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  1. #1
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    Carbon seatstays - why?

    This from "Ask RC" on the Mountain Bike Action magazine website:

    Q. Hi RC! I've noticed that a lot of mountain bikes are coming out with carbon seat stays. I would like to know what are their disadvantages over aluminum seat stays and if your bike has one, what can we do to protect them from damage. Thanks
    Erwin/mbaction.com - 6/14/2007 3:35:51 PM

    A. RC: I know I will incur some wrath here, but, of all the stupid places to use carbon fiber, the seatstay of a mountain bike is the dumbest yet. Does it save weight? No, not unless the previous aluminum stay was poorly designed. Composites are weakest in compression--exactly what the major stresses are on a seatstay. A paper-thin aluminum stay would do a better job and for less money. Basically, it's the easiest place for a bike maker to put carbon where its customers will see it and say "Wow, that is cool."

    Now I know that many people do not agree with a lot of Richard Cunninghame's ideas BUT I tend to agree with the statement above.
    Not sure why the new ML frame has to have carbon seatstays?
    Purely bling factor?
    Marketing hype following the "carbon is cool" trend?
    Just my 2c
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  2. #2
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    I'd tend to agree as well while having a few different opinions. Carbon on the stays is silly but I'd say carbon on the chain stays would be the dumbest yet with seat stays a distant second. I also don't think strength of composite is really that much of an issue on a seat stay but apparently the bonding AL to Carbon is an issue.

    I have a Racer X, not an ML but I would definitely welcome an all AL rear triangle option.
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  3. #3
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    Agree..

    Everyone should inspect the nicks, scratches, & dings on their 1+ yr old aluminum seatstay and chainstay. Imagine if it was made out of a carbon. When I fall, I don't fall pretty, and frame take quite the beating as it rams into the rock and boulder. Carbon bits on frame, I just don't get.
    sth

  4. #4
    the 36 year old grom
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    I think the best place to use carbon on a bike is almost everywhere…..

    In regards to motive…
    My guess as to why the seat stay is a popular place to add carbon is the cost of the part. Its already a complex weldment and probably “expensive” to begin with. Probably a cost effective place to add a carbon part.

    and on the ML is saves 75g

  5. #5
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    Replacement seat-stay

    My 2005 AL seat-stay cracked and Titus warranted the part with their new CF one. I was a bit surprised to say the least when I got it since I was expecting the polished AL variety.

    Well, it is rather sexy and I'm more than happy to give it a beating. Granted, I haven't crashed on it yet, but all is well so far. I do worry about that inevitable crash, however. But, I just ride with the assumption that if it fails within a two year period, I'll just get it replaced again at no charge. Or if I crash it hard I can opt for the crash replacement policy.

    I just hope this isn't one of those material uses that are relegated to MTB infamy and puts me in the hospital.... or worse.

    P.S. The CS regarding this matter was excellent and I was taken care of in a very timely manner.

    Regards,

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  6. #6
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    I have a pre-production ML 2. It has the hydro-formed chain stays and carbon rocker, but still has the aluminum seat stays. Out of curiosity I emailed titus to see what the weight difference on the aluminum vs carbon stays is. They said that most of the weight savings on the ML 2 is actually from the hydro-formed chain stays. The carbon seat stays only make up about 55 grams of the difference.

  7. #7
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    I have just orderes an ML2 . Should I have gone for the alu version instead???? I might have time to change my order.

  8. #8
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    Quote Originally Posted by dareverend
    I have just orderes an ML2 . Should I have gone for the alu version instead???? I might have time to change my order.
    no dood

    take your CF one's off

    all take my Alu ones off my bike

    we will swap them over and I will be happy

    i have broke 3 Alu seat or chainstays on 3 different bikes

    Alu rares and their supposed durability are not all their cracked up to be

  9. #9
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    Quote Originally Posted by dareverend
    I have just orderes an ML2 . Should I have gone for the alu version instead???? I might have time to change my order.
    I agree with AM, stick with the ML2 ... Put me next priority if you want to swap... next to AM of course

  10. #10
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    thanks fellas.got a bit twitchy when i started reading this thread. can now sleep tonight.

