frame question

monkey186

I was wondering what makes the bicycle frame 'good'? There are of course important qualities like lightness and strength, but i also read few articles that mention the differences in 'give' and 'stiffness', and some articles suggest that the end result is often a matter of combined factors - the material of the frame, and how this material has been used (the geometry and engineering of the frame).

My question is am i right to think that the differences in "give" and "stiffness" are going to be somewhat negligible? Leaving aside very low quality bikes, would it be correct to say that the differences in frames between say £600 bike and £2000 bike, even though they might well be present, would usually be minimal - especially taking into account that mountain bikes use front and often back suspension which are also about "give" and "stiffness".

So are the statements like "that frame is superb", or that frame "stiff so not very good", really warranted? Once one is looking at a more or less good bikes, at that stage how important it is to get a "superb" frame as opposite to merely "ok" frame?:)

stoatsngroats

I think it's more about the PERSON making the statement;

If you had 2 different frames, and 2 different people appraising them, but BOTH riders having considerable experience of riding DH or XC, and they disagreed which was better, where would that leave you?

Thjese things are TOTALY subjective, because we don't all ride the same style.
Thje OBJECTIVE part of the matter is in the specifications given by the manufacturer - see if you can locate the specific measurements regarding frame strength/flex!!

monkey186

Cheers, i suppose you're right, i wondered about the question after reading few threads/posts where people recommend bikes to each other, and its there where they often say things like: "that frame has plenty of vertical give" or "that frame is too stiff".

I'm new to this, and it made me wonder how can one REALLY feel that the frame is "too stiff" given the number of other components on the bike, the obvious ones being suspensions.:) Even if one took the identical bikes but for the frame, would one honestly be able to feel the difference? (i mean the difference in "give" and "stiffness")

But you can see people evaluate frames like this quite often, so i wondered if there is something i'm missing.

monkey186

Hmmm here's the article with some data, after the writer tested several frames on stiffness/flexibility.

http://sheldonbrown.com/rinard_frametest.html

The range of deflection between frames was 0.86 inches to 0.26 inches. Which means AT BEST there is 0.60 inch to feel the difference between flexible and stiff frame.

The writer did ask whether this difference can actually matter in real life, he believed it can but only in extreme situations (particularly overweight riders, or particular applications such as high speed downhill etc).


In the other article Sheldon Brown plainly says that 'virtually all of these "differences" are either the imaginary result of the placebo effect, or are caused by something other than the frame material choice.' http://www.sheldonbrown.com/frame-materials.html He refers to tyres, the wheel, the seatstays, the seatpost, the saddle frame, the saddle top, and the fork suspension.