Buncha Carbon Fiber Suckers.... - Page 4

Thats exactly what the bike shop owner said. Because most of the bikes will not be ridden hard most of them won't break. Trek will limit their expense by just replacing the ones ridden hard.

As for the carbon mountain bikes it seems like they have to overbuild the frames to such a degree (because of all of the random stresses in a dirt bike vs the more predictable stresses in a road bike) that the carbon mountain bikes really don't have the weight advantage that the carbon road bikes have. Carbon has the disadvantage of being weak in compression as compared to metal despite it's huge amount of strength in tension. Only stands to reason, it's made of fibers. Because of that it has to be overbuilt for compression loads which are abundant in off road bike.

It's fun getting everyone riled up.

I really like those airborne bikes. Very well executed and great looking.

Are you doing hill climbs? What does your Orca weigh?

You may get one replacement frame out of Trek, but they are under no obligation to replace frames which fail due to normal wear and tear, or fatigue damage, or abuse. The local dealer told me they are pretty liberal with a casual rider, but aren't in business to supply free frames for life to racers.

As you know, any lightweight frame will fatigue and break if ridden long enough and hard enough...which shouldn't be tough on a MTB. In addition to the usual lifetime warranty on defects, the local custom builder offers a 1 year fatigue warranty on full-suspension MTB, and a 2 year warranty on the others, whether built of AL, AL/CF, full CF, or steel. His road bikes come with a 3 or 5 year fatigue warranty, depending on materials and tubeset weights.

To give you an idea of the difference between alum and titanium, Litespeed offers a 3 year warranty on their aluminum bikes and a lifetime warranty on their titanium bikes.

Here is what I don't understand if you've ever flown on a commercial airliner and looked at the wings they flex a lot and the entire wing structure, skin, spars everything is aluminum. How can an airplane be made of aluminum and last for decades flexing like crazy but an aluminum bike can't?

Is it just that they overbuild the airplane to such a degree and underbuild the bikes (for weight)? Or do the major structural components of the airframes (spars) get replaced?

There is a lot of titanium in airplane but it's mostly limited to high speed rotational parts in the engines. Carbon fiber is taking over a larger and larger role in the airframe structure and the fan assembly of the new 777 engine. Carbon fiber blades (I think they have a titanium leading edge)

Airplanes are inspected daily for cracks, and parts do get replaced. There's nothing inherently better about titanium, and it's not the answer to everything (square taper bb spindles anyone?). A material is only as strong as its application. You can build a weak frame out of titanium just as easily as you can build a bomber one out of carbon. Perhaps easier. The fact is that you and your friends bought the wrong bikes for the riding that you do, and you're looking to hold everyone accountable but yourselves. Get over it.

Do some reading on materials. Like anything in engineering each choice is a balance of tradeoffs. The fundamental advanatage that both steel and titanium have over aluminum is fatigue resistance. So as long as steel and titanium flex is kept within the design parameters of the metal they will last forever. Thats why you will never see an aluminum spring. A perfect example of this is a valvespring inside of a combustion engine. A car with 100,000 miles on it will have compressed and released each valve spring hundreds of millions of times. Steel and titanium can do that. Aluminum and carbon fiber can't. Titanium has the advantage over steel of being both less dense and pound for pound stronger. Titanium also has the advantage of being corrision resistant. The cost of titanum is the cost, it's expensive and it's difficult to work with. Both machining and welding titanium are difficult. Where a trained monkey can weld steel.

Carbon fiber has an exceptional strength to weight ratio in tension exceeding that of all the metals. However it's very weak in compression and it doesn't stand up to harsh environmental conditions very well and unlike titanium and to a lesser degree steel, carbon breaks it doesn't bend and spring back. This is why the carbon fiber mountain bikes don't have a weight advantage over their metal counterparts. Unlike road bikes where the loads are fairly predictable mountain bike loads are fairly random. To overcome the disadvantages of carbon fiber (compression loads) carbon mountain bike frames have to be overbuilt to such a degree that it negates the inherent weight advantage of the material.

As far as picking the wrong bikes? We bought Fisher XC race bikes and raced them in XC races... Let me know what we did wrong... I will admit that the replacement bikes have mostly held up. Only 20% or so of the replacement bikes have failed. The owners of the 2nd set of broken bikes bought Titus bikes and haven't had any problems since. But Titus is a small company of craftsmen that handbuild their products. Trek is a giant that stamps out bikes as quickly as possible.

It's nice to know that the 100% failure rate that you insisted on earlier has improved. By the way, I have a whole shelf of materials books here. Which one do you recomend I start with?

I recommend that you take them off the shelf and read one they aren't doing you any good sitting on the shelf.

I don't know. It's an awfully boring wall back there.

This is a gross oversimplification. In order for fatigue to occur in ANY material, there has to be an initial small crack - usually so minute it can't be detected with the naked eye. The initial crack can be caused by a grain irregularity, an impurity, a change in cross section, or microscopic damage from machining, welding, or trauma. Again, this is for ANY material.

So steel and titanium have a fatigue strength as a material property and aluminum doesn't, but a STRUCTURE made out of steel or ti can and will fatigue under any number of scenarios.

The real reason steel bikes were the norm for so many years had more to do with ease of assembly and availability, not material properties. The real reason steel still has a following today is mostly tradition. Most of the people I know who like titanium are steel converts who want lighter weight.

The same goes for the brittle/ductile failure theory. A bar of titanium pulled in tension will elongate quite a bit (some alloys up to 2000%!), but a contaminated weld will fracture without warning.

[QUOTE=IronDonut]To give you an idea of the difference between alum and titanium, Litespeed offers a 3 year warranty on their aluminum bikes and a lifetime warranty on their titanium bikes.

Here is what I don't understand if you've ever flown on a commercial airliner and looked at the wings they flex a lot and the entire wing structure, skin, spars everything is aluminum. How can an airplane be made of aluminum and last for decades flexing like crazy but an aluminum bike can't? [QUOTE=IronDonut]

Have you read the Litespeed warranties? As I said above, the Litespeed Ti "lifetime" warranty (like most major brands) is for defects in materials and workmanship only. It specifically excludes "normal wear and tear".

Of course, for what Litespeed charges for a Ti frame, they can probably afford to eat the cost of a fatigue failure every now and then. It's certainly in their interest to keep up the myth that Ti is a fatigue-proof frame.

Commercial aircraft are made of aluminum because aluminum is the best material for building a light, strong and fatigue-resistant structure at a reasonable cost. Properly designed and built aluminum bikes can last for decades as well. Again, the problem gets back to marketing of thin-wall, ultralight equipment to people like you who need something heavy-duty.

I have had three trek/GF frames break. Just beacause you havent heard ofanyone getting hurt doesnt mean the frames arent breaking. All of my frames have cracked near the BB shell. They were still rideable but they were broken. I guess I just have to much power. Maybe I should be on Discovery getting paid to break Treks piece of crap frames.

most ppl dont know but lance dont ride an "off the shelf" frame, the teams bikes are modified alot. esp in the bottom bracket area.

Ti?
So far evryone in our 200+ member club that has owned a Ti frame has had them crack.
CF and Ti are both over rated.
Read the warning about installing CF products.
Not many suggestions for torque settings huh?