  11. #11
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    Sleep easy, I wanted one when I was at Titus last week, none in stock....

    Sheesh, What about the Scott Ransom Ltd, that is all carbon, no readings on that shiating its pants.....
    The_Lecht_Rocks: whafe - cheeers - may i offer an official apology for the wagon wheeler "dis-belief"

  12. #12
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    Quote Originally Posted by Whafe
    Sheesh, What about the Scott Ransom Ltd, that is all carbon, no readings on that shiating its pants.....
    You mean that bike that breaks at the downtube by the BB and uses a leverage ratio of like 4:1???

    No, thank you, sir...
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  13. #13
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    Quote Originally Posted by Warp
    You mean that bike that breaks at the downtube by the BB and uses a leverage ratio of like 4:1???

    No, thank you, sir...
    The_Lecht_Rocks: whafe - cheeers - may i offer an official apology for the wagon wheeler "dis-belief"

  14. #14
    thats right living legend
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    Quote Originally Posted by Whafe
    Yeah Whafe you "somehow" picked the exact WRONG bike to hold up as an example of of carbon fiber depenabiliity.

  15. #15
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    You forget that Titus (and other manufacturers) have been making bikes for quite a while, and they are experts at the process. The image that CF is a weak material is false in so many ways. I bet it would take a hard pounding for those things to break...

    Leave the design and structural integrity problems to Titus...just enjoy what you have!

  16. #16
    the 36 year old grom
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    ".....Composites are weakest in compression--exactly what the major stresses are on a seatstay...."

    so I wonder what RC says about carbon seat posts. the loading on a seat post is also mostly compression....

  17. #17
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    Quote Originally Posted by demo_slug
    so I wonder what RC says about carbon seat posts. the loading on a seat post is also mostly compression....
    ... only on one side...


    Oddly enough, many hardtails and road bikes have carbon seatstays.
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  18. #18
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    Makes me laugh, when it seems that many think that no companies do any research. Sheesh, when I am on my road bike, which is all carbon at 80kmh downhill, I am not thinking about R Cunningham's comments re carbon being weak as piss etc.... Man alive, the world is full of balloon prickers...

    Go the carbon..................Each to there own though...
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  19. #19
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    Quote Originally Posted by Warp
    Oddly enough, many hardtails and road bikes have carbon seatstays.
    Isn't this done to improve ride quality? Carbon fiber can absorb high frequency vibration very effectively so making the fork and seatstays out of carbon fiber prevents some of this vibration from being transfered to the rider.

    Quote Originally Posted by RC
    Composites are weakest in compression--exactly what the major stresses are on a seatstay. A paper-thin aluminum stay would do a better job and for less money.
    True, single ply carbon fiber is weaker in compression due to microbuckling of the fibers. I would still have to see some cyclic testing results to believe a multi-ply carbon seatstay is weaker than an aluminum seatstay of equivalent weight.

  20. #20
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    Quote Originally Posted by Blofeld


    True, single ply carbon fiber is weaker in compression due to microbuckling of the fibers. I would still have to see some cyclic testing results to believe a multi-ply carbon seat stay is weaker than an aluminum seatstay of equivalent weight.

    It is my belief that carbon is indeed stronger than al pound for pound, but isn't the concern more directed towards scratches and nics compromising the integrity of the entire stay in regards to CF.

  21. #21
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    Quote Originally Posted by Blofeld
    Isn't this done to improve ride quality? Carbon fiber can absorb high frequency vibration very effectively so making the fork and seatstays out of carbon fiber prevents some of this vibration from being transfered to the rider.
    Yeah, bro... That was my point. In a HT, the seatstay has to suck up the hits, big or small. On a FS, it "only" pushes the shock.



