Originally Posted by
SlimRider
The information that I have submitted to the OP is quite pertinent. Any extra weight added to the aluminum frame, whether the cyclist tends to be overweight himself, or not, is going to add additional stress to the aluminum frame. Aluminum bicycle frames can be designed to endure many cycles of stress. Aluminum has both a smaller fatigue strength and yield capacity, than steel. The number of stress cycles for aluminum is indeed a finite number. This is
NOT the case with steel.
For example:
Imagine drinking from a pristine pool of water that's pressure sensitive and in balance with the atmospheric pressure of the cold reservoir supplying it. Everytime you scoop a cup of water from the pristine pool, the reservoir replenishes the pool, restoring the pool to its original volume. That's steel.
Now imagine a pool which is only supplied with an air filter and a cooler. When you scoop up a cup of water, you've just depleted your water supply with no promise of restoring your water to its original volume. The only question here is the following:
What was my original volume of potable water?....That's aluminum!
-And that's the question with which all aluminum framed bicycle owners need to concern themselves...
The longer you use your aluminum framed bicycle and the more force(s) that you subject it to, the faster it reaches its fail date. If you cycle frequently upon an aluminum framed bicycle, then you're drinking larger volumes of water and thus, depleting your pool more rapidly. If you use your aluminum framed bicycle in DH MTB races, then you're depleting your pool much more rapidly.
So there's no
wrong information here. A 200 lb. rider will indeed subject his aluminum framed bicycle to more stress cycles than a 175 lb. rider. However, the question remains, how many stress cycles will the modern-day highly technologically designed aluminum framed bicycle endure?...Will it be millions or billions? ...Just how deep is that aluminum pool?
No matter how deep it is, the steel pool remains much deeper!
If you want to use a 'pool' analogy, the pool of steel framed mountain bikes is next to nonexistant for steel framed bikes from major manufacturers. Your (unfounded) concerns for aluminum frames will only serve to send Eugene_B on a quest for something that simply doesn't exist at his price point. Sure he could buy the Trek 820 with a very low component mix and a pogo stick for a shock or he could spring for a higher quality bike in his price range with a better component mix and a shock that could be locked out for road use. The 820
could be remade with better components but the cost would be about double of the Trek 6000, for example. And you'd still have a boat anchor of a frame.
I'll ask the same question I ask everytime this silliness comes up: If you are so concerned about the fragility of aluminum, do you ride with only steel parts? Aluminum handlebars should be a particular concern if you are worried about fatique cycles.
Eugene_B, I actually weigh more then you do. I
do throw my bikes down mountains on a regular basis and I ride aluminum bikes almost exclusively (my non aluminum bikes are titanium). I give not a second thought to how tough the frames of my aluminum bikes are. I have broken 2 aluminum frames but I've also broken two steel frames. Both steel frames were broken through use...and a little abuse...while only one of the aluminum frames was broken in the same manner. The other aluminum frame was broken because of stupidity on my part.