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CF Seat stays(26 posts)

CF Seat staysDoctorNurse
Dec 11, 2001 9:55 AM
Hey folks,

I would be interested in your opinions of CF seat stays on AL or steel bike frames like the Torelli Stilletto/Express, the new AL Litespeeds, and the Viner hybrids Gary Hobbs has on his website....

The marketing hype is all about shock absorbtion and the like, and granted, CF forks are great in that regard but it seems to me that overall frame material and tire/rim selection should have a greater effect on shock absorbption than seat stay material, no? I mean, do you guys think that its worth it? Does anyone own one of these Steel or AL/CF hybrids? What do you think of its performance and comfort level? Additionally, what do you fokls think of the durability and crash worthiness of CF seat stays on bikes used for racing?

Now mind you, I am not really trying to open the whole CF vs. Steel vs. Al debate, but this new CF seat stay trend intrigues me and I would love to get some other opinions...

Thanks....peace...

DoctorNurse
re: CF Seat staysTig
Dec 11, 2001 11:12 AM
I think too many builders are jumping on the CF seat stay bandwagon just to keep up with the market. That's not to say they have no value or use. CF stays, if designed and built for a certain application and matched to a frame well can provide an improved ride without sacrificing rear triangle stiffness. Some builders claim it improves rear triangle stiffness. We have yet to know the different properties of the various CF seat stays that are manufactured and being used out there. Like forks, the effect on ride and frame stiffness can vary quite a bit from one manufacturer to the next.

You are right on when you say frame & fork material/design, tires, and wheels can make a huge improvement in vibration absorption. What CF seat stays won't help with are the vibrations you feel in the pedals and bars. I think they will help improve comfort the most on stiff aluminum, scandium, or even 6Al-4V titanium frames. To put them on an otherwise well built, smooth riding frame like a nice steel one is just plain silly IMHO.

I've never seen or heard of seat stays made of any material damaged from racing or crashing a bike other than ones that were hit by cars. But CF stays are still fairly new and not common. What will they come up with when they DO become common?! LOL

I'm considering a Merckx Fuga for a race bike this year. It's an aluminum frame with CF stays. I'm a bit hesitant about the ride of a small 52 cm with CF stays though. I want a smooth, all day ride out of it and doubt it can deliver that. I hate spending my own limited money to be a guinea pig, even if the frame/fork are only $1275 (discounted).
re: CF Seat staysterry brownell
Dec 11, 2001 11:44 AM
I am currently riding a steel/CF bike (Opera.) There are certainly differences between it, my steel bike and my carbon bike. The CF stays seem to dampen a lot of the noise at the butt level while the bike itself retains a lot of the "life" attributed to steel that my carbon bike lacks. Many would argue the differences between it and any other steel bike have more to do with the tubing material and less to do with the stays, I'm not sure, and since the Opera is not made in steel only, it cannot be proven one way or another.

In terms of durability, I've never given it a thought. There are lots of AL/CF and Ti/CF bikes in the Tour but maybe pros don't worry about crash worthiness. I'm not sure a CF stay would be any less durable than a straight carbon bike although you could argue the points where the metal and the CF merge might make it less durable than a straight monolithic connection.

Bottom line it, I like the way it rides.
re: CF Seat staysNessism
Dec 11, 2001 11:50 AM
There is some a fair bit of controversy sourounding the functional befifits of CF stays. It's my understanding that they were developed to help soften the ride of oversize aluminum race frames used by the euro pro's. I'm of the belief that the ride smoothing abilities will be small at best since the rear triangle of the classic double diamond bicycle frame has very little vertical compliance by design. Also, the weight savings of CF stays will be next to nill or may even cause the frame weight to increase.

I think the reason that so many builders are starting to use these is two fold: one, they are easy to build with since much of the rear end work is already completed and two, customers want them based on perceived benifits.
agreegtx
Dec 11, 2001 12:08 PM
I can understand why you might want them with an AL frame (like the Merckx Team SC) but don't really see the point with a steel or ti frame, since you should be able to build in a plenty comfy ride with ti or steel stays (though I admit the Colnago CT1 looks kinda cool, and maybe that's reason enough).

For a different take on the concept, check out the Serotta Ottrott

http://www.serotta.com/pages/ottrott.html
I meant agree with Nessism (nm)gtx
Dec 11, 2001 12:08 PM
nm
Sooooo....BAsically what you guys are saying is....DoctorNurse
Dec 11, 2001 12:48 PM
So basically, what you guys are saying is that:

*YES* CF seat stays do/can dampen some of the vibration going to the seat and for that reason CF stays may have more objective utility in a frame that is inherently built to be stiffer than steel (AL/Scandium).