    Quote Originally Posted by Blofeld
    True, single ply carbon fiber is weaker in compression due to microbuckling of the fibers. I would still have to see some cyclic testing results to believe a multi-ply carbon seatstay is weaker than an aluminum seatstay of equivalent weight.
    Yeah, carbon is much like wood in the sense that it depends how the fibers are laid to provide certain stress characteristics.

    RC may have a point in the sense that weight savings are not huge and that Al is cheaper... but I agree the most with Whafe, to each their own.

    As for me, I worry about impacts. I recently managed to bust a brake lever. Totally my fault. Certainly, there are materials that are not made for cavemen like me. It's something I don't want to worry about.
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  22. #22
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    Quote Originally Posted by Blofeld
    Isn't this done to improve ride quality? Carbon fiber can absorb high frequency vibration very effectively so making the fork and seatstays out of carbon fiber prevents some of this vibration from being transfered to the rider.
    I am of the strong opinion that it's done primarily for marketing purposes, not for ride tuning. Using a traditional 32-spoke wheel instead of a 24-spoke deep rim design will yield a smoother ride than slapping CF seat stays on an aluminum/steel/titanium road frame.

    As to the dis/advantages of using CF on the ML, time will tell.
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  23. #23
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    Quote Originally Posted by blackagness
    It is my belief that carbon is indeed stronger than al pound for pound, but isn't the concern more directed towards scratches and nics compromising the integrity of the entire stay in regards to CF.
    I think this is the legitimate concern with carbon fiber parts, even if in some circumstances having several distinct layers and fibers will prevent a crack from growing. I guess I didn't read that into RC's reply in the OP.

    Quote Originally Posted by Warp
    Yeah, bro... That was my point. In a HT, the seatstay has to suck up the hits, big or small. On a FS, it "only" pushes the shock.
    Quote Originally Posted by pinkrobe
    Using a traditional 32-spoke wheel instead of a 24-spoke deep rim design will yield a smoother ride than slapping CF seat stays on an aluminum/steel/titanium road frame.
    How much of the spectrum do you think overlaps between the shock, wheels/tires and seatstays in terms of frequencies absorbed?

  24. #24
    the 36 year old grom
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    Quote Originally Posted by pinkrobe
    I am of the strong opinion that it's done primarily for marketing purposes, not for ride tuning. Using a traditional 32-spoke wheel instead of a 24-spoke deep rim design will yield a smoother ride than slapping CF seat stays on an aluminum/steel/titanium road frame.

    As to the dis/advantages of using CF on the ML, time will tell.
    Time will tell. Nice thing about MTBR is that us consumers get to see/ hear about how all these things break.

    the weak link on the ML has been the aluminum chain stay. they break at the welds.... people been breaking titus seat stays for a long long time, its not just the MotoLite BTW.

    IMHO the whole material argument is silly because this stuff almost always break at a joint. at a weld or a bond. so let the most fatigue resistant joint win!!!

    and firmly disagree that the ML seat stay is "marketing". I have high hopes that they will make the ML stronger and longer lasting.

  25. #25
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    Quote Originally Posted by pinkrobe
    As to the dis/advantages of using CF on the ML, time will tell.
    Here here, pinkrobe has it totally correct here.....Time will tell!

    I am not having any issues with the carbon moulded into my Ti downtube though.
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  26. #26
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    What many people don't realize is how incredibly hard the resin is that they use to set the fiber cloth, which is subsequently baked and made even harder. The resin becomes VERY abrasion resistant. This doesn't mean that any impact won't cause damage, as you only need significant force and a couple other factors to do it. I am less concerned about the compression in stays, but more concerned about the lateral flexing and abrasion. Yeti has made a carbon layered stay inside a tube, which seems to be a good compromise. Otherwise, exposed carbon, no matter how hard the resin is, should not be used. Direct impacts aside, abrasions over its life are a real prospect and again, the resin is extremely hard, but not 100% impervious to all abrasions.

  27. #27
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    I'm with ya... sort of...

