govened by the properties of the frame material, but it is the design of the frame that governs how it rides. Carbon has the most possiblities as it has more scope to change it properties and thus frame design. I am unsure how or if adding carbon seat stays can be enduce a different ride or if most people would really notice if they did the pepsi challange with Alu stays and carbon stays(it is pretty difficult to ride blind folded!).
Alloy ForksAndy M-S
Jan 30, 2002 12:04 PM
I put an alloy fork (Profile BRA) on my steel Bianchi. It was a good deal more comortable than the original steel fork. Indeed, when I later put a carbon fork (BRC) on the bike, it struck me as being not quite as comfortable as the alloy--which I attribute to its being a little more laterally stiff.

Alloy forks can be very comfortable indeed!
Funny thing is...Nessism
Jan 30, 2002 12:13 PM
Almost all aluminum forks that came to market were very soft and compliant. They helped smooth out the ride of the stiff aluminum frames they were installed on at the time.

Check this link for qualitative information regarding Al fork flex. http://www.sheldonbrown.com/rinard/rinard_forktest.html

I'm of the opinion that the order of importance regarding ride comfort are: 1) tires, 2) fork, and distant 3) frame.

Within the frame itself, I think the front triangle of the frame flexes more than the rear by a large margin - vertical flex that is. With that said, I wouldn't spend money on a carbon rear triangle. I can believe that one could FEEL a small difference, but I doubt that the actual force input would be significantly different.

Check the following link for some qualitative information about frame flex.
http://draco.acs.uci.edu/rbfaq/FAQ/106.html
More good info from NessismTroyboy
Jan 30, 2002 12:27 PM
Furthermore, it is my opinion that within reason, stiffness of a fork is more a function of shape and geometry than material to a relative extent. In comparison: I suspect that two forks of identical material in every way except one being a straight fork and one with curve will render the curved fork as being less stiff feeling. This is, of course, assuming the curved fork isn't beefed up to match or exceed the stiffness of a straight fork, or the straight fork isn't so thin or thinned out or lightened so much as to make it less stiff than that of a curved fork.

I have heard personally and directly from the horse's mouth (a well known carbon builder) that carbon can be built to be every single bit as stiff as you want it. I haven't put in my order yet, but we'll see.
Mainly aesthetics, but what's wrong with that?...Ed3
Jan 30, 2002 8:40 AM
No personal experience, but general consensus is that the stays do not make a PERCEPTIBLE difference in ride quality.
But I do think that they look pretty cool...

FWIW,
Ed
gotta have both chain- and seatstays in carbon...Q
Jan 30, 2002 11:55 AM
according to Carrera in the latest Velonews.
I agree.Epic02
Jan 30, 2002 1:09 PM
they do look nice...
Herculeez, Herculeez, Herculeez...Q
Jan 30, 2002 1:39 PM
the original carbon-stayed bike
Another angle'Sakes
Jan 30, 2002 9:44 AM
never has the opportunity to try 2 bikes set up the same apart from the stays, but I do know that curved stays make a helluva difference IME. I would agree with the about on the issue of perceptible difference - go curved stays if you want rear end damping.
Different stays materials... Same tire/pressure and all? Well...tempeteKerouak
Jan 30, 2002 10:33 AM
The only road bikes I've ever ridden were either steel or aluminium, integral frames of butted tubes.

However, the first competitive mountain bike I rode hard enough to learn anything about was a Fischer CR-7. That frame had a front triangle made of 7000 serie Alu, and a BOLTED/riveted Tange prestige rear stays. There was a difference. You could take the Fischer Supercaliber (all alu) and the CR-7 with similar wheels, tire and pressurised tubes and throw yourself down a wash-board descent. Not only could you feel the CR-7 was smoother, you could HEAR it! That bike was as smooth as Bicycling editors after Jalabert's polkadot jersey. Anyway, the whole bike was way heavy too.

Cannondale uses carbon flex to pivot their SCALPEL. Carbon is also used to stiffen other bike parts, or skis or golf shafts. Have you ever played hockey? Try a wood stick, an alu shaft and a carbon shaft. Swap blades from wood to carbon... Alu vibrates (remember that baseball bat feel?) and carbon is stiff and "dead".

You can make carbon do what you want, if you know what to do. A company like Aegis, or Look, or Trek might know what to do with its desings. But I doubt all other "manufacturers" know over a year or two how to wrap carbon stays... (it is a trend all right!)

How about a wooden bike frame!
That was Fisher bike (before Gary Fisher). I'm in ski mode!!(nm)tempeteKerouak
Jan 30, 2002 10:46 AM
you're logic might be working backwards...ohio
Jan 31, 2002 8:31 AM
... you said the bike was so much smoother you could HEAR it. Is it possible that the bike SEEMED much smoother because it wasn't as loud?

You could be right, but in my framebuilding and materials experience you can't build enough compliance into ANY rigid frame to absorb significant bumbs (the exception being the curved stays mentioned above). Materials CAN help filter out high frequency vibrations and "noise", but that's assuming that those vibrations can be transferred through a pneumatic tire, foam saddle, tensioned stainless steel spokes, titanium saddle rails, and an alloy/ti/carbon seatpost...
QUESTION ASKED... (but, yes, perception is subjective)tempeteKerouak
Jan 31, 2002 11:23 AM
Of course, the bike sounded differently. For me my Titanium Hei Hei feels smooth. To some, it feels sluggish. It's a question of words...

We had very similar bikes, by the way, same gruppo from saddle to stem, head set, forks, tires (all Fisher, Shimano XT, toes straps) All we had to do was pump tires to same pressure and swap bikes, which we did often. I believe spoke tension was not really an issue; we were also of different weight... My bike was, to everyone who tried it over the season, more comfortable and did not sound like banging the bumps as much. What else can I say.

Now; carbon chainstays; Like P-tex bases for skis; how many manufacturers can there be for something as tricky as laying carbon fiber.

Merckx has carbon chainstay only
Look: full carbon
Colnago: staight carbon stays
Pinarallo: wishbone carbon...

And even all the small/medium players suddenly have a design offered. I don't believe they all made it in the back of the shop... So, if different steel bikes have different qualities and caracteristics (butting, metal composition, assembly technic) then carbon stays should also differently affect bike "feel". Therefore, carbon is not a garanty of any specific quality. I far as I know, a bike with stays could be harsher than a well made butted alu... One can make carbon flex of stiffen...

An incompetent builder goes with the trend and assembles (or has it done somewhere) a front triangle with a serial made carbon stay and ends up with a superstiff bang-the-butt frame on a century geometry... And advertises it as a comfy vibration soaking bicycle... What gives!!!

What do you think?
re: Carbon seat stays: Function or fiction?RayBan
Jan 31, 2002 7:01 AM
I decided to buy a Pinarello Opera because of the carbon rear and fork. I've had an all carbon frameset in the past so I know how it can add comfort to my rides. I've only had it on the rollers so I can't tell you how it rides in the real world yet. I figured if carbon in the rear of the frame does as good of a job as a carbon fork then I have a winner.