*NO*, CF stays are not *ABSOLUTELY* required in a steel frame already tuned for some degree of comfort and responsiveness.

*YES*, they (may/may not) look cool, and *YES* the marketing push behind the idea is effective enough to where Bike manufactures basically have to offer the option, more than some demonstrable benefit (ie Litespeed) and finally...

*NO* it ain't gonna hurt to have them if that's what I want, but *NO* they ain't gonna make as much of a difference to ride quality as intelligent frame/fork/wheels/tire selections *provided* I choose a good steel frame (that fits appropriately, that I can afford, blah, blah, blah)

Got it about right? Anything I missed?

Thanks!

DoctorNurse
Sooooo....BAsically what you guys are saying is....sprockets2
Dec 11, 2001 2:35 PM
Hate to bring this up, but cf is not as durable nor as long-lived as other materials, and this can be especially true in the case of bonding or joining dissimilar materials. Impact resistance is certainly not a strength of cf materials in bikes. A good bash can damage a tube. Luckily the bonded tubes come apart so that the maker-if still in business and making the tubes-can replace them.

CF has been in use in aerospace, cycles, and other applications, and can be very useful. However, there is a history of separation at junctions, delamination, and breakdown of the matrix material in some of its applications. I have seen lugs separate from tubes, fork blades leave the steerer, and delam. problems myself.

Yes I know Rider X has 200,000 miles on his carbon bike, etc. and blah-blah. Well, X is one of the lucky ones, and that one example doesn't necessarily paint the whole picture. Don't get me wrong it is great stuff, and getting better all of the time. It just isn't prime time, at least for everyone, yet.

On the other hand most of the failures that have occurred have done so in material laid up some time ago. If the manufacturing, and materials, have improved in recent years, things might not be so glum.
prime time CF bikesTig
Dec 11, 2001 2:56 PM
You're dead on about the impact and delam failures. Remember the early Trek CF bikes with aluminum lugs? The recent problems with Woundup forks are just the latest.

One bike everyone forgets when they look at CF's problems are Calfee. The Tetra even has a 25 year warranty. Calfee has been refining CF frame materials and design at a much higher rate than even the bigger names. Maybe the C-40 will step up and use Ti dropouts instead of the aluminum ones or try a boron mix in their tubes. Also, when people say CF can't be made custom due to mold limitations forget that Calfee makes custom frames all the time.

Why do I rave them? I just think Craig has been on the leading edge of CF bikes since 1988 when LeMond spec'ed his designs for the Team Z. Calfee is as close to prime time as it gets.
Custom carbon,TJeanloz
Dec 12, 2001 9:14 AM
Custom carbon bikes are easy to make if you use a lugged system, as Colnago and Calfee do. They only become prohibitively expensive when you use a monocoque design, as Trek, Aegis, Kestrel, et. al. do. Each will tell you that their method is better- and I don't think there is a definitive answer yet.
Correction, Trek is lugged also. nmLen J
Dec 12, 2001 9:29 AM
Not really,TJeanloz
Dec 12, 2001 11:08 AM
You are right that Trek isn't a 'true' monocoque frame, but it's internal lugs make it effectively a monocoque from a custom building standpoint.
Help me understand....Len J
Dec 12, 2001 11:45 AM
I was under the impression that the only thing that varied size to size on the Treks was the length of the carbon tubes the linked the Head, the seatpost junction, the bottom bracket & the dropouts. These tubes were wound and could be made in any length. The head, the seatpost junction & the bottom bracket were molded and were the same on all size frames. The only difference between this and the c-40 is the material the lugs are made of. Consequently if they wanted to they could make custom sized frames just by manipulating the length of the tubes.

Where is my knowledge faulty?

Len
Help me understand....TJeanloz
Dec 12, 2001 12:33 PM
The lugs on OCLV's are really just internal sleeves that hold the bike together during the final molding. They can't make them custom because if you lengthened any tube, one of the angles at the lug would have to change, and then it wouldn't work in the final mold. A C-40 is lugged on the outside- the tubes are put into the lugs just like they are on a steel frame.
Got it, thanks.....Len J
Dec 12, 2001 12:51 PM
so the only way to lengthen a tube is to lengthen all tubes proportiatly.