    Quote Originally Posted by Jerk_Chicken
    Otherwise, exposed carbon, no matter how hard the resin is, should not be used. Direct impacts aside, abrasions over its life are a real prospect and again, the resin is extremely hard, but not 100% impervious to all abrasions.
    My heart agrees with The Jerk's philosophy here, but my head is more objective. Only until a good statistical population of CF stays are in use and on the trails will we really know both the good and the bad. Now, I've seen on mtbr CF stays fail at the bond, but I'm totally unaware of a failure due to an external abrasion.

    This does beg the question: How much damage can CF seat-stay sustain before it fails?

    EDIT: I went to the Ibis board to snoop around and I didn't find posts regarding broken CF stays or frames for that matter. However, there is a certain level of concern about abrasions.

    Regards,

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  28. #28
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    IMO carbon on any part of a MTB frame is not good unless you are building a superlight racebike, and even then beware of it's limitations. due to the brittleness of the material it just doesn't make any sense

  29. #29
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    Quote Originally Posted by salimoneus
    IMO carbon on any part of a MTB frame is not good unless you are building a superlight racebike, and even then beware of it's limitations. due to the brittleness of the material it just doesn't make any sense
    OT, Hi Sal... Hows it goin? have not heard from you here in the forum lately....

  30. #30
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    given similar force (alu vs ca; at same weight), alu would break first.
    However, carbon breaks with no warning / sign.
    Thus, if made right, it is the one to get.

    2 weeks ago Robert Kubica of BMW F1 team crashed in Gilles Villeneuve circuit in Canada. The car spun several times in the air. Yet the cockpit, made of carbon composite, was untouched.
    2 (?) years ago, Ralf Schumacher had ugly crash in Indianapolis, at the oval section. All crushed, but the cockpit was, again, left untouched.

    Imagine if they were made of Aluminum..

  31. #31
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    If I was a bicycle company then I would love to make as many products as possible in my line out of CF,you just can`t beat that kind of profit with things that are that sensitive to damage (while somehow still being promoted and perceived as strong) like scratches.But because I`m a consumer (and not one who embraces disposable culture),I will avoid using CF for MTB.Look at ANY bicycle that is used regularly after a year,you will not find one without scratches or some kind of impact on the frame.
    For the F1 example that was mentioned earlier,yes the cages in the race cars are strong but all they have to work is once.Will you throw your bike or part out after every crash and buy a new one?
    Last edited by yoginasser; 06-20-2007 at 02:11 AM.
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  32. #32
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    I don't think there is anything structurally wrong with the carbon seatstay and it does save weight. So as usually, the "expert" RC has no idea what he's talking about. However, I don't think the carbon stay is worth the $400 upcharge for the MLII over the previous model.
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  33. #33
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    corrosion

    I'm on the side that believes that the geomtery and design of the CF stays can be manipulated to make CF work without issue of breakage under ideal conditions.

    However, my biggest concern about the trend of fusing and mating Carbon Fiber with Aluminum is galvanic corrosion between the two materials. Carbon Fiber and Aluminum are very dissimilar on the galvanic scale. Basically, the farther away two joined materials are on this scale, the more corrosive the interface. After time and exposure to sweat (or salt water) CF will eat away at Aluminum and I can't believe that Titus, or anyone else, would consider the weakened condition caused by corrosion during the design of the materials/interface to provide sufficient strength in the worst case.

    So far I've found two cases of galvanic corrosion between Al and CF on bikes - and I haven't been actively searching:

    1) I found corrosion occuring between my CF seatpost and my RX Alumium frame after six months of not being removed. If you see a white powder that is the evidence of corrosion. I was also suspicious when I tried to adjust the seat post but it wouldn't move after I loosened the collar. I had to hit the nose of the seat hard to break it loose. I take responsibility for neglecting to maintain the interface in this case but my point is that there was corrosion occuring.

    2) I recently looked at buying a lightly used 2006 model road bike that had fused CF with Aluminum (giving full benefit of the doubt to the manufacturer who I thought was probably ahead of me on this issue). Sure enough I could see there were signs of corrosion at the mating points even with the clear coat of paint. Luckily, I got to see this bike in person before deciding whether or not to buy it. I couldn't imagine a mating joint failure while riding!

