Question: I've started to hear creaking/clicking sounds from the saddle tube. **Is the frame giving up?**
I could look for [a longer saddle post](http://www.amazon.de/XXL-ALU-SATTELST%C3%9CTZE-%C3%9CBERL%C3%84NGE-50/dp/B003IB77WC/ref=sr_1_9?ie=UTF8&qid=1405670710&sr=8-9&keywords=fahrrad%20sattelstange), if that would relieve some of the strain on this part of the frame, but I'm not sure what length to get. 

I've measured the outer diameter of the post to be approx. 27mm -- but what is the proper name/size for this dimension?

It's a 58 (cm/in?) aluminum frame with 28" wheels, roughly 10 years old. I've got the saddle fairly high, but I'm a tall guy (192cm, 95kg) so it needs to be like this. When I put a heel on the lowest pedal, my leg is practically straight. Perhaps I should buy a bike with a bigger frame, if that exists, but I am hoping to avoid significant expenses. The bike is otherwise in good condition.

**Updates to comments:**

* Saddle post is 1cm lower than its "max" mark. Close, but okay - perhaps too close, given my weight? (95kg)
* frame and post is metal, presumably both aluminum.
* Creaking goes away when standing. That's why I suspect this area.
* Saddle clamp and rails seem good on visual inspection.

![enter image description here](https://i.stack.imgur.com/NbuHm.jpg)

Answer: 
Most probably, the seatpost just needs to be cleaned (dust gets in) AND/OR tightened a little bit. Don't overdo it, it's best to stay within the 5-6 Nm range so as not to bust your seatpost ring or seat tube. Greasing the seatpost might also help. I wouldn't recommend any actual grease for this (messy, tends to get the seatpost stuck after a year of riding), powdered graphite is more appropriate.
As a fellow tall guy, try temporarily lowering your seat by half and see if the creaking goes away. If yes, your seatpost is simply too high and unsupported, so buy a longer one. 350mm and 400mm are available now, not overly expensive.

Have a good close look at the frame for cracks too - I broke a frame by having the seat too high.