Are all bikes fragile?

[the_killjoy]

After the seat tube broke on the 905 I got a 400mm seat post so I wasn't using it at the maximum mark, IMO the short seat tube coupled with a 300mm seat post is a problem waiting to happen for anyone with a 32" inside leg or more. Unfortunately I guess they are all prone to work hardening and will go at some point, on that point would steel be any better? I ask as I want to get a seat post with more set back and this will put more strain on that area.

Mussles

As someone who also had a 905 with a broken seat tube and now has to ride with a very low saddle to make sure it doesn't happen again, what 400mm seat post did you get?

 

[mike killay]

I broke one of the cro-mo tubes on my saddle.
a. There were no springs in the saddle so all my weight went down on it over bumps.
b. My replacement saddle has springs and solid drawn steel rods not tubes.

 

[Mussels]

Yes I actually agree we you. I've had a fair bit of exposure to cheap chinese motorcycle parts, and in my limited experience it has always been the quality of the actual material that has been below par, aluminium that is more akin to cheese. Crankshafts that simply snap in two, gear teeth that snap off etc etc.

and yes with branded parts you can be paying a lot just for the name, finding quality parts without the B\S imagine is what you want. I wonder if any of the super strong track components will suit your bike? Guessing your bike is Aluminium? a steel bike would lesson the forces your breaking components experience I would think.

I have a steel frame Dawes road bike and like it, I wouldn't mind a steel framed ebike but I'd need to do a kit build for that (the on.one bike looks good for it). Maybe next time I want a new bike I'll go down that route.
I think it's wrong to think of all Chinese parts as substandard, many top quality products are made there. The more expensive ones tend to hide the fact they are made in China which doesn't help the reputation.

Mussles

As someone who also had a 905 with a broken seat tube and now has to ride with a very low saddle to make sure it doesn't happen again, what 400mm seat post did you get?

I got it in Cycle Surgery but can't find it on their website. This time I'm going to get one of these which at 350mm is still enough for me, the 906 had the same length seat tube so has the same problem with a 300mm post being a bit short.
Easton EA30 Seatpost 2010 | Buy Online | ChainReactionCycles.com
Edit: I won't be buying that as they are out of stock.
Edit2: I can't find exactly what I want within my budget (£35) so I've reserved one of these so I can at least use it and then look for the ideal one at leisure.
http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_250198_langId_-1_categoryId_230509

I broke one of the cro-mo tubes on my saddle.
a. There were no springs in the saddle so all my weight went down on it over bumps.
b. My replacement saddle has springs and solid drawn steel rods not tubes.

I get through a few saddles and it's usually the rails that break, the branded San Marco saddle I have now has bucked that trend as the saddle cover has split fairly quickly, at least I can fix that with Duck tape.

 

[the_killjoy]

The thing I like about the Wisper one though is it is sprung.

 

[eTim]

A Thorn Raven Nomad, unbreakable? Probably. Ripe for a conversion, now which kit??

 

[Deleted member 4366]

Durability of materials has very little to do with where they come from. It's more about the experience of the designers and manufacturers. Aluminium alloys work harden when subjected to frequent bending forces so they can faiil due to metal fatigue. If there's anything in the design that raises stresses in these areas - like welds, steps, holes - they can fail very quickly. Cromoloy steel is strong and light, but, when welded, can also suffer from fatigue in the heat affected zone and ideally should be annealed after welding. Manufacturers that have been in the game a long time have learnt, often by experience, how to avoid these problems. New players often start by trying to copy them without understanding the critical points of design or process controls. As an example, a difference in how sharp a corner is (from 0.2mm to 0.1mm) on a crankshaft can mean the difference between early failure and long life. Cheap chinese mild steel is unlikely to break because mild steel doesn't suffer from fatigue or embrittlement around the welds, but it could bend if overloaded. Every failure happens for a reason. When you but expensive stuff, sometimes you are paying for the experience behind them, but sometimes you're getting ripped off. No way of knowing. Any change in employees, sources, materials brings new risks. For us, we pay our money and enter the lottery.
Finally, buying a bike with a steel frame doesn't solve OP's problem when it still has the same light alloy seat pin. High end mountain bikes tend to have much larger diameter seat pins for strength and life, which are still light alloy. A cheapo mild steel one is unlikely to break, but it's heavy. Life's full of dilemmas!

 

[cwah]

+1 for d8v3h.

When you buy have a steel frame, you can extend the rear dropout to add your favorite motor

 

[Mussels]

Durability of materials has very little to do with where they come from. It's more about the experience of the designers and manufacturers. Aluminium alloys work harden when subjected to frequent bending forces so they can faiil due to metal fatigue. If there's anything in the design that raises stresses in these areas - like welds, steps, holes - they can fail very quickly. Cromoloy steel is strong and light, but, when welded, can also suffer from fatigue in the heat affected zone and ideally should be annealed after welding. Manufacturers that have been in the game a long time have learnt, often by experience, how to avoid these problems. New players often start by trying to copy them without understanding the critical points of design or process controls. As an example, a difference in how sharp a corner is (from 0.2mm to 0.1mm) on a crankshaft can mean the difference between early failure and long life. Cheap chinese mild steel is unlikely to break because mild steel doesn't suffer from fatigue or embrittlement around the welds, but it could bend if overloaded. Every failure happens for a reason. When you but expensive stuff, sometimes you are paying for the experience behind them, but sometimes you're getting ripped off. No way of knowing. Any change in employees, sources, materials brings new risks. For us, we pay our money and enter the lottery.
Finally, buying a bike with a steel frame doesn't solve OP's problem when it still has the same light alloy seat pin. High end mountain bikes tend to have much larger diameter seat pins for strength and life, which are still light alloy. A cheapo mild steel one is unlikely to break, but it's heavy. Life's full of dilemmas!

Good explanation, I guess as I have to carry the seat post on occasion I'll stick with lighter alloy and accept it will break occasionally.
Edit: I could get carbon but I'm very weary of cheap carbon parts, I know what a vague term that can be.