    From my limited knowledge from engineering metallurgy 101 class, seeing this in action on my bike, and almost purchasing a bike with this issue thats enough evidence for me to completely avoid any frame that fuses or mates CF to Al in any way. I also got rid of my CF seatpost. For me, I'll stick with Al on Al and suffer the weight or stiffness penalty.

    As a side note, I recall Ti and CF are similar on the galvanic scale so the likehood of these issues occuring on something like exogrid is probably small. I'll need to dust of my metallurgy text book for more info...

    fro

  34. #34
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    Wow

    Thank you Jeffro,good stuff.
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  35. #35
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    Quote Originally Posted by yoginasser
    Thank you Jeffro,good stuff.
    I've been doubting my concerns for a couple of years now but after seeing it first-hand I'm a believer.. I guess time will tell if this is an issue on the stays. Thankfully, I have a 2004 with Al stays - no problems.

  36. #36
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    Quote Originally Posted by yoginasser
    If I was a bicycle company then I would love to make as many products as possible in my line out of CF,you just can`t beat that kind of profit with things that are that sensitive to damage (while somehow still being promoted and perceived as strong) like scratches.But because I`m a consumer (and not one who embraces disposable culture),I will avoid using CF for MTB.Look at ANY bicycle that is used regularly after a year,you will not find one without scratches or some kind of impact on the frame.
    For the F1 example that was mentioned earlier,yes the cages in the race cars are strong but all they have to work is once.Will you throw your bike or part out after every crash and buy a new one?
    for the CF ~ Bike company analogy. I would add that, not only CF rings "higher price" (so a company can charge more as well), but also that CF is "in momentum" (CF insert, CF seatstays, CF rocker arm, etc). A company do not want to lose momentum of gaining more profit & market share.

    As for the scratches thing: warranty obviously does not apply for mis-application. Yet, if the scratches causing the "thing" to fail, then logically it should be honored by the warranty. What I was trying to say: given similar force to similarly weighted CF & Al, CF can take it better than Al. If the product made of CF fails, then the Al version will most certainly fail earlier, provided that both has correct construction (and not just weight saving in mind). Thus, in the case of CF part surviving accident & re-using it, then my take is: if it was made of Al, it would be badly dented & not usable, either. Just my opinion

    As for F1: Crashing the car at hundreds mph, I dont think re-using such cockpit is wise.

    To sum it up: it all depends on cost, and ongoing technology.

    Nice sharing session

  37. #37
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    Quote Originally Posted by paneristi
    given similar force (alu vs ca; at same weight), alu would break first.
    However, carbon breaks with no warning / sign.
    Thus, if made right, it is the one to get.

    2 weeks ago Robert Kubica of BMW F1 team crashed in Gilles Villeneuve circuit in Canada. The car spun several times in the air. Yet the cockpit, made of carbon composite, was untouched.
    2 (?) years ago, Ralf Schumacher had ugly crash in Indianapolis, at the oval section. All crushed, but the cockpit was, again, left untouched.

    Imagine if they were made of Aluminum..
    For those that didn't see it, HERE it is. He was going about 275kph / 170mph when he hit that wall. Realesed from the hospital the next day with a broken leg. Amazing.

  38. #38
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    on the bright side(providing a nasty accident is avoided). brocken stays mean a possible upgrade.... the wife can't argue with damaged equipment.

  39. #39
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    Quote Originally Posted by jeffro
    I'm on the side that believes that the geomtery and design of the CF stays can be manipulated to make CF work without issue of breakage under ideal conditions.

    However, my biggest concern about the trend of fusing and mating Carbon Fiber with Aluminum is galvanic corrosion between the two materials. Carbon Fiber and Aluminum are very dissimilar on the galvanic scale. Basically, the farther away two joined materials are on this scale, the more corrosive the interface. After time and exposure to sweat (or salt water) CF will eat away at Aluminum and I can't believe that Titus, or anyone else, would consider the weakened condition caused by corrosion during the design of the materials/interface to provide sufficient strength in the worst case.