I knew I didn't know something, I just needed your help figuring out just what it was.

As always, you are a fountain of useful info.

Thanks

Len
don't forgetbn
Dec 11, 2001 7:16 PM
Easier to make... you just buy the Columbus Carve rear end. One miter and weld and screw the screws at each dropout and you're done. Simple, looks all cool and expensive, and you can charge the same as more labor intensive options. What a deal.
smaller diameter, round lightweight steel seatstayscolker
Dec 11, 2001 3:44 PM
would provide more comfort than a carbon wishbone.
but the rear wheel will flop every strokeDizzyD
Dec 11, 2001 3:49 PM
kinda cool?djg
Dec 12, 2001 10:40 AM
That's no reason to buy a bike. And for the record, the CT1 does not look "kinda cool." The CT1 looks WAY cool. And way cool starts to seem like a reason.
re: CF Seat staysMe Dot Org
Dec 11, 2001 12:53 PM
I have a custom foco Carl Strong frame ( http://www.strongframes.com ) with Carve carbon seat stays. The ride feels more comfy than a straight steel bike with a carbon fork.

Is it the be-all end-all? As everyone says, it's how well the bike is designed and constructed. It's all a matter of how everything is 'tuned' to work together. I think carbon stays and forks are a cost-effective way to get many of the benefits of carbon into a frame whose geometry is not determined by a specific carbon mold.
Foco tubesTig
Dec 11, 2001 2:26 PM
I like the design of the foco tubing but haven't had a chance to ride it yet. As steel gets stronger/thinner/lighter/larger diameter with shaped tubing like the foco set, is it also getting a little stiffer? If so, that might explain how CF is making your frame's ride so smooth. I don't know how many steel frames with what types of tubing you've ridden. The variety of performance is wider than most people think. Just curious, what frames can you compare the Strong with? I know he makes an excellent bike so I would never question that!
Foco tubeskoala
Dec 11, 2001 6:11 PM
I love my foco bike. Ride is way nicer than my old master light. Road irregularities are soaked up and you would swear its a ti bike with just a hair more road feel. The reynolds all carbon with oversized steerer rides great and has plenty of rigidity. The frame is very stiff sprinting due to the unusual downtube crimping and chainstay shape yet the ride stays plush. The tubes are very thin, though, and can dent easily. If you like the ride steel gives, you will love foco.
re: CF Seat staysallervite
Dec 11, 2001 2:22 PM
So sexy. So useless.
the only way is to test it...Tig
Dec 11, 2001 2:39 PM
Only someone who has ridden a bike can truly know if the CF stays are useless or not. That's not an easy comparison since very few bikes other than custom give you that choice. The CIOCC EOM comes with or without them. That would be a good test for a magizine to run. The bikes are identical other than the seat stays and paint.

Sexy? They are to a point, unless you are doing something with your bike we don't know about! ;o)
Come on, you know you do it too. We all do. (nm)allervite
Dec 12, 2001 12:05 PM
It's a Crutch....grzy
Dec 11, 2001 4:06 PM
....for a too stiff design due to using aluminum elsewhere. Sure it has an effect, but one has to ask yourself why not make the whole thing from CF it's so good? Well, they do. Ultimately it's all about marketing and product differentiation. Trek and Specialized (and others) have done the aluminum/carbon thing for a long time. they've also had a bunch of failures and have learned some lessons. While not impossible it's doubtful that a smaller operation has done as much R & D and fully understands all of the pitfalls. Specialized lost a small fortune on Allez frames that came apart or cracked.

Ask yourself why would you want to go down this road? The shock absorbing properties of CF are not to be sold short - it works. Tire compliance can only take you so far and ultimately you're losing energy through hysteresis. Why not just ride with big fat ballon tires pumped to 40 psi? B/C it's slow. I can tell you from personal experience that CF is way crash worthy - had another roadie run my OCLV bike over at 40 mph and it was fine. I wasn't so lucky. the whole bonded concpet gets you into trouble since there is a discontinuity which acts as a stress riser at the joint. It's not a fatal flaw, but I doubt some small artisan type of frame builder fully understands this. Not that it con't be done - the aerospace guys do it all day, but they went a little further in school and are funded by NASA and the like. Ultimately there's no free lunch - you have to give something up to get something.

The CF/aluminum thing is all about marketing hype and sizzle. Why not stick with something that is race proven - once you dominate the pack you can then experiment.