Everthings coming up carbon...

Check out what Mountain Bike Action's Richard Cunningham has to say about the current trend of adding bits of carbon to frames...

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
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."

R.C. You did get the answer partialy right in regards to no weight savings in you answer to if there is any advantage to carbon seat stays. BUT, your comment about composites being weakest in compression is so far off the truth it is not even funny. If composites were weak in compression as you state they would not be used in race car suspension, race car chassis, wheels, powerboats, sail boats including masts of up to 50 meters in length that withstand tons and tons of compression, let alone bicycle frames wheels and components of which most all work primarily in compression. If you don't know the answer, do a little research first before writing

RC: Blah blah blah carbon, blah blah blah carbon. Yeah, I follow most forms of racing and am up on the strength of carbon composites. Race car suspension and racing sailboat masts are probably not the best examples, however, considering they are usually the causes of the carbon fiber yard sales that quite regularly occur in both sports. It is no secret that carbon composite structures can be optomized for compression--but there are places where metal is more cost effective and a better choice. Carbon fiber dropouts, for instance, are popular weight savers for road bike frames, but are easily broken and do not interface well with existing quick releases--repeated compression breaks down the resin matrix. Still, the answer to the seatstay question remains the same--not because of the properties of the most holy carbon fiber in compression--but because the bonded-in aluminum plugs that attach the brake caliper mounts, seat stay arches, pivot locations and such, eat up any weight savings that the maker might have achieved by substituting a cool-looking carbon tube instead of welding the bits together using a thin aluminum tube and eliminating the overlapping bond interfaces. I aplogize for oversimplifying, but it is a necessary evil in Ask R.C.

HEEEEYYYYY, Interestingamundo! So what do YOU think?