    So far I've found two cases of galvanic corrosion between Al and CF on bikes - and I haven't been actively searching:

    1) I found corrosion occuring between my CF seatpost and my RX Alumium frame after six months of not being removed. If you see a white powder that is the evidence of corrosion. I was also suspicious when I tried to adjust the seat post but it wouldn't move after I loosened the collar. I had to hit the nose of the seat hard to break it loose. I take responsibility for neglecting to maintain the interface in this case but my point is that there was corrosion occuring.

    2) I recently looked at buying a lightly used 2006 model road bike that had fused CF with Aluminum (giving full benefit of the doubt to the manufacturer who I thought was probably ahead of me on this issue). Sure enough I could see there were signs of corrosion at the mating points even with the clear coat of paint. Luckily, I got to see this bike in person before deciding whether or not to buy it. I couldn't imagine a mating joint failure while riding!

    From my limited knowledge from engineering metallurgy 101 class, seeing this in action on my bike, and almost purchasing a bike with this issue thats enough evidence for me to completely avoid any frame that fuses or mates CF to Al in any way. I also got rid of my CF seatpost. For me, I'll stick with Al on Al and suffer the weight or stiffness penalty.

    As a side note, I recall Ti and CF are similar on the galvanic scale so the likehood of these issues occuring on something like exogrid is probably small. I'll need to dust of my metallurgy text book for more info...

    fro
    Good stuff, bro!!

    Somewhere I read this about galvanic corrosion on Al-CF joints and some (most??) manufacturers use a layer of fiberglass on top of CF at the joints to prevent this.

    As consumers get more and more informed, it would be a good marketing point, so to speak... as long as this is true.

    Same as we do on field with dissimilar galvanic materials, put an insulator in the middle. For example when using plain carbon steel bolts on stainless joints. You put insulators in.



    On kubica's crash... he didn't even had a broken leg. It was just a strained ankle. Amazing. I didn't watch the race, but when I saw the accident's clip, I got chills.... Some drivers have died for less than that. Schumacher's crash when he broke a leg was much less serious.
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  40. #40
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    Quote Originally Posted by Warp
    Good stuff, bro!!

    Somewhere I read this about galvanic corrosion on Al-CF joints and some (most??) manufacturers use a layer of fiberglass on top of CF at the joints to prevent this.

    As consumers get more and more informed, it would be a good marketing point, so to speak... as long as this is true.

    Same as we do on field with dissimilar galvanic materials, put an insulator in the middle. For example when using plain carbon steel bolts on stainless joints. You put insulators in.



    On kubica's crash... he didn't even had a broken leg. It was just a strained ankle. Amazing. I didn't watch the race, but when I saw the accident's clip, I got chills.... Some drivers have died for less than that. Schumacher's crash when he broke a leg was much less serious.
    I know that's true - that you can mitigate the corrosive effects of dissimilar materials using a third material in between two dissimilar materials but to my knowledge this isn't used in Titus's stays (I took a tour of Titus a couple of years ago when they started this cf stay thing and asked that question - without much of a response). Maybe they have changed the design?? I dont' know
    A third material definitely didn't appear to be used in the cannondale road bike I looked at either. If it was being used it was completely ineffective.

    So, that's scary for me that the bike companies either don't know much about galvanic corrosion or they simply choose not to prevent the issue with a design countermeasure.

    By the way, I sat amongst a large crowd of very dissapointed Polish people at Indianapolis on Sunday. I tried not to show too much excitement that Hamilton won for fear of being beaten with flagpoles..Thankfully, Kubica is alright.

  41. #41
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    Quote Originally Posted by jeffro
    I know that's true - that you can mitigate the corrosive effects of dissimilar materials using a third material in between two dissimilar materials but to my knowledge this isn't used in Titus's stays (I took a tour of Titus a couple of years ago when they started this cf stay thing and asked that question - without much of a response). Maybe they have changed the design?? I dont' know
    A third material definitely didn't appear to be used in the cannondale road bike I looked at either. If it was being used it was completely ineffective.

    So, that's scary for me that the bike companies either don't know much about galvanic corrosion or they simply choose not to prevent the issue with a design countermeasure.

    By the way, I sat amongst a large crowd of very dissapointed Polish people at Indianapolis on Sunday. I tried not to show too much excitement that Hamilton won for fear of being beaten with flagpoles..Thankfully, Kubica is alright.
    Either the bonding or the resin used can have these corrosion protection characteristics, but either they don't know about it or they don't use it. I don't know. So I will not argue if they use it or not. You seem to have a much clearer idea.

    Yeah, thankfully Kubica's OK and hamilton goes ahead of a*hole Alonso... As long as it's Hamilton, the Maccas can be ahead of Ferrari, no problem. Tifosi here.
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    Umm, hasn't the racer-x been using carbon seatstays for quite awhile now with no reported breakages other than maybe a joint or two coming unglued. So, if this is the case why all the concern about the stays on the motolite? I think Titus knows what they're doing, and for that matter, Yeti as well. Why would a bike company intentionally put a rider at risk? That doesn't make sense. I think they saw the success of the stays on the racer-x and the breakage of the aluminum ones on the motolite and after testing came to the conclusion that the carbon ones would last longer even in the event of crashing in rocks. Titus is in Arizona after all.
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    Quote Originally Posted by Warp
    Either the bonding or the resin used can have these corrosion protection characteristics, but either they don't know about it or they don't use it. I don't know. So I will not argue if they use it or not. You seem to have a much clearer idea.

    Yeah, thankfully Kubica's OK and hamilton goes ahead of a*hole Alonso... As long as it's Hamilton, the Maccas can be ahead of Ferrari, no problem. Tifosi here.
    I'd like to add that maybe its unfair for me to come here and say that Titus doesn't consider corrosion in its design. I'm basing these comments on the blank looks I got when I asked the people at Titus a couple of years ago how they deal with corrosion there. that's all I'm going on here, nothing more.

    I am really shocked to have found that issue on a Cannondale bike. They sell a lot more bikes than Titus so I would think they would have their $hit together and they do claim to be the leader in "testing". but I guess this isn't something you'd necessarily learn on a shaker.
    Last edited by jeffro; 06-20-2007 at 10:47 AM.

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    This isn't a press fit is it?

    Quote Originally Posted by jeffro
    I'd like to add that maybe its unfair for me to come here and say that Titus doesn't consider corrosion in its design. I'm basing these comments on the blank looks I got when I asked the people at Titus a couple of years ago how they deal with corrosion there. that's all I'm going on here, nothing more.

    I am really shocked to have found that issue on a Cannondale bike. They sell a lot more bikes than Titus so I would think they would have their $hit together and they do claim to be the leader in "testing". but I guess this isn't something you'd necessarily learn on a shaker.

    I'd assume that whatever glue they use would be considered the "third material" in terms of galvanic corrosion.

    Dave

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    Consulted with a friend who makes exotic car frames from tubes and carbon fiber construction. He said there is no galvanic corrosion to be considered, nor has he ever seen any. The resin is the barrier, with the gloss coat being in between. For less flashy carbon fiber, they lose the gloss coat and they are working towards less and less resin, but the gloss adds impact resistance. There is still no galvanic corrosion to be considered, nor has he seen himself or heard of this in his years of building ($300k supercar).

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    Quote Originally Posted by Jerk_Chicken
    Consulted with a friend who makes exotic car frames from tubes and carbon fiber construction. He said there is no galvanic corrosion to be considered, nor has he ever seen any. The resin is the barrier, with the gloss coat being in between. For less flashy carbon fiber, they lose the gloss coat and they are working towards less and less resin, but the gloss adds impact resistance. There is still no galvanic corrosion to be considered, nor has he seen himself or heard of this in his years of building ($300k supercar).
    I did a general search and I found this link from calfee designs:

    http://www.calfeedesign.com/pdf/Calfee_TWP.pdf

    Calfee talks about galvanic corrosion as an issue when mating Al/CF on bike frames (page 10 on the link). Calfee also mentions a couple of other issues related to mating CF/Al (difference in Al/Cf thermal expansion properties, inadequate bonding).This document confirms my feeling that Cf/Al don't play well with eachother (but Cf/Ti do).

    I think it's really hard to compare frames on sports cars to those of bikes due to the different stresses and loads placed on them. I personally don't feel confident having an increased possibility of corrosion due to the above reasons, possibly affecting the integrity of frame in a high stress area with almost no way to visually detect it. From my experience and basic textbook knowledge of corrosion I'll pass on anything that mates Cf/Al and leave that for the gram saving people.

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    Quote Originally Posted by jeffro
    I did a general search and I found this link from calfee designs:

    http://www.calfeedesign.com/pdf/Calfee_TWP.pdf

    .
    1994 (up dated in 2002)? maybe bonding technology has changed in the last decade?

    anyway... lots of neat phyics stuff...

    I would take the calfee white paper with a grain of salt...the calfee paper seams to be aimed at why his frame is better to the lugged carbon road bikes of the day.

    Which is interesting as a side note, titus has the moderna which is a lugged carbon bike. so maybe titus/vaytek have no idea how to play with carbon. or maybe they do know something about carbon.

    seems there is some alu on carbon action on roady forks too...


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    Odd I was always under the impression that for the galvanic action you needed some type of
    electrolyte between the metals (usually what is involved) for the ions to pass through. Thus always greasing the al seatpost on steel frames (well any frame really), which is
    the usual place that this is seen (or at least a stuck seatpost is all that I have seen personally)

    I would think that the resin and bonding agents would be enough to stop this.
    In the case of a seatpost you would think that the grease or carbon paste would be enough to stop this.

    In the al-carbon junction which is the anode and which is the cathode (what is being eaten away)?

    going to have to do a bit of searching this evening....

    Not that this reallt effects me as I have no carbon on my motolite.....

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    I looked at Titus website and I couldn't find a Cf/Al lugged roadbike in the bunch.. it seems they don't sell the Modena any longer. titus only offers lugged Cf/Ti road bikes now. maybe this is related or simply a coincidence. I don't know

    Maybe Titus/Vyatec does know something about Cf bonding but I really didn't get that feeling when I asked them about corrosion at the joints. They were able to explain ad nauseum about the suspension behavior, fit, fork compatibility.. but didn't have any answer about their material compatibility. Incidentally, I also looked at their prototype Modena on that same visit which also raised the question.

  50. #50
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    Quote Originally Posted by esilvassy
    Odd I was always under the impression that for the galvanic action you needed some type of
    electrolyte between the metals (usually what is involved) for the ions to pass through. Thus always greasing the al seatpost on steel frames (well any frame really), which is
    the usual place that this is seen (or at least a stuck seatpost is all that I have seen personally)

    I would think that the resin and bonding agents would be enough to stop this.
    In the case of a seatpost you would think that the grease or carbon paste would be enough to stop this.

    In the al-carbon junction which is the anode and which is the cathode (what is being eaten away)?

    going to have to do a bit of searching this evening....

    Not that this reallt effects me as I have no carbon on my motolite.....
    I'm guessing the magic is in the bond agent. but if this is broken somehow from cyclic fatigue or thermal cycling I think sweat or water both make for a really good electrolytes.

    Honestly, I don't recall everything about this. Its been a while since I took the class. I believe the material that is least noble would be corroded (anodic) and the most noble would be the corroder (cathodic). I'm pretty certain Al is close to being least noble and Cf would be almost the most noble - making for a bad fit.

    I need to get my book out when I get home. I hope I didn't sell it for post-exam beer money

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